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A review of tiger conservation studies using nonlinear trajectory: A telemetry data approach

A review of tiger conservation studies using nonlinear trajectory: A telemetry data approach 1BackgroundTiger (Panthera tigris) is the top predator in the food chain. Tigers are territorial and generally solitary animal that requires huge area for habitat, movement, and hunting of their prey [1]. The major landscapes where tigers reside in India range from Shivalik hills to North-East hills, central India, Sundarbans, and eastern and western Ghats. Since “Project Tiger” in 1973, India has decided to conserve this species and has implemented various conservation management strategies to save the tigers. In the year 2019, India has announced that it has increased the population size of tigers from 1,411 to 2,967 [2]. But socio-economic pressure to fulfill the demands of growing population issues like land fragmentation, habitat loss, prey depletion, poaching, climate change, and anthropogenic activities makes conservation of this species very challenging in the long run. Being the top predator, tiger has an impeccable role in ecological sustainability, conserving tiger conserves other species too. Many studies have been conducted on tigers over the past century, one of the studies which presented remarkable improvement in studying habitat selection, movement patterns, and ecology to understand the tiger’s behavior is radio telemetry [1,3,4].Radio telemetry is used to study the behavioral, environmental, and movement patterns of wildlife species which are otherwise difficult to study. The meaning of telemetry is the transmission of data through the atmosphere, and the transmission is done using radio waves. Radio telemetry studies in wildlife is the integration of animal data with environmental data. Radio telemetry use in wildlife finds its genesis in 1960, it was invented in the USA. Radio telemetry is used to study animals that are otherwise very difficult to track such as tigers. Tigers are usually found in remote, rugged areas and in the core of forests that are unreachable to humans.In India, radio telemetry was first performed for Gharials (Gavialis gangeticus) at the Crocodile Research Center of the Wildlife Institute of India, Hyderabad in the year 1983. It was conducted on 12 Gharials and has marked the beginning of radio telemetry in India [5]. Telemetry provides the spatial and temporal data of the species, it gives the locational coordinates of the species to the receiver at the survey site. This information can be used to find their exact location from the survey site.Radio telemetry helps to identify the use of habitat by the species, which can further decode their behavioral patterns. In the majority of studies, radio telemetry is used to understand the movement patterns and space use by the species. But telemetry data analysis holds much more than movement patterns and space use. Telemetry data analysis can boost the existing knowledge about tiger ecology, behavior, and local ecosystems. Capturing the animal to radio collar is an integral part of any telemetry study, but catching tigers is very difficult and highly dangerous for both the tiger and the people [6]. Capturing a tiger requires highly trained staff and experts. It is usually done by locating the tiger and striking it with a dart gun [4,7]. It needs a very accurate amount of anesthesia and one needs to be careful while targeting the tiger with a dart. There have been cases when instead of a tiger another animal was hit or when the tiger took the hit, it was near a water body and fell into it, and this could lead to the death of the animal [7]. All such parameters need to be taken into consideration while capturing the tiger. Tiger is an endangered species which makes its capturing politically a sensitive activity [8].In a study conducted in Russia over Amur tigers, they were captured using foot snares, this method of capturing is also very sensitive. Using foot snare to capture animals agitates them and they try to set themselves free in which they end up hurting themselves. Sometimes, foot snare laid for tigers ends up capturing other animals and also leads to their death. Capturing any animal is a matter of great expertise, and studying and following the animal’s movement needs to be done for days. It is very costly and exhausting work that requires days and months of fieldwork. Experts who conducted a study in Russia over Amur tigers captured 49 tigers using foot snares without any capture-related death [7].Once captured, the tiger is radio-collared and other samples are also taken while it is under anesthesia effect. Other samples usually include taking a blood sample for gene studies, measuring the body length and weight, its age is estimated by checking the teeth length and wear [4]. The tiger is also checked by doctors for any disease as well [4,7].Tigers are solitary animals, found in the core of the forest area and are low in densities. Capturing a sample size to radio collar them to study the rest of the population has its share of difficulties and issues. However, acquiring a diverse sample size and tracking them for certain number of years is dependent on the problem statement for which the sample size has been taken. Before conducting a Telemetry study, it is of utmost importance to assess the problem statement and obtain the appropriate sample size. With the advancement in technology, it is easy to achieve high-quality data without much trouble for the wildlife/species. This high-resolution data can be used to understand their social behavior, movement behavior, faunal richness, and habitat use.2MethodsIn this work, we have provided the review of telemetry studies conducted on tigers in the past decade in India.2.1Database string searchTo capture the maximum number of studies conducted on tigers using telemetry data over database Scopus (www.scopus.com), the strings used are string “wildlife” and “Conservation studies” and “tigers.” Another string used to catch all the literature of telemetry studies is “Telemetry studies or radio telemetry” and “tigers.” To retrieve all the papers relating to telemetry studies on tigers is a challenge as most papers describe the region of study instead of the data used for the conducted study. One more string used to capture all papers is “telemetry studies” and “tigers” and “India.” These strings on Scopus database after removing the duplicate entries have yielded 301 documents. To conduct the review on the yielded documents, the following methodology was used (Figure 1).Figure 1The flowchart shows the process of filtering papers from database search for the review conducted in this study. Here n represents the number of papers for the respective block [52].The selection criteria for the studies to be included in this review was based on the below mentioned criteria. Total no of studies yielded from database search on the abovementioned strings was n = 301.1)The study related to wildlife conservation of terrestrial mammals was found out to be 289 and 8 studies were not related to wildlife conservation and hence were not included.2)It is found out that from these 289 studies, only 242 were related to studies on terrestrial mammals and the rest 47 were conducted on conservation of ocean species, birds, reptiles, and vegetation/fauna of the region. Hence, only 242 studies were included for the further selection criteria.3)From these 242 studies, only 104 were related to tigers and the rest were related to other terrestrial mammals such as leopards, elephants, wolf etc.4)Studies related to tigers are found to be 104 from these studies, and only studies from India or related to India were taken into consideration. The number of studies on tigers from India was found to be 50, and from other countries, a total of 54 studies were conducted from our search string over the Scopus database.5)From these 50 articles, 7 studies were conducted on tigers using radio collar or telemetry data. Rest 43 studies were conducted using camera trap, sign survey, scat analysis, and other methods to understand the tiger’s ecology. These seven studies are tabulated in Table 4.Although these seven articles are peer reviewed research on telemetry studies in India over the past two decades, we also want to declare that this document search string may not have included or captured all the work for this topic. We have presented a systematic review, along with these seven articles, and many more were reviewed as cited in the references.In this work, detailed bibliometric analysis has also been done using VOSviewer [53] to analyze the efforts for conservation studies. The analysis is done on the documents retrieved from document string search over Scopus database. From this analysis, the below table is formed. (Table 1).Table 1Top countries publishing research studies on wildlife conservationIDCountryDocumentsCitationsAverage citationsTotal link strength1India1191,62013.612152United States1143,58431.443353United Kingdom361,09930.531514China2428211.75425Australia171297.59256Nepal1751430.241027Indonesia1229924.921048Malaysia1145641.45279Canada1038938.903610Thailand1030130.103811South Africa912513.891012Germany77210.291213Russian Federation620133.501614Singapore617028.335415Brazil534569.00016Italy5153.001917Myanmar59719.402618Bhutan4389.50419Netherlands45814.501020Sweden49523.751621Czech Republic3237.67522France34113.67023New Zealand33511.67124Portugal35518.33025Spain310334.3314These data show the top countries publishing research on wildlife conservation according to the methodology used in this study. India has substantially more no of studies as compared to other countries followed by United States and United Kingdom among the top countries. It shows the efforts of the countries toward improving the conservation strategies. The data not only show that the average citation is maximum for Brazil but also the total link strength which is the collaboration among the countries is zero. United States shows the maximum collaboration with other countries. But the trend here shows that apart from the countries where remaining tigers of the world are found such as India, Nepal, Bhutan, China, Thailand, Bangladesh, Malaysia, Indonesia, Russia, and Myanmar and few more, other countries in collaboration are also conducting telemetry studies for tigers and contributing in the research publications. Figure 2 shows the link strength of countries among each other. India and United States are top countries in terms of number of research documents published followed by United Kingdom as per the methodology used in this work.Figure 2This figure shows the inter-networking of countries producing research studies in the field of wildlife conservation.Along with top countries contributing to the research on wildlife conservation, top organizations working for conservation of wildlife have also been analyzed. Table 2 shows the top organizations list along with the number of documents published with their average citations. Wildlife Institute of India (WII) has contributed maximum number of documents according to our methodology. Total link strength is 3, which means that it has collaborated with other institutions as well. These numbers are promising for India as it shows the continuous efforts of India toward wildlife conservation in the country.Table 2Top organizations in Wildlife conservation research studiesIDOrganizationDocumentsCitationsAverage citationsTotal link strength1Wildlife Institute of India, Dehradun, India71752532Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, United States517434.833Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, United States428771.7504Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, United States33110.3315Department of Zoology, University of Calcutta, Kolkata, West Bengal, India35317.6706Fauna and Flora International, Cambridge, United Kingdom37324.3317Wildlife Conservation Society, Bronx, NY, United States33812.6703ReviewIn this work, we have provided the review of telemetry studies conducted over tigers in the past 2 decades in India. Figure 3 shows the organization of the review conducted. It explains the radio telemetry and its use in wildlife conservation, which further explains about application and different types of radio telemetry in wildlife. It also outlines the scenario in wildlife conservation before and after radio telemetry.Figure 3Flow Diagram representing the organization of review.3.1How radio telemetry works?Radio telemetry requires a transmitter and a receiver.Transmitter: Signals are transmitted using the transmitter and a power source and antenna to propagate the signals using radio waves.Receiver: Picks up the signals sent by the transmitter with an attached power source.The transmitter is attached to the animal using a radio collar which transmits the signals to the base station or survey site where the receiver is located. Radio collar is fitted around the neck of animals such as tigers, wild dogs, bears, etc., and to the ankle of animals like rhinoceros, elephants, etc. A radio collar is a device that contains a transmitter and power source to send the signals using radio waves to the receiver. These are designed to have less impact on animals and high on its detectability. To avoid the impact of radio collars on animals, the standard weight of the collar should not be more than 5% of their body weight [9,10,55]. With the advancement in hardware and sensors, few collars weigh around 1% of the animal body weight [4,9,54]. Radio collars are equipped with different types of sensors that can record the movement activity, body temperature, and mortality of the animal [11,12].Three different types of radio telemetry uses radio-collars to transmit the data.Very high frequency (VHF) radio collars: it is the standard method of collecting telemetry data of the animals by using VHF-based radio collars. An animal wearing a VHF transmitter transmits the signals which can be received by using antenna and techniques like triangulation and homing.Global positioning system (GPS) radio collar: it tracks the animal from a remote location. GPS collars store the data and transmit them at preset intervals. They store the locational data which can be downloaded in many ways [9]. GPS radio collars use the mobile network to transmit the data. These types of collars also come with attached VHF capabilities [9,10].Satellite radio collar: tracks the animal from a remote location. It uses a satellite to transmit the data to the receiver.Table 3 shows the comparison of different radio telemetry collars used in wildlife. Figures 4 and 5 show the GPS radio collar used for tracking tigers and the tiger fitted with radio collar [4], respectively.Table 3Comparison of radio-tracking/radio collars for tigersVHFSatellite trackingGPS trackingAccuracyMostly accurateLess accurate than VHF (depends on the problem to study)Highly accurateCostLow costHigh initial costHigh initial costDistanceUsed for short distance trackingUsed for monitoring long distancesUsed for short-lived applicationsOn-field personnel requirementRequires personnel on the ground for tracking.Requires no personnel on the groundRequires no personnel on the groundInformation providedProvides more information other than locational dataProvides only locational data of the speciesProvides only locational data of the speciesSuch as behavioral activitiesBattery lifeGood battery life (average 3 years)Consumes more battery than VHF (average 2 years)Consumes more battery than VHF (average 2 years)WeightLighter in weightTotal weight is more than VHFTotal weight is more than VHF (it is usually equipped with VHF capabilities so more weight)Mortality informationProvides data on Mortality (transmitter changes the pulse rate of radio signal in case of no movement for hours)No such feature is availableNo such feature is availableFigure 4GPS radio collar for tigers [4].Figure 5Tiger wearing a radio collar [4].3.2Recent trends and applications of telemetryRadio collars with inbuilt cameras: these collars can help to record audio and video of the surroundings of the species [11,12].Radio collars with temperature sensors: this recent development in radio collars allows the collection of temperature data of the surroundings as well as of the animal body [11].The literature survey presented in this study has not found the use or mentioning of any of these new radio collars but they have promising features which can change the facet of telemetry studies. Telemetry can be used to study the movement patterns, habitat usage, social interaction, home range, food habits, mortality rate, land use, migration patterns, behavioral patterns, and human–animal interaction. There are many conservation areas where it is impossible or very difficult for humans to carry on surveillance activities. This is where telemetry studies play a huge role and provide an understanding of various tiger behaviors as mentioned above. But majorly telemetry is used for studying the movement pattern and habitat use of species.Movement Pattern: the meaning of movement pattern in the wild means how the space is used and how animals move in context to anthropogenic activities. Studying the movement pattern decodes other traits of the species such as:Movement patterns help to understand their territory or their home range size which helps to understand the prey density in the area [10]. This is because prey base is directly proportional to the tiger density in the region.The abundance of prey density determines the presence of tigers in the area [13]. Tigers usually prey on large animals such as bulls, gaurs, rhinoceros, wild boars, etc. [14].Analyzing movement patterns helps to understand their social behaviors and their spatial–temporal interactions. It also suggests the use of demography by the tigers [15]. Due to fragmented land spaces, movement pattern studies suggest how the movement and activities of tigers are influenced by human presence. To study the movement patterns of species, large number of locations per tiger is required. Dispersal data collection is very difficult to collect as they move very long distances very quickly [10]. But radio telemetry has made it possible to collect data in a contiguous manner with the help of VHF/GPS radio collars [16]. Over the past decades, many tigers are radio-collared to understand their movement and ecology. Dispersal movement and its collected data are very crucial as they can provide the basis to create green corridors for already fragmented forest land [17,18].Habitat Use: the meaning of habitat is the space where the animal can rest, take shelter, and eat. Tigers typically have wide home ranges, their typical home range size for male tigers is 60–150 km2 and for female, the home range size is 20–60 km2 [2,17]. Studying habitat use is a challenging task as tigers prefer to stay in the core areas of the forest. These areas are difficult to track, sometimes GPS/satellite collars also do not work properly due to canopy cover [10]. Tigers have a variety of habitat across India from mangrove swamps of Sundarbans to terrain areas of the Himalayas, rain forests of eastern and western Ghats to the tropical moist deciduous forest of central India and dry forest of Rajasthan [18]. Tigers walk at a speed of 5 km/h and can reach any area of their home range within an hour [10]. Telemetry studies on collared tigers at Sundarbans have shown that prey abundance is inverse to the home range of tigers. It has also shown that the breeding tigers have an average home range size of 40 km2 [10].3.3Before telemetryTelemetry research started in 1963 in India. But researchers are studying tigers for over 100 years [18,19]. Before telemetry, scientists and conservationists were using camera trapping, on-site tracking of the tigers for a long period of time to understand the ecology of tigers [1,18]. Their studies have provided the base of tiger ecology. Traditionally, tigers were tracked by the professional shikaris from their pugmarks to hunt the animal. Other sign analysis included scat analysis. Data collected using these methods have their challenges. Tracking the animal on the field is always dangerous, it causes hindrance to animal activities as well. Using these methods, very limited data can be collected as unreachable areas cannot be covered by these methods. But studies based on these methods have shown that for a few ecological questions these methods provide better answers such as to estimate population size and distribution of tigers. These methods along with the latest techniques provide high-quality data for analysis which can be used to infer the behavioral patterns of species [20].Table 4 shows the different data collection methods in wildlife used by the scientist before and after telemetry in India:Table 4Earlier and new data collection methods in wildlife conservationReferencesEarlier data collection methods in the wild (before telemetry)New data collection methods in the wild (after telemetry)[7]Observational studiesGPS/Geographical information system (GIS)[7,21]Mark – recapture/sign analysisMobile phones/applications, e.g.,M-STrIPES, CaTRAT[7]On-field trackingRadio telemetry[22]Camera trappingEmbedded and remote sensors3.4After telemetryRadio collars were first used in the USA on grizzly bears in early 1960s by Craighead Brothers. They tracked these grizzly bears from 1960 to 1968 and later published their research on the collected data explaining home ranges, movement patterns, food habits, and mortality rates [6,17]. Through telemetry data analysis, researchers were able to manage the habitat area. Studying the home ranges gave the ideas of important locations which could be used as habitat, hence more focus could be given to those areas. Breakthrough in wildlife research after telemetry are as follows.3.4.1Emigration and mortalityTelemetry data analytics has helped to identify whether the animal is dead or emigrated to another place. It was difficult to identify this before telemetry studies. Emigration in fragmented land is difficult for the animal but is very necessary for the survival of species in the longer run. Emigrating from one place to another enables gene flows [23]. For genetic diversity, gene flow is crucial which could be achieved if the animal can move from one place to another. Fragmented land and anthropogenic activities limit the emigration among animals [23,24]. India was once enriched with tigers with genetic diversity, but this is reducing now. Gene flow among species ensures their survival in different environments and difficult situations. This feature is required to survive the coming-up changes in climate. Telemetry studies can help in studying the emigration patterns among tigers [25,26].3.4.2Dispersal and movement patternsRadio telemetry can provide the movement patterns of the species. These patterns gave their home range sizes [27]. Movement patterns can provide the basics in detecting the underlying behavior for movement and dispersal [26,27]. There are various methods to study the movement patterns and researchers can choose from a variety of techniques to study the patterns which suit best for their research question. Dispersal in the case of tigers means moving away from other co-predators. Plenty of studies have been conducted to understand the movement ecology of tigers [28,40]. These studies suggested the population dynamics, dispersal, response to climate changes, environmental changes, and anthropogenic activities [27,29,40], and also, whether human activities are impacting all their activities negatively.3.4.3Home range and habitat selectionTelemetry studies help in understanding the home range and habitat selection of the species. Integrating the movement patterns with habitat selection gives insights into how animals use their space [30]. To understand their space use, radio telemetry plays a significant role. The new advancements in the radio collars provide the locational coordinates with great precision. Camera trapping, observing, and tracking the species were not possible in the deep forests [31]. Radio telemetry has provided the solution to these problems and covered the animal in a wider range. Though there is still a limitation to the areas which can be covered by telemetry. Habitat selection plays an important role in species survival and thereby in their population dynamics [28,30]. Therefore, any study conducted on habitat selection is very important. Many studies have been conducted to understand the habitat selection of species using telemetry studies which have shown the relationship between habitat selection and movement of the species [32].To understand the selection of their habitat, it is necessary to record the movements of the species in their environment. Radio telemetry allows to track the animals remotely in their natural space. The radio collars used in telemetry studies are capable of sending the locational data directly to the computer of the researcher and provide huge locational data for analysis. Habitat selection and their home range provide the basis to form conservation strategies for the species.3.4.4Food habit and prey densityTelemetry studies provide the insights into prey and predator relationship. It provides the analysis of species diet and kill rates [33]. Radio telemetry provides the spatial–temporal data of the species. This locational data along with the time suggests the activity of the animal [4,17]. If the time spent at a location is more than 24 h, then the tiger may be feeding itself with a fresh kill [1,7]. Tigers usually take a few hours to consume their kill or sometimes revisit the same location. Researchers go to the location of the kill after the tiger is gone from that area and search for the sign of fresh kill. Before radio telemetry scat analysis, following the animal trail methods were used to determine the kill. These methods are still in use and have their importance. GPS collars provide many more locations with much accuracy, these locations are divided into clusters using existing statistical methods. These statistical techniques are used to identify the sites of prey remains from the clusters of locations received from VHF/GPS radio collars [33]. These studies provide estimates about the kill rate, how the tiger responds to prey density, and its environment during kill [12].The selection of radio collar plays an important role while collecting the data through Radio telemetry. In this study, different types of collars and when to use which type of collar are discussed above.4Discussion4.1How telemetry enhanced the knowledge to understand tiger ecologyRadio telemetry now is extensively used by conservationists. The recent study published in June 2021 was conducted by WII, Dehradun and Maharashtra Forest Department (MFD) in which 15 tigers were radio-collared from 2015 to 2020 to study their movement patterns through telemetry data. This study has shown the pathways and corridors of tiger movement [3]. Through this study, the scientist and researchers were able to identify the pathways of tiger dispersal at Vidarbha landscape, which is home to around 331 tigers [3,9]. The study can guide ways to mitigate human–animal conflict, habitat fragmentation, and how to involve other stakeholders of the land to make better use of land for tiger dispersal without any human–animal conflict. Before the widespread use of telemetry in wildlife, very little was known about their movement and habitat [34]. Studies of telemetry data and with on-field efforts of a conservationist, the habitats of tigers are also known using radio collars/GIS/GPS. These were the landmarks in tiger telemetry in India. These tasks (movement and habitat) were accomplished by the use of technology. Using telemetry data analytics, it was found, how tigers do transboundary movements, satellite technology through radio collar was used to observe tiger translocation from Sariska Tiger Reserve to Panna Tiger Reserve [4].These technologies have also helped other methods of wildlife conservation, for example, the camera trapping technique of observing animals was in use for so long but was not that effective. Using radio collars on animals gave their movement patterns and ecologists were able to identify the correct locations to put the camera trap. It has also helped in estimating the correct population size of tigers.Another telemetry study has shown that the radio-collared tigers in Nagarahole Tiger Reserve were more nocturnal. They were least active during the daytime due to human interference in the area. This is an important finding, it suggests the behavior changes in tigers due to anthropogenic activities [13]. It has been observed through radio-collared tigers that tigers move from 2 to 11 km on daily basis. It has also been found through telemetry data analysis that tigers’ habitat selection depends on the density of prey. They disperse to the areas where their prey or ungulates concentrate [13]. Tigers are territorial and generally solitary animals. Through telemetry studies it is shown that they require a large contiguous area of habitat that supports their prey requirements. It is also shown that the tiger movement is usually for hunting or social interaction with other co-predators [1]. Table 5 shows the different studies conducted using radio-collar on tiger in India in the past decade.Table 5Major telemetry studies conducted on tigers in India from 2010 to 2021Name of the program/research study (publishing year)Radio collaring and monitoring durationObjective of radio telemetry studyTotal no. of tigers in the area in 2021 (approximately)No. of tigers collared for the studyLocation/tiger reserveType of collar usedStakeholdersReferencesEvaluating capture–recapture population and density estimation of tigers in a population with known parameters (2010)2008–2009Home range, population density estimationApproximately 5006Kanha Tiger Reserve, Madhya Pradesh, Central IndiaVHF/GPSProject Tiger Directorate (Government of India) and the WII, Kanha Tiger Reserve[46]Home ranges of Bengal tiger (Panthera tigris tigris L.) in Pench Tiger Reserve, Madhya Pradesh, Central India (2012)2008–2011Ranging and dispersal patternEstimated no. is 443Pench Tiger Reserve, Madhya Pradesh, IndiaSatellite and VHFMadhya Pradesh Forest Department (MPFD), WII and National Tiger Conservation Authority (NTCA)[51]Connecting tiger populations for long-term conservation (2014)2011–2014Mapping of corridors over entire India Tiger ReservesEstimated tiger population (2967)All tiger conservation landscapes of IndiaUnknownNTCA and WII, Dehardun[37]Long-term monitoring of a Bengal tiger (Panthera tigris tigris) population in a human-dominated landscape of central India (2016)2006–2013The population dynamics, dispersal, survival rateEstimated no. is 444Pench Tiger Reserve, Madhya Pradesh, IndiaVHF radio collarMPFD, WII, Dehradun,India[48]Movement and home range characteristics of reintroduced tiger (Panthera tigris) population in Panna Tiger Reserve, central India (2016)2009–2014Behavioral response of reintroduced tiger populationEstimated no. is 709Panna Tiger Reserve, Central India, Madhya Pradesh, IndiaVHF/GPS/UHF collar to three animals, VHF/GPS/Satellite collar to two animals, and VHF radio collar to four animalsMPFD, WII and NTCA[49]Ranging, activity, and habitat use by tigers in the mangrove forests of the Sundarban (2016)2008–2014Ranging patterns and habitat preferenceEstimated no. is 966Sundarbans National Park, West Bengal, IndiaGPS satellite and VHF collarsWII, Dehradun, India[35]Assessment of fine-scale resource selection and spatially explicit habitat suitability modeling for a reintroduced tiger (Panthera tigris) population in central India (2017)2009–2014Habitat selection by the reintroduced tiger populationEstimated no. is 709Panna Tiger Reserve, Central India, Madhya Pradesh, IndiaVHF/GPS/UHF collar to three animals, VHF/GPS/Satellite collar to two animals and VHF radio collar to four animalsMPFD, WII and NTCA[50]Human–tiger interactions (2020)2020–2023 (expected)Human–tiger interactionsEstimated no. is 961 (3 more are expected to be radio collared)Sundarbans National Park, West Bengal, IndiaUnknownBengal Forest Department (BFD)[36]Dispersal of tigers in eastern Vidarbha landscape (2020)2015–2020Patterns of tiger migrationEstimated no. is 31215Eastern Vidarbha landscape, Nagpur, Maharashtra, IndiaIridium, VHF/activityMFD and WII, Dehradun, India[3]Status of tigers, co-predators, prey, and their habitat (2020)2018–2019Population sizeEstimated tiger population ( 2967)All tiger conservation landscapes of IndiaUnknownNTCA in collaboration with WII, State forest departments, conservation NGOs[8]Not a cakewalk: insights into movement of large carnivores in human-dominated landscapes in India (2021)2014–2019Understanding movement patterns in human-dominated landscapesEstimated no. is 31214Eastern Vidarbha landscape, Nagpur and Chandrapur divisions and districts of Pune and Solapur, Maharashtra, IndiaGPS collarsMFD and WII, Dehradun[47]These studies are conducted using telemetry data which are collected using radio collars on tigers. The table above shows the number of tigers radio collared to collect the telemetered data. These data have been analyzed to understand the species ecology in more detailed way. In India,there are 52 tigers reserves which are further divided into core area and peripheral area [45]. Figure 6 shows the region on the map of India, over which these major studies were conducted.Figure 6Map of India showing the regions of major conservation studies along with the type of vegetations found in these regions.Telemetry data analyses have provided the insights into ecology of tigers. The studies conducted above in Table 5 have provided the better understanding and awareness about the behavioral patterns of tigers. One of the studies in the table above suggested that breeding tigers have large home ranges with an average of 40 km2 at Sundarbans of India. This study has also provided the insights into movement hours of the tigers. It concluded that the tigers move more in the early hours of morning, may be to avoid conflict with humans. If the activities by humans are restricted during morning hours human–animal conflict can be reduced in the area [35]. Another study mentioned in the table above showed that radio telemetry has enhanced the understanding of reintroduced tigers in the area where local population is extinct. The study stated that radio telemetry made it possible to closely monitor the reintroduced tigers, which was not possible earlier [49]. Through monitoring of these nine reintroduced tigers in the region, it appeared that these tigers behaved in the same manner as that of the native population of the region [49]. One more study conducted using telemetry data in the central India has presented that the Pench forest of Madhya Pradesh is relatively small and when tigers disperse, the conditions in the buffer zone of Pench forest is not optimal and can impact the dispersed tigers [48]. One of the studies conducted from the table above has provided insights into how increase in the human population is putting pressure on the already fragmented landscapes. If the species like tigers has to co-exist with humans due to increased pressure on land, then it is highly important to understand the movement patterns of tigers and how they adapt to the challenges outside the protected areas. Their response to the human interventions can help the conservationist to plan the strategies for land use and corridors. All these studies have presented the home range, movement patterns, dispersal, response of reintroduced population, habitat suitability, and many other important factors using telemetry studies on the tigers of India.4.2Challenges and issues with telemetry dataThere are a few limitations attached with telemetry data collection and analysis. Many ecological questions are answered through telemetry studies, which could not be answered using any other method of wildlife conservation. But there are a few issues while using telemetry studies.a)The first step to collect telemetry data is to put a radio collar on the tigers, which is a dangerous task as it involves capturing the tiger. To capture the tiger, there are many permissions and approvals required which can be a tedious task [4,8]. Once approved, ecologist and researchers along with the team needs to plan the capture very carefully because while capturing, the animal can be in danger which sometimes can lead to the death of the animal. This can lead to the cancellation of permission for animal capturing that can compromise the research study.b)During the initial days after attaching radio-collar on species, they have reduced activities as they adjust to the collar. Studies conducted for a shorter period may lack or have insufficient data as during the first few days or weeks, the animal adjusts to the radio collar and hence is less active [38,39].c)To collect telemetry data needs a high level of expertise, sometimes it is required to be on-site if a standard VHF radio collar is used. Cost associated with telemetry studies is quite high as it needs proper equipment, trained labor, and staff for capture [4,11].d)It is difficult to study tigers for years as their density is low and they live in remote areas of the forest [26]. One of the major challenges in telemetry studies is that it deals with the locational data of the species which can put the animal at risk. It is of utmost necessity to take proper care of data and it should be protected from unauthorized usage.e)Another big concern over telemetry study is the hacking of radio collars. Poachers can hack the collar and can get the locational data of the animal, risking the animal for poaching [40].f)Another challenge is the lack of fully advanced radio collars and cost. Many researchers complain about the premature expiry of the battery, collar failing, and incompatible data collection from the collar [11]. These issues suggest more technological advancements, training, and government contributions.Telemetry studies pose challenges in data collection, integrating data, and data analysis [41]. The recent advances in telemetry devices allow data to be transmitted from the radio collar to the receiver, which is connected to the computer for data collection [42]. Some devices do not transfer the data to the receiver but store it in the telemetry device. Data received from these devices are unstructured data. Data integration is required to store and analyze the data. Integrating data means telemetry study could involve one or more species, one location, or multiple locations at the same time in the conducted study, hence data received from their collar need to be integrated for the storage [37,43]. Each device has its format of collecting the data, variables in the collected data can also vary according to the sensors used in the collar [30,33]. This makes data integration and data collection a challenging task to achieve. Telemetry devices’ error should also be taken into consideration by the researchers otherwise the inferences drawn from the data provided by these devices can be erroneous [44].5ConclusionRadio telemetry can help in real-time monitoring of the tigers. There is no other alternative to radio-collaring in collecting the data. This can be used in identifying movement patterns thus decoding the habitat selection and its use by tigers. Tiger dispersal can suggest the appropriate green corridor strategies to connect the fragmented Land, to avoid tiger poaching, and human–animal conflict. These studies can also be used to avoid animal deaths due to train or road accidents. It is seen that habitat loss and poaching are the main reasons for the decline in the tiger population drastically. Human–animal conflict is rising due to fragmented home ranges. The future scope of this work could be utilizing the telemetry data of tigers to analyze their movement patterns. Telemetry data can be used to see where they move, why they move and can help in predicting human–animal conflict. Tiger’s ecosystem is greatly impacted by anthropogenic activities. It is very crucial to understand the ecological requirements, landscape use, and tiger behavior towards reduced land, forest, and prey density. It is one of the biggest challenges to understand the ecological patterns that are changing at a very fast pace. Current conservation methods may not be sufficient to conserve this endangered species in the long run. Radio telemetry is a suitable and very effective technique to study the tiger’s ecology. Currently, we know very little about the tigers and radio telemetry is providing promising results. In future studies, the behavioral activities of the tigers can be decoded using telemetry data analysis. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nonlinear Engineering de Gruyter

A review of tiger conservation studies using nonlinear trajectory: A telemetry data approach

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de Gruyter
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© 2023 the author(s), published by De Gruyter
ISSN
2192-8029
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2192-8029
DOI
10.1515/nleng-2022-0235
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Abstract

1BackgroundTiger (Panthera tigris) is the top predator in the food chain. Tigers are territorial and generally solitary animal that requires huge area for habitat, movement, and hunting of their prey [1]. The major landscapes where tigers reside in India range from Shivalik hills to North-East hills, central India, Sundarbans, and eastern and western Ghats. Since “Project Tiger” in 1973, India has decided to conserve this species and has implemented various conservation management strategies to save the tigers. In the year 2019, India has announced that it has increased the population size of tigers from 1,411 to 2,967 [2]. But socio-economic pressure to fulfill the demands of growing population issues like land fragmentation, habitat loss, prey depletion, poaching, climate change, and anthropogenic activities makes conservation of this species very challenging in the long run. Being the top predator, tiger has an impeccable role in ecological sustainability, conserving tiger conserves other species too. Many studies have been conducted on tigers over the past century, one of the studies which presented remarkable improvement in studying habitat selection, movement patterns, and ecology to understand the tiger’s behavior is radio telemetry [1,3,4].Radio telemetry is used to study the behavioral, environmental, and movement patterns of wildlife species which are otherwise difficult to study. The meaning of telemetry is the transmission of data through the atmosphere, and the transmission is done using radio waves. Radio telemetry studies in wildlife is the integration of animal data with environmental data. Radio telemetry use in wildlife finds its genesis in 1960, it was invented in the USA. Radio telemetry is used to study animals that are otherwise very difficult to track such as tigers. Tigers are usually found in remote, rugged areas and in the core of forests that are unreachable to humans.In India, radio telemetry was first performed for Gharials (Gavialis gangeticus) at the Crocodile Research Center of the Wildlife Institute of India, Hyderabad in the year 1983. It was conducted on 12 Gharials and has marked the beginning of radio telemetry in India [5]. Telemetry provides the spatial and temporal data of the species, it gives the locational coordinates of the species to the receiver at the survey site. This information can be used to find their exact location from the survey site.Radio telemetry helps to identify the use of habitat by the species, which can further decode their behavioral patterns. In the majority of studies, radio telemetry is used to understand the movement patterns and space use by the species. But telemetry data analysis holds much more than movement patterns and space use. Telemetry data analysis can boost the existing knowledge about tiger ecology, behavior, and local ecosystems. Capturing the animal to radio collar is an integral part of any telemetry study, but catching tigers is very difficult and highly dangerous for both the tiger and the people [6]. Capturing a tiger requires highly trained staff and experts. It is usually done by locating the tiger and striking it with a dart gun [4,7]. It needs a very accurate amount of anesthesia and one needs to be careful while targeting the tiger with a dart. There have been cases when instead of a tiger another animal was hit or when the tiger took the hit, it was near a water body and fell into it, and this could lead to the death of the animal [7]. All such parameters need to be taken into consideration while capturing the tiger. Tiger is an endangered species which makes its capturing politically a sensitive activity [8].In a study conducted in Russia over Amur tigers, they were captured using foot snares, this method of capturing is also very sensitive. Using foot snare to capture animals agitates them and they try to set themselves free in which they end up hurting themselves. Sometimes, foot snare laid for tigers ends up capturing other animals and also leads to their death. Capturing any animal is a matter of great expertise, and studying and following the animal’s movement needs to be done for days. It is very costly and exhausting work that requires days and months of fieldwork. Experts who conducted a study in Russia over Amur tigers captured 49 tigers using foot snares without any capture-related death [7].Once captured, the tiger is radio-collared and other samples are also taken while it is under anesthesia effect. Other samples usually include taking a blood sample for gene studies, measuring the body length and weight, its age is estimated by checking the teeth length and wear [4]. The tiger is also checked by doctors for any disease as well [4,7].Tigers are solitary animals, found in the core of the forest area and are low in densities. Capturing a sample size to radio collar them to study the rest of the population has its share of difficulties and issues. However, acquiring a diverse sample size and tracking them for certain number of years is dependent on the problem statement for which the sample size has been taken. Before conducting a Telemetry study, it is of utmost importance to assess the problem statement and obtain the appropriate sample size. With the advancement in technology, it is easy to achieve high-quality data without much trouble for the wildlife/species. This high-resolution data can be used to understand their social behavior, movement behavior, faunal richness, and habitat use.2MethodsIn this work, we have provided the review of telemetry studies conducted on tigers in the past decade in India.2.1Database string searchTo capture the maximum number of studies conducted on tigers using telemetry data over database Scopus (www.scopus.com), the strings used are string “wildlife” and “Conservation studies” and “tigers.” Another string used to catch all the literature of telemetry studies is “Telemetry studies or radio telemetry” and “tigers.” To retrieve all the papers relating to telemetry studies on tigers is a challenge as most papers describe the region of study instead of the data used for the conducted study. One more string used to capture all papers is “telemetry studies” and “tigers” and “India.” These strings on Scopus database after removing the duplicate entries have yielded 301 documents. To conduct the review on the yielded documents, the following methodology was used (Figure 1).Figure 1The flowchart shows the process of filtering papers from database search for the review conducted in this study. Here n represents the number of papers for the respective block [52].The selection criteria for the studies to be included in this review was based on the below mentioned criteria. Total no of studies yielded from database search on the abovementioned strings was n = 301.1)The study related to wildlife conservation of terrestrial mammals was found out to be 289 and 8 studies were not related to wildlife conservation and hence were not included.2)It is found out that from these 289 studies, only 242 were related to studies on terrestrial mammals and the rest 47 were conducted on conservation of ocean species, birds, reptiles, and vegetation/fauna of the region. Hence, only 242 studies were included for the further selection criteria.3)From these 242 studies, only 104 were related to tigers and the rest were related to other terrestrial mammals such as leopards, elephants, wolf etc.4)Studies related to tigers are found to be 104 from these studies, and only studies from India or related to India were taken into consideration. The number of studies on tigers from India was found to be 50, and from other countries, a total of 54 studies were conducted from our search string over the Scopus database.5)From these 50 articles, 7 studies were conducted on tigers using radio collar or telemetry data. Rest 43 studies were conducted using camera trap, sign survey, scat analysis, and other methods to understand the tiger’s ecology. These seven studies are tabulated in Table 4.Although these seven articles are peer reviewed research on telemetry studies in India over the past two decades, we also want to declare that this document search string may not have included or captured all the work for this topic. We have presented a systematic review, along with these seven articles, and many more were reviewed as cited in the references.In this work, detailed bibliometric analysis has also been done using VOSviewer [53] to analyze the efforts for conservation studies. The analysis is done on the documents retrieved from document string search over Scopus database. From this analysis, the below table is formed. (Table 1).Table 1Top countries publishing research studies on wildlife conservationIDCountryDocumentsCitationsAverage citationsTotal link strength1India1191,62013.612152United States1143,58431.443353United Kingdom361,09930.531514China2428211.75425Australia171297.59256Nepal1751430.241027Indonesia1229924.921048Malaysia1145641.45279Canada1038938.903610Thailand1030130.103811South Africa912513.891012Germany77210.291213Russian Federation620133.501614Singapore617028.335415Brazil534569.00016Italy5153.001917Myanmar59719.402618Bhutan4389.50419Netherlands45814.501020Sweden49523.751621Czech Republic3237.67522France34113.67023New Zealand33511.67124Portugal35518.33025Spain310334.3314These data show the top countries publishing research on wildlife conservation according to the methodology used in this study. India has substantially more no of studies as compared to other countries followed by United States and United Kingdom among the top countries. It shows the efforts of the countries toward improving the conservation strategies. The data not only show that the average citation is maximum for Brazil but also the total link strength which is the collaboration among the countries is zero. United States shows the maximum collaboration with other countries. But the trend here shows that apart from the countries where remaining tigers of the world are found such as India, Nepal, Bhutan, China, Thailand, Bangladesh, Malaysia, Indonesia, Russia, and Myanmar and few more, other countries in collaboration are also conducting telemetry studies for tigers and contributing in the research publications. Figure 2 shows the link strength of countries among each other. India and United States are top countries in terms of number of research documents published followed by United Kingdom as per the methodology used in this work.Figure 2This figure shows the inter-networking of countries producing research studies in the field of wildlife conservation.Along with top countries contributing to the research on wildlife conservation, top organizations working for conservation of wildlife have also been analyzed. Table 2 shows the top organizations list along with the number of documents published with their average citations. Wildlife Institute of India (WII) has contributed maximum number of documents according to our methodology. Total link strength is 3, which means that it has collaborated with other institutions as well. These numbers are promising for India as it shows the continuous efforts of India toward wildlife conservation in the country.Table 2Top organizations in Wildlife conservation research studiesIDOrganizationDocumentsCitationsAverage citationsTotal link strength1Wildlife Institute of India, Dehradun, India71752532Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, United States517434.833Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, United States428771.7504Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, United States33110.3315Department of Zoology, University of Calcutta, Kolkata, West Bengal, India35317.6706Fauna and Flora International, Cambridge, United Kingdom37324.3317Wildlife Conservation Society, Bronx, NY, United States33812.6703ReviewIn this work, we have provided the review of telemetry studies conducted over tigers in the past 2 decades in India. Figure 3 shows the organization of the review conducted. It explains the radio telemetry and its use in wildlife conservation, which further explains about application and different types of radio telemetry in wildlife. It also outlines the scenario in wildlife conservation before and after radio telemetry.Figure 3Flow Diagram representing the organization of review.3.1How radio telemetry works?Radio telemetry requires a transmitter and a receiver.Transmitter: Signals are transmitted using the transmitter and a power source and antenna to propagate the signals using radio waves.Receiver: Picks up the signals sent by the transmitter with an attached power source.The transmitter is attached to the animal using a radio collar which transmits the signals to the base station or survey site where the receiver is located. Radio collar is fitted around the neck of animals such as tigers, wild dogs, bears, etc., and to the ankle of animals like rhinoceros, elephants, etc. A radio collar is a device that contains a transmitter and power source to send the signals using radio waves to the receiver. These are designed to have less impact on animals and high on its detectability. To avoid the impact of radio collars on animals, the standard weight of the collar should not be more than 5% of their body weight [9,10,55]. With the advancement in hardware and sensors, few collars weigh around 1% of the animal body weight [4,9,54]. Radio collars are equipped with different types of sensors that can record the movement activity, body temperature, and mortality of the animal [11,12].Three different types of radio telemetry uses radio-collars to transmit the data.Very high frequency (VHF) radio collars: it is the standard method of collecting telemetry data of the animals by using VHF-based radio collars. An animal wearing a VHF transmitter transmits the signals which can be received by using antenna and techniques like triangulation and homing.Global positioning system (GPS) radio collar: it tracks the animal from a remote location. GPS collars store the data and transmit them at preset intervals. They store the locational data which can be downloaded in many ways [9]. GPS radio collars use the mobile network to transmit the data. These types of collars also come with attached VHF capabilities [9,10].Satellite radio collar: tracks the animal from a remote location. It uses a satellite to transmit the data to the receiver.Table 3 shows the comparison of different radio telemetry collars used in wildlife. Figures 4 and 5 show the GPS radio collar used for tracking tigers and the tiger fitted with radio collar [4], respectively.Table 3Comparison of radio-tracking/radio collars for tigersVHFSatellite trackingGPS trackingAccuracyMostly accurateLess accurate than VHF (depends on the problem to study)Highly accurateCostLow costHigh initial costHigh initial costDistanceUsed for short distance trackingUsed for monitoring long distancesUsed for short-lived applicationsOn-field personnel requirementRequires personnel on the ground for tracking.Requires no personnel on the groundRequires no personnel on the groundInformation providedProvides more information other than locational dataProvides only locational data of the speciesProvides only locational data of the speciesSuch as behavioral activitiesBattery lifeGood battery life (average 3 years)Consumes more battery than VHF (average 2 years)Consumes more battery than VHF (average 2 years)WeightLighter in weightTotal weight is more than VHFTotal weight is more than VHF (it is usually equipped with VHF capabilities so more weight)Mortality informationProvides data on Mortality (transmitter changes the pulse rate of radio signal in case of no movement for hours)No such feature is availableNo such feature is availableFigure 4GPS radio collar for tigers [4].Figure 5Tiger wearing a radio collar [4].3.2Recent trends and applications of telemetryRadio collars with inbuilt cameras: these collars can help to record audio and video of the surroundings of the species [11,12].Radio collars with temperature sensors: this recent development in radio collars allows the collection of temperature data of the surroundings as well as of the animal body [11].The literature survey presented in this study has not found the use or mentioning of any of these new radio collars but they have promising features which can change the facet of telemetry studies. Telemetry can be used to study the movement patterns, habitat usage, social interaction, home range, food habits, mortality rate, land use, migration patterns, behavioral patterns, and human–animal interaction. There are many conservation areas where it is impossible or very difficult for humans to carry on surveillance activities. This is where telemetry studies play a huge role and provide an understanding of various tiger behaviors as mentioned above. But majorly telemetry is used for studying the movement pattern and habitat use of species.Movement Pattern: the meaning of movement pattern in the wild means how the space is used and how animals move in context to anthropogenic activities. Studying the movement pattern decodes other traits of the species such as:Movement patterns help to understand their territory or their home range size which helps to understand the prey density in the area [10]. This is because prey base is directly proportional to the tiger density in the region.The abundance of prey density determines the presence of tigers in the area [13]. Tigers usually prey on large animals such as bulls, gaurs, rhinoceros, wild boars, etc. [14].Analyzing movement patterns helps to understand their social behaviors and their spatial–temporal interactions. It also suggests the use of demography by the tigers [15]. Due to fragmented land spaces, movement pattern studies suggest how the movement and activities of tigers are influenced by human presence. To study the movement patterns of species, large number of locations per tiger is required. Dispersal data collection is very difficult to collect as they move very long distances very quickly [10]. But radio telemetry has made it possible to collect data in a contiguous manner with the help of VHF/GPS radio collars [16]. Over the past decades, many tigers are radio-collared to understand their movement and ecology. Dispersal movement and its collected data are very crucial as they can provide the basis to create green corridors for already fragmented forest land [17,18].Habitat Use: the meaning of habitat is the space where the animal can rest, take shelter, and eat. Tigers typically have wide home ranges, their typical home range size for male tigers is 60–150 km2 and for female, the home range size is 20–60 km2 [2,17]. Studying habitat use is a challenging task as tigers prefer to stay in the core areas of the forest. These areas are difficult to track, sometimes GPS/satellite collars also do not work properly due to canopy cover [10]. Tigers have a variety of habitat across India from mangrove swamps of Sundarbans to terrain areas of the Himalayas, rain forests of eastern and western Ghats to the tropical moist deciduous forest of central India and dry forest of Rajasthan [18]. Tigers walk at a speed of 5 km/h and can reach any area of their home range within an hour [10]. Telemetry studies on collared tigers at Sundarbans have shown that prey abundance is inverse to the home range of tigers. It has also shown that the breeding tigers have an average home range size of 40 km2 [10].3.3Before telemetryTelemetry research started in 1963 in India. But researchers are studying tigers for over 100 years [18,19]. Before telemetry, scientists and conservationists were using camera trapping, on-site tracking of the tigers for a long period of time to understand the ecology of tigers [1,18]. Their studies have provided the base of tiger ecology. Traditionally, tigers were tracked by the professional shikaris from their pugmarks to hunt the animal. Other sign analysis included scat analysis. Data collected using these methods have their challenges. Tracking the animal on the field is always dangerous, it causes hindrance to animal activities as well. Using these methods, very limited data can be collected as unreachable areas cannot be covered by these methods. But studies based on these methods have shown that for a few ecological questions these methods provide better answers such as to estimate population size and distribution of tigers. These methods along with the latest techniques provide high-quality data for analysis which can be used to infer the behavioral patterns of species [20].Table 4 shows the different data collection methods in wildlife used by the scientist before and after telemetry in India:Table 4Earlier and new data collection methods in wildlife conservationReferencesEarlier data collection methods in the wild (before telemetry)New data collection methods in the wild (after telemetry)[7]Observational studiesGPS/Geographical information system (GIS)[7,21]Mark – recapture/sign analysisMobile phones/applications, e.g.,M-STrIPES, CaTRAT[7]On-field trackingRadio telemetry[22]Camera trappingEmbedded and remote sensors3.4After telemetryRadio collars were first used in the USA on grizzly bears in early 1960s by Craighead Brothers. They tracked these grizzly bears from 1960 to 1968 and later published their research on the collected data explaining home ranges, movement patterns, food habits, and mortality rates [6,17]. Through telemetry data analysis, researchers were able to manage the habitat area. Studying the home ranges gave the ideas of important locations which could be used as habitat, hence more focus could be given to those areas. Breakthrough in wildlife research after telemetry are as follows.3.4.1Emigration and mortalityTelemetry data analytics has helped to identify whether the animal is dead or emigrated to another place. It was difficult to identify this before telemetry studies. Emigration in fragmented land is difficult for the animal but is very necessary for the survival of species in the longer run. Emigrating from one place to another enables gene flows [23]. For genetic diversity, gene flow is crucial which could be achieved if the animal can move from one place to another. Fragmented land and anthropogenic activities limit the emigration among animals [23,24]. India was once enriched with tigers with genetic diversity, but this is reducing now. Gene flow among species ensures their survival in different environments and difficult situations. This feature is required to survive the coming-up changes in climate. Telemetry studies can help in studying the emigration patterns among tigers [25,26].3.4.2Dispersal and movement patternsRadio telemetry can provide the movement patterns of the species. These patterns gave their home range sizes [27]. Movement patterns can provide the basics in detecting the underlying behavior for movement and dispersal [26,27]. There are various methods to study the movement patterns and researchers can choose from a variety of techniques to study the patterns which suit best for their research question. Dispersal in the case of tigers means moving away from other co-predators. Plenty of studies have been conducted to understand the movement ecology of tigers [28,40]. These studies suggested the population dynamics, dispersal, response to climate changes, environmental changes, and anthropogenic activities [27,29,40], and also, whether human activities are impacting all their activities negatively.3.4.3Home range and habitat selectionTelemetry studies help in understanding the home range and habitat selection of the species. Integrating the movement patterns with habitat selection gives insights into how animals use their space [30]. To understand their space use, radio telemetry plays a significant role. The new advancements in the radio collars provide the locational coordinates with great precision. Camera trapping, observing, and tracking the species were not possible in the deep forests [31]. Radio telemetry has provided the solution to these problems and covered the animal in a wider range. Though there is still a limitation to the areas which can be covered by telemetry. Habitat selection plays an important role in species survival and thereby in their population dynamics [28,30]. Therefore, any study conducted on habitat selection is very important. Many studies have been conducted to understand the habitat selection of species using telemetry studies which have shown the relationship between habitat selection and movement of the species [32].To understand the selection of their habitat, it is necessary to record the movements of the species in their environment. Radio telemetry allows to track the animals remotely in their natural space. The radio collars used in telemetry studies are capable of sending the locational data directly to the computer of the researcher and provide huge locational data for analysis. Habitat selection and their home range provide the basis to form conservation strategies for the species.3.4.4Food habit and prey densityTelemetry studies provide the insights into prey and predator relationship. It provides the analysis of species diet and kill rates [33]. Radio telemetry provides the spatial–temporal data of the species. This locational data along with the time suggests the activity of the animal [4,17]. If the time spent at a location is more than 24 h, then the tiger may be feeding itself with a fresh kill [1,7]. Tigers usually take a few hours to consume their kill or sometimes revisit the same location. Researchers go to the location of the kill after the tiger is gone from that area and search for the sign of fresh kill. Before radio telemetry scat analysis, following the animal trail methods were used to determine the kill. These methods are still in use and have their importance. GPS collars provide many more locations with much accuracy, these locations are divided into clusters using existing statistical methods. These statistical techniques are used to identify the sites of prey remains from the clusters of locations received from VHF/GPS radio collars [33]. These studies provide estimates about the kill rate, how the tiger responds to prey density, and its environment during kill [12].The selection of radio collar plays an important role while collecting the data through Radio telemetry. In this study, different types of collars and when to use which type of collar are discussed above.4Discussion4.1How telemetry enhanced the knowledge to understand tiger ecologyRadio telemetry now is extensively used by conservationists. The recent study published in June 2021 was conducted by WII, Dehradun and Maharashtra Forest Department (MFD) in which 15 tigers were radio-collared from 2015 to 2020 to study their movement patterns through telemetry data. This study has shown the pathways and corridors of tiger movement [3]. Through this study, the scientist and researchers were able to identify the pathways of tiger dispersal at Vidarbha landscape, which is home to around 331 tigers [3,9]. The study can guide ways to mitigate human–animal conflict, habitat fragmentation, and how to involve other stakeholders of the land to make better use of land for tiger dispersal without any human–animal conflict. Before the widespread use of telemetry in wildlife, very little was known about their movement and habitat [34]. Studies of telemetry data and with on-field efforts of a conservationist, the habitats of tigers are also known using radio collars/GIS/GPS. These were the landmarks in tiger telemetry in India. These tasks (movement and habitat) were accomplished by the use of technology. Using telemetry data analytics, it was found, how tigers do transboundary movements, satellite technology through radio collar was used to observe tiger translocation from Sariska Tiger Reserve to Panna Tiger Reserve [4].These technologies have also helped other methods of wildlife conservation, for example, the camera trapping technique of observing animals was in use for so long but was not that effective. Using radio collars on animals gave their movement patterns and ecologists were able to identify the correct locations to put the camera trap. It has also helped in estimating the correct population size of tigers.Another telemetry study has shown that the radio-collared tigers in Nagarahole Tiger Reserve were more nocturnal. They were least active during the daytime due to human interference in the area. This is an important finding, it suggests the behavior changes in tigers due to anthropogenic activities [13]. It has been observed through radio-collared tigers that tigers move from 2 to 11 km on daily basis. It has also been found through telemetry data analysis that tigers’ habitat selection depends on the density of prey. They disperse to the areas where their prey or ungulates concentrate [13]. Tigers are territorial and generally solitary animals. Through telemetry studies it is shown that they require a large contiguous area of habitat that supports their prey requirements. It is also shown that the tiger movement is usually for hunting or social interaction with other co-predators [1]. Table 5 shows the different studies conducted using radio-collar on tiger in India in the past decade.Table 5Major telemetry studies conducted on tigers in India from 2010 to 2021Name of the program/research study (publishing year)Radio collaring and monitoring durationObjective of radio telemetry studyTotal no. of tigers in the area in 2021 (approximately)No. of tigers collared for the studyLocation/tiger reserveType of collar usedStakeholdersReferencesEvaluating capture–recapture population and density estimation of tigers in a population with known parameters (2010)2008–2009Home range, population density estimationApproximately 5006Kanha Tiger Reserve, Madhya Pradesh, Central IndiaVHF/GPSProject Tiger Directorate (Government of India) and the WII, Kanha Tiger Reserve[46]Home ranges of Bengal tiger (Panthera tigris tigris L.) in Pench Tiger Reserve, Madhya Pradesh, Central India (2012)2008–2011Ranging and dispersal patternEstimated no. is 443Pench Tiger Reserve, Madhya Pradesh, IndiaSatellite and VHFMadhya Pradesh Forest Department (MPFD), WII and National Tiger Conservation Authority (NTCA)[51]Connecting tiger populations for long-term conservation (2014)2011–2014Mapping of corridors over entire India Tiger ReservesEstimated tiger population (2967)All tiger conservation landscapes of IndiaUnknownNTCA and WII, Dehardun[37]Long-term monitoring of a Bengal tiger (Panthera tigris tigris) population in a human-dominated landscape of central India (2016)2006–2013The population dynamics, dispersal, survival rateEstimated no. is 444Pench Tiger Reserve, Madhya Pradesh, IndiaVHF radio collarMPFD, WII, Dehradun,India[48]Movement and home range characteristics of reintroduced tiger (Panthera tigris) population in Panna Tiger Reserve, central India (2016)2009–2014Behavioral response of reintroduced tiger populationEstimated no. is 709Panna Tiger Reserve, Central India, Madhya Pradesh, IndiaVHF/GPS/UHF collar to three animals, VHF/GPS/Satellite collar to two animals, and VHF radio collar to four animalsMPFD, WII and NTCA[49]Ranging, activity, and habitat use by tigers in the mangrove forests of the Sundarban (2016)2008–2014Ranging patterns and habitat preferenceEstimated no. is 966Sundarbans National Park, West Bengal, IndiaGPS satellite and VHF collarsWII, Dehradun, India[35]Assessment of fine-scale resource selection and spatially explicit habitat suitability modeling for a reintroduced tiger (Panthera tigris) population in central India (2017)2009–2014Habitat selection by the reintroduced tiger populationEstimated no. is 709Panna Tiger Reserve, Central India, Madhya Pradesh, IndiaVHF/GPS/UHF collar to three animals, VHF/GPS/Satellite collar to two animals and VHF radio collar to four animalsMPFD, WII and NTCA[50]Human–tiger interactions (2020)2020–2023 (expected)Human–tiger interactionsEstimated no. is 961 (3 more are expected to be radio collared)Sundarbans National Park, West Bengal, IndiaUnknownBengal Forest Department (BFD)[36]Dispersal of tigers in eastern Vidarbha landscape (2020)2015–2020Patterns of tiger migrationEstimated no. is 31215Eastern Vidarbha landscape, Nagpur, Maharashtra, IndiaIridium, VHF/activityMFD and WII, Dehradun, India[3]Status of tigers, co-predators, prey, and their habitat (2020)2018–2019Population sizeEstimated tiger population ( 2967)All tiger conservation landscapes of IndiaUnknownNTCA in collaboration with WII, State forest departments, conservation NGOs[8]Not a cakewalk: insights into movement of large carnivores in human-dominated landscapes in India (2021)2014–2019Understanding movement patterns in human-dominated landscapesEstimated no. is 31214Eastern Vidarbha landscape, Nagpur and Chandrapur divisions and districts of Pune and Solapur, Maharashtra, IndiaGPS collarsMFD and WII, Dehradun[47]These studies are conducted using telemetry data which are collected using radio collars on tigers. The table above shows the number of tigers radio collared to collect the telemetered data. These data have been analyzed to understand the species ecology in more detailed way. In India,there are 52 tigers reserves which are further divided into core area and peripheral area [45]. Figure 6 shows the region on the map of India, over which these major studies were conducted.Figure 6Map of India showing the regions of major conservation studies along with the type of vegetations found in these regions.Telemetry data analyses have provided the insights into ecology of tigers. The studies conducted above in Table 5 have provided the better understanding and awareness about the behavioral patterns of tigers. One of the studies in the table above suggested that breeding tigers have large home ranges with an average of 40 km2 at Sundarbans of India. This study has also provided the insights into movement hours of the tigers. It concluded that the tigers move more in the early hours of morning, may be to avoid conflict with humans. If the activities by humans are restricted during morning hours human–animal conflict can be reduced in the area [35]. Another study mentioned in the table above showed that radio telemetry has enhanced the understanding of reintroduced tigers in the area where local population is extinct. The study stated that radio telemetry made it possible to closely monitor the reintroduced tigers, which was not possible earlier [49]. Through monitoring of these nine reintroduced tigers in the region, it appeared that these tigers behaved in the same manner as that of the native population of the region [49]. One more study conducted using telemetry data in the central India has presented that the Pench forest of Madhya Pradesh is relatively small and when tigers disperse, the conditions in the buffer zone of Pench forest is not optimal and can impact the dispersed tigers [48]. One of the studies conducted from the table above has provided insights into how increase in the human population is putting pressure on the already fragmented landscapes. If the species like tigers has to co-exist with humans due to increased pressure on land, then it is highly important to understand the movement patterns of tigers and how they adapt to the challenges outside the protected areas. Their response to the human interventions can help the conservationist to plan the strategies for land use and corridors. All these studies have presented the home range, movement patterns, dispersal, response of reintroduced population, habitat suitability, and many other important factors using telemetry studies on the tigers of India.4.2Challenges and issues with telemetry dataThere are a few limitations attached with telemetry data collection and analysis. Many ecological questions are answered through telemetry studies, which could not be answered using any other method of wildlife conservation. But there are a few issues while using telemetry studies.a)The first step to collect telemetry data is to put a radio collar on the tigers, which is a dangerous task as it involves capturing the tiger. To capture the tiger, there are many permissions and approvals required which can be a tedious task [4,8]. Once approved, ecologist and researchers along with the team needs to plan the capture very carefully because while capturing, the animal can be in danger which sometimes can lead to the death of the animal. This can lead to the cancellation of permission for animal capturing that can compromise the research study.b)During the initial days after attaching radio-collar on species, they have reduced activities as they adjust to the collar. Studies conducted for a shorter period may lack or have insufficient data as during the first few days or weeks, the animal adjusts to the radio collar and hence is less active [38,39].c)To collect telemetry data needs a high level of expertise, sometimes it is required to be on-site if a standard VHF radio collar is used. Cost associated with telemetry studies is quite high as it needs proper equipment, trained labor, and staff for capture [4,11].d)It is difficult to study tigers for years as their density is low and they live in remote areas of the forest [26]. One of the major challenges in telemetry studies is that it deals with the locational data of the species which can put the animal at risk. It is of utmost necessity to take proper care of data and it should be protected from unauthorized usage.e)Another big concern over telemetry study is the hacking of radio collars. Poachers can hack the collar and can get the locational data of the animal, risking the animal for poaching [40].f)Another challenge is the lack of fully advanced radio collars and cost. Many researchers complain about the premature expiry of the battery, collar failing, and incompatible data collection from the collar [11]. These issues suggest more technological advancements, training, and government contributions.Telemetry studies pose challenges in data collection, integrating data, and data analysis [41]. The recent advances in telemetry devices allow data to be transmitted from the radio collar to the receiver, which is connected to the computer for data collection [42]. Some devices do not transfer the data to the receiver but store it in the telemetry device. Data received from these devices are unstructured data. Data integration is required to store and analyze the data. Integrating data means telemetry study could involve one or more species, one location, or multiple locations at the same time in the conducted study, hence data received from their collar need to be integrated for the storage [37,43]. Each device has its format of collecting the data, variables in the collected data can also vary according to the sensors used in the collar [30,33]. This makes data integration and data collection a challenging task to achieve. Telemetry devices’ error should also be taken into consideration by the researchers otherwise the inferences drawn from the data provided by these devices can be erroneous [44].5ConclusionRadio telemetry can help in real-time monitoring of the tigers. There is no other alternative to radio-collaring in collecting the data. This can be used in identifying movement patterns thus decoding the habitat selection and its use by tigers. Tiger dispersal can suggest the appropriate green corridor strategies to connect the fragmented Land, to avoid tiger poaching, and human–animal conflict. These studies can also be used to avoid animal deaths due to train or road accidents. It is seen that habitat loss and poaching are the main reasons for the decline in the tiger population drastically. Human–animal conflict is rising due to fragmented home ranges. The future scope of this work could be utilizing the telemetry data of tigers to analyze their movement patterns. Telemetry data can be used to see where they move, why they move and can help in predicting human–animal conflict. Tiger’s ecosystem is greatly impacted by anthropogenic activities. It is very crucial to understand the ecological requirements, landscape use, and tiger behavior towards reduced land, forest, and prey density. It is one of the biggest challenges to understand the ecological patterns that are changing at a very fast pace. Current conservation methods may not be sufficient to conserve this endangered species in the long run. Radio telemetry is a suitable and very effective technique to study the tiger’s ecology. Currently, we know very little about the tigers and radio telemetry is providing promising results. In future studies, the behavioral activities of the tigers can be decoded using telemetry data analysis.

Journal

Nonlinear Engineeringde Gruyter

Published: Jan 1, 2023

Keywords: tiger; radio telemetry; telemetry; radio collars

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