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Revista Brasileira de Ornitologia 27(3): 145–148. ARTICLE September 2019 Beyond a feeding and thermoregulatory structure: toucan's bill as a sword and pincer 1,2,3 1 1 André de Camargo Guaraldo , Letícia Mara Ceolin Antqueves & Lilian Tonelli Manica Laboratório de Ecologia Comportamental e Ornitologia, Universidade Federal do Paraná, Curitiba, PR, Brazil. Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil. Corresponding author: firstname.lastname@example.org Received on 22 August 2018. Accepted on 05 August 2019. ABSTRACT: Toucans (Ramphastidae) have always attracted researcher's attention for their exuberant bill shape and size, which function has been often related to feeding strategies and thermal regulation. In this study, we discuss the importance and use of the bill by Ramphastidae species in intraspecific disputes. We present novel data and video recordings on agonistic encounters between females of the Spot-billed Toucan Selenidera maculirostris, along with a compilation of data from the Brazilian citizen science platform WikiAves and previous studies on six other Ramphastidae species. Until now, only a couple of species was known for using their bill in fights against conspecifics. Our study highlights the between-species behavioral similarities and the widespread occurrence of such behavior in the family, suggesting that this may be more common than previously thought and proposing hypotheses on the likely roles of such intraspecific contests. KEY-WORDS: agonistic behavior, citizen science, female disputes, Ramphastidae, Selenidera maculirostris. INTRODUCTION study we provide a jointly interpretation of the bills' function and the female role in ecological behavior, Since the observations of bill morphology variations in adding to the perspective of bills use as weapons by Darwin's finches and t heir relationships with feeding disputing females. habits (Grant 1981), there has been a noteworthy interest for the relationships of this structure with birds' ecology and behavior (e.g., Podos 2001). Besides its main use for METHODS feeding, some bird species also use their bill as warfare tool against predators (e.g., mobbing) and in agonistic The Neotropical toucans (Aves: Ramphastidae) have one conspecific disputes for resource, territory and mate (e.g., of the most noteworthy bill morphology, which is not Murphy et al. 2009, Rico-Guevara & Araya-Salas 2014). only tightly related to feeding behavior (Bühler 1995) Despite intraspecific agonistic encounters also occur – assisted by a strong leg musculature (Moermond & irrespective of individuals sex, literature is often biased Denslow 1985) – and thermoregulation (Tattersall et towards male-male interactions (Clutton-Brock 2007). al. 2009, Hughes 2014), but also seems to be a dueling Nevertheless, studies show that in some species such as weapon (Van Tyne 1929, Brydon 1995, Ehrlich et al. monkeys (Koenig et al. 2004) and anhingas (Sazima & 2001, Ritterson & Stein 2011). During regular fieldwork D'Angelo 2012) females may fight for resour ces or even days in July 2008, at an Atlantic Forest reserve, in for dominance over each other (e.g., crickets; Delago & southeast Brazil – Ilha do Cardoso State Park, Cananeia, Aonuma 2006). São Paulo state –, we recorded two events of a novel Females were historically perceived as passive, agonistic dispute between females of the Spot-billed little aggressive, or coy (Darwin 1871), but modern less Toucanet Selenidera maculirostris. In the next lines, we biased approaches have been revealing how improper describe these encounters in detail (video recordings this is (e.g., Hrdy 2006). Besides the currently accepted available as supporting material (Suppl. 1), followed by assertion of females' role on sexual selection of male the results of a comprehensive review for similar agonistic traits and ornaments (Andersson 1994, Andersson behavior in other Ramphastidae species. Then, and to the & Simmons 2006), females may also play key-roles best of our knowledge, we conclude with the first ever in territory establishment and competition for mates discussion on the recurrence of this behavior and its likely (Clutton-Brock 2007 & 2009, Rosvall 2011). In this functions in the family. Toucan's bill as a sword and pincer Guaraldo et al. between females A and B, female D could not hold RESULTS & DISCUSSION herself on C, which kept flapping its wings at times and moved along the perch while twisting and shaking the We registered – with binoculars (10 × 42) and camera hanging opponent. After ~13 s, female D beat its wings (Sony DSC-H1) from about 15–25 m distance – the and managed to grab C's throat with its left foot, which first agonistic encounter at a point where a trail crosses in turn reduced the amplitude of the shaking movements. a lowland pristine forest area (approximate coordinate: o o Females remained in this position for ~45 s, when D's 25 04'46''S; 47 55'36''W). At ~07:30 h (GMT -3) on feet got loose and she got being suspended again by C. 10 July 2008, we spotted and heard two females flapping Approximately 13 s latter, D slipped off C's bill (a single and ruffling wings atop (~12 m) of a tree. Females clap sound could be heard) and free fell about 2 m until (hereafter referred to as A and B) were repeatedly beating she flew to a nearb y lower perch ~4 m away. After a and pecking each other using their bill in an apparent couple of minutes, D flew back to the wrestling per ch attempt to dislodge each other from the perch. When and restarted bill strikes and interlocking for another 3–4 females were spotted, female A was biting the right-side min. Then, a male, which remained still and quiet on a facial skin and feathers of female B. Both females were nearby perch (~10 m) during the entire duration of the vigorously flapping their wings and s haking their body fight, flew and per ched aside female C and on the opposite with their legs. Some seconds after this “bill wrestling” side of female D. At this point, females where facing each started, female A managed to push B so the later got other, perched on different branches, and kept fighting hanging down the perch being solely suspended by A's with no noticeable behavioral change upon male's arrival. bite. After ~40 s flapping its wings, B got rid of female A's A few seconds after that, and despite leaves obstructed bill, quickly reverting the situation: female B managed to the observers' sight, female C seemed to have bitten D's, bite A's face and push it hanging down the perch. Then, forcing its head down (noticed through its raising tail). female A's feet slipped off the per ch one at a time and After ~10 s, another bill clap could be heard, at the same she stood belly up while holding female B's head. After time that female D flew away. Female C kept wiping its ~12 s in that position, female B's feet loosened from the bill for a few times and then flew to a nearb y upper perch. perch and both individuals fell for ~5 m high. During the The male remained in the per ch for another 1–2 min and fall, female A remained still and holding B's head which then followed female C. This entire fight lasted ~11 min, opened the tail feathers and flapped wings four times in an vs. ~2 min in the first event, but we caution that these are apparent attempt to control the fall. When both hit some incomplete data since we only spotted both fights when leaves and branches, they got loose and flew to opposite they were already ongoing. We heard no vocalization of directions. During all the fight, a male remained quiet the females or of any other individual during any of the and still on a nearby tree (~15 m), apparently watching events. the fight, and flew to a per ch near female B where both We run an extensive literature review for evidences stayed for a few minutes until fly out of sight. of aggressive behavior in other Ramphastidae species. The second event occurred on 13 July, a bout 1.5 o o In Google Scholar (www.scholar.google.com), we km far from the first (25 5'33''S; 47 55'35''W) in the ran searches combining the family name with all under-canopy of a primary forest area and again involved the following terms (one at a time), both in English two females (C and D). Despite all birds had no natural and Portuguese: female, agonistic behavior, agonistic or artificial markings and o bservations occurred far encounter, aggression, dueling, and fight. This resulted from each other, it is uncertain these were independent in only one reference explicitly describing aggressive behavior, i.e. performed by distinct pairs of females. At behaviors in Ramphastidae (e.g., fence duelling in 08:05 h, we heard one female (C) perching on a tree at Ramphastos sulphuratus brevicarinatus; Van Tyne 1929) ~10 m high, apparently at the end of a pursuit flight after and one record of Pteroglossus aracari killing each other in another female (D), which perched on a nearby branch. captivity in two events with no further details (Pernalete After a few seconds, female D went to the same branch 1989). Further unstructured literature review led us to C was and both started “bill wrestling” as did females A three other references, two for P. torquatus erythropigius and B. In the beginning, both kept striking each other's (Brydon 1995) and one for R. ambiguus swainsonii bill, but at times females kept pulling each other while (Ehrlich et al. 2001, Ritterson & Stein 2011). In addition their bills were interlocked: while one was biting the to the literature review, we also searched for evidences other's lower mandible, the latter was biting the former's in two large citizen science databases, the Internet Bird upper mandible. Females remained around 2 min in this Collection (www.hbw.com/ibc) and WikiAves (www. dispute, when female C finally bit D's left-side facial wikiaves.com.br). We narrowed the research to all species feathers near to its throat. With that, female C pushed D occurring in Brazil, for which there was more available until she got hanging down the perch. After ~12 s, female data (27,707 records at the WikiAves as of 19 April 2016 D slipped off the per ch, but differently from the dispute Revista Brasileira de Ornitologia 27(3): 2019 Toucan's bill as a sword and pincer Guaraldo et al. and 1023 at the IBC), totaling 22 species (Piacentini et al. confrontations reported for two species of the family – R. 2015), about 60% of all 34 extant Ramphastidae (Remsen- ambiguus swainsonii (Ehrlich et al. 2001) and P. torquatus Jr. et al. 2017). We analyzed each and all existing photos erythropygius (Brydon 1995, Ritterson & Stein 2011) – and videos for every species in those databases. With that, are very similar, the latter culminating in death of one we successfully found a few additional evidences that four individual. In all cases, authors suggested intraspecific other species may have similar aggressive behavior: the within-group dominance hierarchy as the motif for the Toco Toucan Ramphastos toco (record made in August at fights, perhaps associated with male-male disputes for Cataguases, southeast Brazil; Filho 2012) the Channel- females. Thus, our study is the first to confirm that females billed Toucan R. vitellinus (in September at Macapá, could also act in such within-sex disputes. Altogether, north Brazil; Albano 2012), the Red-breasted Toucan this behavior is currently recorded for ~23% of all R. dicolorus (in October at Campos do Jordão, southeast Ramphastidae species (n = 9 R. toco, R. a. swainsonii, R. Brazil; Rodrigues 2012), and the Chestnut-eared Aracari s. brevicarinatus, R. vitellinus, R. dicolorus, S. maculirostris, Pteroglossus castanotis (in June at Foz do Iguaçu, south P. t. erythropygius, P. aracari, and P. castanotis) and is Brazil; Bolivar 2012). widespread through all family clades (Hughes 2014). All three Ramphastos species showed agonistic Therefore, it is plausible that this behavior also occurs in behaviors very similar to those described above for the Spot- other species of the family, representing an additional role billed Toucanet. However, it was impossible to assign the of the bill morphology and a likely result of morphological sex of individuals involved in those records because sexes and behavioral coevolution, which deserves further study. are identical or have inconspicuous dimorphism. Thus, Ramphastidae have well developed leg muscles, which insofar our report for the Spot-billed Toucanet aggression importance was so far related to their feeding strategy of is the first in describing ex clusively female-female reaching and picking fruits hanging upside down and at fencing contests in Ramphastidae. In all cases involving the tip of branches (Moermond & Denslow 1985). Our Ramphastos species, one individual used its bill to hold observations add to these findings, since such anatomi cal the other suspended bellow the perch. Observer's notes adaptation seems also to be an important individual for the R. vitellinus record describe that both individuals trait in fights. Individuals with stronger legs should have slipped off the per ch, likely free falling while flapping higher success rates in disputes, as it would be more able its wings. In this case, there is no report of the presence to hold still while pushing and holding its opponent of a third individual. For the other two Ramphastos hanging below the perch. We also suggest additional and species, the individual that remained perched held the more comprehensive anatomical evaluations not only other suspended by its throat, but what happened in R. of leg, but also of jaw muscles (e.g., Bühler 1995), in an dicolorus record after that remains uncertain. From this attempt to reveal further morphological specializations point on, we describe the disputes involving R. vitellinus and their ecological and behavioral roles. and P. castanotis, extracting as many details as possible The context of all aggressive contests described in from the observers reports (Albano 2012, Bolivar 2012). this study allows inferences on the adaptive value of this Prior to the moment when one individual of R. vitellinus behavior within the family. In species which individuals was held hanging by the other, both birds struck each often live alone (e.g., R. toco), flocks (e.g., R. vitellinus), or in other with their bills (Albano 2012). When individual (socially) monogamous pairs such as S. maculirostris (Sick A pushed and held B suspended by its throat, a third 1997), such behavior may represent a dispute for matting bird perched aside A and attacked B for ~90 s (Albano and/or territory. Since only females of the latter species 2012). After that, B fell motionless to the forest floor, were actively observed fighting while males remained as but it remains uncertain if the individual died (Albano spectators, we propose three non-excluding hypotheses 2012). In the P. castanotis record, two birds got their bills that the aggression may be (i) a female's strategy to interlocked, with one of them being held suspended. The compete for food resources or even for nesting cavities observer describes that all other four or five individuals in (e.g., Christianini 2018), (ii) to reduce male extra-pair the flock were apparently trying to break the birds apart copulation, likely ensuring the highest male parental care by hanging themselves on the suspended individual and to the offspring, and (iii) a consequence of sex ratio bias striking both birds bills (Bolivar 2012). After ~4 min, towards males in this species, leading to a more intense the two birds were set apart, fell to the ground for a few and frequent female dispute for a mate (Rosvall 2011). seconds and all flew away (Bolivar 2012). The aggression in S. maculirostris o ccurred a month This is the first time that any intraspecific agonistic prior to its known nesting period at Ilha do Cardoso behavior is formally described for these five ramphastid (Guaraldo & Staggemeier 2009), which could indicate species (R. toco, R. vitellinus, R. dicolorus, S. maculirostris a role as pre-breeding dispute for mating and nesting and P. castanotis). Moreover, the resemblance of such territory establishment. This behavior may be more behavior among species is noteworthy. In fact, the widespread among Ramphastidae species than previously Revista Brasileira de Ornitologia 27(3): 2019 Toucan's bill as a sword and pincer Guaraldo et al. finches: the complex diversity of Darwin's finches may provide a documented, since all but one record (July, dry period in key to the mystery of how intraspecific variation is transformed Costa Rica; Brydon 1995) occurred during each species' into interspecific variation. 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Ornithology Research – Springer Journals
Published: Sep 1, 2019
Keywords: agonistic behavior; citizen science; female disputes; Ramphastidae; Selenidera maculirostris
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