Opportunistic predation reveals a hidden cost of fighting in birds
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Opportunistic predation reveals a hidden cost of fighting in birds Pedro Diniz 1 Received: 25 March 2020 / Revised: 29 July 2020 / Accepted: 13 August 2020 # Sociedade Brasileira de Ornitologia 2020
Abstract Predation risk is often hypothesized to be a cost of escalated fighting, and it relies on the assumption that predators eavesdrop on distracted prey. However, there is no direct evidence supporting these two ideas. Here, I report a predation event that occurred immediately after escalated fighting in birds. Two Rufous Horneros (Furnarius rufus) were engaged in a contest on the ground, while a third hornero watched from a close by (~ 3 m) perch. The hornero that won the contest, having strongly pecked its opponent, then joined the third hornero on the perch. The loser hornero appeared to be injured or fatigued after fighting and crouched motionless, wings down, and belly touching the ground. Approximately 10 s after the fight, a large Aplomado Falcon (Falco femoralis) suddenly flew toward the loser hornero, caught the bird, and flew away. This casual predation record indicates the falcon was eavesdropping on these horneros’ contest, possibly using the opportunity to attack the loser hornero which, due to being injured or fatigued after the contest, was more vulnerable to predation. This anecdotal evidence indicates the existence of a predation cost associated with escalated fighting, stressing the importance of natural history records in animal behavior research. Keywords Aggressive interactions . Animal contests . Aplomado Falcon . Eavesdropping avoidance hypothesis . Escalated fighting . Rufous Hornero
Escalated fighting might incur costs in terms of injuries (Drews 1996) and expenditure of energy and time (Davies 1985), potentially leading to fatigue (Ota 2018) or death (Riechert 1988; Hof and Hazlett 2012). Yet another possible cost of contests is an increased predation risk for individuals engaged in escalated fighting (Jakobsson et al. 1995; DíazUriarte 1999; “the predation-risk hypothesis”). This hypothesis is based on evidence that wild animals become distracted and more exposed during contests (Dunn et al. 2003; Hess et al. 2016; Ota 2018), and thus presumably subject to a higher risk of predation. The predation-risk hypothesis also relies on the idea that an injured or fatigued animal becomes more vulnerable to predation (Krause et al. 2017; Ota 2018). Accordingly, predation risk has been linked to fewer aggressive interactions (Kelly and Godin 2001), reduced territory size (Kim et al. 2011), and altered fighting outcomes (Koga and Ikeda 2010). Communicated by Fabio R. Amaral. * Pedro Diniz [email protected] 1
Programa de Pós-Graduação em Ecologia, Universidade de Brasília, Brasília, DF 70910-900, Brazil
Fights are often conspicuous and might involve vocalizations, chases, and physical aggression (Diniz et al. 2019), which may attract the attention of predators (Jakobsson et al. 1995; Mougeot and Bretagnolle 2000). Birds have behavioral strategies to decrease the conspicuousne
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