In vivo bite and grip forces, morphology and prey-killing behavior of North American accipiters (Accipitridae) and falcons (Falconidae)

Abstract

Raptors exhibit a diversity of strategies to procure their prey but ultimately kill using their beaks and/or talons. Thus, bite and grip forces are ecologically important variables that have direct survival implications. Whereas hawks rely primarily on their feet for killing prey, falcons tend to employ their beaks. Consequently, falcons are expected to achieve relatively greater bite forces, and hawks are expected to generate relatively greater grip forces. Force estimates predicted from musculoskeletal morphology in a previous study indicated that falcons (Falco spp.) possess greater jaw force capabilities than accipiters (Accipiter spp.) but there were no clear differences in predicted grip-force capacity outside of differences in scaling. The objective of this study was to complement those results with measurements of in vivo forces by inducing captive and wild accipiters and falcons to bite and grasp force transducers. Bite force increased isometrically in both groups whereas grip force tended toward positive allometry. After adjusting for body mass, falcons produced greater bite forces, and accipiters produced greater grip forces. Thus, previous anatomical estimates of forces predicted the expected direction and magnitude of differences in bite forces but the overall greater in vivo grip forces of accipiters deviated from the pattern obtained from biomechanical estimates. Although the scaling relationships were similar between data sets, forces generated by live birds were consistently lower than those predicted from biomechanics. Estimated and in vivo jaw and digital forces were nevertheless correlated, and therefore provide an important link between morphology and killing behavior in these raptors.The following sources provided funding for various parts of this project: CSU Northridge Office of Graduate Studies, Sigma Xi (CSUN Chapter), CSUN Bridges and Los Angeles Audubon Society. Special thanks to the following people and entities throughout the USA for access to live raptors: F. Chavez-Ramirez, D. Kim (Platte River Whooping Crane Trust, NE, USA), M. Hensley-Benton (ESA/FACT CSU Bakersfield, CA, USA), C. Carter (California Living Museum, Bakersfield, CA, USA), P. Triem and K. Stroud (Ojai Raptor Center, CA, USA), J. Smith, M. Neal, Z. Hurst, S. Johnson, N. MacKently, C. Neri, T. Hanks, B. Black, and G. Gould (Hawkwatch International, Inc., UT, USA), M. Setter (Lindsay Wildlife Museum, CA, USA) and M. Moreau. K. Vrongistinos provided valuable assistance with equipment outfitting and training. P. Sethi and S. Farley helped build force transducers. Discussions with M. Rubega, G. Yanega, T. Landberg and comments by A. Herrel, A. Rico-Guevara, J. Podos and an anonymous reviewer considerably improved this manuscript. All procedures were carried out in accordance with CSU Northridge IACUC guidelines (protocol #0304-006a)

When hawks attack: animal-borne video studies of goshawk pursuit and prey-evasion strategies

“…For moving prey, interception lets the goshawk reach its prey quickly, but allows only a brief time window for capture. Unlike stooping falcons, which often kill on impact, goshawks typically need time to subdue and kill prey with their talons (Sustaita and Hertel, 2010). Interception followed by CPE allows the goshawk to maneuver accurately as it attacks from behind, a strategy previously reported for bats (Kalko and Schnitzler, 1998) and owls (Hausmann et al, 2008).…”

OSTEOLOGIA CRANIANA COMPARADA E ASPECTOS EVOLUTIVOS DE Caracara cheriway (Jacquin, 1784) E Caracara plancus (Miller, 1777) (AVES: FALCONIDAE)

“…O aumento da massa corporal dos Falconidae está diretamente relacionado ao aumento do crânio, que por sua vez permite uma maior inserção dos músculos do pescoço (M. rectus capitis lateralis e M. splenius capitus), que lhes confere maior vantagem mecânica na alimentação (SUSTAITA, 2008). Dentre as aves de rapina, os carniceiros possuem um crânio mais estreito quando comparado aos avívo-res como as espécies que compõem Micrastur, mas a distância entre a crista opistótica e a crista occipital são comparativamente maiores que nos demais raptores, e a posição do forame magno é mais posterior ao crânio, o que permite uma inserção mais linear da coluna vertebral, e quando somadas, essas características facilitam os movimentos laterais e aumentam a força para que essas aves consigam desprender a carne da carcaça (HERTEL, 1995;SUSTAITA;HERTEL, 2010). Esse comportamento generalista/carniceiro surge nos Caracarinae entre 14 e 6.7 M.a., e essa diversificação comportamental pode estar ligada à aridização do clima na região Neotropical, que acompanhou a expansão das áreas abertas e o aumento da abundância de mamíferos herbívoros, potencial fonte de alimento (FUCHS et al, 2012).…”

“…A sínfise mandibular das espécies de Caracara é menor do que as das duas outras espécies estudadas, e aliado à inserção da musculatura mandibular, a espessura dos ramos mandibulares e o comprimento da sínfise mandibular constituem as principais variáveis relacionadas à força da mordida, pois quanto maior a distância entre a inserção dos músculos mandibulares e o eixo de rotação mandibular, quanto mais largo os ramos mandibulares e quanto maior a sínfise mandibular, maior será a força da mordida e, consequentemente, maior será o sucesso na predação, pois os membros de Falconidae, embora capturem as presas com as garras, matam essas presas com o bico, quebrando sua coluna vertebral com uma força 64% (2.7 N a 24.5 N) superior à empregada pelos Accipitridae (1.4 N a 5.4 N) (SUSTAITA, 2008;SUSTAITA;HERTEL, 2010). Os Accipitridae, Pandionidae e Vulturidae, quando comparados aos Falconidae, possuem a mandíbula mais longa e a sínfise mandibular maior, o que lhes permitem explorar uma maior gama de itens alimentares, como mamíferos, répteis, peixes e até mesmo carcaças em decomposição (HERTEL, 1995).…”

“…Este trabalho descreve a osteologia craniana de Caracara cheriway comparado a C. plancus, pois os trabalhos encontrados em literatura são em sua maioria de comportamento alimentar (ZOTTA, 1940;HERTEL, 1995;MON-TALVO et al, 2011;TRAVAINI et al, 2001;GALETTI;GUIMARÃES, 2004;MORRISON et al, 2007;SAZIMA, 2007), comportamento reprodutivo (MORRISON et al, 2003;ACTKINSON et al, 2007;SKORUPPA;LEE, 2008;DWYER et al, 2013), ecologia (BAUMGARTEN, 1998), histologia (NEGRO et al, 2006), parasitologia (VITA-LIANO et al, 2010) e poucos de anatomia (FRANZO et al, 2007;SUSTAITA, 2008;SUSTAITA;HERTEL, 2010e MOSTO et al, 2013.…”

Measuring Selection on Physiology in the Wild and Manipulating Phenotypes (in Terrestrial Nonhuman Vertebrates)

“…Biting may be important for escaping predators, capturing and processing prey, or fighting rival conspecifics (149,150,182,224,232,324). Despite the vast literature on bite force, surprisingly few studies have investigated its fitness consequences, especially survival.…”