A low‐cost, easy‐to‐build, and portable bite‐force transducer for birds

Abstract

Few investigators have examined in vivo bite-force of birds, likely due, at least in part, to the difficulty in accessing suitable force transducers. We describe a low-cost, easy-to-build, and portable force transducer with the goal of encouraging ornithologists to improve our knowledge of in vivo bite forces of birds. We used a commercial piezo-resistive force sensor (Tekscan © ) to construct our transducer, and measure the bite forces of captive birds with different beak morphologies, including the following species: Greater Rhea (Rhea americana), Black-chested Buzzard-Eagle (Geranoaetus melanoleucus), King Vulture (Sarcoramphus papa), Toco Toucan (Ramphastos toco), and Graylag Goose (Anser anser). Bite forces ranged from 25.1 N for the Toco Toucan to 109.9 N for the King Vulture. By using the bite forces obtained in our study and those reported for other birds in the literature, a regression analysis was performed, revealing that half of the variation in bite force is explained by allometry, with other factors such as beak morphology likely explaining the remaining variation. Our bite-force transducer should allow researchers to obtain low-cost, reliable biteforce data, which will improve our understanding of the relationship between form and function of the avian cranio-mandibular complex. RESUMEN.Un transductor de fuerza de mordida para aves de bajo costo, fácil construcci ón y portátil Pocos investigadores han medido la fuerza de mordida in vivo de aves, principalmente debido a la dificultad para acceder a transductores de fuerza adecuados. Aquı ´se describe un transductor de fuerza de bajo costo, fácil construcción y portátil con el objetivo de incentivar a ornitólogos/as a incrementar el conocimiento sobre la fuerza de mordida real de las aves. Para la construcción del transductor se usó un sensor piezo-resistivo (Tekscan©). Se midió la fuerza de mordida de aves en cautiverio y con distintas morfologı ´as de pico, incluyendo al ñandú (Rhea americana), al águila mora (Geranoaetus melanoleucus), al jote real (Sarcoramphus papa), al tucán grande (Ramphastos toco) y al ganso doméstico (Anser anser). El rango de fuerzas de mordida obtenido fue de entre 25,1 N para el tucán grande y 109,9 N para el jote real. Con los valores de fuerza de mordida aquı ´obtenidos y con aquellos publicados en la bibliografı ´a para otras aves se realizó una regresión que reveló que la mitad de la variación en la fuerza de mordida es explicada por alometrı ´a y que otros factores como la morfologı ´a del pico probablemente explican la variación restante. El transductor de fuerza de mordida aquı ´descrito permitirá a los investigadores obtener datos de fuerza de mordida fiables y de manera económica, lo que mejorará nuestra comprensión de la relación entre la forma y la función del complejo cráneomandibular de las aves.

In vivo bite force in lovebirds (Agapornis roseicollis, Psittaciformes) and their relative biting performance among birds

“…The relationship between bite force and body mass in birds reported here differs slightly from a recent study by Carril et al. (2021). This divergence reflects two differences between these studies: (1) the inclusion herein of a greater number of species (77 versus 60), and more importantly, (2) the present study accounts for phylogenetic signals within regressions, an important inclusion given the strong phylogenetic signal that appears in bite force (Fig.…”

“…Future studies should focus, following recent work by Carril et al. (2021), on in vivo sampling of larger‐bodied avian taxa to rectify this shortfall.…”

“…Within birds, bite force has also been shown to scale positively relative to body size in finches (Van der Meij & Bout, 2004). However, a recent analysis by Carril et al (2021) reported a negatively allometric relationship between body size and bite force across birds as a whole, with larger-bodied taxa characterized by relatively low bite forces. Thus, we predict that when all previously published data on avian bite force are analyzed together, bite force will scale with negative allometry across our avian sample.…”

“…Thus, the relatively low bite forces exhibited by several taxa in Table 3 may also reflect this sampling strategy. Future studies should focus, following recent work by Carril et al (2021), on in vivo sampling of larger-bodied avian taxa to rectify this shortfall. Asterisk denotes anatomically derived estimate of bite force, as opposed to in vivo measurement.…”

“…Using myological proxies, bite force has been estimated in more than a dozen avian taxa, including three Acciptriformes (Sakamoto et al., 2019; Sustaita, 2008), four Falconiformes (Sustaita, 2008), and three Struthioniformes (Gussekloo & Bout, 2005). Additionally, in vivo measurements of biting performance are reported for more than 60 species (Carril et al., 2021; Corbin et al., 2015; Degrange et al., 2010; Herrel et al., 2005; Sustaita & Hertel, 2010; Sustaita & Rubega, 2014; Van der Meij & Bout, 2004). However, this data collection has focused closely on finches, and the majority of in vivo data are sampled from taxa within this group.…”