Skull shape and the demands of feeding: a biomechanical study of peccaries (Mammalia, Cetartiodactyla)

Abstract

A primary requirement of the mammalian skull is to exert forces on different foods and to resist the forces imposed on it during feeding. Skull shape patterns within and among mammals are generally well known, but the biomechanical relevance of this variation remains limited for some groups. By integrating geometric morphometric and biomechanical analyses, we test the hypothesis that skull shape in peccaries reflects biomechanical attributes to generate and dissipate powerful forces, presumably in response to tough foods. We obtained skull shape and size from 213 specimens of the three living peccary species and estimated bite force, bite stress at molars, bending and shear stress on the mandibular corpus, and condylar stress. We found larger estimated bite forces, greater resistance to bending loads, and lower stress emerging from the larger muscle attachment areas and shorter and deeper mandibular corpora for both Pecari tajacu and Tayassu pecari relative to Parachoerus wagneri. Peccaries (P. tajacu and T. pecari) with more powerful biomechanical attributes feed mainly on tougher foods (e.g., palm fruits). These results support the hypothesis that species eating tough foods tend to have a feeding morphology mechanically adapted to stronger bites and greater biting resistance, which must be closely reflected in their craniomandibular shape.Um requerimento primário do crânio de um mamífero é exercer forças em diferentes alimentos e resistir às forças impostas nele durante a alimentação. Os padrões de forma do crânio dentro e entre mamíferos são geralmente bem conhecidos, entretanto a relevância biomecânica desta variação permanece limitada a alguns grupos. Integrando análises de morfometria geométrica e de biomecânica nós testamos a hipótese de que a forma do crânio de tayassuídeos reflete atributos biomecânicos para gerar e dissipar forças de grande magnitude, tal como em resposta à alimentos duros. Nós obtivemos a forma e o tamanho do crânio de 213 espécimes das três espécies de tayassuídeos viventes e estimamos a força de mordida e o stress nos molares, no corpo mandibular e no côndilo. Nós encontramos maiores forças de mordida e de resistência e baixo stress emergindo de áreas mais amplas de inserção muscular e de corpos mandibulares mais curtos e altos de Pecari tajacu e Tayassu pecari em relação a Parachoerus wagneri. Tayassuídeos (P. tajacu and T. pecari) com atributos biomecânicos mais poderosos se alimentam principalmente de alimentos duros (por exemplo, frutos de palmeiras). Estes resultados suportam a hipótese de que espécies que se alimentam de alimentos duros tendem a apresentar uma morfologia do aparato alimentar mecanicamente adaptada a mordidas fortes e grande resistência de mordida, que deve estar intimamente associada as suas formas craniomandibulares.

Quantifying bite force in coexisting tayassuids and feral suids: a comparison between morphometric functional proxies andin vivomeasurements

“…The BiTu proved to be a functional and low-cost tool to measure bite force in field conditions. The in vivo results presented a good correspondence with the predictions based on morphometric-proxies by Oliveira (2002) andHendges et al (2019). The results denote that these studies succeed in capturing the biomechanical signal of the three species' skull-jaw systems.…”

“…Much of what is known about mammalian biomechanics relies on the assumption that function can be inferred from anatomical traits or bones' structural properties. Measurements of muscle scars and lever systems based on bone structures have been used as proxies to infer properties of skull-jaw mechanics and make functional comparisons among mammalian groups (Davis, 1955;Davis, 1964;Turnbull, 1970;Kiltie, 1982;Kiltie, 1985;Emerson & Radinsky, 1980;Radinsky, 1981a;Radinsky, 1981b;Radinsky, 1987;Sicuro & Oliveira, 2002;Therrien, Henderson & Ruff, 2005;Wroe, McHenry & Thomason, 2005;Hendges et al, 2019). In the last two decades, Finite Element Analysis (FEA) became a new way to assess stress resistance of osteological structures to strain forces, such as compression, shearing, and torsion (Richmond et al, 2005;Fletcher, Janis & Rayfield, 2010;Tseng & Binder, 2010;Tseng et al, 2011;Cox, Rinderknecht & Blanco, 2015;Therrien et al, 2016;Lautenschlager et al, 2017;Morales-García et al, 2019).…”

“…Therefore, the synergy of these two ecomorphological arrangements prevents the competitive exclusion of one or the other species. Other independent works also detected the difference in the bite force performance between these peccary species with different methodological approaches and databases (Olmos, 1993;Sicuro & Oliveira, 2002;Hendges et al, 2019).…”

Big in the tropics: Ecogeographical clines in peccary size reveal the converse of Bergmann’s rule

“…Nevertheless, the variable but largely non-overlapping body size distributions of these species suggests that size differences may be important for their coexistence. Functional profiles emerging from biomechanical models have demonstrated similar performance capabilities of these species in exploiting food (Hendges et al, 2019), and the generally high overlap in their diets supports this (Desbiez et al, 2009;Fragoso, 1999). However, larger body size and larger group size affords T. pecari (the behaviourally dominant species) some advantages over D. tajacu with respect to the same foods.…”

On the Supposed Presence of Miocene Tayassuidae and Dromomerycinae (Mammalia, Cetartiodactyla) in South America

“…This species has a great ecological tolerance, but it is generally associated with bodies of water. Some authors (Beck, 2006;Reyna-Hurtado et al, 2009;Sicuro et al, 2011;Hendges et al, 2016Hendges et al, , 2019 have pointed out that this animal has a large range of morphological variability due to food habit, sexual dimorphism and ontogenetic age factors.…”