Beyond size – morphological predictors of bite force in a diverse insectivorous bat assemblage from Malaysia

Abstract

1. Bite force is used to investigate feeding performance in a variety of vertebrates. In all taxa studied, bite force is strongly correlated with body and head size. Studies of bite force in bats have largely centred on neotropical species with a particular focus on species that maximize dietary differences. Little is known about the bite force of bats from the Old World tropics, nor of variation in bite force within diverse assemblages of obligate insectivores. Moreover, factors other than size are poorly known but may be important in driving interspecific differences in bite force, and thereby diet. 2. Here, we examine the correlation between morphological variation and bite force of 35 species of insectivorous bats from a single palaeotropical assemblage. We confirmed the overall relationship between size and bite force across species, but found that bite force is predicted more strongly by head length than body mass or forearm length. 3. From the combined action of jaw muscles and muscle-bone mechanisms, bats generate a mechanical advantage that creates pressure during biting. We calculated the size-independent mechanical advantage for each of five mandible lever systems (three delineated by the temporalis muscle and two delineated by the masseter muscle) operating through three function points (molar, canine and incisor). Size-independent mechanical advantage of the suprazygomatic portion of the temporalis muscle at the molar function point was the only significant predictor of size-independent maximum bite force across all species. 4. Within families, the size-independent mechanical advantage of the superficial portion of the masseter muscle plays a significant role in predicting size-independent maximum bite force in both the Rhinolophidae and Vespertilionidae. For the family Hipposideridae, however, sizeindependent mechanical advantage showed no role in predicting size-independent maximum bite force, suggesting that size really matters in predicting the maximum bite force capacity for this family.

Comparative Anatomy of Bat Jaw Musculature via Diffusible Iodine‐Based Contrast‐Enhanced Computed Tomography

“…Our diceCT findings are consistent with our observations from dissections and previous gross anatomy descriptions of the bat jaw musculature (e.g., Storch , who described the cranial musculature of five species included in our sample and other bats; Herrel et al ; Senawi et al ). However, diceCT revealed finer details of muscle arrangements, attachments, and subdivisions, which highlights the utility of this method for describing and quantifying the anatomy of small muscles.…”

“…Although body mass explains a large amount of the variation in bite performance across noctilionoids and other bats (Herrel et al, ; Senawi et al, ; Santana and Miller, ), their jaw muscles vary significantly in terms of scaling relationships, physiological cross‐sectional areas (PCSA), lever arms, and relative contribution to the forces required to open or close the jaw (Herrel et al ; Santana et al ; Santana and Curtis this issue). Noctilionoids that consume hard fruit and vertebrates have short and broad skulls with a high mechanical advantage, and their m. temporalis produces a greater moment about the temporomandibular joint (TMJ) relative to other jaw adductors (Herrel et al, ; Nogueira et al, ; Santana et al, ; Dumont et al, ; Santana and Cheung, ).…”

Primary productivity explains size variation across the Pallid bat's western geographic range

“…Larger bats exhibit cranial morphologies that may allow them to consume relatively larger and harder prey (Aguirre et al, 2003;Freeman, 1984;Freeman & Lemen, 2010;Santana & Cheung, 2016;Santana et al, 2010) ( Figure 5). Broader zygomatic arches and a more pronounced sagittal crest can accommodate larger temporalis (jaw closing) muscles that can produce more forceful bites (Christiansen & Adolfssen, 2005;Santana et al, 2010;Senawi, Schmieder, Siemers, & Kingston, 2015). Similarly, a relatively shorter and wider rostrum allows for more forceful bites and a greater resistance to torsional forces when chewing hard prey (Dumont, Piccirillo, & Grosse, 2005;Freeman & Lemen, 2010;Santana et al, 2010).…”

Bite force and evolutionary studies in phyllostomid bats: a meta‐analysis and validation

“…In the hypothetical situation of geometric similarity, the expected scaling of muscle force with body mass is 0.67 (Biewener, ). Previous studies in bats found larger slopes (1.17–1.31) for phyllostomids (Aguirre et al ., ; Freeman & Lemen, ) and a slope similar to ours in a study across many old world bat families (Senawi et al ., ). We found the hypothetical isometric value of 0.67 to be close (or equal) to the lower limits of the confidence intervals for slopes in both ivBF and estBF.…”