Go big or go fish: morphological specializations in carnivorous bats

Abstract

Specialized carnivory is relatively uncommon across mammals, and bats constitute one of the few groups in which this diet has evolved multiple times. While size and morphological adaptations for carnivory have been identified in other taxa, it is unclear what phenotypic traits characterize the relatively recent evolution of carnivory in bats. To address this gap, we apply geometric morphometric and phylogenetic comparative analyses to elucidate which characters are associated with ecological divergence of carnivorous bats from insectivorous ancestors, and if there is morphological convergence among independent origins of carnivory within bats, and with other carnivorous mammals. We find that carnivorous bats are larger and converged to occupy a subset of the insectivorous morphospace, characterized by skull shapes that enhance bite force at relatively wide gapes. Piscivorous bats are morphologically distinct, with cranial shapes that enable high bite force at narrow gapes, which is necessary for processing fish prey. All animal-eating species exhibit positive allometry in rostrum elongation with respect to skull size, which could allow larger bats to take relatively larger prey. The skull shapes of carnivorous bats share similarities with generalized carnivorans, but tend to be more suited for increased bite force production at the expense of gape, when compared with specialized carnivorans.

Feeding ecology has a stronger evolutionary influence on functional morphology than on body mass in mammals

“…; Zelditch et al. ), and situations in which shifts in body size facilitate a greater range of dietary options (e.g., an increase in size allows faunivores to consume larger prey; Santana and Cheung ). In contrast, functional morphology may be less evolutionarily labile, such that substantial evolutionary changes only occur with sustained, strong selective pressures.…”

“…; Grossnickle and Polly ; Slater ; Slater and Friscia ). However, it is less common for studies to compare the impact of specific ecological pressures on these two types of traits (Santana and Cheung ; Zelditch et al. ).…”

Peramorphosis, an evolutionary developmental mechanism in neotropical bat skull diversity

“…Species from three related families of bats, P. parnellii (n = 3, Family Mormoopidae), Noctillio leporinus (n = 5, Family Noctilionidae), and M. natalensis (n = 5, Family Miniopteridae) were included as outgroups. Bat species were classified by diet following—(a) insectivorous: insects and arthropods constitute >80% of diet, (b) piscivorous: fish represent >50% of diet, (c) carnivorous: terrestrial vertebrate prey consumed in >60% diet, (d) nectarivorous: nectar and pollen consumed regularly and species has sensory and behavioral specializations to extract nectar from a flower corolla, (e) frugivorous: diet is >70% fruit material, (f) omnivorous: fruit, nectar, and >15% insects consumed or fruit, nectar, insects, and >20% terrestrial vertebrates in natural diet, and (g) sangivourous: diet is >99% blood. Categorizations and cutoffs were based on dietary data and behavioral observations from the literature …”

Ecology and evolutionary biology of fishing bats

“…Studies conducted with Noctilio leporinus and Myotis vivesi show that, although their mandibular shape and mouth features do not differ from those of insectivorous bats (Freeman , Elizalde‐Arellano et al. , Santana & Cheung ), piscivorous bats exhibit differences in the cranial shape compared to their insectivorous counterparts (Ospina‐Garcés et al. , Santana & Cheung ).…”

“…, Santana & Cheung ), piscivorous bats exhibit differences in the cranial shape compared to their insectivorous counterparts (Ospina‐Garcés et al. , Santana & Cheung ). They have a relatively tall, short rostrum that is broad at the zygomatic arches, suitable for producing high bite forces at the expense of lower closing speed.…”