The relationship of head morphology and diet among three sympatric watersnake species

Abstract

Investigating dietary resource utilization and head morphology of gape-limited predators can provide a basis for understanding interspecific competition and species coexistence. For sympatric species, convergence of head morphology can indicate similar prey or foraging strategies while divergence can suggest competition, resource partitioning or expansion into new habitats. Sexual dimorphism can further complicate the head morphology-diet relationship by potentially reducing intraspecific competition. To understand the relationship between head morphology and diet, we studied three sympatric species, the plain-bellied (Nerodia erythrogaster), diamondback (N. rhombifer), and northern (N. sipedon) watersnakes in western Kentucky. All three species inhabit similar wetlands and feed on amphibians and fishes. The anurophagous plain-bellied watersnakes had longer, narrower heads that likely allow snakes to capture anuran metamorphs and froglets while facilitating movement through dense vegetation. The piscivorous diamondback watersnake had a wider head, which would enhance contact with prey in this open-mouth forager, and smaller interocular distance, resulting in dorsally placed eyes that facilitate seeing fish prey from below. The mostly piscivorous northern watersnake had an intermediate, generalized head shape, which may reflect the typically wide diet range of this species. Head shape did not differ between snake sexes but diamondback and northern females had larger heads than males and fed more frequently on fishes. The relationship between head morphology and diet highlights potential interspecific and intersexual competition and aids in the understanding of species coexistence patterns.

A new species of leaf-toed gecko (Phyllodactylidae, Phyllodactylus) from María Cleofas Island, Nayarit, Mexico

“…We analyzed the stomach content from 36 individuals during fieldwork using stomach flushing (Legler and Sullivan 1979). In contrast with dissection techniques that require sacrificing the animals to obtain stomach contents, the aforementioned technique enables individuals to regurgitate prey items for further analysis (Perkins and Eason 2019). We performed this technique three times consecutively to obtain the largest possible volume of stomach contents from each individual (Barraza-Soltero 2019; Barraza-Soltero and Escobedo-Galván 2020).…”