Breaking the diet: How much specialized is the specialist diet of New World pitviper species?

The feeding ecology of snakes is essential for understanding their evolutionary history and ecological adaptations. This study examines a lineage within Viperidae, the New World pitvipers, focusing on the mammal specialist (MS) species, Bothrops alternatus. We analysed dietary data from 291 specimens and compared it with data from other pitvipers to assess dietary specialization and its evolution. Results confirm that B. alternatus feeds predominantly on mammals; however, we identified novel prey items, including amphibians and birds, challenging its classification as a strict MS predator. These prey types are new for this species but are known within the genus, as many Bothrops species consume amphibians and birds. The MS diet of B. alternatus appears to be constrained more by phylogenetic factors than prey availability, with the novel prey potentially linked to anthropogenically disturbed habitats. Phylogenetic analysis indicates that MS diets tend to cluster among closely related species and are likely linked to morphological adaptations. Our findings indicate that even highly specialized snakes may display opportunistic feeding behaviours, demonstrating some dietary flexibility, and highlight the importance of natural history collections in ecological and evolutionary research. Integrating ecological, morphological, and phylogenetic data is vital for understanding the evolution of feeding strategies in snakes.