The Role of Feeding Specialization on Post-Prandial Metabolic Rate in Snakes of the Genus Bothrops

Feeding specialization is a recurrent issue in the evolution of snakes and is sometimes associated to morphological and/or behavioral adaptations that improve snake performance to exploit a particular food type. Despite its importance for animal fitness, the role of physiological traits has been much less studied than morphological and behavioral traits in the evolution of feeding specialization in snakes. In this context, the energetic cost of post-prandial period is an important physiological factor due to the remarkable effect on the snake energy budget. We collected data on post-prandial metabolic rate (SDA) in five species of pit vipers from the genus Bothrops with different degrees of mammal feeding specialization to test the hypothesis that feeding specialist species have lower energy costs during the digestion of their regular food item when compared to species with a more generalist diet. Our results support this hypothesis and suggest that ontogenetic changes in diet can be accompanied by changes in energy cost of the digestion process.

Forest Fragments Surrounded by Sugar Cane Are More Inhospitable to Terrestrial Amphibian Abundance Than Fragments Surrounded by Pasture

In recent years, there has been increasing interest in matrix-type influence on forest fragments. Terrestrial amphibians are good bioindicators for this kind of research because of low vagility and high philopatry. This study compared richness, abundance, and species composition of terrestrial amphibians through pitfall traps in two sets of semideciduous seasonal forest fragments in southeastern Brazil, according to the predominant surrounding matrix (sugar cane and pasture). There were no differences in richness, but fragments surrounded by sugar cane had the lowest abundance of amphibians, whereas fragments surrounded by pastures had greater abundance. The most abundant species,Rhinella ornata, showed no biometric differences between fragment groups but like many other amphibians sampled showed very low numbers of individuals in fragments dominated by sugar cane fields. Our data indicate that the sugar cane matrix negatively influences the community of amphibians present in fragments surrounded by this type of land use.

Diet and energetic constraints of an earthworm specialist, the Mesa Central Blotched Garter Snake (Thamnophis scaliger)

Optimal diet theory predicts that predators optimize energy intake by balancing costs and benefits of foraging. One extreme strategy of snake foraging ecology is shown by specialist species that forage on low-energy prey, such as Thamnophis scaliger (Jan, 1863) which feeds almost exclusively on earthworms. Compared with other prey types such as small mammals, lizards, or arthropods, earthworms are low-energy prey because of their small size and high water content. Given the importance of energy acquisition for fueling snake reproduction, we expect that a low-energy dietary specialist such as T. scaliger needs to forage frequently to store enough fat to reproduce. The high frequency of snakes containing prey, the presence of multiple earthworms in snakes, and the fact that females continue to feed when gravid suggest that T. scaliger is a voracious consumer of earthworms. Despite these foraging behaviours, females did not reproduce in sequential years, suggesting constraints in energy input to reproduce more frequently. A meta-analysis of the diet, body size, and reproductive frequency of some species of the genus Thamnophis Fitzinger, 1843 confirms that consumption of invertebrate prey is associated with small snake size, but not with biennial reproductive frequency within the genus.