Meeting Abstract

66.3  Jan. 7  Implications of meal type effects on specific dynamic action for optimal foraging OTT, Brian D.*; SECOR, Stephen M.; The University of Alabama; The University of Alabama brian.d.ott@ua.edu

Specific dynamic action (SDA), the cost of meal digestion and assimilation, is proposed to be a large component of the energy budget of amphibians and reptiles. If SDA varies among different meal types, theories of optimal foraging would predict the preference for those meals with lower SDA, thereby more energy could be allocated to activities, growth, and reproduction. Therefore, we examined potential meal type effects on SDA for Burmese pythons (Python molurus) and green anacondas (Eunectes murinus) fed rat, bird, and alligator meals, and eastern garter snakes (Thamnophis sirtalis) fed mouse, minnow, frog, tadpole, earthworm, and beetle larvae meals (all meal mass 25% of snake mass). For Burmese pythons, rat and bird meals generated very similar SDA responses, whereas alligator meals produced a lower peak VO₂ and SDA, and a higher SDA coefficient (SDA as a % of ingested energy). For green anacondas, peak VO₂ did not vary among the three meals, bird meals generated a higher SDA, and the SDA coefficients were 19.5%, 25.1%, and 29.4%, respectively, for rat, bird, and alligator meals. For garter snakes, the beetle larvae meal generated a much lower postprandial peak VO2 (2.8-fold of resting metabolism), SDA, and SDA coefficient (9.5%), compared to the other five meals. Mouse meals resulted in the largest peak VO₂ (6.2-fold) and SDA, with tadpole meals producing the highest SDA coefficient (43%). Although alligators are less costly to digest, the advantage of the rat and bird meals for pythons and anacondas is the greater amount of ingested energy. Similarly for garter snakes, the less costly beetle larva and tadpole meals are relatively energy poor and the snake instead benefits energetically from consuming the more costly mouse and minnow meals. Optimal meal selection may more so reflect the tradeoffs between the costs and gains from a meal and meal availability.