Meeting Abstract
75.2 Friday, Jan. 7 Effects of Hatching Age and Predator Cues on the Development of Escape Swimming Performance and Survival with Dragonfly Predators in Red-Eyed Treefrogs. LANDBERG, T.*; COHEN, K. L.; WILLINK, B.; WARKENTIN, K. M.; Boston University, MA; Boston University, MA; Universidad de Costa Rica, San Jose; Boston University, MA tobias.landberg@gmail.com
Red-eyed treefrog embryos hatch early in response to egg predators, at the cost of earlier exposure to aquatic predators. Escape performance is likely to be under selection to develop rapidly because it could reduce mortality of hatchlings. To better understand the effects of hatching timing and development on escape performance we raised early-hatched (age 4 d post-oviposition) and late-hatched (6 d) tadpoles with and without predation cues until age 8 d. We examined the development of tail morphology, escape swimming performance using high-speed video and, in predation trials with dragonfly predators (Anax naiads), recorded movement, escape rates and survival. Preliminary observations reveal that body size, relative tail size and escape performance increased developmentally. Analysis of predation trials (N=154 hour-long trials) show that tadpole age was the dominant explanatory factor while predation cues and hatching treatment had no significant effects. Movement rates increased with age while survival decreased. The seemingly paradoxical result that survival decreased as escape performance increased is likely to be driven by the increase in movement rate through development. Anax is largely a visual predator that cues on movement. Evolutionarily, the developmental increase in tadpole escape swimming performance is likely to be driven by the developmental increase in predation intensity by visual predators as well as the increase in the proportion of hatched animals that are subject to aquatic predation. However, since early-hatched tadpoles have low movement rates, the cost of early hatching may be lower for visual predators than for other types of predators.
