Variation in the Pattern of Predator-Induced Damage to Tadpole Tails

Abstract

Tadpoles in nature are often found with injured tails. We introduce a planimetric technique for compiling data on the injuries sustained by individual tadpoles, which allows us to visualize and quantify the tail damage sustained by a population as a whole. We have used this technique to compare the pattern and severity of damage in tadpoles from seven species (Ascaphus truei, Bufo americanus, Phyllomedusa tomopterna, Pseudacris crucifer, Rana catesbeiana, Rana sylvatica, and Rhinophrynus dorsalis) that differ in microhabitat use (benthic vs pelagic), tail morphology (filamentous vs nonfilamentous) and palatability to predators. We also examined differences in tail damage across developmental stages. Finally, we compared interpopulation variation for R. sylvatica tadpoles from six separate ponds. The tail tip was the most commonly damaged area in all tadpoles, although the pattern and severity of injury varied greatly across species. Unpalatable, benthic larvae sustained small nicks around the margin of the tail, whereas pelagic and palatable species more often had the tail tip sheared off caudally. Little damage was found in any species in the anterior portion of the tail, where most thrust is generated during swimming. Only one species, A. truei, exhibited increased tail damage as the tadpoles aged. Later stage P. crucifer and R. sylvatica larvae in contrast, had significantly less tail damage than younger stage conspecifics. Although this could be the result of different healing rates at different stages, alternatively it suggests that for these species, survivorship is ultimately reduced in individuals that lose a substantial part of the tail when they are young.