Predation-induced effects on hatchling morphology in the common frog (Rana temporaria)

As mortality due to predation is often high at early independent life stages in many animals, it can be expected that predation-induced modifications of early life history and morphology will be common when predation risk varies spatially or temporally. However, studies of such effects are still rare. Predation-induced changes in life history and morphology have often been described in amphibian larvae, but the focus has been on older larvae and little is known about responses of hatchlings or very young larvae. We examined whether predator presence influenced timing of hatching and hatchling morphology in the common frog, Rana temporaria. In a paired design, eggs from 10 clutches were allowed to develop from fertilization to hatching, with or without the nonlethal presence of a larva of the large diving beetle Dytiscus marginalis. We found no evidence that predator presence affected timing of hatching. However, hatchlings raised in the presence of the predator had relatively shorter bodies and deeper tail fins than their full-sibs raised in the absence of the predator, indicating that predation induces morphological responses in R. temporaria hatchlings. This is one of the very few studies showing that predators, or chemical cues released during a predation event, can induce a plastic morphological changes in vertebrates at very early life stages.