Terrestrial burrowing ecology of newly metamorphosed frogs (Rana pipiens complex)

I examined the burrowing performance of newly metamorphosed Rana areolata, Rana blairi, and Rana sphenocephala in laboratory aquaria. Three treatments were used to determine whether metamorphs, when deprived of a water source, actively dig their own burrows, and if they utilize natural irregularities in substrate profiles or preexisting burrows as shelter from evaporative desiccation. Analysis of covariance (initial body mass covariate) revealed that individuals of all three species actively burrowed and passively utilized preexisting experimental burrows, but active burrowing, which consisted of substrate excavation using only the hind limbs, took much longer. Metamorphs that used preexisting burrows conserved water more efficiently than those that actively dug their own burrows. Rana blairi experienced the highest percent water loss across all treatments and was the only species to suffer mortality during the experiment. These data suggest that burrowing, by minimizing evaporative water loss, may be a critical adaptive behavior for metamorphic frogs in semi-arid environments