The effects of shelter availability and substrate quality on behaviour and post-metamorphic growth in three species of anurans: implications for captive breeding

Growth rate strongly influences survival and reproductive success in anurans, particularly during larval and juvenile stages. In tadpoles the availability of shelter has been linked to increased growth rates, but work on recently metamorphosed anurans has been limited. Three species (Physalaemus pustulosus, Leptodactylus fuscus and Mannophryne trinitatis) were used to examine the effects that shelters have on growth rates and behaviour in the laboratory. Shelter availability had a strong effect on growth in M. trinitatis and a weaker effect on L. fuscus and P. pustulosus. Shelter provided advantages in the trade-off between predator avoidance and resource gathering and/or osmoregulatory benefits. Osmoregulatory benefits may have had the greater impact on growth rates for three reasons: (1) the ability to burrow in L. fuscus and P. pustulosus would more likely offset the osmoregulatory benefits of having shelters available, as individuals without shelters spent significantly more time burrowing; (2) individuals with shelter available were more active than those without, but the difference was not significant; and (3) the humidity under the shelters was significantly greater than within the rest of the tank. All frogs spent a large amount of time under shelters, if available. Regardless of the causes for any accelerated growth rate, shelters should therefore be provided in any terrarium for captive breeding colonies. The substrate choice of all three species reflected their natural habitat, with M. trinitatis (the stream frog) spending the majority of time in water and the toad-like P. pustulosus spending < 5% of its time in water. L. fuscus behaviour also reflected its natural habitat preferences. Thus, careful consideration of a species' natural history must be made when selecting the substrates to be used in terraria.