Forest and wetland habitats are experiencing alarming loss in total area, which can also affect habitat quality, partly due to the isolation of patches and edge effects. The conservation of both wetland and forest habitat is particularly important for species with complex life cycles, such as the spotted salamander (Ambystoma maculatum), a species that is aquatic during the larval phase and fossorial during the terrestrial phase. The central objective of this study was to understand the influence of aquatic and terrestrial habitat characteristics on success of spotted salamanders. This insight may contribute to understanding the widespread impacts of habitat loss and degradation on forest biodiversity and assist in conservation efforts to reintroduce and bolster declining ambystomatid (genus Ambystoma) populations. We tested the hypotheses that (1) larval densities with greater prey availability (via lid removal) in experimental mesocosms will raise the greatest number of individuals that are most likely to survive overwintering; and (2) quality of the terrestrial habitat (amount of leaf litter and availability of burrows) will impact terrestrial behavior, growth, and survival. To test these hypotheses, we used experimental mesocosms to rear salamanders that were subsequently followed in the lab and in outdoor enclosures.
Results/Conclusions
Increasing larval density predictably reduced survival and mass at metamorphosis, despite increasing larval period. However, removing mesocosm covers generally relieved some of the effects of density which led to shorter larval periods and increased survival and mass at metamorphosis. These results suggest that when rearing salamanders for release, managers could maximize the number and size of individuals produced by removing covers even when increasing density. After metamorphosis, larval density (and, hence, metamorph size) was not a significant predictor for habitat choice in post-metamorphosis behavior trials in the lab. However, individuals choose treatments with leaf litter (regardless of the presence/absence of a burrow) significantly more than they chose other habitats without leaf litter, which we expect will have impacts on growth and survival in terrestrial enclosures. Metamorphs were also reared through overwintering in outdoor terrestrial enclosures, and survival and growth post-overwintering will be determined in Spring 2020. The present study suggests that rearing conditions in the aquatic and terrestrial environment will have important consequences for successful rearing and reintroduction efforts and that monitoring microhabitat quality may be important for ensuring the persistence of populations facing habitat loss and/or degradation.