Influence of Landscape Arrangement and Wetland Condition on Breeding Dynamics of Ambystoma maculatum (Spotted Salamander) in Maine, USA

Ambystoma maculatum (spotted salamander) breeds in seasonal wetlands (vernal pools) as well as in wetlands with permanent hydroperiods. Ability to successfully recruit young in these latter breeding habitats may be particularly important in landscapes with low vernal pool density but may require alternative breeding strategies. We examined relationships among breeding habitat and landscape characteristics and A. maculatum occurrence, ovipositioning behavior, egg mass morphology, and embryo survival, and occurrences of other amphibian species during 2006-2010 in ten vernal pools and permanent waterbodies (seven fishless lakes and five stocked but naturally fishless lakes) in Maine, USA, and in laboratory experiments. We also used automated audio recording devices to evaluate the effectiveness of generalized listener-based audio surveys for detecting relatively rare or audibly cryptic anurans in Maine. Landscape-scale characteristics (number and area of ephemeral to semi-permanent wetlands within 500 m) were most important for predicting breeding occurrence by vernal pool amphibians (A. maculatum, Lithobates sylvaticus [wood frog]) in lakes, whereas lake-scale characteristics (e.g., vegetative cover, fish presence) were better predictors for species (e.g., L. septentrionalis [mink frog], L. pipiens [northern leopard frog]) associated with permanent waterbodies. Ambystoma maculatum breeding effort was greatest in lakes where more typical breeding habitats (e.g., vernal pools, beaver flowages) within 500 and 4000 m were less abundant. Egg masses and hatching larvae were approximately 13 and 33%, respectively, larger in vernal pools than in lakes. Survival of A. maculatum embryos to hatching while exposed to in situ predation was approximately 180% higher in vernal pools than both lake types. When compared with full-night surveys, generalized listener surveys may result in omissions and misclassifications of chorus sizes for certain species in Maine (e.g., L. septentrionalis, L. palustris [pickerel frogs]). Vernal pool-centric conservation measures may fail to account for connectivity among pools and alternative permanent breeding habitats in maintaining population persistence in long lived species such as A. maculatum. Lakes potentially provide alternative breeding habitat for A. maculatum in landscapes with few or poor quality vernal pools or in drought years; however, vernal pools are the optimal breeding habitat for this species in our study landscape