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Estimating survival for elusive juvenile pond‐breeding salamanders

Citation

Messerman, Arianne et al. (2020), Estimating survival for elusive juvenile pond‐breeding salamanders, Dryad, Dataset, https://doi.org/10.5061/dryad.jm63xsj65

Abstract

Juvenile vital rates have important effects on population dynamics for many species, but this demographic is often difficult to locate and track. As such, we frequently lack reliable estimates of juvenile survival, which are necessary for accurately assessing population stability and potential management approaches to conserve biodiversity. We empirically estimated survival rates for elusive juveniles of 3 complex lifecycle species of salamanders (ringed salamander [Ambystoma annulatum], spotted slamander [A. maculatum], and small-mouthed slamander [A. texanum]) using 2 approaches. First, we conducted an 11-month mark-recapture study within semi-natural enclosures and used Bayesian Cormack-Jolly-Seber models to estimate survival and recapture probabilities. Second, we inferred the expected annual juvenile survival rate given published vital rates for pre-metamorphic and adult ambystomatids assuming stable population growth. For all 3 species, juvenile survival probabilities were constant across recapture occasions, while recapture probability estimates were time-dependent. Further, survival and recapture probabilities among study species did not significantly differ. Post-study sampling revealed that the initial study period median estimate of annual survival probability (0.39) underestimated the number of salamanders known alive at 11 months. We therefore appended approximately 1 year of opportunistic data, which produced a median annual survival probability of 0.50, encompassing salamanders that we knew to have been alive. Calculation from literature values suggested a mean annual terrestrial juvenile ambystomatid survival probability of 0.45. Similar results among our approaches indicated that juvenile survival estimates for the study species were robust and likely comparable to rates in nature. These estimates can now be confidently applied to research, monitoring, and management efforts for the study species and ecologically similar taxa. Our data indicated that similarly robust vital rate estimates for subsets of ecologically and phylogenetically similar species can provide reasonable surrogate demographic information to advance conservation efforts for data-deficient species.

Methods

We collected these data during an 11-month capture-mark-recapture study under semi-natural conditions. We used the Bayesian jagsUI package (Kellner 2017) in R Software 3.5.1 (R Core Team 2018) to build Cormack-Jolly-Seber models to analyze our data.

Funding

Department of Defense Strategic Environment Research and Development Program, Award: RC-2155

Sigma Xi Grants-In-Aid of Research

University of Missouri Life Sciences Fellowship

Sigma Xi, Award: Grant‐In‐Aid of Research

University of Missouri, Award: Life Sciences Fellowship