Population model of an endangered amphibian: implications for conservation management

Abstract

Amphibian populations are declining worldwide, but for many taxa, robust estimates of demographic parameters to assess population state or trends are scarce or absent. We provide robust estimates of adult apparent survival of the endemic Mallorcan midwife toad Alytes muletensis using individual capture-recapture data collected over 4 yr in a 60 m2 cistern. Moreover, we combined the vital rates into a stage-structured population model to estimate the expected long-term growth rate of the population. Apparent survival estimates of males and females were similar (0.737 ± 0.042 and 0.726 ± 0.045, respectively) indicating that the egg-carrying behavior of males, typical of this species, does not reduce its survival probability. We found evidence of a low local survival of juveniles compared with adults, most likely due to permanent dispersal. Adult population size estimation provided higher tadpole:adult ratios than previously reported for this endangered species, suggesting an overestimation of the previous adult population size. Model projections suggested a stable population, since λ, the expected asymptotic growth rate of the population, was close to 1.00.