VONESH, J. R. *; DE LA CRUZ, O.: Modeling the effect of UV-B induced egg-stage mortality on the population dynamics of the Common Toad

There has been increasing evidence of widespread population declines of amphibians from relatively undisturbed habitats. It has been suggested that ultraviolet radiation induced embryonic mortality has contributed to the decline of some species. However, the connection between UV induced mortality and population dynamics has not been examined explicitly. We examine the population-level consequences of UV-B induced egg mortality in the Common toad, Bufo bufo using a stage-structured population model that includes terms for density dependent juvenile recruitment, and juvenile and adult survivorship. Our results suggest that, except for a small range of values for some parameters, the stable adult population size shows little variation under changes in the survival of the eggs. Thus, based on our model increased egg-stage mortality due to exposure to UV-B alone is unlikely to result in declining adult populations for this species. The model exhibits similar behavior under a wide range of parameter values, which leads us to believe it to be an adequate analysis tool. The sensitivity analysis provides information on which parameters strongly affect the stable adult population size, and this could lead to other hypothesis on the causes of the reduction of amphibian populations.