Adult survival and temporary emigration in the common toad

Abstract

In vertebrates exhibiting intermittent breeding, breeding activity is a factor of critical importance in capture–recapture studies using data from individually marked animals. Nonbreeders can be absent from locations used by breeders and can be considered "temporary emigrants". We addressed the influence of sex on survival in common toads, Bufo bufo (L., 1758), using the Joly–Seber model and the existance of temporary emigration in male common toads by assessing trap-dependence and by conducting a robust design analysis. We addressed the hypothesis that the probability of the presence of an individual in the study area depends on the presence of the individual the year before (i.e., that transitions between reproductive states are a first-order Markovian process). Results provided support for the hypotheses of random temporary emigration, of sex-specific differences in survival, and of the presence of "transients" in males. Females had intermediate survival compared with the groups of "transients + residents" and "resident" males. Females had lower recapture probability under the Joly–Seber model, which may be interpreted as evidence of lower breeding probability or lower detectability of breeding females. Behaviour may explain this difference in that females may attend ponds for shorter periods. This may be common in species where females aggregate to seek fertilization and lay eggs in locations attended by males and in species with a "resource-based lek" mating system.