Life Histories and Comparative Demography of Two Salamander Populations

Abstract

Two populations of the plethodontid salamander Desmognathus ochrophaeus inhabiting wet, vertical rockfaces in the southern Appalachian Mtns. were censused by the Jolly-Seber multiple recapture method over a 7-yr period. The populations were known to differ in age at sexual maturity, and a primary goal of the study was to obtain survivorship estimates that would permit comparisons of overall life histories of the two populations. Low elevation juveniles grow faster than high elevation juveniles during fall, winter and spring of their first full year of life. They thereafter grow more slowly than equal-aged high elevation animals and become externally sexable in their third summer, a year earlier than juveniles of the high elevation population. During the summer high elevation individuals of all sizes grow faster than those of corresponding size and sex in the low elevation population, since growth rates decline with attainment of sexual maturity. Estimated densities were about 3 sexable males and 3 sexable females per m2 for both populations throughout the study. The co-occurrence of a potential predator and competitor, D. monticola, at the low elevation site had no discernible effect on density of D. ochrophaeus. Survivorship of sexable animals appears to be higher over the colder months at the high elevation site; survivorship from June to August appears similar for the two populations. Annual survival rates were estimated to be 0.743 and 0.626 for high and low elevation animals that are externally sexable. Recruitment appears to balance losses in both populations. Estimated probabilities of survival from hatching to first oviposition were 0.059 and 0.087 at the high and low elevation sites. The difference reflects differences in age at maturity. Fertility rates appear to be uncorrelated with age in both populations, but larger females lay more eggs so that clutch sizes are higher in the high elevation population.