Population Dynamics of White-Tailed Deer (Odocoileus virginianus) on the Welder Wildlife Refuge, Texas

Abstract

Reproduction among Welder Refuge deer was density independent at densities from 26 to 60 deer per km2. At densities up to 84 deer per km2 resulting from intensive predator control, nonlinear decreases occurred in reproductive rates. Timing of conception was inversely correlated with rainfall prior to and during the breeding season, presumably through a link with forage quantity and quality. Preimplantation and prenatal mortality was low. Fawn survival to 3 months of age was determined primarily by coyote predation. Fawn survival was correlated with rainfall during the gestation period. Adult mortality up to 4.5 years of age was higher among males than among females, even in the absence of selective removals by hunters. The result was a preponder- ance of adult females in the Welder Refuge herd. Basic population information for white-tailed deer, Odocoileus virginia- nus texanus, has been collected since 1962 on the 3,157-ha Rob and Bessie Welder Wildlife Refuge in south Texas. Early studies conducted on the Welder Refuge indicated that rainfall, and the resulting forage conditions, affected deer reproduction and mortality (Knowlton, 1964; White, 1966). Also documented was a high mortality rate among newborn fawns, primarily from predation by coyotes, Canis latrans (Cook et al., 1971). Recent research showed that intensive coyote control, begun in 1973 within a fenced, 391 ha predator exclosure, led to increased fawn survival and a substantial short- term increase in deer population density (Kie, 1977; Kie et al., 1979). Adverse changes in food habits and nutritional levels at the higher population densi- ties (Kie et al., 1980) resulted in poor body condition (Kie et al., 1983), reduced reproductive rates, increased mortality, and a population crash. The purposes of this paper are: 1) to summarize reproductive and mortal- ity patterns of deer on the Welder Refuge over the last 20 years and 2) to examine how these patterns were influenced by rainfall, population density, and other factors.