Demography of a high-density coyote population

Abstract

The demography of a lightly exploited population of coyotes (Canis latrans) in Webb County, Texas, which has had historically high densities, was described from 1976 to 1986. The population fluctuated at high abundance, except for a decline in 1981–1982 following an epizootic of canine parvovirus. Sex ratios were even. Population natality was low, as only 39% of females had viable fetuses. Natality of yearlings (1.5–2.0 years) was lower and more variable than among adults (≥2.5 years). Juvenile (0.8 year) females rarely ovulated. A comparison among 33 radiotelemetered females in 1985 indicated that only territorial adults produced viable fetuses. The proportion of juveniles in spring averaged 0.34. Indices of juvenile survival from birth to the following spring varied from 0.09 to 0.73. Annual survival rates of adults (0.64–0.73) were high and constant. The annual population growth rate (spring to spring) was correlated positively with prey abundance in the preceding winter and negatively with coyote abundance at the beginning of each annual period. Although failure to ovulate and juvenile mortality were identified as key factors in annual variation in population loss, variability in natality among yearlings was identified as the demographic variable associated with relative abundance of coyotes and prey. Body condition of coyotes, as indexed by body mass and internal fat, was not poorer during years of low prey abundance. Interactions between social organization and food availability were implicated in regulation of the lightly exploited high-density population.