Impact of a sarcoptic mange epizootic on a coyote population

Although sarcoptic mange is a mite (Sarcoptes scabiei) infection that occurs as periodic epizootics in wild canids, the effect of this disease on populations has not been explained. We collected data from 1,489 coyotes (Canis latrans) during 1974-91 in southern Texas and examined the effect of a sarcoptic mange epizootic on the coyote population. Mange appeared in 1975, peaked during spring 1980 (69% of coyotes infected), and then decreased until absent among coyotes collected in 1991. The epizootic encompassed 60,000 km2in southern Texas during 1982-89. Adult males were more (P < 0.001) frequently infected than other age-sex classes during the stationary phase of peak prevalence. Mange prevalence in juvenile males increased (P < 0.01) overwinter during the stationary and decline phases of the epizootic. There were more cases of severe mange among adult males (P < 0.01) during the stationary than the decline phase. Reduced ovulation (P = 0.04) and pregnancy rates (P = 0.03) were associated with greater mange severity in adult females. Usually, coyotes with severe mange had less (P < 0.05) internal fat. We suggest that this epizootic was initiated by the appearance of a virulent strain of S. scabiei in the host population, spread of the epizootic was enhanced by high host population densities but moderated by the social organization of coyotes, and decline of the epizootic resulted from selection for mange-resistant individuals in the host population. Understanding the effect of diseases on wildlife populations requires long-term analysis of host population dynamics, with attention to other relevant factors such as behavior.