Factors affecting reproduction and population growth in a restored elk Cervus elaphas nelsoni population

In 1997, the Kentucky Department of Fish and Wildlife Resources began a restoration program intended to translocate 200 elk Cervus elaphus nelsoni per year over a nine-year period. Initially, the age structure of males in this restored elk population was heavily skewed toward the yearling age class. We examined the reproductive performance of this elk herd for two years. During 1998, the male:adult female ratio was 35:65 (corresponding to 54: 100). In 1999, the male:adult female ratio was 45:62 (corresponding to 73: 100). The proportion of yearling males declined from 89% in 1998 to 31% in 1999. We used radio telemetry to locate males and females during the rut and to document calf production. Calving rates during 1998 and 1999 were 53 and 92%, respectively. Post-release movements of adult cows (N = 22) to areas devoid of males averaged 21 km and ranged within 7-57 km. Temporary Allee effects may have been responsible for annual differences in calving rates. The calving season was 67 days when breeding was dominated by yearlings and 37 days when breeding was dominated by adults. A male age structure heavily skewed toward yearlings does not appear to limit population growth. Calving rates could be improved by reducing initial post-release wanderings of adult females. Distribution of potential mates may be more important to population growth rather than balanced sex ratios and age structures.