ALTERNATIVE MATERNAL-CARE PATTERNS IN 2 HERDS OF BIGHORN SHEEP

Suckling and related behaviors of Rocky Mountain bighorn sheep Ovis canadensis canadensis were studied on the National Bison Range, Montana and in the Pecos Wilderness, New Mexico. Lambs obtained 31-85% of suckles from alien females on the Bison Range; no lambs suckled from alien females in the Pecos. Females appeared to invest equally in lambs in both herds, but additional nursing by helpers resulted in higher suckling rates for lambs on the Bison Range. Allomothers on the Bison Range were older and had more surviving offspring than other females in the herd. Allonursing may be a response to high predation levels on the Bison Range. -Author