REPRODUCTIVE SUCCESS IN FEMALE MOUNTAIN GOATS

Kid production by marked females, age ratios from a 24-year study, and the literature are used to evaluate hypotheses that three intrinsic a nd three extrinsic factors affect reproduction by female Rocky Mountai n goats (Oreamnos americanus). On Sheep Mountain-Gladstone Ridge, Colo rado, mountain goat age ratios declined while the herd grew during 196 6-1979, and continued to decline with population stability during 1980 -1989, suggesting a continued increase in ecological density of goats 39 years after they were introduced in 1950. Among intrinsic factors, age and persisting individual characteristics have influenced reproduc tive success of females. Reproductive success in any year has not limi ted success in the following year, except in 4-year-olds. Among extrin sic factors, reproductive success of female mountain goats has been ne gatively influenced by density or ecological density and by snowpack d uring gestation. Reproductive success of females may have been positiv ely influenced by snowpack that enhanced forage conditions prior to br eeding. The relative importance of these six factors in determining re productive success of females may vary among and (temporally) within h erds. Most hypotheses regarding reproductive success in female mountai n goats remain poorly tested. Short-term observational studies hold li ttle promise for testing hypotheses, owing to large among-years variat ion in reproductive success. Long-term, intensive observational studie s, or manipulative experiments, are suggested.