Peninsular Desert Bighorn Sheep Behavior

Space-Use Patterns

Young bighorn sheep learn their habitat use patterns from older animals, and individuals may remain in the same general area their entire lives. This philopatric behavior is more pronounced in females, who have smaller home ranges than males. Size of the home range depends on the juxtaposition of resources (water, forage, and escape terrain) and, therefore, varies geographically. In the Peninsular Ranges, average home range sizes of 25 and 20 square kilometers have been reported for males and females, respectively.

Desert bighorn sheep do not typically exhibit the seasonal migrations along elevational gradients that are observed in northern populations. However, there are some seasonal differences in habitat use patterns, and home ranges are often concentrated around water sources in the summer.

Activity patterns

Bighorn sheep are primarily diurnal but may be active at any time of the day or night. Patterns of resting and feeding are not synchronous within or between groups, and activity patterns may vary with age, sex, season, and habitat quality.

Behavior

Bighorn sheep are gregarious and their social structure is primarily matrilineal (based on female associations). Females exhibit a high degree of philopatry and form “ewe groups”, made up of related females. Males move between ewe groups during the breeding season.

Bighorn sheep have excellent vision, which is presumably important in predator evasion and social communication. Body posture and scent play important roles in social communication. Bighorn sheep rarely vocalize, but do sometimes bleat when seeking another animal (for example a female seeking her lamb), and they may make a coughing sound when alarmed. The dominance hierarchy of bighorn sheep is important in determining an individual’s access to resources and mating opportunities, and is based primarily on horn and body size.

Reproduction

Bighorn sheep are seasonal breeders and females typically produce one lamb per year. The mating season, or “rut”, occurs from July through December. During this period, males compete for the opportunity to mate with females, sometimes exhibiting fantastic head butting competitions. Lambs are born after a gestation period of approximately 6 months (171-185 days). In the Peninsular Ranges, most lambs are born January through June. Lamb survival can vary greatly among groups and across years, with survival to 6 months of age reported to range from 0 to 80%. Survival of lambs is likely influenced by rainfall (via its effect on plant productivity), and the presence of disease.