Reproductive strategies of desert bighorn sheep

We examined temporal breeding patterns of bighorn sheep (Ovis canadensis) i n the Peninsular Ranges of California to determine the degree of seasonalit y and identify potential selection for seasonal breeding in this low-latitu de desert environment. During a 4-year period, births occurred during 7 mon ths of the year, but 87% of young were born in February-April and 55% were born in March. Peak months of mating and parturition remained relatively co nstant across years and among different regions of the Peninsular Ranges, a nd young born in February through April had greater survival than those bor n later. Female age influenced lamb survival but not timing of parturition. Successful recruitment of young by an adult female had a weak but signific ant negative effect on the survival of that female's offspring the followin g year. Previous reproductive history of a female did not influence offspri ng production or timing of parturition. Months of peak parturition followed annual winter rains and, therefore, were Likely to coincide with periods o f high plant productivity. Furthermore, most young were born before the hot , arid summer months. We concluded that bighorn sheep in the Peninsular Ran ges are seasonal breeders and that climate patterns likely act as ultimate factors in shaping the breeding season.