Abundance of California Sea Lions on San Nicolas Island
Odell DK. 1975. Abundance of California Sea Lions on San Nicolas Island. The Journal of Wildlife Management. 39(4):729-736
The seasonal changes in numbers and structure of the California sea lion (Zalophus californianus) population on San Nicolas Island, California, were studied between August 1968 and August 1971. During this period, 39 censuses were taken at approximately monthly intervals. With the exception of 1971, 2 annual population peaks occurred: a winter peak with 9,000-11,000 animals in January and February, and a breeding season peak with 10,000-12,000 animals in July. The maximum numbers of females counted on the breeding areas during the breeding seasons in 1969, 1970, and 1971 were 5,981, 5,163, and 5,187, respectively. The total numbers of territorial males present in late June and early July were 332, 374, and 387, and the total numbers of pups counted in July were 2,857, 2,271, and 3,500. The structure of the breeding population had changed since it was last documented in 1965. The female-to-pup ratios averaged about 2.0 and the female-to-territorial male ratios averaged about 16.0. The data suggested that the San Nicolas sea lion population may have stabilized with regard to total numbers.
- Type
- Journal Article
- Authors
- Odell, Daniel
- Units
- CHIS
- Keywords
- Animal Studies, California Sea Lion (Zalophus californianus), Population, San Nicolas Island Channel Islands CA