<p>Because these animals spend such an extraordinary amount of time in the water, there are many gaps in how much we know about them. It is difficult to discern lifespans of these animals and what might be defined as a "natural" cause of death. Estimates of survival of reproductive females is represented in percentages with the probability of survival decreasing with each year of life. In the first year of life, a female's chances of survival are 35%, at 2 years, 30%, and at 3 years, 20%. Adult males live an average of 11 to 13 years old. Young pups are quite vulnerable to death, particularly by predation and trampling. Trampling usually happens as a result of a large male defending its females, crushing the pup under his weight as he tries to quickly move toward an intruder. By some estimates as many as 10% of the young pup population may perish this way annually.<span> (Bonner, 1990; Klimley et al., 2001; Reeves, Stewart, and Leatherwood, 1992)</span></p>
- Bonner, W. 1990. The Natural History of Seals. New York, NY: Facts On File, Inc..
- Klimley, A., B. Le Boeuf, K. Cantara, J. Richert, S. Davis. 2001. Radio-acoustic positioning as a tool for studying sit-specific behavior of the white shark and other large marine species. Marine Biology, 138: 429-446.
- Reeves, R., B. Stewart, S. Leatherwood. 1992. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books.