2001; Pistorius and Bester 2002b; McMahon et al. 2003, 2005a, b; de Little et al. 2007). In the northern elephant seal, we have likewise found substantial variation in juvenile survivorship this website and annual fecundity (Huber et al. 1991, Reiter and Le Boeuf 1991, Le Boeuf et al. 1994, Crocker et al. 2006), suggesting ample opportunity for either to affect population growth. Except for pup mortality, however, density-dependent variation in survival and fecundity has not been demonstrated (Le Boeuf et al. 2011). On the other

hand, when compared to other large mammals, elephant seals are short-lived. Adult females of most large herbivores have survival rates >90%/yr (Gaillard et al. 1998), as do many pinnipeds (Cameron and Siniff 2004, Hastings et al. 2011). In gray seals (Halichoerus grypus), 95% of adult females survive annually (Harrison et al.

2006) and a 42 yr old has been observed (Bowen et al. 2006). Elephant seals must have higher fecundity than gray seals in order to sustain population growth with their relatively short lifespan. At least one pinniped, though, is similar to elephant seals: in monk seals (Monachus schauinslandi), survival declined starting at age 17 (Baker and Thompson 2007). Our next steps are to study fluctuations in vital rates over time by studying other cohorts, then to build models of the Año Nuevo colony and the entire population of northern elephant seals based on complete life tables. Given our current estimate of a 21 MK-2206 manufacturer yr life span and 86% annual survival of adult females, we will explore variation in juvenile survival to find a rate that would support

the rapid worldwide recovery in the 20th century. We can also use the observed life table at Año Nuevo to quantify the immigration rate needed to account for local population growth. Other pinniped species offer excellent precedents for this sort of modeling (Cameron and Siniff 2004, Harrison et al. 2006). With the northern elephant seal, we will soon have the bonus of observing the cessation of population growth, allowing us to document vital rates across the transition to stability and test hypotheses about environmental and demographic factors important in regulating the population. We thank colleagues and numerous assistants for observations at Año Nuevo, especially D. Costa and his students; Mirabegron D. Adams, J. Adams, H. Jensen, D. Press, and L. Ptak for work at Point Reyes; D. Lee for work at the Farallones; A. Huntley for the brands and much assistance in the field; Clairol for hair dye; the University of California Natural Reserve System for maintenance of the Año Nuevo Island Reserve; the U.C. Santa Cruz Institute for Marine Science, especially S. Davenport, for supporting the field operation; and the rangers at Año Nuevo State Reserve for providing help and access. The analysis was developed as part of the PCAD Marine Mammal Working Group, funded by the Office of Naval Research.