Abstract
The aim of this study was to extend 40 yr of prior demographic work on northern elephant seals ( Mirounga angustirostris ) at Año Nuevo, California, by including the oldest animals. We used a Bayesian mark‐recapture analysis to estimate lifelong survival and lifespan of a cohort of 372 weaned pups branded in 1985–1987 and resighted until 2008. Annual survival probability of females averaged 86.3%/yr at ages 5–16, then declined until age 21, the age of the oldest female. Male survival was lower, averaging 67.7%/yr from age 1 to age 15, the age of the oldest male. Northern elephant seal females in the expanding population at Año Nuevo live longer than southern elephant seal females ( M. leonina ) at colonies whose populations are declining. This comparison suggests that high survival of females is a key factor in population growth.