Pupping-site fidelity among individual Steller sea lions (Eumetopias jubatus) at Chiswell Island, Alaska
Pupping-site fidelity (defined as pupping within 5.8 m of a previous location in ≥2 years) in Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) was investigated during the breeding seasons from 2001 to 2005 at Chiswell Island, a small rookery in the Gulf of Alaska. Density of females was minimal with 54–80 pups born. Photo-identification of individuals and GPS points, including elevation of the rookery, were used to determine locations of 297 births. Sixty-four percentage (35/55) of the females exhibited pupping-site fidelity, and mean frequency of site fidelity was greater for females that gave birth >3 times. Fifty percentage of the births occurred at 22% of the locations for all years, indicating that multiple births occurred at some locations throughout the breeding season. Competition or aggression among females for specific pupping locations before birth was not observed, and there was no temporal order of pupping locations used, indicating that the rookery was not overcrowded and that many suitable pupping locations existed. Multiparous females gave birth at significantly greater distances from the surf zone than primiparous females. Long-term monitoring of pupping-site fidelity in combination with other measures of maternal care will ultimately determine which factors have the greatest effect on pup survival.