DEVELOPMENT OF DISPERSAL, MOVEMENT PATTERNS, AND HAUL‐OUT USE BY PUP AND JUVENILE STELLER SEA LIONS (EUMETOPIAS JUBATUS) IN ALASKA

Abstract

AbstractPopulation declines of Steller sea lions (Eumetopias juhatus) in western Alaska (west of 144°W) may be a result of reduced juvenile survival. We used satellite telemetry to study the at‐sea distribution and movement patterns of pup (1.6–11.9 mo) and juvenile (12.0–35.1 mo) Steller sea lions. We studied trip distance, duration, and interhaul‐out movements of sea lions in relation to age, sex, and month of year in the decreasing western population (WP; Prince William Sound, Kodiak, Aleutian Islands, Alaska) and the increasing eastern population (EP; Southeast Alaska). We deployed 103 satellite transmitters (29 WP; 74 EP) on sea lions between 1998 and 2001. Round trip distance and duration increased with age, trip distance was greater in the WP than the EP, trip duration was greater for females than males, and haul‐out use was clustered. Changes in round trip distance and duration occurred from April to June for all age classes studied indicating that the annual timing of weaning may be less variable than the age of weaning. Overall, 90% of round trips were ≤ 15 km from haul‐outs and 84% were <20 h, indicating nearshore areas adjacent to haulouts are critical to the developing juvenile.