The effects of birth weight and maternal care on survival of juvenile Steller sea lions (Eumetopias jubatus)

PLoS One. 2014 May 7;9(5):e96328. doi: 10.1371/journal.pone.0096328. eCollection 2014.

Abstract

Steller sea lions were listed as endangered following a collapse of the western distinct population beginning in the late 1970s. Low juvenile survival has been implicated as a factor in the decline. I conducted a multistate mark-recapture analysis to estimate juvenile survival in an area of the western population where sea lions are showing signs of recovery. Survival for males and females was 80% between 3 weeks and 1 year of age. Approximately 20% of juveniles continued to be nursed by their mothers between ages 1 and 2 and 10% between ages 2 and 3. Survival for juveniles that suckled beyond 1 year was 88.2% and 89.9% to ages 2 and 3, respectively. In contrast, survival for individuals weaned by age 1 was 40.6% for males and 64.2% for females between ages 1 and 2. Birth mass positively influenced survival for juveniles weaned at age 1 but had little effect on individuals continuing to suckle. Cumulative survival to age 4 was double that estimated during the population decline in this region. Evidence suggests that western Steller sea lions utilize a somewhat different maternal strategy than those in the eastern distinct population. Western adult females generally invest more in their pups during the first year but wean offspring by age 1 more often. This results in better survival to age 1, but greater mortality between ages 1 and 3 compared to the eastern population. Different maternal strategies may reflect density dependent pressures of populations at opposite levels of abundance.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Birth Weight / physiology*
  • Female
  • Male
  • Maternal Behavior / physiology*
  • Population Dynamics
  • Sea Lions / physiology*

Grants and funding

This study was funding by U.S. federal grant appropriations through the National Marine Fisheries Service - NOAA Award NA09NMF4390169 (https://grantsonline.rdc.noaa.gov). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.