Presents: Survival estimates of juvenile Steller sea lions in the Gulf of Alaska 2005-2011
Seminar Speaker: John Maniscalco, Alaska SeaLife Center
When: Wednesday, June 27th
Where: Alaska SeaLife Center, Bear Mt. Conference Room
Free Seminar, Everyone Welcome!
Steller sea lions in much of Alaska were listed as endangered following a precipitous, unexplained collapse beginning in the late 1970’s, but in the Gulf of Alaska they have shown signs of recovery since the early 2000’s. Low juvenile survival has been implicated as a factor in the population decline but current estimates have been unavailable. John conducted a mark-resight study to estimate juvenile survival between 2005 and 2011 in the Gulf of Alaska for a comparison with estimates during the decline and with recent estimates in southeastern Alaska where sea lion numbers have been increasing for more than 30 years. Results show an increase in survival since the late 1980s with estimates similar to the growing population in the southeast. John further tested several covariates related to maternal investment for their effect on model selection and juvenile survival. Age, birth mass, and delayed weaning had strong influences on survival, although these variables affected the sexes differently. Delayed weaning benefitted the survival of female offspring with low birth weights only, whereas survival of males was increased regardless of birth weight when maternal care was extended beyond 1 year. This work provides current survival estimates in a growing population of endangered sea lions and offers new insights into factors affecting the differential survival of male and female pinnipeds which may depend on predator abundance and food availability. The value of delayed weaning to juvenile survival in the species will be highlighted.