Alloparenting, which is the caring for non-filial young, has been observed in mammal and bird species. Since sea lion pups have the ability to recognize their mothers and show a strong preference for them, it is likely that incidents of non-filial nursing represent adoption of orphaned pups by females who have miscarried or lost pups. Adoption events lower the pup mortality rate and contribute to greater population persistence. In this study, scientists used markings on pups and took biopsies of the females while they were nursing in order to identify mismatched female-pup genotypes. It was found that mismatched female-pup pairs accounted for less than 6% of nursing pairs in San Jorge Island. In Los Islotes Island, however, non-filial pairs accounted for over 17% of the female-pup pairs. Adoption is the most likely cause for mismatch pairs among these populations.
Source: Flatz, R., & Gerber, L. R. (2010). First Evidence for Adoption in California Sea Lions. PLoS ONE, 5(11).
