Characterizing alloparental care in the pilot whale (Globicephala melas) population that summers off Cape Breton, Nova Scotia, Canada

摘要

Alloparental care happens when a calf is cared for by an adult that is not their parent. Although alloparental care is common in social mammals, its prevalence is difficult to assess in cetaceans, and has not been studied in Globicephala melas. Apopulation off Cape Breton, Nova Scotia, has been studied from whale-watching vessels since 1998, during July and August each year. From 2009 to 2011, we collected photo identifications of calves and the adults accompanying them. Alloparental care was considered to be occurring when a calf was identified with more than one companion. We found that 85.7% of calves in 2009, 80.6% of calves in 2010 and 63% of calves in 2011 had alloparents. Mothers were difficult to identify. Nevertheless, none of the other companions of calves were assigned to the same unit as the mother. Five carers were sexed, four of them males. There were no cases of within- or between-year alloparental care reciprocity. It is possible that delayed reciprocity is happening on a larger time scale in this population, but the most likely explanation is that alloparental care is a byproduct of this species' social structure, with a very small cost to the alloparent's fitness.