Allomaternal care (maternal care provided by an individual towards offspring other than one’s own) has been demonstrated by numerous species however, more recent observations now include humpback whales.
The NOAA Fisheries Service expedition, which first observed this behavior, was sailing from South America to the Antarctica Peninsula in search of killer whales and recording their hunting tactics. A main component of a killer whale’s diet is Weddell seals. Researchers aboard the vessel, Robert Pitman and John Durban, were shocked as they watched ten killer whales agitate two adult humpback whales. Further observation revealed a Weddell seal swimming between the two humpbacks. However, it could not be proven the humpback whales were truly protecting the seal; oftentimes killer whales will try to antagonize the larger humpbacks to determine if any are sick or weak.
To the expedition’s surprise a week later they witnessed a different pair of humpback whales preventing a killer whale from attacking a seal. As a group of killer whales successfully dislodged the Weddell seal from its ice flow, the helpless seal immediately swam towards the pair of humpbacks (who were swimming nearby). The humpback closest to the seal, rolled on its back and pushed the seal onto its chest (using its flippers). Following the second display of such behavior the researchers concluded humpback whales were indeed exhibiting allomaternal care towards the seals.
*This blog post was derived from the article titled, “Save the Seal” published in Natural History’s November 2009 issue.