Male Alloparenting in Killer Whales

Male Alloparenting in Killer Whales

While not the best photo (thanks autofocus!), this snapshot shows a very cool behavior that is observed in killer whales called alloparenting, and more informally, babysitting!

In this photo we see adult male AP18 in the background with a younger juvenile, probably around 3 years old, in the foreground. This calf belongs to AP3, a reproductive female in the pod (and has not been assigned a formal alpha-numeric designation by researchers yet). When I was documenting the whales during this encounter, I noted that AP3′s calf was not with her. I became worried as I had just seen this calf a week prior. Then, the massive male AP18 showed up with the calf in tow! She was zipping around AP18 (who is probably either her brother or uncle) while her mother lazily followed her from behind several hundred yards away.

Studies on social behavior in male resident killer whales show that males often “babysit” their younger relatives. Mother killer whales may pass off their youngsters to their brothers or sons in order to take a break. Raising a calf is energetically costly to a mother. Calves are bouncy, energetic, and like all kids, don’t want to sit still when mom needs a break. By handing her calf off to a relative, the mother can gain some much needed rest. 

What do the males gain in return? The males may receive inclusive fitness benefits by babysitting their younger siblings and nieces/nephews. There is some evidence that when a female has available alloparents, she may be more reproductively successful. Males stand to benefit from their female relatives reproducing frequently as this also spreads some of their genes around (and in the eyes of evolutionary biology, the ultimate driver of all behaviors is the passing on of genetic information).

Reference:

Rose, Naomi A. 1992. The social dynamics of male killer whales, (Orcinus orca), in Johnstone Strait, British Columbia. Ph.D. dissertation, University of California, Santa Cruz.