August 10, 2016

Humpbacks to the Rescue!

For decades, there have been mysterious reports about humpback whales coming to the rescue when animals are being attacked by orcas (large black-and-white dolphins known as "killer whales"). But why would humpbacks spend energy risking their own safety to help others? Could this be an example of animals acting selflessly?

Source: Christopher Michel (flickr), "glacier bay." (CC BY 2.0)
Orcas are top ocean predators. Source: Christopher Michel (flickr) (CC BY 2.0)

new study sheds some light on the mystery by analyzing 115 interactions between humpbacks and orcas. BBC filmmakers caught one such interaction on film. In May 2012, the crew was documenting an orca attack when several humpbacks showed up and tried to help the victim, a gray whale calf, by placing their giant bodies between the orcas and the wounded calf.

Here is the footage:

Orcas are top ocean predators, but they're usually only a threat to young humpbacks. Marine-mammal-eating orcas (versus the fish-eating varieties) often hunt whale calves by working together to separate the babies from their mothers, just like in the BBC footage.

It's in humpbacks' best interest to protect other humpbacks and their calves, so one possible explanation for the whales' heroic behavior is that they're simply trying to protect their own kind. However, the study suggests that in most cases, other species were the victims of the orca attacks, but the humpbacks stuck around to help anyway. These "good Samaritans" have been known to come to the aid of gray whales, California sea lions and Steller sea lions, harbor seals, and in one case, an ocean sunfish!

This behavior could be an example of "altruism." In zoology, altruism is when an animal behaves in a way that helps another animal, even if it harms itself in the process. Humpbacks' heroism seems to fit this definition, but the reality is that animal behavior is complex and interspecific altruism (altruism between different species) is often difficult to prove.

Until the scientific community learns more, these "rescues" are just one more reason to appreciate humpback whales--the heroes of the high seas! (Unless, of course, you're a hungry orca!)

A humpback whale breaching. Source: Gregory "Slobirdr" Smith (flickr) (CC BY-SA 2.0)
A humpback whale breaching. Source: Gregory "Slobirdr" Smith (flickr) (CC BY-SA 2.0)

Journal Citation: Pitman, R. L., Deecke, V. B., Gabriele, C. M., Srinivasan, M., Black, N., Denkinger, J., Durban, J. W., Mathews, E. A., Matkin, D. R., Neilson, J. L., Schulman-Janiger, A., Shearwater, D., Stap, P. and Ternullo, R. (2016), Humpback whales interfering when mammal-eating killer whales attack other species: Mobbing behavior and interspecific altruism?. Mar Mam Sci. doi:10.1111/mms.12343

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