A few years ago, researchers working with southern right whales breeding off Argentina revealed that the hefty cetaceans were being viciously attacked by gulls. When the whales leisurely surface for air, the opportunistic birds land on their backs, rip off their skin, and feed on their blubber. It doesn’t seem to kill the whales, but these nasty lesions from repeated attacks can be up to 10 centimeters deep and one-meter-and-a-half long. Now, a team studying these interactions over the last three decades have discovered that a precautionary response is spreading among the whales: They breathe with just their heads above water to avoid the ravenous attacks.
Between June and December, southern right whales (Eubalaena australis) gather in the thousands to mate and calve in the waters surrounding Peninsula Valdes in Chubut, Argentina. That’s also where they’re being targeted by kelp gulls (Larus dominicanus), and the attacks have been rapidly increasing since they were first documented in 1972. About 77 percent of whales in the area now carry gull-inflicted wounds. Well, pain is a major impetus for quickly learning an avoidance behavior, and the whales have since developed a technique called “oblique breathing.” That’s when they come up at a 45 degree angle so that only their head is exposed up to their blowhole, National Geographic explains. They also take shorter but stronger breaths, before quickly submerging again.
To document the rise and spread of this tactic, a trio of Centro Nacional Patagónico researchers led by Ana Fazio studied oblique breathing in two areas of Golfo Nuevo around the peninsula during whale reproductive season in 2010, 2012, and 2013. These regions have especially high numbers of gull attacks, and Fazio’s team have previously shown that the birds target mother-calf pairs, which account for 80 percent of the attacks.
The team found that all age and sex classes of these southern right whales can breathe obliquely, and the behavior is becoming increasing common. In 2010, three percent of the whales were using the technique, National Geographic reports, and 70 percent were doing it by 2013. The emergence of this behavior proceeded in three stages: the origin, the spread, and finally the establishment. During the spread step, the behavior was used only during gull attacks, but in the establishment phase, the whales were performing oblique breathing in a preventive manner -- even when they weren’t being attacked.
Unfortunately, oblique breathing is likely to pose extra energy costs, which are likely detrimental to the whales, especially newborn calves. However, the increasing prevalence of this behavior suggests that it’s a useful strategy to prevent harassment by gulls, for now.
The findings were published in Marine Biology last month.