The southern right whale is a huge fortress of animal—50 feet and 60 tons of muscle and blubber. At its size, this giant should have nothing to fear from ocean predators, except possibly for killer whales. But in the waters around Argentina, southern rights have been so badly tormented by an unusual threat that they have been forced to take stealthy precautions.
Their nemesis is the kelp gull.
Kelp gulls, like most of their kind, are opportunists. They’ll pluck fish from the sea, and scraps from landfill sites. And those near Peninsula Valdes in Argentina have started stripping flesh from the backs of whales.
Thousands of southern rights gather in those waters to breed between June and December. As they come up for air, the gulls land on their backs and tear off chunks of skin and blubber, leaving 20-centimetre long wounds. As many as eight birds can target one unfortunate whale.
As I reported two years ago, scientists first documented these attacks in 1972. They were rare then, but have been getting steadily worse. By 2008, some 77 percent of the whales were swimming around with gull-inflicted gashes. Partly, that’s because gull populations have soared thanks to the food provided by human fisheries and dumps. They may also be learning the behaviour from each other.
“Nowadays, gull attacks are so widespread in waters surrounding Península Valdés that it seems that there is no place without this interaction,” writes Ana Fazio from CONICET, an Argentinian institution.
The wounds might riddle the whales with skin infections, especially if the gulls are sticking their faces in rubbish heaps beforehand. They might also be distractions. Fazio found that the whales spend a quarter of their daylight hours trying to avoid the gulls, which might exhaust them, while depriving them of feeding opportunities. The calves suffer most: some 80 percent of the gulls’ attacks are aimed at mother-calf pairs.
Local government authorities have recently decided to take action, prompted in large part by pressure from visitors and tour operators. They have kick-started a management programme to protect the whales, including everything from killing the attacking birds, to closing landfills and reducing the waste that sustains the large gull populations.
Meanwhile, the whales have started taking matters in their own flippers. Clearly, they’re not keen on being flayed alive by gulls. They react by flinching strongly, arching their bodies so their heads and tails come up while their backs submerge. Scientists have described this posture as the “galleon position” or “crocodiling”.
Then, in 2008, they started doing something new.
Usually, when they come up for a breath, they do so in a leisurely way, lying parallel against the water surface with much of their backs exposed. But in 2009, Fazio’s team saw that a few of the whales would instead rise at a 45 degree angle so that only their heads were exposed, and only up to their blowhole. Their breaths were shorter and stronger than usual, and they quickly submerged again.
This technique, which the team called “oblique breathing”, exposes as little flesh as possible to the marauding gulls. It’s especially common at a site called El Doradillo, where the gull attacks are especially common. In 2010, 3 percent of the whales in El Doradillo were using oblique breathing. By 2013, 70 percent were doing it, and the behaviour had spread to neighbouring tracts of water. And most recently, the whales have started doing it even when they aren’t attacked, possibly as a preventive measure or to teach the trick to their calves.
It looks like the whales have won this round, but Fazio notes that oblique breathing isn’t an easy technique. These animals are naturally buoyant at the sea surface, so it takes energy to keep their backs and tails underwater. The technique may be especially taxing for the calves and this, combined with the actual attacks, may explain why the calves of Peninsula Valdes are dying in higher numbers than expected.
Reference: Fazio, Belen-Arguelles & Bertellotti. 2014. Change in southern right whale breathing behavior in response to gull attacks. Marine Biology http://dx.doi.org/10.1007/s00227-014-2576-6