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Gulls Bully Whales, Steal Their Breath

Jun 06, 2015 02:57 PM EDT
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It's hard to believe that anything can bother the southern right whale. Fifty feet long and weighing up to a stunning 60 tons, this behemoth of our southern oceans has no known natural predators. However, that doesn't save it from some intense bullying by your everyday seagulls, of all things.

According to a study recently published in the journal Marine Biology, the kelp gull (Larus dominicanus) is such a successful bully that southern right whales (Eubalaena australis) are changing how they swim and even breathe in order to avoid them.

An Unwitting Bully

Gull-on-whale 'bullying' was first noticed by experts more than four decades ago, when naturalists witnessed what looked like kelp gulls literally tearing skin and blubber off surfacing right whales near Península Valdés in Argentina. While seemingly far too aggressive for these normally opportunistic scavengers, experts quickly discerned that the gulls were not actually out for the whale's skin, but instead were targeting parasites, called cyamids, which feed on dead flesh.

Normally, cyamids are good for the whales, actively cleaning wounds and keeping their insulating blubber fresh and healthy. That alone is enough reason for the whales to want these gulls off their backs. However, because the parasites are often embedded relatively deep, the gulls will also peck and tear at a whale's hide, leaving painful wounds that can be up to 20 centimeters long.(Scroll to read on...)

Now, here's where things get weird. Originally, researchers suspected that this 'digging' for parasites was a rare behavior, with only the hungriest of kelp gulls pecking away at a whale's back.

However, by 2008, nearly 80 percent of southern right whales in breeding waters off the Argentinean coast were boasting fresh wounds from harrying gulls. As many as eight birds could be spotted pecking away at a single whale's back, according to a 2012 study. Researchers theorized that the gulls were learning the behavior from one another, and it would only become more common with each generation.

"There is also concern of possible transmission of infectious diseases in the attacks since increasing number of whales with different patterns of skin lesions have been observed," wrote whale immunology expert U. Siebert, who was not involved in the study.

Worryingly, it is estimated that after extensive whaling in the past century culled their numbers, there are a mere 7,000 southern right whales left in all the world. So what is being done to stop this bullying? (Scroll to read on...)

Whales Left Breathless

As things stand, conservationists will simply wring their hands, hesitant to interfere with what appears to be a completely natural turn of events.

Thankfully, the whales seem to have taken things into their own flippers, completely changing how and when they surface to take a breath.

The same researchers behind the 2012 study revisited Península Valdés between 2010 and 2013, this time not in search of gulls and wounds, but instead to study the victims directly.

They found that right whales who commonly encountered gull harassment were surfacing more frequently, but only for very short moments before quickly slipping back into the safety of the ocean depths. This is a technique called "oblique breathing," and was previously thought to be uncommon in large whales. (Scroll to read on...)

However, in a breeding site called El Doradillo, where kelp gulls can be found en masse, the great majority (70 percent) of right whales began using the breathing strategy by 2013. Three years prior, the researchers saw only three percent of the local whales using this technique. Knowing this, the team theorized that oblique breathing has become a learned behavior, much like pecking for whale parasites was picked up by the gulls.

"Because this region in Argentina is a breeding ground, the whales here are mostly mother-calf pairs, and whale calves are very receptive to imitating the behavior of their mothers," marine science expert Erin McLean, who was not involved in the work, recently explained. "Interestingly, adults breathe obliquely even when there aren't gull attacks, which could mean that they're showing their calves how to avoid those attacks when they eventually happen."

Still, even with the whales finding a way to avoid the gulls' harassment, there are still some concerns. That's because for large and naturally buoyant baleen whales, oblique breathing isn't easy. Not physically designed to breathe this way, the behavior may be especially taxing on newborn calves - a factor that may explain for persistent newborn deaths around Península Valdés.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

 

- follow Brian on Twitter @BS_ButNoBS

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