National Geographic

Argentinian gulls are eating whales (or at least bits of whales)

Photo by Mariano Sironi, Instituto de Conservación de Ballenas, Argentina, via BBC

Like most seagulls, the kelp gull is an opportunist. It will catch fish and other small prey, but it’s not above scavenging at landfill sites. And off the southern coast of Argentina, some kelp gulls have developed a taste for whale.

Between June and December, Southern right whales gather to breed in the waters off Peninsula Valdes in Argentina, and every year, thousands of tourists go out to watch them.  Kelp gulls are watching too. As the whales surface for air, the birds land and rip pieces of skin and blubber form their backs, inflicting gaping wounds up to 20 centimetres long. The whales violently arch their backs to submerge whatever they can below the water, before hurriedly swimming away.

The first of these attacks was documented in 1972, and they have been getting worse. In 1974, just 1 per cent of whales had gull-inflicted wounds. By 2008, 77 per cent of them carried such injuries.

It certainly doesn’t help that the gull population has exploded in the last 25 years, probably because human dumps and fisheries have provided them with a glut of food. The behaviour may also be spreading between the birds, with new individuals learning to peck the whales after their attention is directed to the blubbery buffets by their peers.

Babies suffer most. A few years ago, Mario Sironi found that mother-calf pairs account for 40 per cent of whale sightings, but 80 per cent of gull attacks. Ana Fazio from CONICET, an Argentinian institution, has now confirmed this trend. She spent more than 1,000 hours over three years watching the gulls and the whales, and found that most of the attacks were directed at mother-calf pairs, and most often at the calves – perhaps their rough skin makes for easier pickings.

Fazio and Sironi both found that most of the attacks involved a single gull, which suggests that certain troublesome individuals may be behind much of the whales’ woes. That’s actually encouraging – it means that killing specific birds would greatly ease the pressure on the whales. But new generations may already have learned to feast on whale flesh. In 2006, just 4 per cent of the attacking gulls were juveniles, but that proportion rose to 17 per cent in 2007. The youngsters often attacked in groups, with as many as eight birds pecking one poor whale.

Despite years of observations, no one knows whether the gull attacks are harming the whale populations beyond giving them some nasty sores. Certainly, the whale numbers are still going up, but it may take time before the true effects on these long-lived animals become clear.

The whales spend around a quarter of their daylight hours fleeing from the gulls’ attacks, which could conceivably rob them of valuable rest, and soak up their energy reserves. This might matter most for the calves, who are also robbed of important chances to socialise with their peers. Fazio is also worried that the gulls could carry skin infections, implanting bacteria from rubbish dumps and sewers into the skins of their unfortunate victims.

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.

References:

Sironi, Rowntree, Snowdon, Valenzuela & Maro. 2008. Kelp gulls (L. dominicanus) feeding on southern right whales (E. australis) at Penıinsula Valdes, Argentina: updated estimates and conservation implications. Scientific Committee of International Whaling Commission. SC/61/BRG19

Fazio, Bertellotti & Villanueva. 2012. Kelp gulls attack Southern right whales: a conservation concern? Marine Biology. http://dx.doi.org/10.1007/s00227-012-1985-7

There are 10 Comments. Add Yours.

  1. Chris Lindsay
    July 6, 2012

    It’s like Hitchcock’s “The Birds” but Tippi Hedren et al. are whales instead of people. Oh the whalemanity.

  2. Old Geezer
    July 6, 2012

    Everything’s going to be fine now. Humans are going to start “managing” the problem. What could possibly go wrong?

  3. ortzmet
    July 7, 2012

    How can we be certain that early exposure to gull-born bacteria isn’t bestowing these whales with the robust immune system necessary to cope later in life?

  4. Sibylline NGO
    July 7, 2012

    The only means to protect whales without damaging birds is to bring in a falconer to deprogram the behavior of attacks (as already successfully done in France), on one hand, and to treat the open-air discharges, on the other hand. It’s time for the human being to face up to its responsibilities !

  5. Henrique Niza
    July 7, 2012

    “In 1974, just 1 per cent of whales had gull-inflicted wounds. By 2008, 77 per cent of them carried such injuries.”

    Can’t that be a reflection of a much larger whale sample rather than an increase of such behavior?

  6. Ignacio
    July 9, 2012

    Hi,

    A couple of clarifications.

    First, the CONICET is the Argentinean equivalent of the NSF in the US. So stating “Ana Fazio from CONICET, a Patagonian natural sciences institution…” is not exactly right:
    http://en.wikipedia.org/wiki/National_Scientific_and_Technical_Research_Council

    Second, regarding the picture, the right spelling is: “Instituto de Conservación de Ballenas” instead of “Instituto de Conservacion e Balenas”

    [Thanks Ignacio. Corrected. - Ed]

  7. Steve Cripe
    July 12, 2012

    LOL @ Old Geezer! Yep, every time we get involved in solving nature’s problems, it all turns out just right!

  8. Brad
    July 14, 2012

    Let natural selection work it’s magic. Let this happen for 100,000 years and the whales and birds will adapt competitively, if it’s a big enough problem for the whales, and enough of a boon to the gulls.

    We don’t need to intervene any more than we need to intervene to protect dunes. The natural world doesn’t need our help. Heck, if people who wanted to kill these birds were around long enough ago, humans never would have evolved, because they would be too busy preventing any change from ever taking place.

  9. Alan
    July 15, 2012

    The world has long ago stopped being a “natural” place. Man has wrought such profound and dramatic changes to the natural ecosystem, we can no longer assume anything is “natural”. With such a profound impact on the world, with so many human beings on this planet, we must resolve to accept responsibility. The world is no longer a wild place ruled by natural selection and evolution. It is our backyard. It can be a trash dump or a garden. the only way it can return to a wild “Eden” is if we disappear entirely or at least return to living as the native americans did, and in tiny numbers. A garden takes planning, management, and hard work, a lot of it.

  10. Jimmy Cracks Capricorns
    July 17, 2012

    The gulls are now behaving just like a parasite.

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