Beset By Human Competition, Penguins Must Take Marathon Food Trips To Avoid Starvation, A Researcher Finds

May 14, 1997

They're waddling across the ice to grab a soda, hawking cough drops and lending their "well-dressed" image to vodka, cookies, books, golf shirts and frozen yogurt. They're driving BMWs, riding trains and pushing through the jungle to get a Bud Ice. Indeed, the penguin seems to be on every advertiser's fantasy list these days.

But in the real world, the penguin's very existence is being threatened by fishing fleets and oil tankers.

Starvation is a major cause of death for newly hatched penguins, the result of dwindling marine food reserves. To feed their families, adult birds are forced to forage great distances from their breeding colonies, says Dee Boersma, professor of zoology at the University of Washington and one of the world's leading authorities on temperate-zone penguins. Indeed, her latest research shows that birds from the Punta Tombo penguin reserve in southern Argentina sometimes travel more than 300 miles from their nesting sites.

Boersma's research is the first to show that the temperate species of penguin, ranging from Magellenics to Humboldts, do not forage close to shore as previously thought. Instead, these small, flightless birds are capable of swimming hundreds of miles, journeys that take three weeks or more, to find food for themselves and their chicks.

"The major cause of chick mortality is starvation, often the result of a parent failing to return from a long foraging trip in time with food, " says Boersma. For the past 15 years she has been following the fortunes of the roughly half million birds at a 500-acre reserve at Punta Tombo, the largest penguin colony on the South American continent. Boersma is the director of the Magellanic Penguin Project, supported by the Wildlife Conservation Society under an agreement with the province of Chubut.

In past years, other researchers followed breeding penguins on their food expeditions by monitoring radio signals from transmitters glued to the birds' feathers. These signals indicated that the birds foraged close to their colonies. But there also were suggestions that some birds traveled well outside the four-mile range of the ground- based receivers.

Two years ago, Boersma began tracking two birds from her colony using satellite telemetry. She found that one male traveled at least 324 miles and the other 147 miles from the reserve. The furthest points of all but two of the birds' 10 recorded trips were more than 37 miles out to sea. It was the first proof that the foraging range of the temperate species can be so great. Last year, Boersma repeated the experiment with a single male. She recorded the penguin as being as far as 124 miles from the colony.

Although Boersma credits the penguins for their "natural wanderlust," she believes that the huge distances traveled by the birds are due to a scarcity of food close to the colony. Two possible reasons for the depletion of the penguins' preferred foods -- squid, hake and anchovy -- are the big increase in commercial fisheries in the South Atlantic and the change in ocean fish populations caused by climate change, possibly the result of global warming.

The males' longest foraging trips come when the female is incubating her two eggs and is fasting. The first trip for the male is usually about two weeks. Then the female is gone on a food trip for about two weeks. Then the couple switch nest-sitting duties every other day until the eggs hatch. For the first 30 days of the chicks' life, each parent will be gone for no more than 36 hours at a time, returning with digested fish which is regurgitated for the offspring. But then, as the chicks grow and become more demanding, the parents are gone for much longer periods, sometimes up to a week, in search of food.

Boersma has witnessed many tragedies during her years at Punta Tombo. She has seen chicks hatch and slowly starve and die as the mother patiently waits for her foraging mate to return. Often, the parents will have only enough food for one chick, and the sibling is left to starve. "The rule seems to be, feed the heaviest chick first," says Boersma. "If a chick is small, its fate is death."

So great has been the competition for food, that the numbers of temperate penguins have been slowly diminishing over the years. The Punta Tombo colony declined by about 20 percent between 1987 and 1995. However, last year, inexplicably, the numbers rose by 3 percent from the previous year.

The trick for penguin survival is getting beyond the first fledgling year, says Boersma. "Once they get to be adults, about 90 percent survive from year to year."

Fishing fleets are not the penguins' only harbinger of death. Oil tankers also are plying the waters along the Argentine coast, and they frequently dump their ballast water, resulting in heavy oil slicks that can result in a slow death for penguins. Oil mats the birds' feathers, removing the air pockets that provide insulation. The penguins become so cold, they are forced to shore. There they slowly starve to death, unable to return to the ocean because of the cold. "It is a very long and painful death. And so unnecessary," says Boersma.

The dangerous period for the Punta Tombo penguins is when they migrate north in April and south in September. The oil-covered carcasses of banded birds from the colony have been found along the coasts of Argentina, Uruguay and Brazil.

The UW researcher calls for the creation of marine management zones in which commercial fishing and oil transportation are regulated. Although some nesting areas along the Argentine coast are protected, the penguins' marine environment remains uncontrolled. There is, however, a local proposal for a marine reserve around Punta Tombo.

"Most species don't do well under pressure, and that includes penguins," says Boersma. "These charismatic birds must be protected."

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Boersma can be reached at 206-616-2185, or boersma@u.washington.edu



University of Washington

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