Africa's Penguins Still Reeling From "Guano Craze"

John Roach
for National Geographic News

August 16, 2004

After a century-long population crash, African penguins face a tough
road to recovery, conservationists say. The birds face problems old and
new—from the lingering aftereffects of a 19th-century guano craze
to modern woes like oil pollution and a dwindling food supply.

"Before artificial fertilizers were invented, guano [bird excrement] was the best source of nitrogen. [It was] white gold," said Les Underhill, the director of the avian demography unit at the University of Cape Town in South Africa.

Seabird dung was heavily harvested by 19th-century European and North American traders and sold to farmers to replenish exhausted soils. The islands off the coast of South Africa were waist deep in the stuff. Resident penguins burrowed into the guano to make nests.

Today the islands are largely denuded of guano. As a result, penguins are often forced to nest out in the open, where they are exposed to the elements, according to Rob Crawford. Crawford is a marine conservationist with South Africa's Department of Environmental Affairs and Tourism in Cape Town.

"Many of the islands have no, or very few, bushes and no sand to burrow into, hence birds nest on the surface," he said. He noted that burrows offer penguins favorable conditions, "with less extreme fluctuations in temperature."

Early Nesters

African penguins are known as jackass penguins for their donkeylike braying. Most of the birds take up residence on their nesting islands in April—autumn in the Southern Hemisphere. Breeding tails off in October.

However, some early nesters arrive on their nesting islands off the South African coast in January and Febrary—mid-summer in the Southern Hemisphere.

Jackass penguins will abandon their nests for cool ocean waters when the air temperatures begin to rise above 80 degrees Fahrenheit (27 degrees Celsius). Such hot days usually occur in the summer and, as a result, tend to impact early nesting penguins.

When temperatures climb, early nesters desert their eggs to avoid heat stress and dehydration. The penguins typically return about six weeks later, when temperatures have dropped. In the birds' absence, kelp gulls eat most of the penguins' eggs.

"When—and if—this happens, desertion is a gradual process, over days, and unless the hot weather is in the early autumn, not a large proportion of the population is impacted," Underhill, the University of Cape Town researcher, said.

He added that heat waves are natural today and that current global warming is having no impact on the penguin populations.

The World Conservation Union, which lists the African penguin as "vulnerable," notes, however, that potential global warming in the future could cause more nest desertions and less reproductive success.

Conservationists say other threats, including oil pollution and a dwindling food supply, are the major factors behind the penguins' vulnerable status today.

Penguin Decline

The guano harvests of the mid 1800s were among the first intrusions of humans into the jackass penguin world. Most of the islands off South Africa were scraped clean of bird dung by the start of the 20th century. But humans continued to have a devastating impact on the birds.

"Probably the main cause of decrease in the early 1900s was harvesting of penguin eggs," Crawford said. The South African government marine conservationist estimates the total African penguin population at the time was around 1.5 million.

In the first half of the 20th century, 48 percent of the eggs produced on South Africa's Dassen Island (one of the penguin's main nesting sites) were harvested, according to data supplied by the World Conservation Union and the field guide Robert's Birds of Southern Africa. The practice was outlawed in 1967.

In more recent decades, the penguins have been harmed by increased oil pollution. Oil reduces the insulating properties of the penguins' feathers. Many affected birds die from hypothermia as a result.

The problem has been fueled by accidental tanker spills as well as intentional bilge cleaning by ships rounding the Cape of Good Hope on their way to the Persian Gulf.

Other threats to the penguins include competition with cape fur seals for overfished stocks of anchovy and sardines. The seals also displace the penguins from breeding sites and, together with great white sharks, prey on the penguins.

"I would rate food limitation as the most important present cause of the unfavorable conservation status, followed by oil spills and adverse interactions with seals," Crawford said.

Recovery

According to the World Conservation Union, a minimum viable population of about 50,000 nesting pairs is required to give the African penguins a less than 10 percent risk of extinction, which is about where the population stands today.

To help the penguins on the road to recovery, most of their nesting islands are protected. Recently established mainland colonies are also fenced off to prevent predation. Conservationists provide the birds with nest boxes to shield them from the elements.

Organizations like the Southern African Foundation for the Conservation of Coastal Birds, meanwhile, are meeting with success in their efforts to clean, rehabilitate, and release back into the wild penguins that become coated with oil.

Crawford hopes that conservation efforts will result in a population rebound to at least a hundred thousand nesting pairs, a number sufficient to reduce the risk of extinction in the wild to about 5 percent.

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