In 1956, the population was estimated at 300,000 birds.
In 1993, that number was down to perhaps 140,000.
By 2009, the time of the most recent in-depth survey, there were about 81,000.
The scientific name of the African penguin is Spheniscus demersus, or “plunging wedge,” referring to the bird’s superb swimming and diving abilities. But it might just as well refer to the species’ plunging population.
Eleven penguin species are classified as vulnerable or endangered. The Humboldt penguin, which is found from Chile to Peru, numbered more than a million birds in the 19th century. The population now may be just 25,000. Northern rockhopper penguins, which live on a few islands in the southern seas, have declined 90 percent in recent decades.
Historically, the problems facing penguins seemed clear: hunting, egg collecting, alien predators like cats and rats, and oil spills. These problems still beset penguins, and each species faces its own particular threats. The wreck of the ship MV Treasure in 2000, for example, spilled 1,300 tons of petroleum near Robben Island, oiling 19,000 birds. The latest dangers are more elusive, more global and more difficult to solve: overfishing, climate change and marine degradation. African penguins are susceptible to nearly all these threats, and Sherley warns they could be caught in an “extinction vortex.”
Dee Boersma, a penguin expert from the University of Washington, has studied the Magellanic penguin in Argentina for about 30 years. She says penguins are “marine sentinels,” indicators of the general state of the world’s oceans. “Penguins are reflecting rapid changes in the marine environment,” she writes, and their falling numbers suggest that, so far, “people are doing a poor job of managing the oceans.”
Still, research on the African penguin has benefited the species. The penguins had been forced to nest in the open, vulnerable to storms and floods and predators like gulls, largely because the island’s soil had been stripped by guano collectors. Researchers began building little huts for the birds to nest in—penguin “igloos.” Sherley says “birds in the artificial nest boxes breed more successfully than those in the bushes or natural burrows on Robben Island.”
Another crucial advance came after the 2000 oil spill. Getting oiled by a spill reduces a bird’s ability to rear chicks successfully for the rest of its life, even when it has been professionally washed and rehabilitated. But chicks hand-reared after a spill have fared as well as normal chicks, perhaps even better—a finding that has catalyzed increased efforts to take care of abandoned or imperiled chicks.
Flipper-banding studies have shown that protecting these penguins is urgent. The survival rate in adults, which commonly live 10 to 14 years, has decreased by 22 percent since the early 2000s. “In long-lived species like seabirds,” Sherley says, “decreased adult survivability is pretty much a sure sign that something is seriously wrong.”