March 27, 2013
Researchers Uncover Plight Of Africa’s Ancient Penguins
Lawrence LeBlond for redOrbit.com - Your Universe Online
When you think of penguins you probably think of cold, harsh climates, like those around Antarctica where the Emperor Penguin reigns supreme. However, not all penguin species live in cold regions of the world. In fact, several species live in more tropical climes such as the Galapagos and other equatorial regions.Penguins can also be found in Africa. And while only one species exists along the continent´s southern coast today, newly found fossils confirm that as many as four penguin species coexisted in Africa in the past. But why the diversity declined to only a single species today is a mystery; researchers think sea level could be to blame.
Publishing a paper in the March 26 issue of the Zoological Journal of the Linnean Society, researchers from the National Museum of Natural History (NMNH) and the National Evolutionary Synthesis Center (NESC) describe their fossil discovery as the oldest evidence of these flightless seabirds in Africa, predating previously discovered fossils by at least five million years.
Daniel Thomas of NMNH and Dan Kspeka of NESC happened upon the 10-to-12-million-year-old fossils in 2010 while sifting through rock and sediment excavated from an industrial steel plant near Cape Town, South Africa. In a mix of fossils including shark teeth, Thomas and Ksepka found 17 bone fragments they easily recognized as backbones, breastbones, wings and legs, later pinpointed to several extinct penguin species.
By measuring the fossils and comparing them to modern penguins, the duo estimated that the new species ranged in size from a foot to more than three feet tall. The modern African penguin, Spheniscus demersus, stands about 26 to 28 inches tall. It is the only endemic species of penguin that is found in Africa today. The researchers said it is still unclear what really led to the decline in penguin diversity on this continent.
They explain that gaps in the fossil record make it difficult to determine whether extinctions happened all of a sudden or over time.
"[Because we have fossils from only two time periods,] it's like seeing two frames of a movie," said co-author Daniel Ksepka. "We have a frame at five million years ago, and a frame at 10-12 million years ago, but there's missing footage in between."
Ksepka said humans cannot be blamed for this disappearance, because by the time early man arrived in South Africa, all but one of the continent´s penguins had already disappeared. The more likely scenario would be rising and falling sea levels, wiping out once-safe nesting sites along the coast.
Although penguins are known to spend most of their lives swimming at sea, they do rely on offshore islands to build nests and raise young. Land surface reconstructions suggest that five million years ago — when there still existed at least four penguin species — sea level on the South African coast was as much as 300 feet higher than it is today, turning much of South Africa into a vast network of islands. More islands meant more beaches where penguins could breed while staying safe from mainland predators.
But the sea levels started to drop and islands became sparse, diminishing the habitat for penguins. Once-isolated islands became reacquainted with mainland, which likely wiped out beach nest sites and provided access to mainland predators.
While humans weren´t to blame for the past extinctions of penguins, we will play a key role in the fate of the one species that remains today, Thomas and Ksepka added.
The population of the black-footed penguin has dropped by 80 percent in just the last 50 years, and is now classified as endangered. The decline is largely due to oil spills and overfishing of sardines and anchovies — the bird´s favorite food.
"There's only one species left today, and it's up to us to keep it safe," Thomas said.