Cameroon, the wettest part of Africa, is home to more than half the species of amphibians that live on the continent, including dozens of endemic frogs—which have been under attack around the world by the chytrid fungus (Batrachochytrium dendrobatidis).
The fungus latches onto the frog’s skin and can spread internally to the animal’s organs, quickly leading to death. Chytrid has wiped out entire species in Australia, Madagascar, and Panama, but Africa has been mostly spared—until now.
“It’s looking like some of these frogs may not be around by the time my kids are old enough for me to take them to Cameroon to see them.”
Researchers have documented declines in frog species on Cameroon’s Mount Oku and Mount Manengouba over a span of more than 12 years. They link the decline of at least five species of frogs found only in these mountains to chytrid.
“There’s been this perception that frogs in Africa are not affected by chytrid at all, but we have evidence of the disease in some animals,” says David Blackburn, an associate curator of herpetology at the Florida Museum of Natural History at the University of Florida. “This is the first real case of a decline across multiple amphibian species in Africa.”
Scientists collected and documented abundance and diversity of frog species living on the two mountains before and after the immergence of chytrid in the area between 2008-2010.
Many of the once common species, like the bright red Cardioglossa manengouba—a frog he discovered and named during graduate fieldwork in the early 2000s—are now scarce and nearly impossible to find.
“It’s looking like some of these frogs may not be around by the time my kids are old enough for me to take them to Cameroon to see them,” says Blackburn, coauthor of the study published in the journal PLOS ONE.
While chytrid is to blame for most of the patterns of decline in frogs worldwide, scientists have linked the emergence of the fungus in some places to climate change.
Research in Latin America led by Jason Rohr, a University of South Florida herpetologist, suggests unpredictable climate fluctuations can increase chytrid-related die-offs.
“Our research has shown there may be an under-appreciated link between climate change, disease, and biodiversity losses,” Rohr says. “Global warming and the severity of unpredictable variations in temperature increase chytrid growth on amphibians.”
Extreme temperature changes may affect the biology of the frogs by making them more, or less, susceptible to pathogens, Blackburn says, and this could easily be a factor in Cameroon, though he and colleagues have not yet collected enough data to make that call.
In captivity, frogs with chytrid are treated with an effective fungicide bath. In the Sierra Mountains of California, scientists have successfully released frogs inoculated with bacteria that make them less vulnerable to chytrid. But these methods are less practical in the mountains of Cameroon.
“Even if a cure was found, it would be hard to inoculate all of the individual frogs out there,” Blackburn says. “Promoting a healthier environment in general for Africa’s amphibians in terms of water quality and habitat protection is our best shot for keeping these species around.”
Researchers from the Museum für Naturkunde in Berlin Cameroon contributed to the work.
Source: University of Florida