THE STAR (Toronto, Ontario) 11 May 08 Death-Dealing Frogs (Peter Calamai)
Are bullfrogs a four-legged version of Typhoid Mary, spreading a lethal plague among their fellows but remaining unaffected themselves?
That's one of the newer hypotheses for a global die-off of frogs, toads, salamanders, newts and other amphibians, which may already have led to the extinction of more than 100 species since the 1980s. Other theories include increased ultraviolet-B radiation, pesticides, habitat loss, and a mystery parasite.
"It's never going to be one single cause," cautions Purnima Govindarajulu, a biologist who has been tracking the exploding bullfrog population on Vancouver Island for the past decade.
A fungus known as Bd may be a major reason that bullfrogs are supplanting common Island denizens such as the western toad and the red-legged frog.
Bd is short for Batrachochytrium dendrobatidis, a fresh-water mould identified in 1998 as responsible for a disease that's deadly to many amphibians, but not to bullfrogs, which all carry Bd.
Govindarajulu began investigating the Island's bullfrog explosion in 1997 for her PhD at the University of Victoria, supervised by evolutionary ecologist Brad Anholt.
Now a herpetofauna specialist with the B.C. environment ministry, she is co-ordinating amphibian collections across the province but keeping an eye on Bd and bullfrogs as an adjunct professor at UVic.
"We've found Bd in places here where there are no bullfrogs. For instance, rough-skinned newts also carry it, and they are native to Vancouver Island," she says.
The province is now appealing to all biologists to report dead frogs to get a better handle on the extent of the problem.
Meanwhile Anholt's lab is preparing molecular family histories of both bullfrogs and the Bd fungus.
"If the two family histories are congruent then there's a good chance that bullfrogs are the carriers," says Anholt.
Moral of the tale: It's possible for public-good science to outlast a PhD thesis when universities and government co-operate.
Death-Dealing Frogs