Tasmanian devils are losing a hellish battle: A contagious cancer—called devil facial tumor disease—is spreading across their island home, their last bastion of safety from human encroachment. Populations of this carnivorous marsupial have declined in parts of Tasmania by as much as 95 percent, and the species is now officially endangered. Only animals in the far northwest of the island seem to show some resistance to the malady. Scientists in the field are examining population sizes, behavior changes, immunology and genetics with the aim of helping to forestall extinction.

In this slide show Menna Jones and Hamish McCallum, authors of "The Devil's Disease," in the June 2011 issue of Scientific American, share some photos that they and their colleagues have taken of wild devils in the field. With the exception of the first slide, all of the animals shown here are healthy.

» View the Slide Show