Tasmanian devils are an endangered species largely due to devil facial-tumor disease (DFTD), an unusual type of cancer that can be spread to other devils through bites. The tumors do not necessarily kill by themselves, but their growth makes it impossible for the devils to eat, and they die of starvation.
Tasmanian devils are carnivorous marsupials about the size of a small dog that range throughout the island of Tasmania. They first became endangered in 1941 because farmers, believing they were a threat to livestock and humans, hunted them down as varmints. Through the 1990s, their numbers were recovering until DFTD suddenly appeared in the population. In addition to this disease, devils are often killed by vehicles when they eat carrion on or near roads, further endangering their numbers.
According to National Geographic, scientists are not yet sure where the disease came from. As of 2014, the current working theory is that somehow, flame-retardant chemicals like hexabromobiphenyl ether and decabromobiphenyl ether are getting into the food supply of the devils. High to very high levels of each are prevalent in devils that have DFTD. Scientists speculate that devils, known to be carrion scavengers, are eating human trash like mattresses or clothing contaminated with the chemicals that are discarded near carcasses or food garbage.