"The diseases that cause the most mortality in ottersseem to be newly emerged. In some cases, humans may have influenced the spread and emergence of these new diseases," say Kevin Lafferty of the U.S. Geological Survey at the University Of California, Santa Barbara, and Leah Gerber, who did this work while at the National Center for Ecological Analysis in Santa Barbara and is now at Arizona State University, in the June issue of Conservation Biology.
Managers rarely explicitly consider the threat of infectious diseases to wildlife populations. However, many of the factors that threaten species -- from habitat degradation to introduced species to pollution -- may also affect the transmission of infectious diseases. These factors typically limit the spread of infectious diseases, making most pathogens die out in populations of rare species. That said, domestic animals can harbor diseases that can spread to wildlife, which can be particularly devastating to rare species. For instance, domestic sheep diseases have wiped out populations of bighorn sheep. In addition, an introduced infectious disease can make common species become rare because they are not adapted to the new pathogen. For instance, introduced bird malaria has decimated many Hawaiian song birds that used to be common.
"Many of these wildlife diseases are viewed as emerging, particularly as we introduce species around the globe and as our domestic plants and animals encroach on natural habitat," says Lafferty.
In their analysis of the link between disease and conservation, Lafferty and Gerber highlighted the California sea otter. While the Alaska population has been growing at about 18% per year, the California population has been declining by 2-3% per
Contact: Kevin Lafferty
Society for Conservation Biology