Lone Wolves

A return to the wild involves a host of growing pains for grey wolves as they are reestablished in their native habitat.  A new case study of wolves reintroduced to Yellowstone traces their susceptibility to parasites and its impact on population health. Without herd immunity, these pioneering wolves may be entering habitats that present significant risk of infection.

To improve survival odds in wildlife reintroduction efforts, conservationists typically only select the strongest animals for the return to the wild. But such a healthy start may make them more vulnerable to parasite invasion. After time in captivity, these animals have no native defenses against the parasites they once encountered, and vaccines only protect the first generation. 

In the case of the grey wolf reintroduction in Yellowstone, researchers found that coyotes served as a reservoir for some diseases that once hounded the wolves. Viruses like canine parvovirus quickly found their way to wild-born wolves from coyotes. In addition, mite infestation and canine distemper reappeared despite their apparent absence from the park prior to reintroduction. Together, parasitic mites and distemper slowed population growth, and mite infection even eliminated some packs. The best and most densely populated habitats in Yellowstone also provided the greatest opportunity for infection to spread.

Despite these challenges, the population appears to be stabilizing and thriving. “In contrast to the North American black-footed ferret and bighorn sheep reintroductions, where repeated parasite invasions via spillover have posed a substantial challenge to recovery efforts, wolf recovery has remained a success despite the invasion of infectious disease,” the study authors write. “The protection of Yellowstone that has afforded the wolf reintroduction effort such great success has also allowed us to watch the natural transition from population growth to limitation or regulation, in which parasites appear to play a significant role.”Caitlin Stier | 11 September 2012

Source: Almberg, E. S. et al. 2012. Parasite invasion following host reintroduction: a case study of Yellowstone’s wolves. Philosophical Transactions of The Royal Society B doi: 10.1098/rstb.2011.0369

Image ©Ken Canning | iStockPhoto.com