"Our results suggest that conservation action to protect even the smallest populations of Ethiopian wolves from rabies is both worthwhile and urgent," say Daniel Haydon of the University of Guelph in Ontario, Canada; Karen Laurenson of the University of Edinburgh in Roslin, UK; and Claudio Sillero of Oxford University, UK, in the October issue of Conservation Biology.
Ethiopian wolves are restricted to seven isolated montane populations, one with about 250 and the rest with roughly 20-80 wolves. Each population is surrounded by domestic dogs that carry rabies, and evidence suggests that when a wolf gets rabies, the disease spreads to about 90% of its pack. In the early 1990s, a rabies outbreak cut the largest Ethiopian wolf population by two-thirds. This population (Bale Mountain) has recovered, thanks to a dog vaccination program that began there in 1996.
To see if disease management would also benefit the other Ethiopian wolf populations, Haydon and his colleagues used a model that accounted for factors including the level of rabies incidence in the dog population and the wolves' habitat sizes (from 25-250 km2, which is the range of habitat sizes of the remaining wolf populations). The model predicted the likelihood that a given population would survive for the next 50 years.
Haydon and his colleagues found that when there was no rabies, all the wolf populations were fairly stable -- even those as small as 25-50 and in the smallest habitat patches. However, at current rabies levels, all the wolf populations were more likely to become extinct. Notably, the likelihood of extinction rose to 28% in 50 km2 patches and to 46% in 25 km2 patches. "Disease appears to be a significant threat to these smaller populations and could be a critical factor in determining their persistence," say the researchers.
The current option for controlling rabies in the wolf populations -- vaccinating the surrounding dogs -- can be costly and difficult. This could entail vaccinating at least 70% of the dogs in a band of up to 9 miles around the wolf habitat. Thus, the researchers investigated the effectiveness of vaccinating the wolves.
The model showed that vaccinating wolves against rabies could greatly increase the species' chances of survival. For instance, the likelihood of persistence increased from about 83% to 100% by vaccinating about a third of the wolves in a 75 km2 patch, and from 54% to 90% by vaccinating two-fifths of the wolves in 25 km2 patches.
While these findings suggest that vaccinating Ethiopian wolves against rabies would be effective, this is not yet an option because there is no rabies vaccine for wolves. However, there are oral rabies vaccines for foxes, raccoons and skunks, and these treatments have eradicated the disease from France and Switzerland, and are helping to control it in the U.S. and Canada.
To figure out the best way to protect Ethiopian wolves from rabies epidemics, Haydon and his colleagues call for comparing the relative costs and benefits of vaccinating the dogs with those of developing an oral rabies vaccine for wolves.
ADDITIONAL CONTACT INFORMATION:
*Claudio Sillero (44-186-528-1264, claudio.sillero@zoo.ox.ac.uk)
FOR PHOTOS AND DISTRIBUTION MAPS:
*Claudio Sillero (44-186-528-1264, claudio.sillero@zoo.ox.ac.uk)
FOR MORE INFORMATION:
Ethiopian Wolf Conservation Programme:
http://www.wildcru.org/endangeredspecies/ethiopianwolf/intro.htm
For PDFs of papers, contact Robin Meadows: robin@nasw.org
; http://nasw.org/users/rmeadows
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For more information about the Society for Conservation Biology: http://conservationbiology.org/
Journal
Conservation Biology