By David Ausband and Mike Mitchell
By the 1930s, gray wolves (Canis lupus) had been extirpated in the Rocky Mountains. Natural recolonization from Canada into Montana, as well as reintroductions to Idaho and Yellowstone National Park brought back the wolves—but also the conflicts with livestock producers.
Generally, in the Rockies, wolves that prey on domestic livestock are killed by government agencies or private landowners. While these actions typically stop depredations in the short-term, wolf packs generally reestablish within one year and livestock predation often continues. Most tools currently available for nonlethal control of wolves are short-lived in their effectiveness, as well, or require constant human presence.
Wolves, like most canids worldwide, use scent-marking (deposits of urine, scat, and scratches at conspicuous locations) to establish territories on the landscape and avoid intraspecific conflict. We hypothesized that human-deployed scent-marks consisting of scat and urine (i.e., "biofence") could be used to manipulate wolf pack movements in Idaho.
We tested the effectiveness of biofencing within three wolf pack territories near Garden Valley, Idaho, from June to late August, 2010 and 2011. Each year, we deployed approximately 65 km of biofence, consisting of a primary line of feces and urine and an offset secondary line of additional feces and urine running parallel to the primary line. Overall, we used 440 scats and 11.4 liters of urine collected in winter 2009/2010, and 505 scats and 12.0 liters of urine collected in winter 2010/2011, from wolves other than those in the resident packs.
Location data of satellite collared wolves in 2010 showed little to no trespass of the biofence, even though the excluded areas were used by the packs in previous summers. Two of the packs either did not trespass or trespassed less than expected given historic home range data during 2010 and 2011. The data suggested that these wolves approached the biofence, and even walked along it, but then returned in a direction toward the center of their territory rather than trespass the biofence.
In addition, sign surveys at predicted rendezvous sites in areas excluded by our biofence yielded little to no recent wolf use of those areas. We deployed a biofence between a resident wolf pack’s rendezvous site and a nearby active sheep grazing allotment totaling 2,400 animals. This pack had killed sheep every year since 2006, as well as one guard dog in 2006; they were not implicated in any depredations in the summer of 2010, even though their rendezvous site was in close proximity to the sheep.
In 2011, wolves in two of the packs demonstrated little to no trespass of the biofence. Wolves in the third pack, however, particularly the alpha female, showed little aversion to trespassing the biofence.
Our results suggest the biofence is effective for manipulating the movements of most, but not all wolves. Additional studies will look at the potential for total exclusion via more frequent refreshing, an adequate buffer distance (2-3 km) from the area to be excluded, and the use of automated howling devices.
David Ausband and Mike Mitchell of the Montana Wildlife Cooperative Research Unit were recipients of a Christine Stevens Wildlife Award to study the effectiveness of “biofencing”—natural scent barriers—to keep wolves away from livestock and out of harm’s way.