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Individual study: The effectiveness of translocation of problem wolves Canis lupus in reducing livestock predation conflict in Idaho, Montana and Wyoming, USA

Published source details

Bradleye H., Pletscher D.H., Bangs E.E., Kunkel K.E., Smith D.W., Mack C.M., Meier T.J., Fontaine J.A., Niemeyer C.C. & Jimenez M.D. (2005) Evaluating wolf translocation as a nonlethal method to reduce livestock conflicts in the northwestern United States. Conservation Biology, 19, 1498-1508

Summary

Non-lethal management of livestock predators through translocation is an important technique for conserving some species of rare carnivores such as brown bear Ursus arctos, black bear U.americana, wild cats and wolves Canis lupus. In northwestern USA, wolves have been translocated away from livestock rearing areas to mitigate conflicts with farmers and to promote wolf recovery in suitable areas where they were formerly present (extirpated largely because they preyed on livestock) or still persist but at much reduced population densities.

An assessment was made of livestock predation, pack establishment, survival and homing behaviour of 88 translocated wolves in areas of Montana, Idaho and Wyoming using radio telemetry, to determine the effectiveness of translocations and consider how they could be improved.

Translocation and monitoring: Livestock predation, pack establishment, survival and homing behavior of all translocated wolves Canis lupus in northwestern Montana, central Idaho and the Greater Yellowstone Area of Wyoming (USA) were assessed from 1989 to 2002. Data was compiled on wolves translocated in response to livestock conflicts. Translocations involved both individuals and groups of wolves. Some individuals were relocated more than once.

Captured wolves were transported, and either hard or soft released. Prior to release they were fitted with a radio-tracking collar. Hard releases were defined as those wolves released within seven days of capture. Soft-released wolves were held at least 28 days; wolves given a standard soft release were released directly from their holding facility (0.4 ha enclosure), whereas wolves given a modified soft release were transported away from the enclosure before release. Modified soft releases were used in Montana, standard soft releases were used in Wyoming, most in Idaho were hard released.

Release sites were selected in areas with abundant wild game (deer), without livestock and with no other known wolf packs present. Monitoring was conducted by radio-tracking. Wolves were located two to four times per month but efforts were increased when livestock conflicts occurred.

Livestock predation and pack establishment: Fish and Wildlife Service personnel confirmed wolf predation on livestock. Individual wolves were implicated in livestock predation if they were located close to predation sites, returned to a carcass, or were a known member of a pack that killed livestock. Wolves that returned back to original packs from which they were translocated, were considered established only if they survived and did not kill livestock for more than one year after release.

Survival: Annual survival rates of translocated wolves from 1989 to 2002 were compared with all other (non-translocated) radio-collared wolves in Montana, Idaho and Wyoming in these years. All wolf deaths were investigated and cause of mortality ascertained whenever possible.

Homing behaviour: Homing back to capture sites is generally undesirable as it defeats the purpose of translocation. Investigations were therefore made to determine what factors were associated with homing behaviour in terms of recovery area, release method, sex, age class and translocation distance.

Sampling: Some wolves translocated in groups remained together after release and were therefore not independent of each other regards their behaviour. Such groups in analyses were therefore treated as an individual, except when measuring survival rates. Some individuals were relocated multiple times. Wolves translocated more than once may have returned to home territories under different circumstances. Therefore, homing behavior was assessed for each translocation.

A total of 88 wolves were translocated, seven were moved twice and five moved three times. Including these multiple relocations, there were 42 translocations involving 1 to 10 individuals (average 2.5 per translocation). Thirteen wolves were moved preemptively (as it was thought that they would imminently predate on livestock) and the rest in response to actual livestock conflicts. Wolves were relocated from 74 to 515 km from capture sites.

Livestock predation and pack establishment: Nine cohesive groups and 63 individuals were assessed to see if they preyed on livestock and established or joined a pack after release. Nineteen wolves (27%) preyed on livestock after release. Thirteen of these caused new livestock conflicts, the remaining six returned and resumed livestock predation in their original territory. Wolves preemptively moved appeared no less likely to avoid conflicts, with three of seven (43%) of these individuals or groups preying on livestock after release.

Most translocated wolves (67%) never established or joined a pack. This estimate included 13 wolves that disappeared and 26 that died before pack establishment was recorded. Of those that established, eight new packs were formed and four existing packs were supplemented. All of these new packs produced young.

Survival: Translocated wolves had lower annual survival (0.60) than other radio-collared wolves (0.73). In northwestern Montana, where most wolves settled in human-populated areas with livestock, survival was lowest (0.41) and more wolves proportionally failed to establish packs (83%). Annual survival of translocated wolves was highest in central Idaho (0.71) and more wolves proportionally established packs (44%) in this region than in the other areas.

For the 88 translocated wolves (58 mortalities; 42,160 radio days) and 399 radio-collared, non-translocated wolves (214 mortalities; 248,513 radio days) annual survival was lower for translocated (0.60) than for non-translocated wolves (0.73). Annual survival was lowest in Montana (0.41) compared with Idaho (0.71) and Wyoming (0.65). Most mortality of translocated wolves was caused by humans (Montana - 84%; Idaho - 50%; Wyoming - 72.5%), with legal and illegal killing the first and second leading causes respectively. The two main natural causes of death included starvation (5% overall) and hunting injury (4% overall).

Homing behavior: Translocated wolves showed a strong homing tendency, most that did not home still showing directional movement towards their home territory. Sixteen (20%) of 81 individuals or cohesive groups (12 individuals, three pairs, and one group of six wolves) successfully returned to capture sites, traveling distances of 74–316 km. More adults (36%) than subadults (11%) returned to capture sites. More hard-released (30%) than soft-released (8%) wolves returned home. Hard-released wolves generally traveled farther after release than soft-released wolves. (with no difference between the two soft-release methods).

Success of translocations varied and was most affected by the area in which wolves were released. Fewer wolves returned home in Montana (6%) than in the Wyoming (33%) and Idaho (28%). Wolves that were translocated shorter distances were more likely to return home. Sex was the only variable not related to whether a wolf returned to their original territory.

Conclusions: Most wolves, whether attempting to return home or not, moved away from the release site. Only four translocations resulted in release site fidelity, these all involved groups of wolves relocated together. Three of these comprised almost complete family groups, and they were the only cases for which nearly complete groups were relocated together.

The authors suggest that managers translocating wolves should consider soft releases in family groups when feasible, because this may decrease homing behavior and increase release-site fidelity.


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