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Individual study: Augmentation to bolster an endangered population of grizzly bears Ursus arctos horribilis in the Cabinet Mountains, Montana, USA

Published source details

Servheen C., Kasworm W.F. & Their T.J. (1995) Transplanting grizzly bears Ursus arctos horribilis as a management tool - results from the Cabinet Mountains, Montana, USA. Biological Conservation, 71, 261-268

Summary

A study of grizzly bears Ursus arctos horribilis in the Cabinet Mountains (3,960 km²; 48°N, 116° W) of Montana (northwest USA) indicated that the population was in danger of extirpation due to the low population size. In response, The US Fish and Wildlife Service (USFWS) issued an augmentation plan in 1987, aiming to introduce four 2-6-year-old wild females.

During 1990-1993, efforts were made to capture suitably aged female bears (sub-adults selected because they were thought most likely to remain in the release area).
 
Trapping (using foot snares placed in and near wooden cubbies baited with deer carcasses and meat scraps) was conducted in southeast British Columbia (Canada).
 
Bears appropriate for translocation were marked with numbered rubberized button ear tags and radio-collared prior to release. Movement and habitat use data of released female grizzlies were analysed and compared with native grizzly bears in the Cabinet Mountains.

In July 1990, the first female (a 5-year-old) was released. She was radio-monitored for 13 months until the radio-collar was lost, but was visually relocated on 15 May 1992 (22 months after release) approximately 19 km from the release site. Her home range (July 1990-May 1992) encompassed 555 km².
 
Eight bears were caught in 1991, but none met the required sex/age criteria. In 1992, a second suitable female (6 years old) was caught and released at the same location as the first female, 2 years later (22 July 1992). Her movements from July through November 1992 encompassed 388 km². She emerged from hibernation with a cub in May 1993 and was radio-monitored until July 1993 when found dead (cause of death unknown) in the target release area. The cub was not found (although seen with its mother in late June).
 
Movement patterns and home ranges (derived from aerial radio locations of these two released bears) were similar to native grizzly bears (monitored 1983-1989). Average elevation was 1,664 m during 1990-92, a little higher than that of native grizzlies (1,591 m) during 1983-89. Habitat use (mainly forest, shrubfield and mixed shrub/snowchute) were broadly similar.
 
A third sub-adult (2-year-old) female was captured and released on 16 July 1993; she remained in the release area during October 1993.
 
Whilst initial survival has been good and releasesd bears have remained in the target area, as yet, the success of the augmentation program remains inconclusive.
 

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