Correlates to colonizations of new patches by translocated populations of bighorn sheep
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Abstract
By 1950, bighorn sheep were extirpated from large areas of their range. Most extant populations of bighorn sheep (Ovis canadensis) in the Intermountain West consist of <100 individuals occurring in a fragmented distribution across the landscape. Dispersal and successful colonizations of unoccupied habitat patches has been rarely reported, and, in particular, translocated populations have been characterized by limited population growth and limited dispersal rates. Restoration of the species is greatly assisted by dispersal and successful colonization of new patches within a metapopulation structure versus the existing scenario of negligible dispersal and fragmented, small populations. We investigated the correlates for the rate of colonizations of 79 suitable, but unoccupied, patches by 31 translocated populations of bighorn sheep released into nearby patches of habitat. Population growth rates of bighorn sheep in the release patches were correlated to Ne of the founder group, and early contact with a second released population in a nearby release patch (logistic regression, p = 0.08). Largest population size of all extant released populations in 1994 was correlated to potential Ne of the founder group, the number of different source populations represented in the founder, and early contact with a second released population (p = 0.016). Dispersal rates were 100% higher in rams than ewes (p = 0.001). Successful colonizations of unoccupied patches (n = 24 of 79 were colonized) were associated with rapid growth rates in the released population, years since release, larger area of suitable habitat in the release patch, larger population sizes, and a seasonal migratory tendency in the released population (p = 0.05). Fewer water barriers, more open vegetation and more rugged, broken terrain in the intervening habitat were also associated with colonizations (p = <0.05). We concluded that high dispersal rates and rapid reoccupation of large areas could occur if bighorn sheep are placed in large patches of habitat with few barriers to movements to other patches and with no domestic sheep present. Many restorations in the past that did not meet these criteria may have contributed to an insular population structure of bighorn sheep with limited observations of dispersal.
Study Area
Publication type | Article |
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Publication Subtype | Journal Article |
Title | Correlates to colonizations of new patches by translocated populations of bighorn sheep |
Series title | Restoration Ecology |
DOI | 10.1046/j.1526-100x.2000.80068.x |
Volume | 8 |
Issue | 4S |
Year Published | 2000 |
Language | English |
Publisher | Wiley |
Description | 9 p. |
First page | 66 |
Last page | 74 |
Country | United States |
State | Colorado, Montana, North Dakota, South Dakota, Utah |
Other Geospatial | Arches National Park, Badlands National Park, Bear Mountain, Beaver Creek, Bighorn Canyon, Black Canyon, Bureau of Land Management, Chateau, Cross Mountain, Dillon, Hole-in-Rock, Island Sky, Ladore Canyon, Lake Fork, Lockhart Road, Lone Buttes, Magpie Creek, Maze, Mesa Verde, Monument, Moody, Moody Canyon, Needles, North Bullion, Pool Creek, Potash Road, Red Slide, Sheep Creek, South Bullion, Theodore Roosevelt National Park, Wanagan |
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