Sweanor, Linda L., Kenneth A. Logan, and Maurice G. Hornocker. 2000. Cougar dispersal patterns, metapopulation dynamics, and conservation. Conservation Biology 14(3): 798-808.
RELEVANT TO: |
WILDLIFE |
HABITAT LINKAGES |
|
HUNTING |
DOCUMENT DESCRIPTION
This article describes cougar dispersals, emigration, and immigration in the San Andres Mountains, New Mexico from 1985 to 1995. Over 200 cougars were captured, tagged, and radio collared. The researchers' objectives were to 1) describe the dispersal characteristics of the cougars born in a large, relatively isolated study population; 2) assess the importance of dispersers to other subpopulations; and 3) determine the importance of immigrants to the study population. Metapopulation structure is defined as "a network of semi-isolated populations with some level of regular or intermittent migration and gene flow among them, in which individual populations may go extinct but can then be recolonized from other populations". (p. 799) Cougar populations are often separated by natural or human-made barriers, hence understanding metapopulation dynamics is important for successful management.
This study represents "the only long-term information on the relationships of a study population of cougars to surrounding subpopulations prior to any large scale, human caused habitat fragmentation". (p. 799) Therefore, this study population offers insight into how unhindered populations may function.
MAJOR FINDINGS
- Of progeny, or offspring, tracked after independence, males dispersed 8.1 times farther than females
- Females stayed near the territory in which they were born
- 62% of progeny recruits (offspring that stayed in the area after independence) and 45% of immigrant recruits (newcomers to the study area) produced offspring
- Of the estimated 65 progeny that survived to adulthood (44 emigrants and 21 recruits) about 68% (83% male, 59% female) emigrated, suggesting males disperse more often than females (Table 2)
- After expansion of Highway 70 from 4 to 6 lanes, only two documented crossings occurred, and both animals were killed by vehicles. Prior to expansion at least 7 cougars successfully crossed, often more than once
- Dispersal appears to be independent of male cougar density and at least partially independent of female cougar density (p. 604)
- Total recruitment almost equaled successful emigration (8.4 recruits vs. 8.5 emigrants per year)
- Emigration probably influences genetic structure in cougar subpopulations
- Gene flow between widely separated subpopulations occurs through the movements of male dispersers
- Frequent exchange of animals allows smaller subpopulations to survive and resist catastrophic events better than isolated subpopulations
QUESTION RAISED FOR THE THREE FORESTS
- Do current policies ensure cougar subpopulation offspring are able to disperse to sustain gene flow and metapopulation dynamics?
- Do the Forests know where source and sink cougar populations are located?
FOREST MANAGEMENT SIGNIFICANCE
Understanding metapopulation dynamics is essential to sustain cougar populations across the region. Our recommendations include:
- Identifying and mapping cougar subpopulations
- Identifying source and sink subpopulations
- Banning hunting from source population areas to ensure healthy population and to sustain hunting endeavors in sink populations
- Identify critical linkages to maintain metapopulation balance and allow for gene flow