Proceedings of the Ninth Mountain Lion Workshop - Carnivore ...

The Idaho Backcountry: Is it Still a Source Population for Cougars in
Idaho?
Holly Akenson, Taylor Wilderness Research Station, University of Idaho, HC 83 P.O.
Box 8070, Cascade, ID 83611, USA, tayranch@uidaho.edu
Bruce Ackerman, Idaho Department of Fish and Game, 600 S. Walnut St., Boise, ID
83709, USA, backerman@idfg.idaho.gov
Toni Ruth, Selway Institute, 76 Sunflower Rd, Salmon, ID, 83467, USA,
truth@centurytel.net
Jim Akenson, Taylor Wilderness Research Station, University of Idaho, HC 83 P.O. Box
8070, Cascade, ID 83611, USA, tayranch@uidaho.edu
Maurice Hornocker conducted the first major research on cougar (Puma concolor)
ecology and determined that cougars living in the remote central Idaho wilderness
functioned as a source population (Hornocker 1970). Hornocker (1970) concluded that
the wilderness population was stable, despite high productivity of the study population,
because subadult cougars dispersed long distances from the wilderness rather than remain
in their natal population. Pulliam (1988) defined a source population as one with high
productivity and reproductive surpluses that contributed immigrants to sink habitats.
Sinks were populations where mortality exceeded reproduction and the population could
not be maintained without immigration. Large source populations stabilize
metapopulations, while large sinks can contribute to population decline over a large area
(Logan and Sweanor 2001).
Prior to Hornocker’s research and the classification of the cougar as a big game animal in
Idaho in 1972, most cougars occupied the less-accessible central Idaho wilderness.
Wilderness access for cougar hunting was limited to flying to backcountry airstrips,
staying in camps and traveling and hunting with hounds by horseback and on foot. More
accessible areas, those outside of wilderness, had roads that could be driven with a truck
or snowmobile in winter to look for tracks, where hounds could be released. Cougar
numbers increased in Idaho over the next 25 years as cougars recolonized much of the
state. Changes in distribution and numbers of cougars occurred in more accessible areas
where they had been heavily harvested prior to 1972 (Power 1985). Idaho Department of
Fish and Game Mountain Lion Management Plans have incorporated the role of
wilderness source populations in contributing dispersing cougars to areas with higher
harvest levels (Power 1985, Harris 1991, Rachael and Nadeau 2002), therefore allowing
high harvest levels to be maintained locally through immigration (Nadeau 2007). Annual
cougar harvest in Idaho increased from 1973 until 1997 and has declined and stabilized
since that time (Fig. 1). Wildlife agencies in other western states and provinces have
reported similar cougar harvest trends, despite varying hunting regulations, including
British Columbia (Austin 2005), Montana (DeSimone et al. 2005), Utah (McLaughlin
2003), and Wyoming (Wyoming Game and Fish Department 2006). Statewide harvest
trends and cougar depredation trends are likely correlated with changes in cougar
populations. In contrast, smaller-scale Data Analysis Unit (DAU) harvest trends may be
more influenced by local source and sink dynamics, differences in hunting regulations
Proceedings of the Ninth Mountain Lion Workshop
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