Outside the Florida Everglades, cougars haven’t lived east of the Rockies in over 100 years. But, a new study finds there’s a strong likelihood that states like Illinois, Missouri and Wisconsin could become home to healthy populations of the large carnivores in the next few years.
Photos: Johanna Turner, unless otherwise noted.
Across America, ungulate populations have rebounded from near-extinction levels seen at the turn of the 19th century. In the case of deer and elk, this is due to successful conservation efforts funded by sport hunting. But while prey species are at an historic high, populations of predators have not yet matched them. This has created significant gaps for an apex predator in local eco-systems. And nature is trying to fill them. Out west, wolves are returning. In the northeast, coyote/wolf hybrids now run wild in New York City and Washington DC. In the mid-west, that new apex predator might just be the mountain lion. This is a great time to be a predator in America.
Conducted by researchers at the University of Minnesota and Southern Illinois University Carbondale, this is the first large-scale population viability study conducted on the big cats. It looks at data on cougar demographics and sightings from the last 40 years, then combines it with geographic information to determine likely areas that could support permanent populations.
Photo: Dennis Martin
“We didn’t just look at where they are now, but where they could go,” explains Michelle LaRue, a researcher who authored the study. “These are predictive models, but we feel that our study could be an important tool for conservation of this species and education about a large carnivore that can sometimes incite fear.”
Call them cougars, mountain lions or pumas; the big cats were once one of the most widespread predators on earth, with populations spread from the Atlantic to Pacific oceans, as far north as British Columbia and as far south as southern Chile. Habitat loss, market hunting and human pressure had an almost immediate impact on the species as Europeans settled the continent. They’ve been limited to a small patch of southern Florida and the western United States for over 100 years.
“The reason cougars used to exist across the country and now they don’t is because of people,” explains co-author Clayton k. Nielsen. “Now that this large carnivore is expected to come back into new areas, we need have a clear plan for education and conservation.”
Confirmed cougar sightings east of their established range, by year.
But, over the last two decades, sightings outside of that range have been on the rise. While these mostly come from individuals roaming far outside their home ranges, this does indicate a potential for populations forming in new areas.
Like we’ve seen with wolves, first re-introduced to the Rockies and then spreading first west, and now as far south as California, certain geographic areas have a certain “holding capacity” for large predators. Once exceeded, “subadults” need to “disperse,” finding new places where they can set up shop.
And also like wolves, cougars are capable of dispersing over incredibly long distances. The study describes a male who dispersed over 2,500km eastwards from the Black Hills of South Dakota before being struck by a car in Connecticut. A female dispersed from Utah managed 1,300km. Distances of 400 to 1000km are common.
Study area for modeling demographic matrix for cougars, and confirmed locations of585 cougars in midwestern North America during 1990-2008.
“Based on confirmed locations and the emergence of new breeding populations in the Midwest over 18 years, cougars are recolonizing the region via stepping stone dispersal,” says the study.
Females are particularly important. Not only do they disperse less frequently and less far than males, but their presence is obviously central to the viability of a breeding population. The study models population viability only on female presence, ruling out erroneous data points created by sightings of far-ranging male loners.
The eight most likely sites to see cougar re-population in the next 25 years.
To identify potential areas for cougar habitation, the study needed to find viable dispersal corridors leading to large enough areas of habitat for breeding females. “We created an expert opinion survey that included five habitat variables: cover type, slope, human density, distance to water, and distance to roads, and sent our survey to 29 cougar or wildlife biologists from the study region,” explains the study.
This was put into a analytical hierarchy model and applied to patches of potential habitat of 64 square kilometers or larger. Dispersal rates were then calculated based on reproduction rates and their ability to produce females. Combining the two data sets resulted in viable areas east of current cougar ranges likely to see the cats move in during the next 25 years.
Photo: Jim Tredeau
This data was controlled for sport hunting of the species; no substantial difference was found between the model controlling for cougar harvests and the one without.
We found 9.6% of the study region was suitable habitat, comprised of 136 habitat patches ≥64 km2. Approximately 35% of patches were located east of established cougar populations. Total patch area available in the Midwest was 120,960 km2 and mean patch size was 606 ± 96 km2. Large patches in Texas, New Mexico, Minnesota, and Missouri accounted for >50% of total patch area. We found the mean dispersal distance of female cougars to be 112 km.
Can a largely human-altered landscape support the large predators?
The Midwest…contains variably-sized patches separated by poor habitat (in this case, row-crop fields, prairies, and pastures; though we recognize that row-crops represent suitable dispersal habitat for short periods during the year when they may provide cover and prey), and so we further suggest that a metapopulation of cougars across large expanses may emerge in the Midwest. We found that regardless of harvest scenario, female cougars are likely to recolonize large patches of habitat in midwestern North America within 25 years, with seven of eight large patches occupied in the harvest scenario. Recolonization was dependent on dispersal rates and distances, and not on variation in demographic rates; this suggests that despite harvests in western populations, female cougars are likely to disperse far enough to encounter large habitat patches in the Midwest such that these patches are likely to be recolonized. Even patches as far east as Minnesota and Wisconsin were predicted to contain at least one female cougar during this time.
What’s this all mean?
We have now provided the information necessary for states and federal agencies to plan for ecosystem-based management that recognizes the potential for addressing competition between cougars and existing large predators and societal attitudes toward this recolonizing predator. Given large habitat patches in the Midwest are likely to have cougars in the future this will undoubtedly pose considerable challenges to wildlife managers.
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