Eric Swenson and Dr. Keith A. Crandall, Zoology

The mountain lion, Puma concolor, is the last widespread species of top predator remaining in the United States (2). Despite this, P. concolor is the subject of annual hunts, except in Florida and South Dakota, where they are threatened, and California (4). The impact of hunting on these populations is not well understood, but sport hunting constitutes the highest source of mortality in Utah (5). Indications are that increased hunting activity over the past few years may be causing a decline in the P. concolor population in Utah (1). The impact of hunting practices on the genetic variation of mountain lion is unknown.

We used microsatellites of DNA markers to obtain information on the population structure of Felis concolor in Utah. The aims of my project were:
1. To collect multilocus genotypes for all 50 sampled animals.
2. To quantify genetic variation in Utah’s Mountain Lions, by estimating population genetic parameters such as allelic diversity and heterozygosity.
3. To estimate population subdivision and migration rates among sampled populations, and effective population size.
4. To determine whether individual animals can be identified by their multi-locus genotypes.
5. To determine the Sex of 13 unidentified individuals.

We have successfully genotyped 50 animals (from ten sampled management units in Utah) for nine microsatellite loci. Of the 50 samples genotyped, 13 were from animals of unknown sex. The sex of these individuals was successfully determined using a molecular sex determination protocol. Amplification of F. concolor DNA using microsatellites has shown that we can uniquely identify individuals, determine the sex of unknown samples, estimate genetic diversity, and infer population structure and gene flow. All individuals had unique multilocus genotypes.

Estimates of genetic diversity (q = 4Neμ) using maximum likelihood suggest that there is some variation in amounts of genetic diversity from population to population. The estimates ranged from a high of q = 0.7352 for the Beaver population to a low of q = 0.2050 in the Bookcliffs population. The average level of genetic diversity summed over all nine loci was q = 0.4687.

There was no evidence for subdivision among the sampled P. concolor populations (Rho = 0.456, Nem = 5.2, p = 0.021). However, it should be noted that pairwise comparisons between the Bookcliffs and Oquirrh Mountains, (p = 0.03) and Bookcliffs and Vernon (p = 0.01) were significant at the 0.05 level, suggesting low gene flow between these populations.

The identification of individual animals is extremely useful to both managers and those interested in behavioral ecology. The number of loci required to obtain unique multilocus genotypes for identifying individuals is dependent on the number of alleles at each locus and heterozygosity, as well as overall variation in the species. In this study all individuals were uniquely identified using the nine loci.

Our resulting estimate of inbreeding effective population size was 117 individuals. This is very low compared to the census size of 2000 – 3000 individuals. Clearly, past attempts at extirpation have resulted in a reduction in the effective number of individuals in the Utah cougar population, i.e. the population may have gone through a population bottleneck. Alternatively, current hunting practices may have an effect on lowering the overall genetic variation in the population by nonrandom sampling of animals. Moreover, this estimate is very near the suggested lower limit of inbreeding effective population size for short-term viable populations (effective population size of 50) and well below the suggested size for long-term viability (effective size of 500) (3). However, since no population structure was observed within Utah, sampling beyond the state borders would be required for a more accurate estimate of the population’s inbreeding effective population size. Of course, the estimate of 2000-3000 individuals simply represents individuals within the State of Utah, and not necessarily a functional population as well. Since these animals are capable of movement well beyond the Utah state borders, a better understanding of migration rates, patterns of dispersal, (and hence better management plan) will be achieved by sampling a much broader geographic region.

References

• Bates, J.W. and A. E. Henry. 1999. Utah Cougar Harvest, 1997-98. Utah Division of Wildlife Research publication.
• Diamond, J. 1993. Cougars and corridors. Nature 365:16-17.
• Franklin, I. R. 1980. Evolutionary change in small populations. Pages 135-150 in M. E. Soulé and B. A. Wilcox, editors. Conservation Biology: An Evolutionary-Ecological Perspective. Sinauer Associates. Sunderland, MA.
• Logan, K.A. and L. L. Sweanor. 2000. Puma. Pages 347-377 in S. Demarais and P. R. Krausman, editors. Ecology and management of large mammals in North America. Prentice-Hall Inc., New Jersey.
• Utah Division of Wildlife Resources 1999. Utah Cougar Management Plan Salt Lake City, Utah.