Current Research
My Master's Thesis Project will examine the effects of habitat fragmentation on cougars (Puma concolor).
Due to their position within the food web and functional roles, cougars (Puma concolor) are both apex predators and keystone species. Cougars structure their communities, in part, by reducing herbivore abundance which in turn reduces herbivory on primary producers (Ripple and Beschta 2008). This is an example of a tropic cascade, which Hairston et al. (1960) posited was responsible for the dynamic equilibrium that allows ecosystems to persist over very long periods of time. In some cases, the benefits of predators may be more indirect and difficult to ascertain unless the predator is removed. A study by Baiser et al (2008), in New Jersey, showed that in the absence of cougars, white-tailed deer populations increased dramatically. This increase was followed by changes to the forest understory structure, which, in turn, reduced the number of bird species present that had relied on the under-canopy. These examples demonstrate the profound effect that cougars have on their ecosystems, but this is not a one way street: habitat quality can have a tremendous effect on cougar populations as well.
Habitat fragmentation occurs when large patches of land become discontinuous, usually through anthropogenic disturbance. Many researchers have argued that as habitat fragmentation increases, the deleterious impacts on wildlife increase (Andren 1994). This may be due to increased edge effects (Harrison and Bruna 1999), in which habitat quality is decreased due to the increased areas of marginal quality between adjacent habitats. However, in a survey of primary literature, Debinski and Holt (2000) found that some species did not respond as expected to habitat fragmentation. Moreover, some have argued that there may be positive benefits from habitat fragmentation (Fahrig 2003). Clearly, the impact of habitat fragmentation is unknown. However, habitat fragmentation has been shown to limit gene flow between adjacent cougar populations (McRae et al. 1976). Given the ecological importance of cougars, it is clear that management and conservation agencies need reliable information about the impact of habitat fragmentation on cougars in order to design effective management plans.
Since 1972, California state law has classified cougars as a species of special concern and bans game hunting entirely. Citizens may only kill a cougar if the animal has threatened humans or domesticated animals and if they have been issued a depredation permit by the California Department of Fish and Game (DFG). The DFG reports that requests for depredation permits and reported kills have been steadily declining since 1995. This may be due to deceased willingness to shoot cougars or to decreasing numbers of cougars to warrant depredation permits. Surveys conducted in 1986 and 1992 by Smallwood (1994) indicated that cougar populations in northern California have declined 52%. Unfortunately, there are no population estimates for Butte County or the surrounding counties to determine if declines are occurring in this region. The current lack of knowledge concerning cougar populations may have a myriad of deleterious effects both on cougars themselves and on the ecosystems of which they are a part.
References
Andrén, H. (1994). Effects of Habitat Fragmentation on Birds and Mammals in Landscapes with
Different Proportions of Suitable Habitat: A Review. Oikos, 71(3), 355-366.
Baiser, B. Lockwood, J.L., La Puma, D. & Aronson, M.F.J. (2008). A perfect storm: two
ecosystem engineers interact to degrade deciduous forests of New Jersey. Invasion
Biology, 10(6) 785-795
Debinski, D. M., & Holt, R. D. (2000). A Survey and Overview of Habitat Fragmentation
Experiments. Conservation Biology, 14(2), 342-355.
California Mountain Lion Depredation Statistics. (2010, May 27). California Department of Fish
and Game. Retrieved October 1, 2012, from http://www.dfg.ca.gov/news/issues/lion/
depredation.html
Fahrig, L. (2002). Effect of Habitat Fragmentation on the Extinction Threshold: A Synthesis.
Ecological Applications, 12(2), 346-353.
Hairston, N. G., Smith, F. E., & Slobodkin, L. B. (1960). Community Structure, Population
Control, and Competition. American Naturalist, 94(879), 421-425.
M. G., & Negri, S. (Eds.), Cougar: Ecology and conservation. (3-16). Chicago: The
University of Chicago Press. McRae et al. 1976
Ripple, W. J., & Beschta, R. L. (2008). Trophic cascades involving cougar, mule deer, and black
oaks in Yosemite National Park. Biological Conservation, 141(5), 1249-1256.
Smallwood, K. (1994). Trends in California Mountain Lion Populations. The Southwestern
Naturalist, 39(1), 67-72.
Due to their position within the food web and functional roles, cougars (Puma concolor) are both apex predators and keystone species. Cougars structure their communities, in part, by reducing herbivore abundance which in turn reduces herbivory on primary producers (Ripple and Beschta 2008). This is an example of a tropic cascade, which Hairston et al. (1960) posited was responsible for the dynamic equilibrium that allows ecosystems to persist over very long periods of time. In some cases, the benefits of predators may be more indirect and difficult to ascertain unless the predator is removed. A study by Baiser et al (2008), in New Jersey, showed that in the absence of cougars, white-tailed deer populations increased dramatically. This increase was followed by changes to the forest understory structure, which, in turn, reduced the number of bird species present that had relied on the under-canopy. These examples demonstrate the profound effect that cougars have on their ecosystems, but this is not a one way street: habitat quality can have a tremendous effect on cougar populations as well.
Habitat fragmentation occurs when large patches of land become discontinuous, usually through anthropogenic disturbance. Many researchers have argued that as habitat fragmentation increases, the deleterious impacts on wildlife increase (Andren 1994). This may be due to increased edge effects (Harrison and Bruna 1999), in which habitat quality is decreased due to the increased areas of marginal quality between adjacent habitats. However, in a survey of primary literature, Debinski and Holt (2000) found that some species did not respond as expected to habitat fragmentation. Moreover, some have argued that there may be positive benefits from habitat fragmentation (Fahrig 2003). Clearly, the impact of habitat fragmentation is unknown. However, habitat fragmentation has been shown to limit gene flow between adjacent cougar populations (McRae et al. 1976). Given the ecological importance of cougars, it is clear that management and conservation agencies need reliable information about the impact of habitat fragmentation on cougars in order to design effective management plans.
Since 1972, California state law has classified cougars as a species of special concern and bans game hunting entirely. Citizens may only kill a cougar if the animal has threatened humans or domesticated animals and if they have been issued a depredation permit by the California Department of Fish and Game (DFG). The DFG reports that requests for depredation permits and reported kills have been steadily declining since 1995. This may be due to deceased willingness to shoot cougars or to decreasing numbers of cougars to warrant depredation permits. Surveys conducted in 1986 and 1992 by Smallwood (1994) indicated that cougar populations in northern California have declined 52%. Unfortunately, there are no population estimates for Butte County or the surrounding counties to determine if declines are occurring in this region. The current lack of knowledge concerning cougar populations may have a myriad of deleterious effects both on cougars themselves and on the ecosystems of which they are a part.
References
Andrén, H. (1994). Effects of Habitat Fragmentation on Birds and Mammals in Landscapes with
Different Proportions of Suitable Habitat: A Review. Oikos, 71(3), 355-366.
Baiser, B. Lockwood, J.L., La Puma, D. & Aronson, M.F.J. (2008). A perfect storm: two
ecosystem engineers interact to degrade deciduous forests of New Jersey. Invasion
Biology, 10(6) 785-795
Debinski, D. M., & Holt, R. D. (2000). A Survey and Overview of Habitat Fragmentation
Experiments. Conservation Biology, 14(2), 342-355.
California Mountain Lion Depredation Statistics. (2010, May 27). California Department of Fish
and Game. Retrieved October 1, 2012, from http://www.dfg.ca.gov/news/issues/lion/
depredation.html
Fahrig, L. (2002). Effect of Habitat Fragmentation on the Extinction Threshold: A Synthesis.
Ecological Applications, 12(2), 346-353.
Hairston, N. G., Smith, F. E., & Slobodkin, L. B. (1960). Community Structure, Population
Control, and Competition. American Naturalist, 94(879), 421-425.
M. G., & Negri, S. (Eds.), Cougar: Ecology and conservation. (3-16). Chicago: The
University of Chicago Press. McRae et al. 1976
Ripple, W. J., & Beschta, R. L. (2008). Trophic cascades involving cougar, mule deer, and black
oaks in Yosemite National Park. Biological Conservation, 141(5), 1249-1256.
Smallwood, K. (1994). Trends in California Mountain Lion Populations. The Southwestern
Naturalist, 39(1), 67-72.