Why Study Urban Carnivores?
Local researchers actively studying two carnivores in our study area: bobcats and mountain lions. These wild cats are mammalian carnivores that tend to exist in low density populations because they are solitary. They also have large territories, or home ranges. The result of their solitary nature and large home ranges means that there are very few animals in a given region when compared to more social animals with smaller ranges.
Mammalian carnivores existing in low-density populations are especially sensitive to habitat fragmentation1,2 that occurs as a result of urban development. Since there are already few individuals per region, habitat fragmentation can easily isolate populations such that there are not enough individuals to prevent inbreeding. Inbreeding has been observed to have genetic consequences in other wild cat populations such as the Florida panther and cheetah populations3,4. Further, the high trophic level, or high place on the food web, of carnivores leaves them vulnerable to bioaccumulation of toxins5. Carnivores can therefore be sensitive to multiple consequences associated with habitat fragmentation and urban development.
Predators play essential roles in ecosystems, for example, by reducing rodent populations that may act as reservoirs for zoonotics (diseases that can be transmitted from animals to humans). Some biologists6 have suggested that the loss of predators may be an important pathway by which anthropogenically driven environmental change drives emergence of infectious disease that can have significant impacts on human populations.
Within the Santa Monica Mountains, a number of mammalian carnivores are found including: long-tailed weasel, raccoons, badgers, skunks (striped and spotted), ring-tailed cats, bobcats, grey foxes, coyotes and mountain lions. Since 1996, the National Park Service has conducted research focusing primarily on three carnivores: coyotes, bobcats, and mountain lions. Research is ongoing on bobcats and mountain lions and they are the focus of this website.
This image is taken from the Cougar Network site (see 'Links' page for more information).
Mountain Lions vs. Bobcats
Bobcats are found through the Santa Monica Mountains National Recreation Area (see below for more info) while confirmed evidence of mountain lions has only been documented in the Santa Monica Mountains between Camarillo (Point Mugu State Park) east to just the western side of the I-405. More recently in 2012, one mountain lion, P22, was captured in Griffith Park, and genetic testing in the Robert Wayne Lab at UCLA revealed that he originated in the Santa Monica Mountains. Griffith Park is not a large enough area to support a mountain lion population, and it is unlikely that P22 will remain in Griffith Park longterm. He is the only mountain lion in the park, and so his biological need to find a mate will likely drive him to leave the park in search of female mountain lions. Mountain lions have also been observed and captured in the Simi Hills and north in the Santa Susanas. Many people who live near bobcat and mountain lion habitat have trouble distinguishing the two. This isn’t surprising considering how elusive these two wild cats are and that we rarely see them in the wild. However, as seen in the picture above, there are a number of physical differences between the two cats apparent to the eye.
- Body Size: Mountain lions are much larger than bobcats at 7-8 feet in length, while bobcats are only around 3 feet in length.
- Tail length: Mountain lions have long, black-tipped tails while bobcats have the short, bobbed tail for which they get their name.
- Coat Color and Pattern: Mountain lions are nearly unicolor, for which they get their species name Puma concolor. Bobcats have a tawny color marked by spots and a white, spotted belly.
For more information on identifying mountain lions, please visit the Cougar Network: www.cougarnet.org
Threats to Urban Carnivores
Housing development destroys suitable habitat for wildlife, reducing available habitat to sustain wildlife populations and fragmenting available habitat. Smaller habitat size can mean fewer individuals which can have genetic effects if inbreeding occurs. Domestic pets can be sources of disease for wildlife. Humans also use poisons around their homes which affects widlife.
Roads can be barriers to movement for animals as well as signficant sources of mortality. Sometimes when roads are significant barriers to movement, this can lead to genetic effects within populations separated by roadsUrbanization i s a primary threat to wild cats worldwide7. With urban development comes the loss of habitat and habitat fragmentation. Fragmentation of habitat by roads and other development may create barriers to movement and gene flow. With reduced gene flow between populations, genetic effects may occur, including the possiblity of inbreeding within populations. Roads are frequently a source of mortality for urban wildlife, including urban carnivores. The increasing urban interface may also be a source for human-introduced toxicants (ie., anticoagulant rat poisons) into surrounding wildlife habitat. Further, with humans frequently come domestic animals, which may also be reservoirs for diseases that can negatively impact wildlife populations.
There are many things we can do to alleviate the stress of human development on wildlife populations. A great thing to do is educate yourself about what animals live near you. Be aware of their presence and how we may affect them. We are neighbors to local wildlife. Obey leash laws in parks that require you to keep your dogs on leash. And be aware that domestic cats roaming free outside have detrimental effects on our native wildlife. They can be a source of disease for native wildlife and they kill our native birds, lizards, and small mammals. Finally, don't use rat poisons. There are no safe rat poisons that do not have potential secondary poisoning of native wildlife. There are many other things people can do such as support local land conservancy groups and research teams and promote broader public education.
References
1. Crooks, K.R. 2002. Relative sensitivities of mammalian carnivores to habitat fragmentation. Conservation Biology, 16: 488-502.
2. Noss, R.F. et. al. 1996. Conservation biology and carnivore conservation in the Rocky Mountains. Conservation Biology, 10: 949-963.
3. O’Brien, S.J., Roelke, M.E., Marker, L., Newman, A., Winkler, C.A., Meltzer, D., Colly, L., Evermann, J.F., Bush, M., and Wildt, D.E. 1985. Genetic basis for species vulnerability in the cheetah. Science, 227: 1428-1434.
4. Roelke, M.E., Martenson, J.S., and O’Brien, S.J. 1993. The consequences of demographic reduction and genetic depletion in the endangered Florida panther. Current Biology, 3: 340-350.
5. Funk, S.M., Fiorello, C.V., Cleaveland, S., and Gompper, M.E. 2001. The role of disease in carnivore ecology and conservation. In: Carnivore Conservation (Gittleman, J.L., Funk, S.m. Macdonald, D. and Wayne, R.K., eds.) Pp. 443-466. Cambridge University Press.
6. Ostfeld, R.S. and Holt, R.D. 2004. Are predators good for your health? Frontiers in Ecology and the Environment,2(1): 13-20.
7. Sunquist, M. E. and F. C. Sunquist. 2002. Wild Cats of the World. Chicago. (Univ. Chicago Press)