Carnivores and Roads: Driving Away Our Wild Cats
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Despite a general lack of research on road-carnivore interactions (Ruediger 1996), enough studies have been done to get a rudimentary idea of the impact roads have on some major North American predators (Noss et al. 1996; Gibeau and Heuer 1996). This review highlights some of the effects of roads on members of the Felidae familyincluding mountain lion (Felis concolor), lynx (Lynx canadensis) and bobcat (Lynx rufus). Keep in mind that this scientific review is only the tip of a very large informational iceberg.
Roads and associated disturbances have noticeable and well-recorded impacts on felids (Van Dyke et al. 1986a; Beldon and Hagedorn 1993; Beier 1995; Lovallo and Anderson 1996). Most of these impacts are decidedly negative and, unless we place a more concentrated effort on understanding and mitigating these effects, Americans can expect a decline not only in rare cat populations, but in all rare carnivore populations (Ruediger 1996; Noss et al. 1996).
Roads affect felids in the following five ways (adapted from Ruediger 1996):
1) Direct MortalityMountain lion, lynx and bobcat populations are just as adversely impacted by road mortality as other carnivore populations (Brocke et al. 1992; Gibeau and Heuer 1996). Since they have relatively large home ranges, low population densities and low reproductive rates, felids are not able to compensate, biologically, for additional significant sources of mortality (Ruediger 1996). In the 1996 final EIS for mountain lion management in Montana, the State's Department of Fish, Wildlife & Parks documented forty-three lion fatalities due to vehicle/train collision from 1988 to 1994second only to hunting as the primary cause of adult mortality.
Along similar lines, fatalities due to vehicle collision have also been documented in studies (Mech 1980; Maehr et al. 1991; Beier 1995; Gibeau and Heuer 1996).
2) Indirect MortalityNoss et al. (1996) identified legal and illegal hunting/trapping of carnivores as a major threat posed by roads. More roads allow for more public access to wildlands. Using open road densities to measure road access, researchers found that as road densities increase, carnivore habitat suitability decreasespartially due to hunting and trapping (McLellan and Shackleton 1988; Mech et al. 1988). Felid-specific studies have supported this statement (Van Dyke et al. 1986b; Lovallo and Anderson 1996) and revealed that hunting/trapping plays a significant role in creating rare populations of mountain lion (Beldon and Hagedorn 1993), bobcat (Lovallo 1993) and lynx (Mech 1980).
3) Displacement and AvoidanceStudies show that mountain lions and bobcats usually avoid crossing primary and secondary hard-surfaced highways and improved dirt roads, in favor of unimproved dirt roads and trails (Van Dyke et al 1986a; Beldon and Hagedorn 1993; Lovallo and Anderson 1996). Analysis of lion home ranges has found a similar avoidance of roads: "...85% of 26 [cougar] home ranges included unimproved dirt roads, 58% contained improved dirt roads, and 23% contained paved roads..." (Van Dyke et al 1986a:106).
4) Habitat Fragmentation/Associated DevelopmentsRoadways, powerline corridors and other linear networks fragment habitats used by a variety of species (Noss and Cooperrider 1994). Research on mountain lions and the issue of fragmentation found: 1) near human presence, lions shift their activity patterns (Van Dyke et al 1986b); 2) lions move through areas containing low density housing (1 unit/16 ha) but show an aversion to intermediate and high density areas (Beier 1995); and 3) roads and associated human developments effectively fragment local population of lions - leading Beier to say, "for cougars, any connection between two isolated patches is better than no connection." (Beier 1995).
5) Direct Habitat Loss - Very few studies attempt to quantify direct habitat losses from roads, nevertheless, some sources can be found in A. Andrewsí "Fragmentation of habitat by roads and utility corridors: A review," in Australian Zoologist 26(3&4):130-141. In addition, Ruediger (1996) found, "a 300 ft cleared right-of-way consumes 5.7% of each section it crosses."
Solutions
Research indicates that road mitigation techniques, including underpasses and overpasses (Foster and Humphrey 1995; Gibeau and Heuer 1996), and the habitat corridor model (Beier 1995), can help protect North American felids from some road impacts. Nevertheless, road construction and improvement projects should be deemed unavoidable before mitigation techniques are even considered (Noss and Cooperrider 1994). Though felids use corridors and passageways across roads, (Beier 1995, Foster and Humphrey 1995; Gibeau and Heuer 1996) studies indicate that passageway construction is not enough. A few important elements that contribute to the use of passageways by felids include: the establishment of crossing zones in locations along stream scour beds, ridgelines and dirt roads/human trails (Beier 1995), the creation of underpasses with an unobstructed view of the other side (Foster and Humphrey 1995), fence construction along highways in order to "channel" species into crossing zones (Gibeau and Heuer 1996) and the removal of artificial lighting (Beier 1995).
For readers who wish to explore this topic further, the following articles are especially relevant: Beier 1995, Lovallo and Anderson 1996, the Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996, and Noss et al. 1996.
Bibliography
Beier, P. 1995. Dispersal of juvenile cougars in fragmented habitat. Journal of Wildlife Management 59(2):228-237.
Beldon, B.C. and B.W. Hagedorn. 1993. Feasibility of translocating panthers into northern Florida. Journal of Wildlife Management 57:388-397.
Brocke, R.H., K.A. Gustafson, and L.B. Fox. 1992. Restoration of large predators: potential and problems. In: Deck, D.J., M.E. Krasny, G.R. Goff, C.R. Smith, and D.W. Gross, eds. Challenges in the Conservation of Biological Resources, A Practitioner's Guide. Westcliff Press: Boulder, Colorado.
Foster, M.L. and S.R. Humphrey. 1995. Use of highway underpasses by Florida panthers and other wildlife. Wildlife Society Bulletin 23(1):95-100.
Gibeau, M.L. and K. Heuer. 1996. Effects of transportation corridors on large carnivores in the Bow River Valley, Alberta. Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996. U.S. Department of Transportation. Federal Highway Administration. FHWA-PD-96-041, Washington, DC.
Lovallo, M.J. 1993. Bobcat Behavior and Home Range Use in Northwestern Wisconsin: In Reference to Censusing Populations. M.S. Thesis., University of Wisconsin-Stevens Point. 126 pp.
Lovallo, M.J. and E.M. Anderson. 1996. Bobcat movements and home ranges relative to roads in Wisconsin. Wildlife Society Bulletin 24(1):71-76.
Maehr, D.S., E.D. Land, and M.E. Roelke. 1991. Mortality patterns of panthers in southwest Florida. Proceedings of the Annual Conference of Southeastern Fish and Wildlife Agencies 45:201-207.
McLellan and Shackleton, 1988, Journal of Applied Ecology 25:451-460.
Mech, L.D. 1980. Age, sex, reproduction, and spatial organization of lynxes colonizing northeastern Minnesota. Journal of Mammalogy 61(2):261-267.
Mech et al., 1988, Wildlife Society Bulletin 16:85-87.
Noss, R.F. and A.Y. Cooperrider. 1994. Saving Nature's Legacy. Island Press: Washington, DC. 416 pp.
Noss, R.F., H.B. Quigley, M.G. Hornocker, T. Merrill, and P.C. Paquet. 1996. Conservation biology and carnivore conservation in the Rocky Mountains. Conservation Biology 10(4):949-963.
Ruediger, B. 1996. The relationship between rare carnivores and highways. Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996. U.S. Department of Transportation. Federal Highway Administration. FHWA-PD-96-041, Washington, DC.
Van Dyke, F.G., R.H. Brocke, and H.G. Shaw. 1986a. Use of road track counts as indices of mountain lion presence. Journal of Wildlife Management 50(1):102-109.
Van Dyke, F.G., R.H. Brocke, H.G. Shaw, B.B. Ackerman, T.P. Hemker, and F.G. Lindzey. 1986b. Reactions of mountain lions to logging and human activity. Journal of Wildlife Management 50(1):95-102.
Willis Lambertson is a graduate student in geography at the University of Montana.
Roads and associated disturbances have noticeable and well-recorded impacts on felids (Van Dyke et al. 1986a; Beldon and Hagedorn 1993; Beier 1995; Lovallo and Anderson 1996). Most of these impacts are decidedly negative and, unless we place a more concentrated effort on understanding and mitigating these effects, Americans can expect a decline not only in rare cat populations, but in all rare carnivore populations (Ruediger 1996; Noss et al. 1996).
Roads affect felids in the following five ways (adapted from Ruediger 1996):
1) Direct MortalityMountain lion, lynx and bobcat populations are just as adversely impacted by road mortality as other carnivore populations (Brocke et al. 1992; Gibeau and Heuer 1996). Since they have relatively large home ranges, low population densities and low reproductive rates, felids are not able to compensate, biologically, for additional significant sources of mortality (Ruediger 1996). In the 1996 final EIS for mountain lion management in Montana, the State's Department of Fish, Wildlife & Parks documented forty-three lion fatalities due to vehicle/train collision from 1988 to 1994second only to hunting as the primary cause of adult mortality.
Along similar lines, fatalities due to vehicle collision have also been documented in studies (Mech 1980; Maehr et al. 1991; Beier 1995; Gibeau and Heuer 1996).
2) Indirect MortalityNoss et al. (1996) identified legal and illegal hunting/trapping of carnivores as a major threat posed by roads. More roads allow for more public access to wildlands. Using open road densities to measure road access, researchers found that as road densities increase, carnivore habitat suitability decreasespartially due to hunting and trapping (McLellan and Shackleton 1988; Mech et al. 1988). Felid-specific studies have supported this statement (Van Dyke et al. 1986b; Lovallo and Anderson 1996) and revealed that hunting/trapping plays a significant role in creating rare populations of mountain lion (Beldon and Hagedorn 1993), bobcat (Lovallo 1993) and lynx (Mech 1980).
3) Displacement and AvoidanceStudies show that mountain lions and bobcats usually avoid crossing primary and secondary hard-surfaced highways and improved dirt roads, in favor of unimproved dirt roads and trails (Van Dyke et al 1986a; Beldon and Hagedorn 1993; Lovallo and Anderson 1996). Analysis of lion home ranges has found a similar avoidance of roads: "...85% of 26 [cougar] home ranges included unimproved dirt roads, 58% contained improved dirt roads, and 23% contained paved roads..." (Van Dyke et al 1986a:106).
4) Habitat Fragmentation/Associated DevelopmentsRoadways, powerline corridors and other linear networks fragment habitats used by a variety of species (Noss and Cooperrider 1994). Research on mountain lions and the issue of fragmentation found: 1) near human presence, lions shift their activity patterns (Van Dyke et al 1986b); 2) lions move through areas containing low density housing (1 unit/16 ha) but show an aversion to intermediate and high density areas (Beier 1995); and 3) roads and associated human developments effectively fragment local population of lions - leading Beier to say, "for cougars, any connection between two isolated patches is better than no connection." (Beier 1995).
5) Direct Habitat Loss - Very few studies attempt to quantify direct habitat losses from roads, nevertheless, some sources can be found in A. Andrewsí "Fragmentation of habitat by roads and utility corridors: A review," in Australian Zoologist 26(3&4):130-141. In addition, Ruediger (1996) found, "a 300 ft cleared right-of-way consumes 5.7% of each section it crosses."
Solutions
Research indicates that road mitigation techniques, including underpasses and overpasses (Foster and Humphrey 1995; Gibeau and Heuer 1996), and the habitat corridor model (Beier 1995), can help protect North American felids from some road impacts. Nevertheless, road construction and improvement projects should be deemed unavoidable before mitigation techniques are even considered (Noss and Cooperrider 1994). Though felids use corridors and passageways across roads, (Beier 1995, Foster and Humphrey 1995; Gibeau and Heuer 1996) studies indicate that passageway construction is not enough. A few important elements that contribute to the use of passageways by felids include: the establishment of crossing zones in locations along stream scour beds, ridgelines and dirt roads/human trails (Beier 1995), the creation of underpasses with an unobstructed view of the other side (Foster and Humphrey 1995), fence construction along highways in order to "channel" species into crossing zones (Gibeau and Heuer 1996) and the removal of artificial lighting (Beier 1995).
For readers who wish to explore this topic further, the following articles are especially relevant: Beier 1995, Lovallo and Anderson 1996, the Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996, and Noss et al. 1996.
Bibliography
Beier, P. 1995. Dispersal of juvenile cougars in fragmented habitat. Journal of Wildlife Management 59(2):228-237.
Beldon, B.C. and B.W. Hagedorn. 1993. Feasibility of translocating panthers into northern Florida. Journal of Wildlife Management 57:388-397.
Brocke, R.H., K.A. Gustafson, and L.B. Fox. 1992. Restoration of large predators: potential and problems. In: Deck, D.J., M.E. Krasny, G.R. Goff, C.R. Smith, and D.W. Gross, eds. Challenges in the Conservation of Biological Resources, A Practitioner's Guide. Westcliff Press: Boulder, Colorado.
Foster, M.L. and S.R. Humphrey. 1995. Use of highway underpasses by Florida panthers and other wildlife. Wildlife Society Bulletin 23(1):95-100.
Gibeau, M.L. and K. Heuer. 1996. Effects of transportation corridors on large carnivores in the Bow River Valley, Alberta. Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996. U.S. Department of Transportation. Federal Highway Administration. FHWA-PD-96-041, Washington, DC.
Lovallo, M.J. 1993. Bobcat Behavior and Home Range Use in Northwestern Wisconsin: In Reference to Censusing Populations. M.S. Thesis., University of Wisconsin-Stevens Point. 126 pp.
Lovallo, M.J. and E.M. Anderson. 1996. Bobcat movements and home ranges relative to roads in Wisconsin. Wildlife Society Bulletin 24(1):71-76.
Maehr, D.S., E.D. Land, and M.E. Roelke. 1991. Mortality patterns of panthers in southwest Florida. Proceedings of the Annual Conference of Southeastern Fish and Wildlife Agencies 45:201-207.
McLellan and Shackleton, 1988, Journal of Applied Ecology 25:451-460.
Mech, L.D. 1980. Age, sex, reproduction, and spatial organization of lynxes colonizing northeastern Minnesota. Journal of Mammalogy 61(2):261-267.
Mech et al., 1988, Wildlife Society Bulletin 16:85-87.
Noss, R.F. and A.Y. Cooperrider. 1994. Saving Nature's Legacy. Island Press: Washington, DC. 416 pp.
Noss, R.F., H.B. Quigley, M.G. Hornocker, T. Merrill, and P.C. Paquet. 1996. Conservation biology and carnivore conservation in the Rocky Mountains. Conservation Biology 10(4):949-963.
Ruediger, B. 1996. The relationship between rare carnivores and highways. Proceedings of the Florida Department of Transportation/Federal Highway Administration Transportation-related Wildlife Mortality Seminar, April 30-May 2, 1996. U.S. Department of Transportation. Federal Highway Administration. FHWA-PD-96-041, Washington, DC.
Van Dyke, F.G., R.H. Brocke, and H.G. Shaw. 1986a. Use of road track counts as indices of mountain lion presence. Journal of Wildlife Management 50(1):102-109.
Van Dyke, F.G., R.H. Brocke, H.G. Shaw, B.B. Ackerman, T.P. Hemker, and F.G. Lindzey. 1986b. Reactions of mountain lions to logging and human activity. Journal of Wildlife Management 50(1):95-102.
Willis Lambertson is a graduate student in geography at the University of Montana.