The End Of The Road? Woodland Caribou And Human Developments
The boreal forest, named after Boreas, the greek god of the north wind, stretches around the northern reaches of the globe. One inhabitant of this expansive ecosystem of spruce, fir, aspen and birch is the woodland caribou, Rangifer tarandus caribou. Closely related to its more familiar cousin, the barren-ground caribou, this secretive and ancient deer has largely escaped attention as human development has spread northwards into its boreal forest realm.
The range of woodland caribou has been greatly reduced since the European settlement of North America (Edmonds 1991). The combination of human settlement, industrial and agricultural encroachment, and overhunting has taken its toll throughout the USA and Canada along the southern boreal forest fringe, westwards to the Rocky Mountains (Bergerud 1974). Woodland caribou are currently considered endangered in the USA, where a remnant population clings to existence in the Selkirk mountains of Idaho.
Human encroachment into caribou habitat has many demographic and behavioural consequences, including direct mortality from vehicle collisions and poaching (Johnson 1985), changes in predator-prey relationships (Edmonds and Bloomfield 1984), energetic costs associated with disturbance (Murphy and Curatolo 1987), barrier effects (Curatolo and Murphy 1986), and displacement and avoidance (Nelleman and Cameron 1998). This review focuses on how human developments affect caribou habitat use and the role of linear features, like roads, as barriers to caribou movements.
Avoidance Effects
Direct habitat loss occurs when developments such as roads, wells and seismic lines intrude into woodland caribou habitat. However, these ‘footprints' may be insignificant relative to the functional habitat loss as a result of avoiding human developments. Caribou generally avoid roads with traffic, supporting similar findings for elk (see RIPorter 1:5).
Barren-ground caribou have been shown to avoid roads with regular traffic around the Prudhoe Bay complex in Alaska (Murphy and Curatolo 1987; Cameron et al. 1992), while Mercer et al. (1985) found that centers of caribou activity were "maximum distances" possible from roads in Newfoundland. They attributed this to a combination of hunting and disturbance.
Nelleman and Cameron (1998) demonstrated that caribou density in the Kuparuk Development Area in Alaska was inversely related to road density. Road densities of >0.6-0.9 km/km2 (approximately 1 mile/mile2) resulted in an 86% decline in caribou density and virtually excluded cow-calf pairs. The authors cautioned that exclusion from preferred areas could lead to increased competition for forage, increased risk of predation, and lower productivity. Others have argued that caribou displaced from critical areas, such as late-winter range, may be susceptible to increased predation (Geist 1978).
Woodland caribou avoid roads, wells and seismic lines* in Alberta (Dyer 1999). The degree of avoidance varies with the level of human activity around these developments, and with the season, since female caribou with calves are particularly sensitive to human disturbances. Avoidance distances generally range from 250 — 1000 m.
Other types of direct habitat loss and disturbance may displace caribou. Clearcutting in Ontario and Newfoundland displaced woodland caribou from cut areas (Darby and Duquette 1986; Chubbs et al. 1992), and caribou have abandoned areas frequented by snowmobiles (Simpson 1987).
Barrier Effects
Linear developments such as roads, seismic lines and pipeline right-of-ways are dominant anthropogenic features in the wild places of North America. In addition to the direct mortality associated with linear corridors, there is increasing concern that these features may act as barriers to the movement of woodland caribou, as they do for other mammals (see RIPorter 4:2). Fragmenting populations in this way can reduce local population sizes and cause local extinctions (Fahrig and Merriam 1994).
Most studies addressing barriers to caribou movements concern short-term responses of migratory barren-ground caribou to human structures, while some anecdotal accounts and descriptive studies have tried to assess the effects of human developments on caribou movements (see Bergerud et al. 1984 for a comprehensive review). Roads and railways have been implicated in causing reindeer to abandon traditional migration routes in Eurasia (Klein 1971), although Bergerud et al. (1984) challenged this assertion, arguing instead that overhunting caused populations to decline and abandon the routes.
Methods to examine the crossing success of small mammals are well defined and generally involve the capture and recapture of individuals on opposite sides of the obstacles (Oxley 1974). Studies with larger mammals have examined the importance of culverts, non-wildlife passages (Rodriguez et al. 1996), and specialized structures (Singer and Doherty 1985) to crossing success, but it has been harder to quantify results. Murphy and Curatolo (1987) demonstrated that study plots containing roads and pipelines were crossed less by caribou than were control plots in Alaska, but studies generally have failed to address the barrier effects of human developments on the larger landscape.
Recent advances in the use of Geographic Information Systems (GIS) and animal tracking with Global Positioning System (GPS) collars have enabled biologists to examine whether linear developments are barriers to caribou movements. One study from the boreal forests of Alberta indicates that caribou cross roads up to 6 times less than expected, based on road density (Dyer 1999). If roads do act as barriers to caribou movements, this may exacerbate functional habitat loss through avoidance and may further fragment endangered caribou populations in North America.
* A seismic line is generally 7-8 m wide, cut through forested areas for geophysical exploration. These persist for long periods and can provide access for hunters and ORVs.
Conclusion
The area affected by roads and other human development far exceeds the physical footprint associated with these developments. Studies with caribou demonstrate the sensitivity of large animals to roads, and the habitat alienation that occurs when corridors intrude on their habitat.
Additional seismic corridors should be minimized through cooperation between industrial companies and by using low-impact and heli-portable seismic operations. Disturbance can be mitigated by completely rolling back trees and debris onto seismic and pipeline right-of-ways, gating essential roads, and revegetating others. The large home range requirements of woodland caribou mean that protecting small areas from human development will do little to conserve them in North America. Instead, we must all tread lightly on the landscape and take a conservative approach to human development in caribou habitat.
References
Bergerud, A.T. 1974. Decline of caribou in North America following settlement. J. Wildl. Manage. 38:757-770.
Bergerud, A.T., R.D. Jakimchuk, and D.R. Carruthers. 1984. The Buffalo of the North: Caribou (Rangifer tarandus) and Human Developments. Arctic 37(1):7-22.
Cameron, R.D., D.J. Reed, J.R. Dau, and W.T. Smith. 1992. Redistribution of calving caribou in response to oil field development on the Arctic Slope of Alaska. Arctic 45:338-342.
Chubbs, T.E., L.B. Keith, S.P. Mahoney, and M.J. McGrath. 1992. Responses of woodland caribou (Rangifer tarandus caribou) to clearcutting in east-central Newfoundland. Can. J. Zool. 71:487-493.
Curatolo, J.A., and S.M. Murphy. 1986. The effects of pipelines, roads and traffic on the movement of caribou, Rangifer tarandus. Can. Field-Nat. 100:218-225.
Darby, W.R. and L.S. Duquette. 1986. Woodland caribou in Northern Ontario, Canada. Rangifer, Special Issue No. 1: 87-93.
Dyer, S.J. 1999. Movement and Distribution of woodland caribou (Rangifer tarandus caribou) in response to industrial development in northeastern Alberta. MSc. Thesis, Department of Biological Sciences, University of Alberta, Edmonton, AB. 109pp.
Edmonds, E.J. 1991. Status of woodland caribou in western North America. Rangifer 7:91-107.
Edmonds, E.J. and M. Bloomfield. 1984. A study of woodland caribou (Rangifer tarandus caribou) in west central Alberta, 1979-1983. Alberta Energy and Nat. Res. Fish & Wildl. Div. rep., Edmonton, AB. 203pp.
Fahrig, L. and G. Merriam. 1994. Conservation of fragmented populations. Conservation Biology 8:50-59.
Geist, V. 1978. Behaviour. in J.L. Schmidt, and D.L. Gilbert (eds). Big Game of North America: Ecology and Management. Stackpole Books. Harrisburg, PA. pp283-296.
Klein, D.R. 1971. Reaction of reindeer to obstructions and disturbances. Science 173:393-398.
Oxley, D.J., M.B. Fenton, and G.R. Carmody. 1974. The effects of roads on populations of small mammals. J. Appl. Ecol. 11:51-59.
Johnson, D.R. 1985. Man-caused deaths of mountain caribou, Rangifer tarandus, in southeastern British Columbia. Can. Field-Nat. 99(4): 542-544.
Mercer, E., S. Mahoney, K. Curnew and C. Finlay. 1985. Distribution and abundance of insular Newfoundland caribou and the effects of human activities. In Meredith, T.C. and A.M. Martell (eds), Proc. Second North Am. Caribou Workshop. McGill Subarctic Research Paper No.40, Montreal, PQ. Pp16-32.
Murphy, S.M., and J.A. Curatolo. 1987. Activity budgets and movement rates of caribou encountering pipelines, roads and traffic in northern Alaska. Can. J. Zool. 65:2483-2490.
Nelleman, C. and R.D. Cameron. 1998. Cumulative impacts of an evolving oil-field complex on the distribution of calving caribou. Can. J. Zool. 76: 1425-1430.
Rodriguez, A., G. Crema, and M. Delibes. 1996. Use of non-wildlife passages across a high speed railway by terrestrial vertebrates. J. Appl. Ecol. 33(6):1527-1540.
Singer, F.J. and Doherty, J.L. 1985. Managing mountain goats at a highway crossing. Wildl. Soc. Bull.13: 469-477.
Simpson, K. 1987. The effects of snowmobiling on winter range use by mountain caribou. B.C. Minist. Environ. Parks Wildl. Working Rep. No. 25 13pp.
The range of woodland caribou has been greatly reduced since the European settlement of North America (Edmonds 1991). The combination of human settlement, industrial and agricultural encroachment, and overhunting has taken its toll throughout the USA and Canada along the southern boreal forest fringe, westwards to the Rocky Mountains (Bergerud 1974). Woodland caribou are currently considered endangered in the USA, where a remnant population clings to existence in the Selkirk mountains of Idaho.
Human encroachment into caribou habitat has many demographic and behavioural consequences, including direct mortality from vehicle collisions and poaching (Johnson 1985), changes in predator-prey relationships (Edmonds and Bloomfield 1984), energetic costs associated with disturbance (Murphy and Curatolo 1987), barrier effects (Curatolo and Murphy 1986), and displacement and avoidance (Nelleman and Cameron 1998). This review focuses on how human developments affect caribou habitat use and the role of linear features, like roads, as barriers to caribou movements.
Avoidance Effects
Direct habitat loss occurs when developments such as roads, wells and seismic lines intrude into woodland caribou habitat. However, these ‘footprints' may be insignificant relative to the functional habitat loss as a result of avoiding human developments. Caribou generally avoid roads with traffic, supporting similar findings for elk (see RIPorter 1:5).
Barren-ground caribou have been shown to avoid roads with regular traffic around the Prudhoe Bay complex in Alaska (Murphy and Curatolo 1987; Cameron et al. 1992), while Mercer et al. (1985) found that centers of caribou activity were "maximum distances" possible from roads in Newfoundland. They attributed this to a combination of hunting and disturbance.
Nelleman and Cameron (1998) demonstrated that caribou density in the Kuparuk Development Area in Alaska was inversely related to road density. Road densities of >0.6-0.9 km/km2 (approximately 1 mile/mile2) resulted in an 86% decline in caribou density and virtually excluded cow-calf pairs. The authors cautioned that exclusion from preferred areas could lead to increased competition for forage, increased risk of predation, and lower productivity. Others have argued that caribou displaced from critical areas, such as late-winter range, may be susceptible to increased predation (Geist 1978).
Woodland caribou avoid roads, wells and seismic lines* in Alberta (Dyer 1999). The degree of avoidance varies with the level of human activity around these developments, and with the season, since female caribou with calves are particularly sensitive to human disturbances. Avoidance distances generally range from 250 — 1000 m.
Other types of direct habitat loss and disturbance may displace caribou. Clearcutting in Ontario and Newfoundland displaced woodland caribou from cut areas (Darby and Duquette 1986; Chubbs et al. 1992), and caribou have abandoned areas frequented by snowmobiles (Simpson 1987).
Barrier Effects
Linear developments such as roads, seismic lines and pipeline right-of-ways are dominant anthropogenic features in the wild places of North America. In addition to the direct mortality associated with linear corridors, there is increasing concern that these features may act as barriers to the movement of woodland caribou, as they do for other mammals (see RIPorter 4:2). Fragmenting populations in this way can reduce local population sizes and cause local extinctions (Fahrig and Merriam 1994).
Most studies addressing barriers to caribou movements concern short-term responses of migratory barren-ground caribou to human structures, while some anecdotal accounts and descriptive studies have tried to assess the effects of human developments on caribou movements (see Bergerud et al. 1984 for a comprehensive review). Roads and railways have been implicated in causing reindeer to abandon traditional migration routes in Eurasia (Klein 1971), although Bergerud et al. (1984) challenged this assertion, arguing instead that overhunting caused populations to decline and abandon the routes.
Methods to examine the crossing success of small mammals are well defined and generally involve the capture and recapture of individuals on opposite sides of the obstacles (Oxley 1974). Studies with larger mammals have examined the importance of culverts, non-wildlife passages (Rodriguez et al. 1996), and specialized structures (Singer and Doherty 1985) to crossing success, but it has been harder to quantify results. Murphy and Curatolo (1987) demonstrated that study plots containing roads and pipelines were crossed less by caribou than were control plots in Alaska, but studies generally have failed to address the barrier effects of human developments on the larger landscape.
Recent advances in the use of Geographic Information Systems (GIS) and animal tracking with Global Positioning System (GPS) collars have enabled biologists to examine whether linear developments are barriers to caribou movements. One study from the boreal forests of Alberta indicates that caribou cross roads up to 6 times less than expected, based on road density (Dyer 1999). If roads do act as barriers to caribou movements, this may exacerbate functional habitat loss through avoidance and may further fragment endangered caribou populations in North America.
* A seismic line is generally 7-8 m wide, cut through forested areas for geophysical exploration. These persist for long periods and can provide access for hunters and ORVs.
Conclusion
The area affected by roads and other human development far exceeds the physical footprint associated with these developments. Studies with caribou demonstrate the sensitivity of large animals to roads, and the habitat alienation that occurs when corridors intrude on their habitat.
Additional seismic corridors should be minimized through cooperation between industrial companies and by using low-impact and heli-portable seismic operations. Disturbance can be mitigated by completely rolling back trees and debris onto seismic and pipeline right-of-ways, gating essential roads, and revegetating others. The large home range requirements of woodland caribou mean that protecting small areas from human development will do little to conserve them in North America. Instead, we must all tread lightly on the landscape and take a conservative approach to human development in caribou habitat.
References
Bergerud, A.T. 1974. Decline of caribou in North America following settlement. J. Wildl. Manage. 38:757-770.
Bergerud, A.T., R.D. Jakimchuk, and D.R. Carruthers. 1984. The Buffalo of the North: Caribou (Rangifer tarandus) and Human Developments. Arctic 37(1):7-22.
Cameron, R.D., D.J. Reed, J.R. Dau, and W.T. Smith. 1992. Redistribution of calving caribou in response to oil field development on the Arctic Slope of Alaska. Arctic 45:338-342.
Chubbs, T.E., L.B. Keith, S.P. Mahoney, and M.J. McGrath. 1992. Responses of woodland caribou (Rangifer tarandus caribou) to clearcutting in east-central Newfoundland. Can. J. Zool. 71:487-493.
Curatolo, J.A., and S.M. Murphy. 1986. The effects of pipelines, roads and traffic on the movement of caribou, Rangifer tarandus. Can. Field-Nat. 100:218-225.
Darby, W.R. and L.S. Duquette. 1986. Woodland caribou in Northern Ontario, Canada. Rangifer, Special Issue No. 1: 87-93.
Dyer, S.J. 1999. Movement and Distribution of woodland caribou (Rangifer tarandus caribou) in response to industrial development in northeastern Alberta. MSc. Thesis, Department of Biological Sciences, University of Alberta, Edmonton, AB. 109pp.
Edmonds, E.J. 1991. Status of woodland caribou in western North America. Rangifer 7:91-107.
Edmonds, E.J. and M. Bloomfield. 1984. A study of woodland caribou (Rangifer tarandus caribou) in west central Alberta, 1979-1983. Alberta Energy and Nat. Res. Fish & Wildl. Div. rep., Edmonton, AB. 203pp.
Fahrig, L. and G. Merriam. 1994. Conservation of fragmented populations. Conservation Biology 8:50-59.
Geist, V. 1978. Behaviour. in J.L. Schmidt, and D.L. Gilbert (eds). Big Game of North America: Ecology and Management. Stackpole Books. Harrisburg, PA. pp283-296.
Klein, D.R. 1971. Reaction of reindeer to obstructions and disturbances. Science 173:393-398.
Oxley, D.J., M.B. Fenton, and G.R. Carmody. 1974. The effects of roads on populations of small mammals. J. Appl. Ecol. 11:51-59.
Johnson, D.R. 1985. Man-caused deaths of mountain caribou, Rangifer tarandus, in southeastern British Columbia. Can. Field-Nat. 99(4): 542-544.
Mercer, E., S. Mahoney, K. Curnew and C. Finlay. 1985. Distribution and abundance of insular Newfoundland caribou and the effects of human activities. In Meredith, T.C. and A.M. Martell (eds), Proc. Second North Am. Caribou Workshop. McGill Subarctic Research Paper No.40, Montreal, PQ. Pp16-32.
Murphy, S.M., and J.A. Curatolo. 1987. Activity budgets and movement rates of caribou encountering pipelines, roads and traffic in northern Alaska. Can. J. Zool. 65:2483-2490.
Nelleman, C. and R.D. Cameron. 1998. Cumulative impacts of an evolving oil-field complex on the distribution of calving caribou. Can. J. Zool. 76: 1425-1430.
Rodriguez, A., G. Crema, and M. Delibes. 1996. Use of non-wildlife passages across a high speed railway by terrestrial vertebrates. J. Appl. Ecol. 33(6):1527-1540.
Singer, F.J. and Doherty, J.L. 1985. Managing mountain goats at a highway crossing. Wildl. Soc. Bull.13: 469-477.
Simpson, K. 1987. The effects of snowmobiling on winter range use by mountain caribou. B.C. Minist. Environ. Parks Wildl. Working Rep. No. 25 13pp.