Canada Lynx Habitat Model
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Draft Date:
March 2001

Species:
Canada lynx, Lynx canadensis

Use of Study Area Resources:
All life stages: the Canada lynx typically occurs in boreal and high altitude forests of the northern United States and Canada. It is a rare year-round resident of boreal forests of northern New Hampshire, and northern and western Maine.

Habitat Requirements:
McKelvey et al. (1999) summarized lynx habitat preferences in the Northeast, based on occurrence data.  They concluded there is a preference for terrain between 250 - 750 m in elevation, with lynx making limited use of terrain below 250 m. Occurrences were rare in dry forests and non-forests, and they avoid wetlands with cattails, oak, maple and hemlock. Habitats typically are "mixed forest-coniferous forest-high tundra vegetation" (88% of occurrences were in this cover, encompassing 29% of this region). On a finer scale lynx show a preference for red spruce-balsam fir/sugar maple-birch-beech forest; the addition of sugar maple-birch-beech forest and of red spruce-balsam fir forest included the habitat for 84% of occurrences in the northeast (McKelvey et al. 1999). Trapping records from the White Mountains of New Hampshire during the 1960's and the Adirondack mountains of New York indicated that lynx were taken from forests dominated by spruce-balsam fir and hardwoods, at elevations over 900 m, where the greatest snowfall occurred (Brocke 1982 in Aubry et al. 1999). However, it is important to recognize that trapping records are biased by trapper effort.

Legendre et al. (1978 in Mowat et al. 1999) showed that in northeast Quebec, lynx were most abundant in the boreal forests, and their distribution was associated with the distribution of snowshoe hare. In the southwestern Yukon Territory lynx avoided shrub habitat while foraging, and rarely used open habitats (Murray et al. 1994). Studies in Nova Scotia (Parker 1981, 1983) suggested that early successional forests (5-15 years) and advanced successional forests (16-30 years) are important for lynx, followed by open mature conifer and open black spruce bogs. Parker (1983 in ch 13) also found a decrease during the summer in the use of successional forest and an increase in use of mature conifer habitat. Koehler and Brittell (1990) speculated that woodlands of 420-640 trees/ha could provide adequate cover for travel habitat.

Microhabitat with a dense understory structure of woody debris appears to be a critical component for maternal dens, providing security and thermal cover for kittens (Aubry et al. 1999). Four maternal den sites in Washington state were found to be on north facing slopes (Koehler 1990). Appropriate cover may be provided by blowdowns in mature forest, root tangles, windthrown snags, or deadfalls (Kesterson 1988 in Aubrey 1999). Lynx have been shown to use mature forest stands with relatively open understory as travel habitat between foraging and denning sites (Koehler and Brittell 1990). Female lynx are believed to establish temporary dens throughout their home range once kittens are old enough to travel, but not yet capable of hunting (Bailey 1981).

Home range sizes for lynx are highly variable. Koehler and Aubry (1994) estimated lynx ranges to be 16 to 20 km². However, McKelvey et al. (1999) estimated that average male and female lynx home ranges were 150 and 75 km², respectively. Vashon (1999) reporting on radio collared lynx in Maine found a home range of about 47 km². Aubry et al. (1999), summarizing home ranges across North America, found minimum average home ranges were about 12 to 17 km², while maxima were over 200 km².

Foraging: Snowshoe or varying hare (Lepus americanus) are well known as the primary prey of lynx, but in times of hare scarcity red squirrels and other small mammals are important alternate prey, as well as grouse, ducks, small birds, ungulates and carrion (Parker 1983, Apps 1999). Lynx may capture prey by stalking in sparse cover, and by ambush in dense cover (Murray et al. 1995). Lynx may have a competitive advantage over coyotes and bobcats during winter foraging because of their greater ability to travel on the surface of snow. Murray et al. (1994) found an average February snow depth of about 60 cm in the Yukon, where competition was from coyotes. There coyotes selected foraging areas with harder snow crust and shallower depth (average about 30 to 50 cm).

Disturbance:  It is not clear that roads have direct effects on lynx habitat value. Home range data in the southern Canadian Rockies suggested that major roads may act as boundaries to spatial distribution (Apps 1999).  On the other hand, Aubry et al. (1999) concluded that lynx "readily cross highways and establish home ranges in proximity to roads ". Snow tracking surveys by Koehler (1990) showed that lynx traveled the edges of meadows, but only crossed where openings were less than 100 m wide. Large openings were avoided (Apps 1999). Trappers report that lynx show little fear of human scent, and may become bolder when prey is scarce (Mowat et al. 1999). Moderate levels of snowmobile traffic appear to be tolerated (Mowat et al. 1999).

Model:
Three sets of occurrence data were used to develop the habitat model. Because the spatial resolution of these data was coarse (typically to township level, or within several miles, at best) these points were only used to establish the distribution of lynx within the study area, within which habitat was further defined using vegetative cover and snowfall data. Occurrences represented sightings of animals, tracks, animals trapped or hunted, and data from museum specimens. Ron Joseph (U.S.F.W.S. Maine Field Office) researched and compiled data for Maine, to the township level. These include date, township, circumstances, and sometimes a landmark. McKelvey et al. (1999) assembled lynx data for the entire U.S., documented by source, date, precision of location, and reliability of source. Additional location information for Maine was obtained from the M.D.I.F.W. Ashland Office, which were documented only by date and observer. Duplicate entries among these sets were removed using date and location.

We used the occurrence information to inspect lynx distribution in relation to elevation and snowdepth.  For 91 occurrences in the study area, the average elevation was 365 m, with a standard deviation of is 164 m.  The minimum elevation was 51 m and maximum was 1109 m. The suggested elevation range (250 - 750 m, McKelvey et al. 1999) bracketed only 67 of these occurrences.  

Snow depth data was obtained from the Maine Geological Survey, Gray, Maine (Maine) and Barry Keim, New Hampshire State Climatologist (New Hampshire). The point data for average February snow depth since 1980 were interpolated; it was observed that an average depth of 11" or more corresponded with 89 of 91 lynx occurrences in that time frame.  The snow depth data explained occurrences more efficiently than did elevation, fitting more known occurrences within a smaller overall area.

Large contiguous forest stands within the study area experience natural events (insect infestations, severe weather events, fire) and/or forest management which may create a mosaic of successional stages suitable to meet foraging and denning needs of lynx. We lacked sufficient information on habitat requirements of lynx, and on localized forest conditions to map habitat suitability at the stand scale. We developed a landscape scale map based on cover type, snow depth and minimum home range size.  Habitat was mapped by selecting mixed, coniferous, and early successional upland forest within the range indicated by a snow depth of 11 inches, and which had a patch size of 15 sq km or more.

NWI Designations
(wetlands only)
Cover Types Cover Suitability
(0 - 1 scale)
Upland deciduous forest
Upland coniferous forest 1.0*
Upland mixed forest 1.0*
Grassland
Upland scrub/shrub 1.0*
Cultivated
Developed
Bare ground
PEM, L2EM Lake/pond, emergent vegetation
PFOcon Palustrine forest, conifer
PFOdec Palustrine forest, deciduous
PSSdec Palustrine scrub shrub, deciduous
PSScon Palustrine scrub shrub, conifer
PAB, L2AB Lake/pond, aquatic vegetation
L1UB, PUB Lake/pond, unconsolidated bottom
L2US Lake, unconsolidated shore
L2RS Lake, rocky shore
R1UB Riverine subtidal unconsolidated
Rper Riverine perennial
E1AB Estuarine subtidal vegetated
E1UB Estuarine subtidal unconsolidated bottom
E2AB Estuarine intertidal algae
E2EM Estuarine intertidal emergent
E2RS, R1RS Estuarine, tidal river rocky shore
E2SS Estuarine intertidal shrub
E2US Estuarine intertidal unconsolidated shore
M1AB Marine subtidal vegetated
M1UB Marine subtidal unconsolidated bottom
M2AB Marine intertidal algae
M2RS Marine intertidal rocky shore
M2US Marine intertidal unconsolidated shore
NOTES *only if part of a patch => 15 sq km

We mapped as habitat (scored 1.0) those areas having suitable vegetation types and extent, within the snow depth zone of 11" in February.

Model testing: Lynx occurrences since 1980 were buffered at 2.185 km (to create a 15 sq km "range" around each point), and overlain on the habitat. For 94 lynx occurrences, 91 "ranges" contained modeled habitat. John Organ (U.S.F.W.S. Northeast Regional Office) provided telemetry data indicating home ranges of five other lynx. All of the radio tracked ranges contained modeled habitat. In contrast, only 456 of 798 randomly generated "ranges" of the same area intersected habitat, indicating that the model based on snow depth and forest clusters significantly agrees with lynx distribution within the study area.

Sources:
Apps, C.D. 1999. Space-use, diet, demographics, and topographic associations of lynx in the southern Canadian Rocky Mountains: a study, pp 351-371, Chapter 12, in L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey and J.R. Squires (eds.). Ecology and Conservation of Lynx in the United States. University Press of Colorado and the USDA Rocky Mountain Research Station. Website: http://www.fs.fed.us/rm/pubs/rmrs_gtr30.html

Aubry, K.B., G.M. Koehler and J.R. Squires. 1999. Ecology of Canada lynx in southern boreal forests, pp 373-396, Chapter 13, in L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey and J.R. Squires (eds.). Ecology and Conservation of Lynx in the United States. University Press of Colorado and the USDA Rocky Mountain Research Station. Website: http://www.fs.fed.us/rm/pubs/rmrs_gtr30.html

Bailey, T.N. 1981. Factors of bobcat social organization, pp 984-1000 in Worldwide Furbearer Conference proceedings, J.A. Chapman and D. Pursley, eds., Frostburg, MD.

Brocke, R.H. 1982. Restoration of the lynx, Lynx canadensis, in Adirondack Park: a problem analysis and recommendations. Unpublished, Federal Aid Project E-1-3 and W-105-R. New York State Department of Environmental Conservation Study X11, Job 5.

Buskirk, S.W., L.F. Ruggiero, K.B. Aubry, D.E. Pearson, J.R. Squires and K.S. McKelvey. 1999. Comparative ecology of lynx in North America. pp 397-417, Chapter 14, in L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey and J.R. Squires (eds.), Ecology and Conservation of Lynx in the United States. University Press of Colorado and the USDA, Rocky Mountain Research Station. Website: http://www.fs.fed.us/rm/pubs/rmrs_gtr30.html

Kesterson, B.A. 1988. Home range and spatial organization in relation to population density and prey abundance. Unpublished M.S. Thesis, University of Alaska, Fairbanks, AK.

Koehler, G.M. 1990. Population and habitat characteristics of lynx and snowshoe hares in north central Washington. Can. J. Zool. 68:845-851.

Koehler, G.M. and J.D. Brittell. 1990. Managing spruce-fir habitat for lynx and snowshoe hares. Journal of Forestry 88:10-14.

Legendre, P., F. Long, R. Bergeron and J-M. Levasseur. 1978. Inventaire aerien de la faune dans le Moyen Nord quebecois. Can. J. Zool. 56:451-462.

McKelvey, K.S., K.B. Aubry and Y.K. Ortega. 1999. History and distribution of lynx in the contiguous United States pp 207-264 Chapter 8 in L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey and J.R. Squires (eds.), Ecology and Conservation of Lynx in the United States. University Press of Colorado and the USDA, Rocky Mountain Research Station. Website: http://www.fs.fed.us/rm/pubs/rmrs_gtr30.html

Mowat, G., K.G. Poole and M. O'Donoghue. 1999. Ecology of lynx in northern Canada and Alaska. pp 265-306 Chapter 9 in L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey and J.R. Squires (eds.), Ecology and Conservation of Lynx in the United States. University Press of Colorado and the USDA, Rocky Mountain Research Station. Website: http://www.fs.fed.us/rm/pubs/rmrs_gtr30.html

Murray, D.L., S. Boutin, M. O'Donoghue and V.O. Nams. 1995. Hunting behaviour of a sympatric felid and canid in relation to vegetative cover. Anim. Behav. 50:1203-1210.

Murray, D.L, S. Boutin and M. O'Donoghue. 1994. Winter habitat selection by lynx and coyotes in relation to snowshoe hare abundance. Can. J. Zool. 72:1444-1451.

Parker, G.R. 1981. Winter habitat use and hunting activities of lynx (Lynx canadensis) on Cape Breton Island, Nova Scotia, pp 221-248 in Worldwide Furbearer Conference proceedings, J.A. Chapman and D. Pursley (eds.), Frostburg, MD.

Parker, G. R., J.W. Maxwell and L.D. Morton. 1983. The ecology of the lynx (Lynx canadensis) on Cape Breton Island. Can. J. Zool. 61:770-786.

Vashon, J. 1999. Canada lynx research study, January-July 1999 field report. Manuscript submitted to MDIFW/USFWS.