Download SPECIES ACCOUNT – SNOWSHOE HARE (m

SPECIES ACCOUNT – SNOWSHOE HARE (m-leam)
General
The snowshoe hare (Lepus americanus; LEAM) is a medium-sized mammal that lives in young forests with dense cover
(either shrub or regenerating conifers) 1-3 m above the ground. Hares are important prey species to many predators
including the fisher, marten, lynx and Northern Goshawk, and hare habitat quality can be an indirect assessment of
predator habitat quality.
Snowshoe hares are crepuscular mammals who remain active all winter. Their activity is governed by light. They are
more active on cloudy winter afternoons than on sunny days and are very active during moonlit nights. Wind and light
are a main deterrent to widespread foraging. When not foraging, snowshoe hares will often seek shelter under a bush,
stump or log during the day. These animals have acute hearing and vibration sensing. When threatened, young hares
usually freeze to escape detection. As they mature, they rely more on a flight response to evade predators. They are
also known to occasionally swim across rivers and small lakes when pursued by predators. Snowshoe hares are an
important link in food chain. Their chief predators are Great Horned, Great Grey, and Barred owls, lynx, bobcat, red
fox, coyote, wolf, mink, fisher and marten (Banfield 1987; Bateman 1986).
Snowshoe hare populations peak every 9-10 years on average. Although disease and predation are often the immediate
cause of death, impact seems to be greatly influenced by both weather and nutritional stresses. Pease et al. (1979)
found that variations in nutrient content of available browse species were not sufficient to cause population cycles.
They believe that malnourishment, due to reduced availability of food in combination with low winter temperatures,
causes large numbers of hares to die.
Juveniles in Dolbeer & Clark=s (1975) study used open habitat in June & August to a greater extent than adults. This
habitat use by juveniles may have been due to high population density forcing juveniles into non-preferred habitat. The
study was conducted in 1969/70 which was a peak population year (Dolbeer & Clark 1975). During their first year of
life snowshoe hares have a 3 to 40% survival rate. As adults, the annual survival rate ranges from 12 to 50% (Banfield
1987). Keith (1980) found during cool wet weather, young males have higher mortality during the first 3 weeks of life
than during warm weather. Prolonged periods of below -20oC and food shortages increase mortality.
This document provides a preliminary description of the seasonal habitat requirements of snowshoe hares in the
Morrison River study area. The intent of this report is to help provide a consistent approach when applying habitat
suitability/capability ratings in the field as part of the Terrestrial Ecosystem Mapping (TEM) project. Seasonally
important habitat attributes have been described and potentially high value ecosystem units identified for each of the
biogeoclimatic subzones that occur in the Morrison River study area. The model focuses on habitat attributes that are
measurable on a polygon basis and therefore represent primarily stand-level ratings.
Critical Seasons
The critical season for snowshoe hares is the dormant season due to increased thermo regulatory costs and a reduced
quality and quantity of food plants. For the purpose of this model the dormant season has been defined as September to
April. The growing season has been defined as May-August.
Migration
Snowshoe hares do not migrate seasonally. However, they will utilize different areas of their home range at different
times of the year because of the succession of new foods which becomes available (Bider 1974).
Densities
The cyclic nature of snowshoe hare populations results in a wide range of densities from 1 hare/km2 to 800-1200
hares/km2 (Keith 1974)..
Diets
During the dormant season, snowshoe hares depend primarily on the twigs and bark of woody plants (Klein 1977).
They feed on buds, twigs, bark and evergreen leaves of woody plants and the lower stems of ferns after snowmelt
(Wolff 1978; Banfield 1987; Keith 1980). Their favourite winter foods include: willows, birches, hazelnut,soopolallie,
willow, trembling aspen, rose, hemlock, white spruce, balsam & fir (Wolff 1978; Banfield 1987; Keith 1980; Smith
1988). During peak population years snowshoe hares kill many saplings by girdling.
During the summer snowshoe hares feed on a wide variety of green grasses and forbs. Their favourite food items
include: blue grass, brome, vetches, asters, jewel weed, wild strawberry, raspberry, fireweed, pussy-toes, dandelions,
clovers, daisies, horsetails, tender leaves of trembling aspen, birches and willow (Banfield 1987; Keith 1980).
Species known to be unpalatable to hares include subalpine fir, red-osier dogwood, black spruce, Labrador tea,
Lonicera, Symphoricarpos and green alder (Alnus viridis) Keith et al. 1984).
Pease et al. (1979) found that captive hares required 300g of woody browse with a maximum diameter of 3-4 mm.
Hares will consume twigs and stems up to 1.5 cm in diameter (Keith et al. 1984).
Territoriality
Snowshoe hares do not defend territories. The average home range for a female snowshoe hare is 0.28-1.4 km2 while
the average size for a male is .72-2.8 km2 (Bider 1974; Ferron and Ouellet 1992). Banfield (1987) stated the average
daily range is .16 km2 with home ranges usually overlapping. , Studies in Colorado suggested the average adult home
range in Engelmann spruce- (Picea engelmanni) subalpine fir (Balsam lasiocarpa) forests was .23 km2 (Dolbeer and
Clark 1975). Dolbeer and Clark (1975), O=Farrell (1965) and Radvanyi (1975) found no difference in the size of male
and female hare home ranges.
Snowshoe hares are familiar with their home range. As evening approaches they leave shelter to feed, often using
familiar runways to travel to feeding areas. Along these runways they Aclip@ vegetation along paths in summer to
maintain access. During the winter they Apad down@ the snow along these paths to maintain an escape route.
Lairs
Snowshoe hares are social animals, sharing dusting spots and lairs. Lairs can be found in depressions in the grass at the
base of a bush or beside a rock, log, under a low-growing branch, entrance to a animal den or self-excavated short
tunnels in snow.
CALIBRATION AND STANDARDIZATION IN BC
Provincial Distribution
Snowshoe hares are resident throughout BC except on Vancouver and the Queen Charlotte Islands.
Best Habitats
The best habitats for hares are those that provide the dense shrub layer 1-3 m tall which they require for cover in
combination with preferred food plants. However, the best habitats in BC are not known at this time. Populations are
cyclic; status of population with regards to the cycle is not known at this time.
Information Sources
Information was used from studies in the Yukon (Krebs et al. 1987; Rohner and Krebs 1996; Smith et al. 1988),
western Canada (Litvaitis et al. 1985), eastern Canada (Ferron and Oellet 1992); Washington (Koehler 1989;1990),
other areas of the US (Klein 1977; Keith et al. 1993). A habitat suitability index model from Alberta was also used
(Hoover et al. 1995).
Information Gaps
There is no local information on habitat preferences or population densities of hares within the study area, nor their
position within the population cycle.
SEASONAL NEEDS AND KEY HABITAT ATTRIBUTES
Assumptions
The following assumptions were made when developing this model:
• Habitat preferences recorded in the literature from other study areas accurately describe snowshoe hare preferences
within the study area.
• Recorded habitat preferences reflect habitat requirements.
• The effects on fitness of habitat use or choice are not significant.
•
•
The stand level attributes identified and used in this model accurately reflect high value snowshoe hare habitats.
Predation, disease, intra/interspecific competition and trapping will have minimal impacts on the hare population.
Limiting Habitat
It is not known for certain what factors limit snowshoe hare populations (drive the population cycle). For the purposes
of the model hares are assumed to be food limited.
Growing Season Habitat Security Habitat
Snowshoe hares are typically associated with 10-30 years old conifer regeneration forests with dense understorey cover
as well as the edges of swamps and riverside thickets. Snowshoe hares are often found in the densest cover by day and
forage in open forest by night (Banfield 1987). They prefer valley bottom and flat habitats over high elevation steep
habitats in northern BC (Penner and Jalkotzy 1982). Koehler (1990, 1991) found hare numbers in north-central
Washington were greatest in successional forests <25 years old. The ability of growing season habitat to continually
support a snowshoe hare population is dependent upon its interspersion with winter habitat (Keith 1980).
Hare populations flourish if recurrent fires create situations where dense stands of young conifers or brushy deciduous
growth provide abundant food and cover. Use of clear cut and burned areas increased as the amount of cover between
1-3 m increased (Parker 1986). Hare activity is usually concentrated along the edge of recent clear cuts (Radvanyi
1987). Mature forests have low numbers of hares.
Subalpine fir & lodgepole pine forests with dense undercover had more use than aspen with sparse understorey in Utah
(Dolbeer & Clark 1975). Understorey density appears to be more important than vegetation species composition
(Ferron and Ouellet (1992). The dense understories provide security and thermal cover. Several authors (in Hoover et
al. 1995) found that stands with 16320 stems/ha provide sufficient forage, escape and thermal cover for snowshoe hares.
Rohner and Krebs (1996) found that hares in open habitats were most vulnerable to predation by owls.
Parker (1986) found that stands with conifer cover values greater than 60% 1-3 m above ground supported the largest
populations of hares. Dense coniferous understories support greater hare densities than do deciduous stands because
conifers provide hares with superior cover from predators and climatic extremes. Litvaitis et al. (1985) reported that
deciduous stands dominated by aspen, balsam poplar and paper birch comprised the best habitat for snowshoe hares in
western Canada.
Feeding Habitat
Hares use different types of cover for feeding and resting (Ferron and Ouellet 1992). Feeding sites had a higher ground
cover of herbaceous plants, higher vegetation closure and less ligneous plants, humus and moss than resting sites.
Density of deciduous species was also higher in feeding sites. Resting sites had a higher density of coniferous species
(Ferron and Ouellet 1992). Hares will use more open areas for foraging in the growing season because vegetative
growth provides the cover they need. Hares tend to concentrate near openings (bog edges, etc.) that support willow,
alder, hazel and other low-growing woody vegetation (Keith 1980). Hares will forage further from forest cover into
clearcuts if slash piles are present as obstruction refugia (Radvanyi 1987). Ferron and Ouellet (1992) found hares
preferred to use ecotones between habitats. They also found that stands with high foliage density of deciduous plants
were used more commonly than other stands. They believe that hares must trade-off between optimal feeding sites and
predator avoidance. Habitats used by hares for feeding are near resting sites.
Dormant Season Habitat Security Habitat
Conroy et al. (1970) found that in winter, hares preferred interspersed areas, which generally have denser shrub and
slash cover than do uniformly forested areas. Wolfe et al. (1982) found a strong correlation between hare use and
horizontal cover densities at heights of 1-2.5 m. Hares used those areas in which cover above the snow was at least
40%. Deciduous understoreys may not usually provide sufficient cover during the dormant season.
Feeding Habitat
Feeding habitats used in winter are similar to those used in summer, but tend to be closer to thermal cover (dense
conifer regeneration). Deciduous areas are used less during the dormant season as cover is generally not sufficient.
One measure of winter forage availability is the density of live woody stems <1.5 cm in diameter within 3 m of the
ground (Hoover et al. 1995).
Confounding Factors
The primary factor that will influence snowshoe hare habitat use is the position of the population in the 10 year cycle.
Summary
In summary, there is little difference in habitat preference between the growing and dormant seasons.
Key habitat attributes for snowshoe hares can be summarized as follows (Tables S1; S2):
• young forests (structural stages 4 and 5),
• coniferous understorey under deciduous canopy,
• dense understorey of shrubs 1-3 m tall,
• high density of woody stems <1 cm in diameter within 3 m of the ground
• presence of willow and aspen in shrub layer,
• wetlands (in the growing season).
Table S1. Summary of key habitat attributes for hares in the growing season (May-September).
Habitat
Attributes Required
Structural Stage
Thermal cover and
Security cover (ST)
Young forests <20 years
Deciduous present
Dense understorey (>60%) of shrubs 1-3 m tall
4 and 5
Feeding (FD)
High ground cover of herbaceous plants,
Presence of willow and aspen in the shrub layer,
Open forests,
Swamp edges,
Riverside thickets.
4 and 5
Table S2. Summary of key habitat attributes for hares in the dormant season (November to April).
Habitat
Attributes Required
Structural Stage
Thermal cover and Security cover
(ST)
Young coniferous understorey <20 years
Dense understorey of shrubs 1-3 m tall (>40%).
4 and 5
Feeding (FD)
Young coniferous understorey,
Dense understorey of shrubs 1-3m tall,
Presence of deciduous shrubs,
Abundant twigs < 1.5 cm in diameter must be
present in shrub layer <3m from ground.
4 and 5
ECOSYSTEM UNIT (EU) VALUES AND ASSUMPTIONS
Using information available on the site series occurring in the study area (ie. moisture regime, canopy closure, tree
species composition, shrub density), the site series TC (05), BF (07), SS (12), CF (31), AF (33), CA and WT in the
SBSmc2 and FB (01), FD (07),CF (31) and AF (33) in the ESSFmc are expected to provide high value habitats for
snowshoe hares. Table 3 lists these habitats, their attributes important to hares and the expected season of use.
Table S3. Expected high value snowshoe hare habitats in the Morrison study area.
Expected use
Habitat attributes important to
hares
Site series name
Code
Dense shrub layer, deciduous
present
Sxw-Twinberry-Coltsfoot
TC (05)
Dense shrub layer
Sxw-Devil's club
SD(09)
SBSmc2
feeding, security
and thermal cover
Expected use
Habitat attributes important to
hares
Site series name
Code
feeding, security
cover
Presence of deciduous and early
herbaceous growth
Willow-twinberry shrub carr
WT
feeding
Presence of early herbaceous
growth
Sxw-Scrub birch-Feathermoss
SbSxw-Scrub birch-Sedge
Carex fen/marsh
Sitka alder-Lady fern
Herb rich meadow-Cow parsniplarge leaved avens
BF (07)
SS (12)
CF (31)
AF (33)
CA
Bl-Huckleberry-Leafy liverwort
FB (01)
Bl-Devil=s club-Lady fern
FD (07)
ESSFmc
feeding, security
and thermal cover
Well developed shrub and herb
layers
feeding, security
cover
Presence of deciduous and early
herbaceous growth
Willow-twinberry shrub carr
WT
feeding
Presence of early herbaceous
growth
Carex fen/marsh
CF (31)
Sitka alder-Lady fern
AF (33)
DRAFT ECOSYSTEM RATINGS
Assumptions
The regional field guide (Banner et al. 1993) is assumed to accurately predict habitat characteristics of ecosystem units
in the study area.
Ratings Scheme
Habitats will be rated for two seasons: growing (May-August) and dormant (September-April). A six class rating
scheme (1=very high, 2=high, 3=moderate, 4=low, 5=very low, 6=nil) will be used to rate habitats for each season.
Ratings will be assigned for thermal cover (TH), security cover (SH) and feeding (FD); when TH and SH can not be
separated, the habitat will be rated for both and the code ST will be used (Appendix 1). These codes correspond to the
codes that will be used when filling out the new Wildlife Habitat Assessment Form that will be used during field
sampling.
Preliminary Ecosystem Ratings for Snowshoe Hare Habitat in the Growing Season
See Appendix S1.
Preliminary Ecosystem Ratings for Snowshoe Hare Habitat in the Dormant Season
See Appendix S1.
Map Adjustments
If the polygon is adjacent to a wetland, bog or meadow increase the rating for ST by 1 for habitats rated 2-4 (ie 2
increases to 1; 4 increased to 3).
If the polygon is adjacent to moist forests increase the rating for ST by 1 for habitats rated 2-4 (ie 2 increases to 1; 4
increased to 3).
If the polygon is adjacent to structural stages 3b or 4 increase rating for ST by 1 for habitats rated 2-4 (ie 2 increases to
1; 4 increased to 3).
If the polygon is extremely steep (>80% slope) decrease the rating by 1 (ie 2 decreased to 3).
Field Sampling Scheme for Identifying Key Snowshoe Hare Habitat Attributes
In order to qualitatively rate habitats for snowshoe hares the following information must be collected (Table S4) at all
sites visited during field sampling.
Table S4. Attributes to be recorded during field sampling for snowshoe hares.
Attribute
Field sampling/recording technique
Shrub density (1-3 m)
Recorded on the Ecosystem Field Form
Abundance of live woody stems <1.5 cm in
diameter <3 m from ground
Record on wildlife form.
Forest structural stage
Recorded on the Ecosystem Field Form
Presence of slash piles (clearcuts only)
Recorded on Coarse Woody Debris form
Use of habitat
Complete pellet transects follow methodologies developed
by Krebs et al. (1987) and Kohler (1990)
REFERENCES
Banfield, A.W.F. 1986. The Mammals of Canada. University of Toronto Press. 438pp.
Banner, A., W. MacKenzie, S. Haeussler, S. Thomson, J. Pojar and R. Trowbridge. 1993. A field guide to site
identification and interpretation for the Prince Rupert Forest Region. BC Ministry of Forests, 1993.
Bider, J.R. 1974. Snowshoe hare in the North Woods. Nature Canada. 3:21-24.
Conroy, M. J., L. Gysel and G. Dudderar. 1979. Habitat components of clear-cut areas for snowshoe hares in
Michigan. J. Wildl. Manage. 43:680-690.
Dolbeer, R.A. and Clark, W.R. 1975. Population ecology of snowshoe hares in the central Rocky Mountains. J. Wildl.
Manage. 39(3):535-549.
Ferron, J. and J.P. Ouellet. 1992. Daily partitioning of summer habitat and use of space by snowshoe hares in southern
boreal forest. Can. J. Zool. 70:2178-2183.
Hoover, A, J. Watson, J. Beck, B. Beck, M. Todd and R. Bonar. 1995. Snowshoe hare (Lepus
range: Draft habitat suitability index (HSI) model. Foothills Model Forest, Hinton Alberta.
americana)
winter
Keith, L.B. 1980. Snowshoe hare. Canadian Wildlife Service, Hinterland Who=s Who. 3pp.
Keith, L. B. 1974. Some features of population dynamics in mammals. Pp. 17-58 in S. Lundstrom (ed.). Proc. Of Xth
Intl. Congr. Of Game Biol., National Swedish Env. Protect. Board, Stockholm, Sweden.
Keith, L.B, J.R. Carey, O.J. Rongstad and M.C. Brittingham. 1984. Demography and ecology of a declining snowshoe
hare population. Wildl. Monogr. 90:43pp.
Klein, D.R. 1977. Winter food preferences of Snowshoe hares (Lepus americana) in Interior Alaska.
International Congress of Game Biologists. Atlanta, Georgia USA March 11-15, 1977.
XIIIth
Krebs, C.J, B.S. Gilbert, S. Boutin and R. Boonstra. 1987. Estimation of snowshoe hare population density from turd
transects. Can. J. Zool. 65:565-567.
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. 1991. Snowshoe hare, Lepus americanus, use of forest successional stages and
during 1985-1989 in north-central Washington. Can. Field Nat. 105(2):291-293.
population
changes
Litvaitis, J.A, J.A. Sherburne and J.A. Bissonette. 1985. Influence of understory characteristics on snowshoe hare
habitat use and density. J. Wildl. Manage. 49(4):866-873.
O=Farrell, T. 1965. Snowshoe hare ecology. J. Mammal. 46(3): 406-418.
Parker, G.R. 1986. The importance of cover on use of conifer plantations by snowshoe hare in
Brunswick. Can. Field-Nat. 100(1):74-77.
northern
New
Pease, J.L, R.H. Voles and L.B. Keith. 1979. Interaction of snowshoe hares and woody vegetation. J. Wildl. Manage.
43(1) 43-60.
Penner, D.F. and P. Jalkotzy. 1982. Studies on furbearing mammals in the Stikine-Iskut river drainages, British
Columbia. Preliminary consultants report prepared for BC Hydro. 147 pp.
Radvanyi, A. 1987. Snowshoe hares and forest plantations: A literature review and problem analysis. Information
report NOR-X-290. Canadian Forest Service.
Rohner, C. and C.J. Krebs. 1996.
Oceologia 108:303-310.
Owl predation on snowshoe hares: consequences of antipredator behaviour.
Smith, J. N. M, C. J. Krebs, A. R. E. Sinclair and R. Boonstra. 1988. Population biology of snowshoe hares. II.
Interactions with winter plants. J. Anim. Ecol. 57:269-286.
Wolfe, M.L., N.V. Debyle, C.S. Winchell, T. R. McCabe. 1982. Snowshoe hare cover relationships in northern Utah. J.
Wildl. Manage 46(3):662-670.
Wolff, J.O. 1978. Food habits of snowshoe hare in interior Alaska. J. Wildl. Manage 42(1):148-153.
Appendix S1. Draft Capability Ratings for Snowshoe Hare in the Morrison Study Area.
Habitat
Unit
Dormant Season (October-April)
1
2
3a
3b
4
5
6
Gr
7
1
2
3a
SBSmc2
SB (01)
6
6
4FD,
ST
4FD,
ST
5FD, ST
4FD, ST
4FD, ST
4FD, ST
6
6
4FD, 3ST
PF (02)
6
6
4FD,
ST
4FD,
ST
4FD, ST
4FD, ST
4FD, ST
4FD, ST
6
6
4FD, ST
BM (03)
6
6
4FD,
ST
4FD,
ST
4FD, ST
4FD, ST
4FD, ST
4FD, ST
6
6
4FD, ST
TC (05)
6
6
4FD,
ST
3FD,
ST
1FD, ST
4FD, ST
4FD, ST
1FD, ST
6
6
1FD, 4ST
SO (06)
6
6
4FD,
ST
4FD,
ST
4FD, 3ST
4FD, SH
4FD, ST
4FD, ST
6
6
4FD, 3ST
BF (07)
6
6
4FD,
ST
4FD,
ST
2FD, 4ST
4FD, ST
4FD, ST
4FD, ST
6
6
1FD, 4ST
SD (09)
6
6
4FD,
ST
4FD,
ST
3FD, ST
4FD, SH
4FD, ST
4FD, ST
6
6
3FD, ST
SH (10)
6
6
4FD,
ST
4FD,
ST
3FD, ST
4FD, ST
4FD, ST
3FD, ST
6
6
3FD, ST
SS (12)
6
6
4FD,
ST
4FD,
ST
3FD, ST
3FD, ST
4FD, S T
4FD, ST
6
6
2FD, 3ST
CF (31)
6
WL (31)
5FD
5FD
5FD
5FD
AF (33)
6
6
4FD,
ST
4FD,
ST
6
6
2FD, ST
CA
6
6
6
6
1FD,
6ST
1FD,
6ST
1FD, 6ST
WT
5ST,6
FD
5ST,
6FD
5ST,
6FD
5ST,6F
D
1FD,
6ST
1FD,
6ST
1FD, 6ST
1FD,
6ST
2FD
4FD, ST
4FD, ST
4FD, ST
4FD, ST
ESSFmc
FB (01)
6
6
6
6
2ST, FD
2ST, FD
4ST, FD
4ST, FD
6
6
6
LC (02)
6
6
6
6
6
6
6
6
6
6
6
FC (03)
6
6
6
6
5ST, FD
5ST, FD
6
6
6
6
6
HH (04)
6
6
6
6
5ST, FD
5ST, FD
6
6
6
6
6
FT (05)
6
6
5ST,
6FD
4ST,
6FD
3FD, ST
3FD, ST
5FD, ST
5FD, ST
6
6
5ST, 3FD
FO (06)
6
6
5ST,F
D
4FD,
ST
3FD, ST
3FD, ST
5FD, ST
5FD, ST
6
6
5ST, 3FD
FD (07)
6
6
5ST
4FD
2FD, ST
2FD, ST
4FD, ST
4FD, ST
6
6
5ST, 2FD
FV (08)
6
6
6
6
3ST, FD
3ST, FD
4ST, FD
4ST, FD
6
6
6
HG (09)
6
6
6
6
6
6
6
6
6
6
6
Habitat
Unit
Dormant Season (October-April)
Gr
1
2
3a
3b
4
5
6
7
1
2
3a
FH (10)
6
6
6
5FD,
ST
4FD, ST
4FD, ST
5FD, ST
5FD, ST
6
6
6
AF (33)
6
5FD,
ST
5FD,
ST
5FD,
ST
5FD, ST
5FD, ST
5FD, ST
5FD, ST
6
6
3FD, ST
AC (35)
6
5FD,
ST
5FD,
ST
5FD,
ST
5FD, ST
5FD, ST
5FD, ST
5FD, ST
6
6
4FD, ST
CF
6
1FD,
6ST