Nuttall’s cottontail (nuttallii subspecies) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

In the western United States, S. n. nuttallii occupies shrub-steppe habitats with Antelope-Bush (Purshia tridentata), Big Sagebrush (Artemisiae tridentata), Rabbit-Brush (Chrysothamnus nauseosus), and Western Juniper (Juniperus occidentalis). The most important habitat attributes are the presence of sagebrush and rocky outcrops (Orr 1940; MacCracken and Hansen 1982; Verts and Carraway 1998). In Canada this subspecies occupies similar habitats. Using faecal pellet densities as an index of habitat use, Sullivan et al. (1989) found that this rabbit mostly used sagebrush habitats with 30% or more vegetative cover (Table 1). Ponderosa Pine (Pinus ponderosa) parkland with sagebrush is also used. Faecal pellets were sparse or absent on cultivated lands. Live-trap captures on a 25.6 ha grid showed a similar pattern (Sullivan et al. 1989) with most captures of Nuttall’s Cottontail in traps located in natural steppe habitat in the study area. Few captures were made in traps set in the parts of the study area with cultivated orchard and old-field habitat (Sullivan 1985; 1986). Carter et al. (1993) reported similar habitat use based on spotlight surveys and estimates of faecal pellets in various habitats. They found that several habitat types not assessed by Sullivan et al. (1989) such as meadow/hayfield, riparian, and Douglas fir/Ponderosa Pine were rarely used by S. nuttallii. Nuttall’s Cottontail does not excavate burrows; abandoned burrows of other mammals and rocky outcrops are essential as refuges from predators.

Sullivan et al. (1989) and Carter et al. (1993) demonstrated that S. n. nuttallii is rare in cultivated lands such as orchards and old fields. Nevertheless, the level of use of agricultural lands by this species is not clear. Irrigated areas may provide herbaceous forage for this rabbit. At the Federal Agricultural Research Station at Summerland, this species feeds on ornamental plants (Carter et al. 1993). Its use of vineyard habitats has not been studied.

Table 1. Faecal pellet densities (mean number/1.8 m²) for Nuttall’s Cottontail (Sylvilagus nuttallii) in natural and cultivated habitats in the southern Okanagan-Similkameen valleys. Based on surveys done in 1984 and 1985; modified from Sullivan et al. (1989).
Study Area Habitat 1984
Mean Cover ClassTable notea
1984
Pellet Density
1984
± Standard Error
1984
Number Plots
1985
Mean Cover ClassTable notea
1985
Pellet Density
1985
± Standard Error
1985
Number Plots
Grid System Mixed sagebrush-Ponderosa Pine parkland
-
118.5
18.9
103
-
41.1
7.5
94
Grid System Orchard/old field
-
2.8
1.8
56
-
3.5
2.1
56
Summerland Big sagebrush
1.7
38.7
16.1
20
1.7
36.3
11.8
20
Summerland Mixed sagebrushTable noteb
1.8
0.7
0.6
20
1.8
0.6
0.4
20
Summerland Grassland-sage
1.7
17.3
7.7
20
1.7
30.6
12.0
18
Summerland Mixed sagebrushTable noteb
1.5
242.0
106.7
20
1.5
122.1
52.5
20
Summerland Small sagebrush
1.1
117.4
70.0
20
1.1
45.9
24.7
20
Keremeos-Nighthawk Big sagebrush
1.6
14.7
7.1
20
1.6
12.9
5.7
20
Keremeos-Nighthawk Small sagebrush-rock outcrop
1.5
43.3
15.3
20
1.5
17.8
8.0
20
Keremeos-Nighthawk Grassland
0.2
0.0
0.0
20
0.2
0.0
0.0
20
Keremeos-Nighthawk Small sagebrush
1.3
3.5
1.8
20
1.3
0.3
0.3
20
Keremeos-Nighthawk Ponderosa Pine
0.8
0.1
0.1
20
0.8
0.1
0.1
20
Nighthawk-Osoyoos Grassland
0.1
0.0
0.0
20
0.1
0.0
0.0
20

Habitat trends

The southern Okanagan-Similkameen valleys were first used for livestock grazing in the late 1880s. Agricultural development associated with orchards, irrigated hay fields, and vineyards that began in the early 1900s and more recent urban growth have resulted in significant declines in grassland and shrub-steppe habitat (Cannings et al. 1987; Ministry of Environment, Lands and Parks 1998). According to Redpath (1990) more than 90% of the land in the southern Okanagan-Similkameen has been altered from its 'normal' state. Because the most intense agricultural activity and urban development are in the valley bottoms, potentialNuttall’s Cottontail habitat has been lost. Lea (unpublished data) estimated declines of 57% for Antelope-Bush habitats, 47% for Big Sage Needle Grass habitats, and 29% for Big Sage-Bunchgrass habitats from the 1800s to 2001. From 1939, when S. n. nuttallii was first recorded, these shrub-steppe habitats have continued to decline (Table 2). No quantitative data exist, but with the recent proliferation of vineyards, and continued urban growth more shrub-steppe habitat has been lost since 2001.  

Table 2. Historical changes in area (hectares) of some Nuttall’s Cottontail (Sylvilagus nuttallii) habitats in the south Similkameen-Okanagan valleys of British Columbia from 1939-2001. Based on unpublished data from Ted Lea, British Columbia Ministry of Water, Land and Air Protection. Note that S. nuttallii was first recorded in British Columbia in 1939. Lea’s analysis does not include habitat types such as sagebrush rock outcrops that are used by Nuttall’s Cottontail.
Habitat Type Year
1939Table notec
Year
1995Table noted
Year
2001Table noted
Lost % Lost
Antelope-Bush
7046
4279
4093
2952
41.9
Big Sage-Needle Grass
3439
2364
2364
1075
31.3
Big Sage-Bunchgrass
2128
2005
2005
123
5.8

Habitat protection/ownership

The precise amount of habitat legally protected is unknown. Protected areas within the known range (i.e., extent of occurrence) include 10 provincial parks, 3 provincial ecological reserves, and a national wildlife refuge (see Existing Protection or Other Status Designations section). Other conservation lands include the South Okanagan Wildlife Management Area, Nature Trust, and The Land Conservancy lands. These protected areas represent about 10% of the extent of occurrence of Nuttall’s Cottontail. The amount of shrub-steppe habitat in these protected areas is unknown. A GIS analysis with a habitat suitability model is needed to estimate the amount of Nuttall’s Cottontail habitat actually contained in these areas. Federal lands within the known range include 11 Indian Reserve lands (40,850 ha), theVaseux-Bighorn National Wildlife Area (792 ha), National Research Council lands (2,152 ha), and the Agricultural Research Station, Summerland (320 ha). Land tenure for the known range of S. nuttallii is given in Table 3. The proportion of these land types actually occupied by Nuttall’s Cottontail is unknown.

Table 3.  Land tenure for land within the known range (extent of occurrence) of Nuttall’s Cottontail (Sylvilagus nuttallii) in British Columbia.
Tenure Area (km²)
Crown Land-Federal and Provincial
619.1
Indian Reserve Lands
357.2
Private Land
408.5
Total
1384.8

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