Nuttall’s cottontail (nuttallii subspecies) COSEWIC assessment and status report: chapter 2

Executive Summary

Nuttall’s Cottontail nuttallii subspecies
Sylvilagus nuttallii nuttallii

Species information

Nuttall’s Cottontail is a small rabbit with a total length of 319 mm (263-363) and a body mass of 496 g (342-778). It has a pale brown dorsal pelage, a distinct pale brown nape on the back of the head, black-tipped ears, grey on the sides and rump, a white-grey tail, and white ventral pelage. Smaller size, the brown nape on the back of the head, and the greyish-rump distinguish Nuttall’s Cottontail from the Snowshoe Hare.

Distribution

Nuttall’s Cottontail is distributed across the Great Plains, Rocky Mountains and intermountain regions of the western United States ranging as far north as southern Canada (Saskatchewan, Alberta, British Columbia). The subspecies S. n. nuttallii ranges from California, Nevada, and Arizona north through Oregon, Washington, Utah and Idaho to British Columbia where it is confined to the southern Okanagan-Similkameen valleys. It was first recorded in British Columbia in 1939 and is known from about 40 distinct sites with an extent of occurrence of about 1,380 km².

Habitat

Nuttall’s Cottontail is associated with shrub-steppe habitats dominated by Antelope-Bush, Big Sagebrush, Rabbit-Brush, and Western Juniper. The most important habitat attributes are the presence of sagebrush with a cover of 30% or more and rocky outcrops. Since 1939, when S. n. nuttallii first appeared in Canada, shrub-steppe habitats have continued to decline because of urban and agricultural development. About 10% of the species’ Canadian range is within protected areas. Federal lands within the known range include 11 Indian Reserve lands, a National Wildlife Area, National Research Council lands, and the Agricultural Research Station at Summerland.

Biology

S. n. nuttallii eats grasses (Wheatgrasses, Needle-and Thread, Cheatgrass), forbs and shrubs such as Big Sage and Common Juniper. The breeding season probably extends from March to July in Canada with females producing two or three litters per year. Breeding in young-of-the-year is rare; the generation time is about one year. Survival rates are higher for females than males. High mortality in juvenile cohorts is related to precipitation and the quality of summer forage. Adult Nuttall’s Cottontails are solitary and only interact during the breeding season.

Population sizes and trends

In shrub-steppe habitats, population densities may reach 0.23 to 0.43 animals per ha in British Columbia. Average population densities fluctuate from year-to-year in response to variation in precipitation, but no information is available on long-term population trends. The total population of S. n. nuttallii in Canada is unknown but based on the available habitat is unlikely to exceed 3500 individuals.

Limiting factors and threats

The only imminent threat is ongoing habitat loss from urban and agricultural development. Since 1939, when this subspecies was first recorded in Canada, shrub-steppe habitat has declined in the southern Okanagan-Similkameen valleys. With the human population projected to increase by 27% in this region by 2021 more habitat will be lost. The few other potential threats include livestock grazing and pesticides.

Special significance of the species

S. n. nuttalliiis largely unknown to the public and naturalists. It is not a game animal and has little commercial significance as an agricultural pest. With a very limited range confined to the southern Okanagan-Similkameen valleys, it is one of several mammalian taxa associated with the intermontane regions of western North Americathat reach their northern limits in this region of Canada.

Existing protection

S. n. nuttallii was designated Special Concern by COSEWIC in 1994. British Columbia has designated this species as S3 (vulnerable). It is protected from killing or collecting under the provincial Wildlife Act, and is not hunted. Its habitat has no protection under the province’s Forest and Range Practices Act. A network of protected areas encompass its distributional area including 10 provincial parks, 3 provincial ecological reserves, a national wildlife refuge, the South Okanagan Wildlife Management Area, and Nature Trust and The Land Conservancy lands. Largest protected areas include the various conservation lands in the White Lake-Vaseux Lake area and South Okanagan Grasslands Provincial Park.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2006)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)Footnotec
A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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