Nuttall’s cottontail (nuttallii subspecies) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Nuttall’s Cottontailis 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). S. n. nuttallii ranges from California, Nevada, and Arizona north through Oregon, Washington, Utah and Idaho to British Columbia (Figure 1).

Canadian range

In Canada, S. n. nuttallii is confined to the Okanagan Basin of British Columbia where it ranges as far north as Keremeos in the Similkameen valley, and Summerland and the south end of Okanagan Mountain Provincial Park in the Okanagan Valley (Figure 3). Most occurrences are below 700 m elevation. It is known from about 40 distinct locations. The extent of occurrence based on historical and recent occurrences is about 1,380 km². This represents about 5% of the global range of the subspecies. The area of occupancy is unknown.

This rabbit was first documented in British Columbia in 1939 when two specimens were taken on Anarchist Mountain near Osoyoos (Cowan and Hatter 1940). In the 65 years since its first appearance, S. nuttallii rapidly spread throughout the low elevation shrub-steppe grasslands of the southern Okanagan and Similkameen valleys. By 1951, for example, Guiguet (1952) described it as common throughout the benches on the eastern side of Osoyoos Lake and by 1956 (Cowan and Guiguet 1956) it had nearly reached the present limits of its range. With little suitable habitat available in the northern Similkameen and Okanagan valleys, it now occupies most of its potential range in the province. The arrival and spread of S. nuttallii in British Columbia occurred while the White-tailed Jackrabbit (Lepus townsendii) was disappearing from this region (Nagorsen 2005).

It is conceivable that S. n. nuttallii occurred in British Columbia before 1939 but was not detected because of rarity. Nevertheless, given that the southern Okanagan Valley was the focus of various naturalists and museum collectors in the early 1900s, it seems unlikely that Nuttall’s Cottontail would have gone undetected and its appearance in 1939 probably represents a natural range expansion from Washington. The earliest museum collections of mammals from the southern Okanagan-Similkameen valleys were made in 1903 and 1904 by W. Spreadborough and E.M. Anderson in 1913 (Anderson 1914). Neither collector took specimens nor reported observations of this rabbit. In 1928 and 1929, H.M. Laing surveyed mammals in this region making large collections and recording observations in detailed field notes. He found no evidence of S. nuttallii (Laing, 1928; 1929).  Carter and Merkens (1994) implied that Nuttall’s Cottontail was present in British Columbia in prehistoric time, but was extirpated in response to environmental changes. With no information on the mammalian fauna of the southern Okanagan valley before 1900, it is difficult to evaluate this hypothesis. Aboriginal Traditional Knowledge (ATK) or mammalian faunal remains recovered in archaeological sites from the Okanagan Basin could be explored to address this issue.

Figure 3. Canadian range of Nuttall’s Cottontail, Nuttall’s subspecies (Sylvilagus nuttallii nuttallii).  Solid circles represent occurrence records based on known historical museum specimens and observations 1939-2002.

Figure 3. Canadian range of Nuttall’s Cottontail, Nuttall’s subspecies (Sylvilagus nuttallii nuttallii).  Solid circles represent occurrence records based on known historical museum specimens and observations 1939-2002.

There are also few data on the history of Nuttall’s Cottontail in Okanogan County of Washington, the county adjacent to the Canadian population.  In his range map, Dalquest (1941) showed this rabbit distributed throughout most of the Columbia Plateau in eastern Washington and ranging north to the Canadian border in the Okanagan Valley.  However, there is no information on its distribution in Okanogan County before the 1940s.

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