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Distribution and Abundance of Predators that Affect
Duck Production: Prairie Pothole Region

Species Accounts -- Carnivores


Habitat and History. Raccoons in the prairie pothole region are at the northern fringe of their geographic range (Hall 1981). At the time of settlement, raccoons were only in wooded hills and wooded river valleys in the southeastern portion of the region and were absent throughout nearly all of the region in Canada, except portions of southern Manitoba (Bailey 1926; N. Criddle 1929; S. Criddle 1929; Soper 1961; Kiel et al. 1972; Houston and Houston 1973; Cowan 1974). After settlement, raccoons became more widely distributed throughout the United States portion of the region, but populations in most areas remained low until the 1940's (Bailey 1926; Adams 1961). Thereafter, raccoons became relatively abundant throughout much of the southeastern portion of the region.

Beginning in the 1950's, raccoon populations in Canada began to expand (Sowls 1949; Santy 1958; Lynch 1971; Kiel et al. 1972; Houston and Houston 1973; Cowan 1974). During the 1960's, raccoons were sufficiently abundant in the Minnedosa area of southwest Manitoba (near the Moore Park study area) to be considered a major predator of clutches of canvasbacks (Aythya valisineria; Stoudt 1982). At that time, their presence was also noted near Redvers in southeastern Saskatchewan (Stoudt 1971) and near Delburne in southcentral Alberta (Smith 1971). The latter observation seems inconsistent with other information on the occurrence of raccoons in Alberta and probably represented a localized population. Raccoon populations continue to expand in Canada (Friesen 1983; Jorgenson 1987).

The raccoon is highly suited to coexisting with humans and has benefitted greatly from agricultural development. Raccoons in the prairie pothole region make extensive use of buildings for resting and for rearing young (Cowan 1973; Fritzell 1978b) and make extensive use of cereal grains for food (Cowan 1973; Greenwood 1981). Principal causes of mortality in raccoons are killing by humans (especially trapping for furs and collisions with vehicles), disease (especially canine distemper), and starvation during winter (Mech et al. 1968; Lotze and Anderson 1979; Fritzell and Greenwood 1984; Clark et al. 1989).

Population Structure. Raccoon populations in spring are composed of adult males, which may have large contiguous territories, and individuals of other age and sex categories. Home ranges of individuals of the latter groups are usually much smaller than those of adult males and may overlap considerably with those of conspecifics (Fritzell 1978a). In each adult male territory are usually one or more adult females and two or more yearlings, but many yearling males disperse from parent territories in mid- to late spring (Fritzell 1978a). Raccoon populations are much lower in the prairie pothole region than in many other parts of North America, and average home ranges are much larger than elsewhere (Lotze and Anderson 1979; Sanderson 1987). In North Dakota, home ranges of raccoons averaged 26 km2 for adult males and 7-13 km2 for individuals of other age and sex categories (Fritzell 1978a) but are generally <1 km2 in other regions (Sanderson 1987).

Distribution and Abundance. Raccoons were in all study areas except five in western sites, but abundance decreased from southeast to northwest across the region (Fig. 8). Raccoons were common or more abundant in a greater percentage of study areas in the United States than in Canada (Appendix Table 6). In the United States, raccoons were numerous in eight study areas (47%), common in eight (47%), and undetected in one (6%). In Canada, they were numerous in one study area (6%), common in six (38%), and uncommon or less abundant in nine (56%). Removal of predators from three study areas (Eldridge, Fredonia, Lake Park) probably had little effect on the track indices because only two raccoons were caught before the first searches for tracks were completed.

Seven of nine study areas with a numerous abundance of raccoons were in western Minnesota, eastern North Dakota, and eastern South Dakota (Fig.8) where the climate is the most moderate and agriculture the most diverse in the region. Survival of raccoons probably benefits from these factors (Mech et al. 1968). In one of those study areas (Lake Park) 11 adult raccoons were captured in 1987 and 6 adults were captured in 1988 during predator removal (Appendix Table 3).

Raccoon populations in study areas in Canada were generally low or absent, especially in the western half of the region (Fig. 8). No evidence of raccoons was found in four of the five western-most study areas and raccoon tracks were found in only 1-4 quarter sections each year in three study areas (Hanley, Holden, Leask; Appendix Table 5). Deaths in these low populations affected track counts. In 1983, tracks were found in 18 quarter sections (45%) in one study area (Ceylon) during the first search period. Eight of those quarter sections were in a contiguous block that included an abandoned farmstead in its center. Between searches, three dead raccoons (an adult female and two kits) at the farmstead were seemingly killed by humans. During the second search, tracks were found in only 13% of quarter sections and no tracks were found in the 8 quarter sections with the abandoned farmstead. An exception to low raccoon populations in Canada was one study area (Yorkton), where raccoon tracks were found in 80% of quarter sections (Appendix Table 5). That area had more abandoned farm buildings suited for use by raccoons than any other study area in Canada.

Fig. 8. Percentage of searched quarter sections (in black) by study area in which raccoon tracks were found or in which the abundance of tracks was estimated during two systematic annual searches in April-June in >= 1 study year and ratings of the abundance of raccoons in each area, 1983-88. Results for study areas searched >1 year were averaged; study areas are in the prairie pothole region.

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