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

Factors of Abundance and Distribution

Direct Human Influences

The effect of deliberate killings of predators in the prairie pothole region by humans was substantial during certain periods, especially from the onset of settlement to the mid 1930's. During the latter half of that period, the region was occupied by many more rural residents than now (Strange 1954; Robinson 1966). Those rural residents were knowledgeable of the land and its resources, and many of them used fur as a source of income (Hamilton and Fox 1987). Moreover, many rural people had an ingrained dislike of predators. Although records of the abundance of predators during this period are scant, many species were clearly under severe attack by humans for a variety of reasons (e.g., egg collecting, food gathering, fur harvesting, bounties, predator control), and populations of many species were reduced to or held at low levels. The effect of extensive killing of mammals by humans is exemplified by extirpation (by trapping, shooting, and poisoning) of the gray wolf from nearly all of the region by the early 1900's. Fur harvesting was especially intense during the 1910's and 1920's when pelts were valuable and regulations were limited and weakly enforced (Dearborn 1920; Lawyer and Earnshaw 1921; Sargeant 1982). Populations of nearly all carnivore species probably were greatly reduced, at least locally (Osborn and Anthony 1922; N. Criddle 1929; Bird 1930; Drescher 1974; Sargeant 1982). Even though habitat was favorable, intensive harvesting of species that were not common when settlement began (e.g., red fox, raccoon) coupled with human-inflicted mortality for other reasons and interspecific competition probably prevented population expansion for several decades. Because of their size and relatively small home ranges, weasels were perhaps less affected than most other predator species by human inflicted mortality but were also extensively trapped (Fagerstone 1987).

During the 1940-60's, when fur prices were generally low, animal damage (livestock and wildlife) and control-of-diseases programs that included widespread use of toxicants and bounties resulted in deaths of tens of thousands of carnivores annually in various provinces and states of the prairie pothole region. For example, 10,000-35,000 red foxes were submitted for bounty annually in North Dakota during 1945-58 (Adams 1961), and about 250,000 coyotes were killed in the agricultural region of Alberta during 1951 -56 (Ballantyne 1958). These programs failed to reduce red fox populations to low levels but probably had considerable effect on abundance of coyotes in many intensively cultivated areas (Adams 1961).

Population changes of avian predators were similar to that of mammals but for different reasons. Initially, egg collectors helped reduce certain raptor populations (Houston and Bechard 1982). Later, raptors (collectively called chicken hawks) were regarded as harmful because of their actual or presumed threats to poultry and small game (Mitchell 1924; Fox 1939; Newton 1979) and were indiscriminately killed (N. Criddle 1929; Fox 1939; Salt 1939; Williams 1946; Kirkpatrick and Elder 1951; Evans 1982; Houston and Bechard 1984). This indiscriminate killing continued largely unabated into the 1950's and seemingly persists in some localities at greatly reduced levels (Houston and Bechard 1984).

American crows and black-billed magpies were severely persecuted during the 1920-50's to reduce predation on game birds, including waterfowl (Sowls 1955; Johnson 1964). People in many areas were encouraged by bounties and other rewards to destroy the birds and their nests, but the effects of these controls are largely undetermined. After settlement, gull colonies were decimated by egg collectors and by other factors (Stewart 1975; Salt and Salt 1976).

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