Impact of Red Fox Predation on the Sex Ratio of Prairie Mallards
Canid Composition and Population Trends
The North American mallard breeding range has always been occupied by one or more canid species. The gray wolf, coyote, and red fox, which have had the greatest range overlap with that of the mallard, have at one time or another occupied all of the Prairie Pothole Region (Hall and Kelson 1959; Banfield 1974). The density and distributions of these species in the prairie have changed markedly during the past 100 years. Because of strong interspecific relationships that affect canid composition and densities, the history of each species warrants attention. A fourth species, the kit fox (Vulpes velox), was locally common in much the Prairie Pothole Region during presettlement times, but this, the smallest North American canid, all but disappeared from region in the early 1900's (Bailey 1926; Rand 1948; Soper 1964); a remnant population still exists in southern Alberta and southern Saskatchewan (Novakowski 1970).
Gray Wolf
During pristine times, the gray wolf was clearly the dominant canid. From 1860 to 1885, populations declined dramatically, largely because of an extensive wolf-poisoning campaign conducted throughout the region coupled with the slaughter of the large ungulates, the wolf's primary food source. That poisoning campaign, unparalleled in intensity, was conducted by "professional wolfers" seeking pelts that sold for about $1.00 to $2.50 each. The steel trap of the earlier fur takers was replaced by strychnine, "widely and promiscuously applied to carcasses of buffalo, antelope, deer, elk, and birds as bait" (Young and Goldman 1944:336). According to early explorers, "wolves were extremely abundant over all of North Dakota, but after the disappearance of the buffalo they were poisoned and trapped in such great numbers that they rapidly disappeared from most of their old haunts" (Bailey 1926:150). "In 1887 the wolves were practically gone from most of the country across the state" (Bailey 1926:154). At present only occasional intruding gray wolves are found in the Prairie Pothole Region, though they are still common in the boreal forest adjoining the region on the north.
Coyote
Coyotes too were widely distributed during pristine times (Seton [1909] 1953), but apparently were not generally abundant on the northern plains. Bailey (1926:157) reviewed writings about North Dakota by early 19th century explorers such as Alexander Henry, Lewis and Clark, Maximilian, and J. J. Audubon, and concluded, "In the early days of trapping and exploration, little mention is made of coyotes, and apparently they were less common or less conspicuous than the large wolves." Coyotes, however, became very numerous during the settlement period following the decline of the gray wolf (Bailey 1926; Young and Jackson 1951). Whether or not pristine coyote populations were suppressed to any significant degree by gray wolves is speculative, but recent evidence from other areas shows that coyotes generally fare poorly in areas where wolves are abundant. Young and Jackson (1951:93) stated, "The large wolf does not treat the coyote as an equal," and "It seldom permits the coyote to come near it." Mech(1970:284) said, "What little is known about the relations between the coyote and the wolf suggests that they are not friendly." He mentioned several instances in which coyotes have not thrived in the presence of wolves, including Isle Royale in Lake Superior, where a long-established coyote population disappeared within 9 years after wolves arrived; he also reported several instances of wolves killing coyotes.
Coyotes were unusually abundant in North Dakota from about 1895 to 1915, when statewide populations probably reached the highest densities ever. Alin (1900) reported that in Dickey County, in the Drift Plain, coyotes were unusually numerous in 1900 and made many raids on poultry flocks but that a few years earlier they were almost unknown. Many similar recollections in the "Old Timer Statements" recorded by Johnson (undated North Dakota Game and Fish Department report) also suggest an abundance of coyotes during that period.
Like gray wolves, coyotes competed with man by killing livestock and poultry and as early as 1893 bounties were paid in North Dakota to encourage killing them (Johnson 1964). From about 1915 to 1950 Statewide coyote densities declined noticeably. The decline was earlier and more pronounced in the intensively cultivated Drift Plain than in the more rugged and less densely populated parts of the State. The decline was most likely due to human-caused mortality which increased steadily, first from methods such as poisoning, trapping, and hunting on foot or horseback (often with the aid of dogs), and later from more sophisticated methods such as shooting from airplanes and use of 1080 poison (sodium monofluoroacetate). The average number of wolves and coyotes (nearly all coyotes) bountied each year in North Dakota during 1906-15, when we believe that coyote populations were at a peak, was 12,697 as compared to only 1,413 during the 1950's, when we believe that populations were at the lowest levels since settlement (Adam 1965).
Coyote densities remained low in North Dakota throughout the 1950's, but conversations with residents suggest that the population has been expanding since. Coyotes, however, are still absent or scarce throughout most of the pothole region. Only one sighted on the six townships that were censused for foxes by Sargeant et al. (1975) from 1969 to 1973. The recent expansion coincides with a gradual easing of coyote control: state-paid bounties were eliminated, federally supervised predator control programs were reduced and directed increasingly toward specific problem animals, and most recently aerial hunting been curtailed and the use of toxicants restricted. All of these factors have lessened coyote mortality.
Coyote populations in North Dakota are still in a state of flux. Much of the State is suited for them and their absence seems to be the result of direct human-caused mortality. The potential for repopulation remains high and, agriculture, human attitudes, and laws and regulations change, coyotes may again become common in some areas where they have been largely eliminated. In other parts of the Prairie Pothole Region, coyotes have been reduced to low densities much more recently than in North Dakota; some areas, however, they are still abundant. The trend in Manitoba was similar to that in North Dakota (Seton 1909; Bird 1961). Stoudt (1971) reported that in 1952 Saskatchewan completed a coyote eradication program using 1080 poison, and that coyotes on his study area in southeastern Saskatchewan have since been extremely rare. Keith (1961) referred to coyotes as being numerous on his study area in southeastern Alberta during 1953-57 and Dekker (1973) indicated they were common in central and southern Alberta during the past 40 years, although the numbers were apparently reduced at the time of his writing.
Red Fox
Red fox pups at a rearing den. An original pen-and-ink drawing by Dawn Phillips.
The abundance of red foxes in the Prairie Pothole Region during presettlement times is unknown, but evidence suggests that they were much less numerous than during recent years. By today's standards, populations during pristine times were probably very low. Before settlement, foxes were competing in one way or another with wolves and coyotes, as well as other predator species; the fox was not the dominant canid. Furthermore, habitat conditions and the food base were probably less stable before agriculture and thus more conducive to supporting wide-ranging canids such as the gray wolf rather than high populations of smaller and more sedentary red fox. Bailey's (1926) summary of early information for North Dakota indicated that red foxes were at least locally common during the 1800's. He stated (1926:161), "While probably never very numerous over the state, foxes were evidently much more so in the earlier trapping days than at present." Bailey (1926:161) also quoted the explorer Maximilian as stating that in 1833 while staying at Fort Clark on the Missouri River, "The red fox (Canis fulvus) is very handsome and at the same time common, though by no means so numerous as the wolves."
The red fox population in North Dakota was very low from 1895 to 1935 but began to expand about 1936 (North Dakota State Game and Fish Department 1949). Populations were so low during the early part of the century that many long-time residents thought foxes were absent and they refer to the mid-1930's as the time when the species first appeared in the State. By 1944, high fox populations existed throughout most of North Dakota's pothole region, but red foxes were still absent or very scarce in the more rugged southwestern third of the State (North Dakota State Game and Fish Department 1949). Bounty records provided by Adams (1961) showed that red foxes did not become common in the southwestern part of the State until the mid-1950's, after coyote populations were reduced.
The increase in the red fox population in North Dakota was a direct result of man's activities. Coincidental with settlement, man systematically destroyed the gray wolf population, thereby reducing competition for coyotes. Settlement created an environment favorable to both coyotes and red foxes, but coyotes dominated and, as they became abundant, red foxes became very scarce. The coyote population expanded rapidly but was eventually brought under control by man, especially in intensively cultivated areas. The coyote population in most of the pothole region was greatly reduced after 1915, setting the stage for expansion of the red fox population. The expansion, however, did not occur until 20 years later, apparently because the human-caused pressures that effectively reduced the coyote population were sufficiently intense to delay expansion of the red fox population.
The drought and depression of the mid-1930's created conditions (e.g., crash of the fur market and abandonment of many farms) that were favorable for rapid expansion of the red fox population in areas where coyote densities were low. Since then the red fox population mushroomed, beginning in the eastern part of the State and gradually spreading west in the wake of a declining coyote population. By the mid-1950's, red foxes were abundant throughout nearly all of the State.
Red fox populations followed a delayed but parallel course throughout much of the Canadian Prairie Pothole Region. Wrigley (1974) summarized literature available for the sandhills of southwestern Manitoba and found that red foxes were originally common but almost exterminated in the early 1900's. Bird (1961) wrote that the red fox was very scarce in southern Manitoba from the early 1900's up to about 1930, when populations began to increase as the commercial value of the fur decreased and trapping was reduced. A marked increase in fox numbers after 1940 and periods of abundance since then were also reported by Soper (1961 b) and Wrigley (1974). In Saskatchewan, Soper (1961a) found red foxes generally but sparingly distributed in the parklands but he did not detect them anywhere in the shortgrass plains region of the Southwest. Stoudt (1971) stated that red foxes moved into the southeastern part of Saskatchewan and became very abundant following the coyote eradication program in the early 1950's. Dzubin and Gollop (1972) reported that at Kindersley in western Saskatchewan red foxes were virtually unknown until the 1960's. For Alberta, Soper (1964:271) stated, "It [the red fox] is apparently absent on the treeless plains of the south." More recently, however, Dekker (1973:43) wrote, "It appears that during the past 40 years some significant changes have taken place. From the thirties to the late sixties, foxes were virtually absent from all of central Alberta. Recently, they are staging a comeback." By the early 1970's, red fox populations in the Prairie Pothole Region probably reached an all-time high but reversals of that trend might occur in the future if coyote populations expand significantly.
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