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Prairie Basin Wetlands of the Dakotas:
A Community Profile

Chapter 3 -- Biotic Environment

3.7 -- Mammals

Historic Use of Prairie Wetlands

There can be little doubt that the activities of the wild bison (Bison bison), which was extirpated from the Prairie Pothole Region of the Dakotas in the 19th century, had a major biotic influence on prairie wetlands in pristine times. Unfortunately, there is no documentation of how wetlands were impacted by the feeding, drinking, dusting, or other activities of millions of these huge, shaggy beasts as they roamed the prairies. Other grassland mammals extirpated from the region are the grizzly bear (Ursus arctos), kit fox (Vulpes velox) and plains wolf (Canis lupus). These carnivores probably made only minor use of prairie wetlands.

Uncounted numbers of wapiti (Cervus elephus) and pronghorn (Antilocapra americana) and smaller numbers of mule deer (Odocoileus hemionus), the only other large herbivores of open grasslands, once inhabited the region and undoubtedly used the wetlands, at least for drinking. These three species are still found in small numbers in the region. Also nearly extirpated from the prairie region are the river otter (Lutra canadensis), mountain lion (Felis concolor), lynx (F. lynx), and bobcat (F. rufus). Although once distributed throughout the region, it is unlikely that any of these species were strongly associated with the wetlands dealt with in this report.

Modern Use of Prairie Wetlands

A review of modern use of prairie wetlands by mammals has recently been completed by Fritzell (1989). He states that no mammals other than muskrats (Ondatra zibethicus) are typically considered major elements of prairie wetland ecosystems, but cites strong evidence to show that wetlands are vital to many prairie mammals. He lists 17 species of terrestrial or semiaquatic mammals whose geographic range encompasses most of the Prairie Pothole Region and which commonly use wetlands for cover or obtain a substantial portion of their food from wetlanddependent organisms. He also mentions several other species that have been trapped in small numbers in prairie wetlands. We have added species to his list and added information on range and habitat use. The latter was presented in Jones et al. (1983) in an attempt to categorize mammals into groups, often arbitrary, that would indicate the degree of dependence of current wild mammals upon basin wetlands in the region (Table 9). Only wild mammals in Groups 1 and 2 will be discussed in this report.

In the following discussions note that all data on the sale of North and South Dakota pelts by hunters and trappers are for in-state sales only, resulting in a probable understatement of their total worth.

Pelts of the beaver have been sought after since the opening of the region to the fur trade in the 18th century. Beaver occasionally occupy semipermanent wetlands in the Prairie Pothole Region of the Dakotas, especially basins in the northwestern portion of the region where aspen (Populus tremuloides) is sometimes common in the wet-meadow zone and adjacent uplands (A.B. Sargeant, Northern Prairie Wildlife Research Center, pers. comm.), but even there drought can cause mass emigration or decimate populations. Fritzell states that beaver are occasionally reported, but do not establish permanent breeding populations in semipermanent wetlands in the southern portion of the region.

This species occupies primarily riverine wetlands in the region. Populations have increased in recent years, but, compared to its former abundance, beaver numbers are still relatively low. Beaver often cause extensive damage to shade and ornamental trees where rivers flow through residential areas; their dam-building activities can also cause nuisances along watercourses, and offending animals usually are quickly destroyed.

The beaver is a moderately important furbearer in the Dakotas. Dealer surveys indicate an average of 9,025 animals were sold annually in North Dakota during the 1983-84 to 1985-86 seasons, for an average total of $106,766 (Steve Allen, North Dakota Game and Fish Dept., pers. comm.). Buyers in South Dakota paid a total of $57,669 for 3,238 pelts during the 1986-87 season (Larry Fredrickson, South Dakota Game. Fish and Parks, pers. comm.).

The muskrat is the only native mammal that still has a great impact on wetland ecology in the region. Semipermanent wetlands are the most important habitat for muskrat in the region because these basins are abundant, deep enough to sustain under-ice activity in winter, and support growth of emergent plants, especially Typha spp. and Scirpus spp., which provide both food and house-building materials. Muskrats also dig burrows in the banks of wetlands.

Consumption of hydrophytes by high muskrat populations often causes great changes in the interspersion of cover and open water in prairie wetlands. Fritzell states that muskrat densities >50/ha are not unusual. Errington (1948) recorded maximum winter populations of 86 muskrats/ha on a fertile Iowa marsh.

In the extreme southeastern portion of the Dakota pothole region, the importance of muskrat activity on marsh ecology is great. The milder winter climate and more stable water levels there are similar to conditions in Iowa, where high muskrat populations can decimate nearly all emergent hydrophytes and result in mass migration and high mortality, as well as greatly affecting the use of the wetland by other animal species. Here, as semipermanent wetlands cycle between extreme dryness and high water levels, muskrat activity greatly influences nearly all aspects of marsh ecology (Weller and Spatcher 1965; Weller and Fredrickson 1974; van der Valk and Davis 1978a). Van der Valk and Davis (1978a) recognize four stages in this cycle: dry marsh, regenerating marsh, degenerating marsh, and lake marsh (Appendix A, Figure 12). The food and cover requirements of expanding muskrat populations is thought to be an important factor contributing to the decline in emergent hydrophytes that marks the end of the regenerating-marsh phase. If high water levels continue, muskrat populations increase until emergent plants are almost totally destroyed. This leads to the lake-marsh phase, where submersed macrophytes dominate and muskrats are forced to emigrate or suffer high mortality (Errington et al. 1963). The lake-marsh stage will persist until water levels again decline.

The effects of muskrats on the ecology of semipermanent wetlands become much less pronounced in North Dakota, where colder winter climates prevail and wetlands often freeze to the bottom, especially when fall water levels are below average. Under such conditions, foraging is curtailed and populations can be decimated (Seabloom and Beer 1963). Because of increased frequency of drought, muskrat populations in the more arid western portion of the region also do not usually build to levels high enough to greatly diminish emergent vegetation.

Muskrats are an economically important furbearer in the region. Buyer surveys show an average of 64,181 pelts sold in North Dakota during the 1983-84 to 1985-86 trapping seasons, for an average annual return of $103,331 to the takers (Steve Allen, North Dakota Game and Fish Dept., pers. comm.). The harvest in South Dakota averaged about 55,000 during the 1982-83 and 1983-84 seasons (Linscombe and Satterthwaite in press), but better water conditions during the 1986-87 season resulted in sales of 248,126 pelts, for which in-state buyers paid a total of S617,834 (Larry Fredrickson, South Dakota Game, Fish and Parks, pers. comm.).

The mink is common throughout the Prairie Pothole Region and is closely associated with basin wetlands. No reliable census techniques have been developed for this solitary, primarily nocturnal or crepuscular species (A.B. Sargeant, Northern Prairie Wildlife Research Center, pers. comm.). Data from Errington (1943), however, suggest that when surface water is present about 50 ha of semipermanent wetland will support a female with young. Mink populations probably fluctuate greatly in the Prairie Pothole Region in response to drought (Adams 1962; Eberhardt 1974; Fritzell 1989).

Dens are usually located in abandoned muskrat burrows along wetland shorelines (Schadweiler and Storm 1969; Eberhardt 1973; Sargeant et al. 1973; Eberhardt and Sargeant 1977). Females with young in dena can concentrate their activity in relatively small (<20 ha) semipermanent wetlands (Sergeant et al. 1973; Eberhardt and Sargeant 1977) whereas the home ranges of males average 646 ha from May through July and include as many as 30 temporary, seasonal, semipermanent, and permanent wetlands, at least in the Prairie Pothole Region of Manitoba (Arnold 1986).

The concentration of nesting birds in prairie wetlands and the relative scarcity of fish, semiaquatic mammals, and large invertebrates, such as crayfish, in these habitats result in levels of mink predation that can cause significant mortality of marsh birds. For example, Eberhardt and Sargeant (1977) found that on a semipermanent North Dakota wetland, a single mink family can kill 8% of the adult and 52% of the juvenile coots and 20% of the adult and 6% of the juvenile pied-billed grebes. They also found an average of 6.3 adult and 5.3 juvenile ducks taken per mink family, and noted that the preponderance of female diving ducks taken could account for the disparate proportion of males commonly observed among this group of waterfowl. Arnold and Fritzell (1987a, b) estimated that avian prey comprised 55%-75% of the volume of the May-July food of male mink in prairie wetlands in Manitoba.

Economically, mink are a moderately important furbearer in the Dakotas. An average of 4,571 animals were sold to North Dakota buyers during the 1983-84 to 1985-86 seasons, for an average return of $64,497 (Steve Allen, North Dakota Game and Fish Dept., pers. comm.). About 6,000-10,000 mink are estimated to be harvested annually in South Dakota (Linscombe and Satterthwaite in press). During the 1986-87 season, 8,557 pelt" were sold to South Dakota buyers, for a return to takers of $203,828 (Larry Fredrickson, South Dakota Game, Fish and Parks, pers. comm.).

The remaining mammals discussed in this report (Group 2 of Table 9) range across at least 10% of the pothole region of the Dakotas, and either regularly make extensive use of prairie wetlands, often during the winter months, or likely can complete their life-cycle in moist, often shrubby, meadows.

Little is known about the life histories of the arctic, masked, and pygmy shrews in the grassland biome, except that marshes or moist habitats, often dominated by cattails or hydrophytic grasses, are used by these tiny carnivores (Jones et al. 1983). Of the three, the arctic shrew seems to be the most wetland oriented, as aquatic invertebrates are a known food item. However, a recent study in the Prairie Pothole Region of northcentral South Dakota indicated that pygmy shrews are more abundant than arctic shrews in shallow-marsh zones (Gruebele and Steuter 1988).

The eastern cottontail is primarily a dweller in thickets and brushlands, and the dense stands of willow (Salix spp.) that are sometimes found in wet-meadow zones of prairie wetlands provide permanent habitat. This cottontail is mostly herbivorous, but in times of food shortage may eat mollusks and even carcasses of other cottontails. (Jones et al. 1983). The presence of cottontails around some prairie wetlands is undoubtedly a prime attractant to mustelid and canid carnivores.

The range of the snowshoe hare encompasses roughly the northern half of North Dakota. This hare can be found in wetland wet-meadow zones dominated by willow or aspen (Populus tremuloides). Jones et al. (1983) stated that alder (Alnus spp.) swamps and burned areas with woody regrowth are especially favored. Snowshoe hares are herbivorous, but occasionally eat carrion.

The western harvest mouse ranges throughout the southern two-thirds of the region. Jones et al. (1983) list cattail as a typical habitat and state that the species often associates with meadow voles and uses their runways. Seeds and small amounts of insects are the main food of this small rodent, which is active year around. Up to 18% of the small mammals trapped in South Dakota wetlands by Pendleton (1984) were western harvest mice.

Meadow voles are common herbivores throughout the region, where they inhabit surface runways and tussocks in stands of grasses, sedges, and rushes found in wet-meadow zones (Jones et al. 1983). Cycles of abundance are very pronounced for this species, and population densities as low as 2.5/ha and as high as 617/ha have been reported (Jones et al. 1983). Up to 75% of the small mammals trapped in North Dakota wetlands by Eberhardt (1974) were meadow voles.

This vole is prominent in the diet of the coyote, red fox, mink, longtailed and least weasels, great horned owl (Bubo virginianus), short-eared owl (Asio flammeus), and northern harrier. The cyclical abundance of voles can greatly affect the seasonal abundance of some of their avian predators.

The meadow jumping mouse occurs throughout the pothole region of the Dakotas, but the western jumping mouse is mostly restricted to the North Dakota portion (Jones et al. 1983). Both species are mostly found in tall, lush herbaceous or graminoid cover typical of low prairies or wet meadows in the northern plains. Adequate ground cover is essential for nests. Both species are active about 5 months of the year in this area. Material cited in Fritzell (1989) shows that up to 17% of the small mammals trapped in North Dakota wetlands were meadow jumping mice.

The coyote is now the largest common carnivore in the Prairie Pothole Region of the Dakotas and occurs throughout the area, but is most numerous in the western part. Territories for coyote families in south-central North Dakota averaged 61.2 km2 (Sergeant et al. 1987). Although primarily terrestrial, the coyote hunts in peripheral wetland zones when surface water is present in interior zones, and uses dry and ice-covered wetlands for hunting, traveling, and resting. It also feeds on prey associated with wetlands at various times of the year, including insects, birds and their eggs, cottontails, small rodents, muskrats, beaver, and deer (A.B. Sargeant, Northern Prairie Wildlife Research Center, unpubl. data).

Coyotes are an important furbearer in the region. During the 1983-84 to 1985-86 seasons, North Dakota buyers purchased an average of 7,913 pelts annually, for an average annual combined return to takers of $255,458 (Steve Allen, North Dakota Game and Fish Dept., pers. comm.). In 1986-87, South Dakota buyers purchased 8,149 pelts for a total of $349,674 to takers (Larry Fredrickson, South Dakota Game, Fish and Parks Dept., pers. comm.).

The red fox is common in both Dakotas, and, like the coyote, is primarily a terrestrial species that uses only the shorelines of wetlands when surface water is present, but hunts, travels through, and rests in wetlands when they are dry or ice covered. Territories of red fox families sympatric with coyotes in south-central North Dakota averaged 11.9 km2 (Sergeant et al. 1987).

Red fox eat a huge variety of foods, mostly animal matter. Foods eaten depend on season and habitat. Common foods found in or at the edges of prairie wetlands include cottontails, meadow voles, harvest mice, jumping mice, young raccoons, and birds and their eggs.

Perhaps the most significant role of the red fox in the ecology of prairie wetlands is as a predator of upland-nesting waterfowl and other semiaquatic birds. Sargeant et al. (1984) estimated the average annual take of adult ducks (both killed and scavenged) by the red fox in midcontinental North America at about 900,000. This impact was greatest in the high-density wetland area of the Missouri Coteau in North Dakota, where a 5-year average of 17.0% of the total prey biomass consumed by foxes during the annual denning season was dabbling ducks.

The red fox has recently been an economically important furbearer in the Prairie Pothole Region, although current (1987) pelt prices are relatively low. During a recent 10year period (1970-1980), annual harvest in the pothole region of North Dakota alone was 10,000-62,000 pelts that returned $59,000-$2,389,000 to takers (Sergeant et al. 1984). Buyer surveys conducted by Larry Fredrickson (South Dakota Game, Fish and Parks Dept., pers. comm.) indicate that the 17,512 animals purchased there during 198687 returned a total of $368,102 to takers.

Before settlement of the Prairie Pothole Region by European man, the omnivorous raccoon inhabited only wooded river valleys in the pothole region of the Dakotas, with greatest densities found in drainages in the eastern part of the region. However, populations expanded greatly after settlement, and raccoons can currently be found throughout the region. Cowan (1973) and Fritzell (1978) found spring raccoon densities of 0.5-3.2 individuals/km in various parts of the region. These studies also showed that wetlands, particularly the seasonal (Class 3) and semipermanent (Class 4) basins of Stewart and Kantrud (1971) were commonly used habitat.

Fritzell (1978) found that raccoon use of wetlands increased greatly from spring to summer as food. become available in these habitats. Greenwood (1982) found that 94% of the nocturnal raccoon activity in eastern North Dakota wetlands was related to foraging, and that the most important food items gathered in these habitats were aquatic insects, birds, bird eggs, snails, and crustaceans.

During the day, raccoons in the pothole region rest, and are seldom found in the same locations on consecutive days from April to July. Use of wetlands for resting sites increases greatly during this period, and by July, 70% of the sites can be located there (Schneider et al. 1971; Cowan 1973; Fritzell 1978).

Raccoons in the northern portions of the Prairie Pothole Region probably do not use wetlands as sites for winter dens, but wintering animals have used dense cattail "teepees" in South Dakota (Fritzell 1989).

The expansion of raccoon populations in the prairie region has been associated with decreased waterfowl nesting success over the past 40 years (Kiel et al. 1972; Duebbert and Kantrud 1974; Trauger and Stoudt 1974; Duebbert and Lokemoen 1976; Sargeant and Arnold 1984). Raccoons feed extensively on waterfowl eggs, especially those of the overwaternesting diving ducks (Cowan 1973; Greenwood 1981, 1982). Although the total negative impact of this predation on waterfowl populations remaina to be determined, it will likely increase a" the wetland habitat base continues to decline (Fritzell 1989).

The raccoon has recently become an important fur resource in the pothole region. During the 1983-84 to 1985-86 North Dakota trapping seasons, takers sold an average of 15,881 pelts annually in the state, for which buyers paid a total of $202,006 (Steve Allen, North Dakota Game and Fish Dept. pers. comm.). Recent (1986-87) sales of 34,038 pelts to in-state buyers in South Dakota resulted in a total return of $715,138 to takera (Larry Fredrickson, South Dakota Game, Fish and Parks Dept., pers. comm.).

Few ecological data are available for least and long-tailed weasels in the Prairie Pothole Region. Both species range throughout the region. Weasels prey mostly on voles in this area, and the wet-meadow zones of wetlands are important vole habitat. The long-tailed weasel is a known predator of waterfowl eggs (Keith 1961; Teer 1964), but the likely impact of this mammal on waterfowl is "mall.

Weasels are unimportant as a fur resource in both Dakotas. Reported annual sales to buyer. in both states in the mid-1980's was <100 animals, with prices paid to takers averaging <$0.90/animal (Steve Allen, North Dakota Game and Fish Dep., pers. comm.; Larry Fredrickson, South Dakota Game, Fish and Parks Dept., pers. comm.).

The Prairie Pothole Region lies near the center of the range of the striped skunk. This primarily nocturnal mammal is a ubiquitous predator often associated with wetlands. Densities in the prairie region have varied from 0.4 to 3.1 animals/km2 (Scott and Selko 1939; Upham 1967; Bjorge et al. 1981; Greenwood et al. 1985).

Literature reviewed by Fritzell indicates that skunks are active in the Prairie Pothole Region from January to November. Eight of twelve winter dens in a large Manitoba marsh were in stands of Phragmites australis (Mutch 1977). rest areas can be underground or abovearound in dense grasses in uplands or aboveground in stands of emergent hydrophytes in portions of wetlands where surface not present.

Striped skunks in the Prairie Pothole Region feed largely on insects during the warmer months, although mice, frogs, birds, shrews, bird and turtle eggs, berries, fruit, worms, and spiders are eaten (Jones et al. 1983). Skunks are major predators of clutches of eggs of upland nesting dabbling ducks (Stoudt 1971: Duebbert and Kantrud 1974; Duebbert and Lokemoen 1980), including many that are likely encountered incidentally as skunks search grasslands for insect prey (A.B. Sargeant, Northern Prairie Wildlife Research Center, pers. comm.). Skunks can also destroy overwater nests of diving ducks if drought conditions increase nest accessibility (Stoudt 1982).

The striped skunk is unimportant economically as a furbearer in both Dakotas. North Dakota dealers reported a total purchase of <200 animals/yr during the 1983-84 to 1985-86 seasons. Takers received an average of only $2.40 each for these pelts (Steve Allen, North Dakota Game and Fish Dept., pers. comm.). Total purchase by South Dakota dealers was 1,878 animals during the 1986-87 season; these pelts returned an average of $2.22 each to takers (Larry Fredrickson, South Dakota Game, Fish and Parks, pers. comm.).

Few quantitative data are available, but anyone who has observed or hunted white-tailed deer in the Prairie Pothole Region is aware of the importance of basin wetlands to this species, especially during the fall and winter. The primary functions of these wetlands are to provide refuge and thermal cover, although some browse (Populus spp. and Salix spp.) and forage (Sonchus spp. and Cirsium spp.) are also obtained (Sparrowe and Springer 1970; Kucera 1976; Fritzell 1989). In North Dakota, dry wetlands are also used as fawning sites (Harmoning 1976).

Dense stands of Typha spp., Scirpus spp., Phragmites australis, and Salix spp. seem to provide the most attractive cover for whitetailed deer in wetlands in this area (H.A. Kantrud pers. obs.). These plants are mostly found in semipermanent wetlands.

White-tailed deer populations have expanded greatly in the Prairie Pothole Region in the last 20 years, likely because of a combination of better management and law enforcement and the great increase in area planted to row crops (corn, sorghum, and sunflower) that provide cover and high-energy winter foods.

The white-tailed deer is an important game species in both states. Latest available estimates place the 1986 harvest in the pothole region of North Dakota at 42,085 (Jim McKenzie, North Dakota Game and Fish Dept., pers. comm.). An estimated 30,424 animals were harvested in 1986 from the area of South Dakota east of the Missouri River (Les Rice, South Dakota Game, Fish and Parks, pers. comm.). Estimates of annual cash flow associated with white-tailed deer hunting in the United States indicate that a single animal is worth $1,657 (Williamson and Doster 1981). Although this figure is undoubtedly high for the Dakotas, it suggests that the income generated to state and local economies by sport hunting of this species is significant.


Fritzell (1989) summarized the role of wetlands in the life cycle of mammals in the Prairie Pothole Region. He concluded that these habitats are of direct importance to many species, and that some mammals markedly affect other components of wetland ecosystems and the values humans extract from them. He cited in particular the effects of the muskrat on nutrient exchange and vegetative structure in wetlands and the importance of wetlands in predator-prey relationships that can significantly affect the production of waterfowl and other wetland wildlife. He also noted that the harvest of furbearers and whitetailed deer in prairie wetlands is an important contribution to local economies.

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