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Foods of American Badgers in West-central Minnesota and Southeastern North Dakota During the Duck Nesting Season

Discussion


Badgers have been largely overlooked as predators of duck eggs. However, our findings show that duck eggs were commonly consumed by badgers. We believe that eggs of dabbling ducks are especially available to badgers because of the propensity of dabbling ducks to nest in grassland (Klett et al., 1988), the favored habitat of badgers (Messick and Hornocker, 1981). Badgers foraging for small mammals or insects in grassland are likely to encounter nests of dabbling ducks. Loss of grassland habitat, primarily to agricultural practices, probably increases vulnerability of hens and their eggs to depredation by badgers because nests are concentrated in remaining fragmented grassland areas. There is no information available to indicate whether badgers purposefully search for bird nests.

The preponderance of small mammals in diets of badgers in our study and the increase in occurrence of insects from spring to summer are similar to findings reported by others (Errington, 1937; Lampe, 1982; Messick et al., 1981; Snead and Hendrickson, 1942). Insects were generally represented by only a few individuals and comprised a small percent of the volume. We attribute the increases in occurrence of insects and bird eggs from spring to summer to the increasing seasonal availability of these foods. The extent to which badgers ate carrion is unknown. The occurrence of residue of cattle (Table 1) provide evidence of scavenging by badgers.

Plant material was often present in samples, but quantity was small and most likely ingested incidentally, except for sunflower seeds. Sunflower seeds were sometimes consumed in large quantities in early spring, similar to the observations of Jense (1968) in South Dakota. Sunflower seeds are a significant winter food item for red foxes (Vulpes vulpes) in North Dakota (Sargeant et al., 1986) and may be an important food of badgers in early spring when animal foods are scarce.

Because of the small sample size of juvenile badgers, it is difficult to draw inferences about their food habits compared to adult badgers. Messick and Hornocker (1981) suggested juvenile badgers may forage on the more easily captured insects and less on mammals that might be more difficult to capture, while they improve their predatory skills.

Food-habit studies of badgers have shown a wide diversity of prey species, which strongly indicates opportunistic foraging behavior. Although our data highlight the importance of small mammals to badger diets, we identified a diversity of foods in badger diets. Our data also include a high frequency of ducks and duck eggs, from a sample of badgers obtained specifically from an area where nesting waterfowl were abundant. This suggests that badgers are influenced by prey availability (Errington, 1937; Snead and Hendrickson, 1942; Jense, 1968; Messick and Hornocker, 1981; Lampe, 1982). Although we lack information on food availability, our study was conducted during a drought, which might negatively influence the availability of ducks and duck eggs (Krapu et al., 1983; Jackson et al., 1985; Greenwood et al., 1987). In years of good wetland conditions we would expect increased proportions of ducks and duck eggs in badger diets. Badger populations in North Dakota seem to have increased in the past 5-10 y based on numbers of captures (U.S. Department of Agriculture, 1996, Animal Damage Control, Bismarck, North Dakota, unpubl.). Increasing badger populations could increase the impact of badger predation on success of nesting ducks and other birds. Our findings indicate that the influence of badgers on local nesting populations of dabbling ducks could be substantial.


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