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

Results


We obtained 65 badgers (23 females, 42 males) ranging from 6-mo to 11-y-old. Six badgers were juveniles (3 females, 3 males), 28 were 1-y-old (11 females, 17 males) and 31 were ≥2-y-old (9 females, 22 males). Two of the 1-y-old females were pregnant or parous, 8 showed no evidence of reproduction and reproductive status of 1 female was not determined. Of females ≥2-y-old, 8 were pregnant or parous and 1 showed no evidence of reproduction in the current year.

We examined gastrointestinal tracts of 59 adult and 6 juvenile badgers; gastrointestinal tracts of 12 adults and 1 juvenile were not usable because they were empty. Seventeen female and 30 male adult badgers were included in food habits analyses. Twenty-four samples were obtained in spring and 23 in summer.

We detected no difference in occurrence of animal foods between female and male badgers for all food classes (P > 0.26) and therefore combined results from females and males. Mammal remains were found in 96% of samples (Table 1) and we found no seasonal effect (P = 0.33). Mice (Muridae, Heteromyidae or Zapodidae) were most prevalent, occurring in 68% of samples. Pocket gophers (Geomyidae) and ground squirrels (Sciuridae) were other common mammals. Northern pocket gophers (Thomomys talpoides) were in 39% of 38 adult badgers obtained in North Dakota, which includes the range of this species (Jones and Birney, 1988). Plains pocket gopher (Geomys bursarius) were in 33% of the 9 adult badgers obtained in Minnesota, which includes the range of this species. In juvenile badgers, pocket gophers were the most common mammal, found in 3 of 5 samples; Cricetinae were the only other mammal found in 1 of the 5 juvenile badgers.

Insect remains were second in frequency following mammals (Table 1). Insect remains were more frequent in summer (52%) than spring (29%; P = 0.06). Four orders were identified; Coleoptera was the most common (28%). Although insects occurred frequently, their contribution to the total volume of samples generally was low, only trace amounts in 18 of the 22 samples with insect remains. Insects were found in three of five juvenile badgers.

Bird remains (feathers or eggshells) were more common in summer (61%) than spring (4%; P < 0.01). We found remains of birds in 32% of samples from adult badgers; most frequently as eggshell fragments (Table 1). Most birds were ducks or ducklings present in 9% of samples. Contents of gastrointestinal tracts included remains of a dabbling duck female and 2 ducklings. Eggshell fragments (three size categories identified separately) were found in 23% of samples. Duck eggshell fragments were especially prevalent, occurring in 19% of samples. One gastrointestinal tract with remains of ducklings also contained duck eggshell fragments, indicating ducklings may have been consumed in the nest, possibly as embryos in eggs. The only evidence of birds in juvenile badgers was duck eggshell fragments found in 1 of 5 samples.

Remains of reptiles included snakes and turtle eggs (Table 1). We detected no seasonal differences in occurrence of reptiles (6% spring, 4% summer; P = 0.31). Four garter snake (Thamnophis sp.) embryos (2.5-cm long) were found in 1 sample.

Amphibians were present more often in spring (20%) than summer (0%; P = 0.05). Tiger salamander (Ambystoma tigrinum) remains represented the only amphibian identified in adult badgers (Table 1). One gastrointestinal tract contained 4 intact adult salamanders. A frog (Anura) was the only amphibian found in samples from juvenile badgers.

Residues of plants were present in 85% of samples (Table 1). Sunflower seeds (Helianthus sp.) were found only in spring samples; 2 of 3 samples were nearly 100% sunflower seeds. Grass was found in 55% of samples, most often in small amounts.

Table 1. — Occurrence (n) of animal and plant residues found in gastrointestinal tracts of 47 adult and 5 juvenile badgers and percent frequency of occurrence (adult badgers only). Badgers were obtained during April-July in west-central Minnesota and southeastern North Dakota, 1987-1990
  Adult Juvenile   Adult Juvenile
n % n n % n
Mammals 46 98 4 Insects 19 40 3
   Leporidae (Lepus townsendii) 1 2 0    Coleoptera 13 28 3
   Sciuridae 13 28 0    Hymenoptera 1 2 1
       Spermophilus tridecemlineatus 6 13 0    Diptera 1 2 0
       Unknown 10 21 0    Orthoptera 1 2 1
   Geomyidae 18 38 3    Unknown 4 9 0
       Thomomys talpoides 15 32 2        
       Geomys bursarius 3 6 1 Reptiles 5 11 2
   Heteromyidae (Perognathus sp.) 1 2 0    Squamata 5 11 2
   Muridae 30 64 1    Chelonia (turtle eggs) 1 2 0
       Microtinae 14 30 0        
       Cricetinae 19 40 0 Amphibians 5 11 1
       Unknown 5 11 1    Urodela 5 11 1
   Zapodidae (Zapus hudsonicus) 1 2 0    Anura (frog) 0 0 1
   Bovidae 1 2 0        
   Unknown 1 2 0 Gastropods (snails) 2 2 1
               
Birds 15 32 1 Plants 40 85 5
   Scolopacidae (Limosa fedoa) 1 2 0    Grass 26 55 2
   Anatidae1 4 9 0    Sunflower seeds 2 4 0
   Unknown 2 4 0    Woody 1 2 0
   Bird eggs 11 23 1    Unknown 19 40 3
       Large (duck) 9 19 1        
       Medium 2 4 0        
       Small (passerine) 4 9 0        
1 Includes dabbling duck female adult (2%) and ducklings (6%); does not include duck eggs

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