The ‘omnivorous badger dilemma’: towards an integration of nutrition with the dietary niche in wild mammals

Laboratory studies have demonstrated that, given plenty of food, many animals can achieve a species‐specific macronutrient intake target by selecting nutritionally balanced foods or combining complementary foods. Wild‐living, broad‐scope omnivorous species often face great heterogeneity in the composition of available resources. Hence they may be precluded, either locally or seasonally, from meeting their nutritional preferences. With the aim of shedding light on the nutritional niche breadth of a wild‐living omnivore, the European badger Meles meles, we reviewed available scat‐based studies on badger diet and applied right‐angled mixture triangles to examine the relationships between macronutrient availability and composition of diets. Moreover, to assess the potential of scat analysis to investigate nutritional balancing, we analysed badger diet in two habitats of NW Italy, focusing on identifying the total weight of each food item ‘as ingested’ as accurately as possible. The average macronutrient content of the European badger's diet comprised 40–45% protein‐energy, 30–35% lipid‐energy, and 20–25% carbohydrate‐energy. Macronutrient intake was not constant throughout the year, suggesting that, in some seasons, badgers may be unable to reach their macronutrient target, and that diet balancing is achieved over longer periods. The macronutrient selection strategy of badgers suggests that their feeding habits are close to those of obligate carnivorous mammals, although badgers were found to be more tolerant towards carbohydrates than obligate carnivores. Macronutrient ratios as assessed by scat analysis matched well with those obtained by reviewing available data, confirming that meta‐analyses of diet studies can provide useful information on the macronutrient requirements of elusive wild mammals.