Nutritional implications for nitrogen and mineral budgets from analysis of guano of the big brown bat Eptesicus fuscus (Chiroptera: Vespertilionidae).

1. Analysis of nitrogen, sodium, calcium, magnesium, iron, and potassium levels in big brown bat guano throughout much of the summer roosting period was performed. 2. Based on the tenet that low, non-variable levels of an element in feces indicate dietary inadequacy for that element, female big brown bats are routinely and severely stressed for calcium and may become stressed for iron by the end of the summer. Similar elemental stresses, although not as severe, exist for males.