NUTRIENT LEVELS IN GUANO FROM MATERNITY COLONIES OF BIG BROWN BATS

Samples of typical guano, collected weekly during the summer roosting period from six maternity roosts of big brown bats (Eptesicus fuscus), were analyzed for levels of nitrogen, sodium, potassium, calcium, mag nesium, and iron. Total time and variability patterns, unique for each nutrient, suggested limiting or inadequate dietary intake of calcium for most of the summer and of iron from the end of lactation onward. S amples of atypical guano often contained high levels of calcium or iro n. Levels of some nutrients in guano, and, therefore, nutrient budgets , differed between roosts within weekly collections, especially early in the roosting period, and generally reflected differences in levels of those nutrients from insects available as prey near those roosts. C ertain insects (e.g., plecopterans and noctuids) apparently were not c onsumed in proportion to their availability. Big brown bats foraging o ver permanent streams showed nutrient budgets that differed from those of bats feeding over land.