ACCRETION OF NITROGEN AND MINERALS IN SUCKLING BATS, MYOTIS-VELIFER AND TADARIDA-BRASILIENSIS

Levels of nitrogen, sodium, potassium, magnesium, calcium, and iron we re determined for suckling young of known-age, lactating Myotis velife r and Tadarida brasiliensis, and milk from T. brasiliensis nursing kno wn-age young. From birth to weaning, relationships of both nutrient co ncentrations and nutrient accretion to age are similar for both specie s but differ for each nutrient and generally reach adult concentration by weaning. While total mass of body sodium and potassium reach adult levels in both species well before weaning, levels of other elements do not. Although comparable data are limited, element concentrations i n suckling bats are similar to those for other suckling small mammals and nestling birds. Growth requirements for measured nutrients in thes e bats are lower than published values for rodents. Most mineral nutri ents that were measured in milk for T. brasiliensis varied with stage of lactation and were comparable in concentration with milk of other m ammals. Using daily accretion of nutrients and their concentrations in milk, we calculated the minimal mass of milk needed to meet growth re quirements in suckling T. brasiliensis. Among measured nutrients, calc ium is the Limiting nutritional factor that determines mass of milk ne eded by suckling young during postnatal growth.