Pregnancy in the Little Brown Bat

Abstract

Body weights of bats of the species Myotis lucifugus lucifugis increase exponentially during pregnancy. The rate of increase differs with the year. At birth the single offspring weighs 28.8% of the mother's weight. The metabolic rate increases fivefold during pregnancy but is always less than the expected metabolic rate for a nonpregnant mammal of the same weight. The heat increment of gestation is 2.2 kcal, an amount less than would be expected from the birth weight. The bat fetus is produced at a very low cost that is spread over a relatively long period.