| Torpor in many small bats is variable and unpredictable. It was hypothesized that foraging success and body fat would explain this variation and that metabolic rate would be directly proportional to foraging success, with the bat's fat content explaining the remaining variation. Metabolic rates of 30 big brown bats (Eptesicus fuscus) were measured using open-flow respirometry throughout the day. Feces were collected to estimate food consumption and their fat content determined using a volumetric apparatus. To calibrate the apparatus, 45 bats were measured, sacrificed, and had their fat extracted using petroleum ether. This study showed that although the apparatus makes accurate measurements of volume, factors such as gut contents and embryo weight do not allow this method to predict reliably fat content by calculating density. The poor estimate of fat, along with the stress of being captured and handled, may be reasons metabolism was not correlated with fat or foraging success. |
