Renee BakkerFollow


Marine Biology


Sartini, Becky, L.

Advisor Department

Animal and Veterinary Science




Testosterone; Diurnal Variation; Cetaceans; Blow; Unihemispheric Slow Wave Sleep; Reproductive Condition; Immunoassay


Studies on the concentrations of certain hormones in cetaceans and their effects on cetacean biology are useful to determining physical conditions such as age, sex, and reproductive status of individuals. Hormone concentrations can be determined through blood samples, but collection of blow (exhaled respiratory vapor) has proven to be a noninvasive method of obtaining samples that can be analyzed for hormone concentrations. The existence of diurnal variation in hormone concentrations greatly affects the value of what time of day samples are collected. Previous studies have found that other mammalian species exhibit diurnal variation of testosterone and that for many species the secretion of the hormone is dependent on sleep cycles. Cetaceans are unique in that they engage in a method of sleep called unihemispheric slow wave sleep. This allows for half of their brain to sleep while the other half remains awake, therefore they are never fully asleep. The aim of this study was to determine whether or not beluga whales housed at an aquarium expressed diurnal variation in their testosterone concentrations. Blow was collected from two male belugas at three different times throughout the day. A competitive enzyme immunoassay (EIA) was used to determine the testosterone concentrations. It was found that the relationship between time of day and testosterone concentration was not significant and there was not a significant difference in concentration between the collection times that were tested. This suggests that diurnal variation of testosterone secretion is not occurring in these beluga whales during daylight hours.