Paper Type

Master's Thesis


College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)



NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Julie Richmond

Second Advisor

Dr. Jim Gelsleichter

Third Advisor

Dr. Robert Bonde

Department Chair

Dr. Daniel C. Moon

College Dean

Dr. Barbara A. Hetrick


The metabolic hormones ghrelin, growth hormone, and insulin-like growth factor I are influenced by developmental age, sex, and nutritional status in domestic and free-ranging species. However the role these hormones play has not previously been explored in sub-tropical/ tropical mammals. Furthermore, the seasonality of species with less dynamic environmental cues, such as the West Indian manatee, have not been studied. The West Indian manatee is and endangered species distributed in the southeastern United States and throughout the Caribbean basin, and its nutritional physiology is influenced by environmental factors. Understanding the hormone response to nutritional status in this species and its seasonality will enhance our knowledge of the links between season, nutrition, and life history.

The purpose of this research is to understand the biology and seasonal patterns of metabolic hormones in free-ranging manatees which will allow us to assess the nutritional status of wild populations. The research objectives include validation assays to accurately quantify hormone concentrations in manatees. Hormones were quantified in manatee serum using heterologous radioimmunoassay. Hormones were then evaluated between summer, fall, and winter and compared to body composition. Developmental patterns were also assessed. Lastly, hormones were examined between Florida and Antillean manatee populations.

Manatees exhibited differences in GH, IGF-I, and body composition demonstrating seasonality similar to other species. Manatees exhibited differences between age classes suggesting decreased growth rate as the animals age. Differences were detected between populations. This research suggests that ghrelin, GH, and IGF-I can be used to indicate nutritional status and detect seasonality and developmental age in the manatee. This could prove to be a valuable tool in rehabilitation facilities and during captures and health assessments to provide better veterinary care and further improve overall health and body condition to better manage the survival of the species.