Michael T. Walsh1; Robert Bonde2; Martine deWit3; Cathy Beck2; Andy Garrett3; J.P. Reid2; Arthur W. Wong4; Jennifer Meegan1; John Fricott5
Health assessments of wild animal populations have become more common as a means of evaluating the incidence of current disease, evidence of past disease, exposure to natural toxins, industrial compounds, pesticides, pharmaceuticals, microorganisms and trace elements from anthropogenic sources.1,2 Population health assessments for manatees in Florida incorporate the evaluation of different subpopulations throughout the state to clarify the differences in disease incidence, environmental exposure to site related variables, forage use and availability, and seasonal pressures such as cold stress. These approaches have also been applied for sirenian populations in other geographic locations.
The Florida manatee is well known for the lethal effects of watercraft trauma, cold environments, and exposure to harmful algal blooms on individuals in the population. These and other common mortality categories such as perinatal deaths have often overshadowed the development of a wider knowledge base regarding other possible disease factors that may have past, present and future implications for the health and survival of the population. Early versions of health assessments were conducted during manatee captures initiated to place tracking devices on targeted animals to study habitat use. Veterinarians from rehabilitation facilities often participated to assist in additional sample collection and evaluate the health of individuals that were caught and restrained. With an increase in concern for the incidence of infectious diseases such as papilloma virus and the ever changing environmental impacts, the role of the health, research and diagnostic portions in manatee assessments have also increased.
The health assessment team is composed of experienced capture personnel, field biologists and veterinarians to maximize the safety and well being of the animals involved. This cooperative approach has resulted in a number of improvements. The health assessment procedure includes restraint and handling, monitoring of restrained animals, photographic documentation, and sample and measurement data collection. Monitoring of restrained manatees may include heart rate from auscultation, electrocardiogram, respiratory rate over 5 minute intervals, oral body temperature, exhaled CO2, i-STAT measurements of blood gases, thermography to monitor skin heat relationships, and behavioral observations. This level of monitoring has resulted in the ability to intervene where respiratory parameters such as hypercapneaand acidosis are of concern. Restraint during cold weather may be modified to shorten the out of water time, and include the use of space blankets to help retain body heat. Whole blood glucose levels are checked with a glucometer in any animal that is young or thin.
To offset a decreased inspiratory capability while on land oxygen supplementation is provided to each animal throughout the examination. In general, the handling procedure is limited to one hour which is also amended further for pregnant individuals. Blood, urine, feces, tear fluid, milk and skin samples are collected for multiple research projects that include both individual health parameters and specific population parameters. At the end of the procedure most animals are weighed just prior to release.
Information collected from these assessments can aid rehabilitation centers in their evaluation of what constitutes normal versus abnormal in animals presented for treatment. Clarifying the health status of the free-ranging manatee population can help wildlife managers and administrators to better understand the interactions between the species, the changing environment, prey or food item requirements, and factors that are tied to human influence.
The authors would like to thank the dedicated crews from FWC, USGS, US Fish and Wildlife Service, Volusia County, Melanie Pate from the University of Florida, students and the volunteers who have contributed to these programs. The health assessments are carried out under US Fish and Wildlife permit nos. MA791721 and MA773494.
1. Bonde, R.K., A.A. Aguirre and J. Powell. 2004. Manatees as sentinels of marine ecosystem health: are they the 2000-pound canaries? EcoHealth 1: 255-262.
2. Bossart, G.D. 2006. Marine mammals as sentinels for ocean and human health. Oceanography 19(2): 134-137.