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geer > 2000 > poster > thermoregulation of the american alligator in the everglades

Thermoregulation of the American Alligator in the Everglades

Poster presented December 2000, at the Greater Everglades Ecosystem Restoration Conference

H. F. Percival 1, S. R. Howarter 1, K. G. Rice 2, C. R. Morea 1, 3, C. L. Abercrombie 4, K. Portier 5, A. G. Finger 1

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Abstract | Introduction | Methods
Results | Conclusions | Acknowledgements

ABSTRACT

line drawing of an alligatorFourteen adult alligators (Alligator mississippiensis) from two study sites in the Florida Everglades, 10 from Water Conservation Area (WCA) 3A North and 4 from Shark River Slough, Everglades National Park, were implanted intraperitoneally with data loggers that recorded core body temperature (Tb) simultaneously at 72 minute intervals. Alligators were recaptured one year later and data loggers removed. Alligator Tb’s were high and stable in summer. Fall Tb decreased corresponding to a decrease in ambient temperatures. Winter Tb remained low, occasionally elevating to activity levels. In spring, daily minimum Tb increased as ambient temperatures increased. However, unlike fall, spring Tb was elevated to activity levels on nearly a daily basis. The increased frequency of elevated Tb in spring corresponds with both the breeding season and the peak of the dry season. Elevated Tb is likely aid sperm and egg production, as well as prey digestion. Since the Everglades is normally a nutrient poor environment, increasing the rate of digestion while prey are concentrated in pools by the decreased water levels allow acquisition of energy. Further examination of annual Tb patterns of Everglades alligators across seasonal hydropatterns may reveal information about their physiology and ecology.

INTRODUCTION

Photo of 2 alligators
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Range of the American Alligator
(Alligator mississipiensis)

Map showing the range of the American alligator
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In South Florida, alligators face ambient temperature patterns unlike elsewhere in their range. The consistently high temperatures lead to increased metabolic cost.

Alligators in the Everglades have reduced length to weight ratio, reduced total length, and delayed onset of sexual maturity compared with other parts of their range. The reason for this poor condition is currently suspected to be a combination of low food availability and sustained high temperatures.

METHODS

Photo of a captured alligator
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Alligators were captured from airboats at night using snares or toggle darts. About 50% of animals equipped with data loggers were recaptured in the same manner, except implanted radio transmitters enabled researchers to target study animals. Innate wariness of alligators makes recapture quite difficult.

Photo of a Tidbit Stowaway Temperature Logger
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Technological advances have allowed miniaturization of temperature data logging devices so that continuous data collection is now possible. Tidbit Stowaway Temperature Loggers manufactured by Onset Computer Corporation were programmed to synchronously record temperature from a range of -5 to 37 °C with an accuracy of +/- 0.2 C every 72 minutes, allowing 396 days of continuous data collection.
Photo of a data logging device
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Photo of implant operation
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Both data loggers and radio transmitters were implanted intraperitoneally into alligators. The veterinary team led by Drs. Timothy and Denise Gross (USGS, FL Caribbean Science Center) employed novel anesthesiology which is more compatible with large reptiles than previously available techniques.

Alligators implanted with radio transmitters were then able to be tracked by plane or airboat.
Aerial photo
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Aerial photo
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Photo of scientist tracking from an airboat
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Illustration of an alligator on a line
1 - Florida Cooperative Fish and Wildlife Research Unit
U.S. Geological Survey, Biological Resources Division
University of Florida
Gainesville, FL 32611
Florida Cooperative Fish and Wildlife Research Unit logo
2 - U.S. Geological Survey, BRD
Restoration Ecology Branch
Everglades National Park Field Station
40001 S.R. 9336, Homestead, FL 33034
USGS banner
3 - Florida Fish and Wildlife Conservation Commission
620 South Meridian Street
Tallahassee, FL 32399
Florida Fish and Wildlife Conservation Commission logo
4 - Wofford College
429 N. Church St.
Spartanburg, SC 29303
Wofford College logo
5 - University of Florida
Department of Statistics
Gainesville, FL 32611
U. of Florida logo



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Related information:

SOFIA Project: American Alligator Distribution, Thermoregulation, and Biotic Potential Relative to Hydroperiod in the Everglades (a submodel within the ATLSS Project)


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