SREL Reprint #0391

 

 

 

Distribution of Alligators in Response to Thermal Gradients in a Reactor Cooling Reservoir

Thomas M. Murphy, Jr. and I. Lehr Brisbin, Jr.

 

Abstract

Seasonal changes in the distribution of American alligators inhabiting heated and unheated portion of a large reactor cooling reservoir were studied.  Abundance indexes, calculated from 4 years of daylight head counts conducted three times a month, were combined with 1 year of weekly night-cruise counts of alligators along the entire reservoir periphery.  In winter alligators congregated and remained active in the area of the heated effluent, but, in the remainder of the reservoir, they entered a semindormant state.  Maximum abundance indexes in the unheated areas occurred during the summer months, but the numbers in the heated area were at a low.  Water temperature predicts the alligator abundance index better than air temperature or photoperiod.  Decreasing water temperatures in the fall appeared to stimulate the movement of animals throughout the reservoir.  Animals that encountered warmer waters apparently restricted their movements to these heated areas.

 

SREL Reprint #0391

Murphy, T.M. and I.L. Brisbin Jr. 1974. Distribution of alligators in response to thermal gradients in a reactor cooling reservoir. p. 313-321. In Thermal Ecology, edited by J.W. Gibbons and R.R. Sharitz. CONF 730505. Atomic Energy Commission.

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