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53
LONG-TERM POPUT-A.TION S'ruDIES OII AMERICAN AILTGATORS INHABITINC
A RESERVOIR: INITIAL RESPONSES TO WArER LEVEL DRAWDOWN
I. L€hr B.isbitr, Jr., J.Merlin Benner, Laura A. Brandtr,
Roberr A. Kennamer and Thomrs M. MurDhl
Savrnnah Rrver Ecolory Laboralory
P.O. Drawer L:
Aiken, South Carolina 29802, U.S.A.
ABSTRACT: A population of Americ^n ^llieators (AlUgator n $'rr"pieari') irhabiting a 1130
ha nuclear reactor cooling reservoir has been studied for more than 20 years, producing a data
base th^l now can bc used to evaluate the responses of these animals to subsequent changes itr
their habitat. Beginning in June and conlinuing lhrough September 1991, the waler level in this
reservoir was lowered 6m lo allow for repair work 1() thc d:lm. Thc stuE reported here
extend€d from July l99l through the summer of 199, during which time thc reservoir remained
at the lowered level. The drawdown reduced the waler surface area by 507r, exposing and
killing the m.jority of the lake's subnerged/emergent aquatic vegeration. Both during and
immediately after drawdown activities, the number of alligalors counted in the reservoir by night
eyeshining techniques increased possibly ^s a rcsult of increased visibility of smaller animals due
to the lack of emergcnt vegetative cover. High numbers of alligators were also obse ed during
aerial census flights during the spring following drawdowtr. Fourteen adult alligators outfitted
wilh radio tr&smitters in Septernber 1991 revealed differences in spalial distributions and
movement patterns between the s€xes during lhe fall and following winter in the drawdown
reservoir. Males showed more €xtensivc fall movemcnts while most females tended to remam
close to the locations where they were originally caplured. There was no evidence thnt tbc
drawdown adversely affecled the winler survival of adult alligators in Par Pond- Six of the
telemetered alligators spenl the winler in moderately deel water along a