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56
Nisht Eveshinc Counts ard Aerial Census Survcvs:
Nighr eyeshine counls and ncri^l census surveys were designed to incorporate, as much
as possible, the samc techniques used by Murphy (1977, l98l) and Brardt (1989, 1991) m
determining pre-drawdown population numbers ot alligalors in Par Pond. Briefly, eyeshinc
counts wcrc conducted fron an airbont on nights with reduc€d wind and wavc .crion in order to
maximize alligator visibiliry, wilh thc cntire periphery of the rcscrvoir (inilially 53 km but rhen
later reduced as the drawdown progrcssed) being surveye during cach census. Night eyeshine
counts were conducted on 3, 8 and 29 July, 26 August, 24 September and 23 Ocrober, 1991.
Aerial census suneys were conducted from a fixed-wing aircraft flown at a speed of 130 knors ^t
an ahitude of about 90 m. Again, the entire periphery o{ the reservoir was suweyed on each
aerial census, with flights bcing conducled on 1l July, 12 Scplember, :ud 17 and 25 October in
1991, and on 9, 17 and 2s Miuch,22 April, 12 and 19 May,9 and 30 June, and 3 July in 199.
Discussions of sourccs of bias and assumptions th^t must b€ made or mct in thc desigr ot nighr
eyeshine counts and rcrial ccnsus suweys are providcd by Woodward and Marion (19787 anu
Caughley ( I 974), respectively.
None of the surveys conducled during the present study produced esdmatcs of actual
popul.lion size either during or after the drawdown of thc reservoir. Howevcr, botb night
eyeshinc counts and daylime aerial surveys can estimate the minimum numbers of alligators
present, and if certain assumptions concerning the probability of sighling of individuals .rre made
or can be discounted, information tiom such counts crn be osed ns indices of DoDulalion sizr.
Capture and lhdiotolemelrv:
Adull alligators werc c.ptured for ou(filting with radiotmnsmitters using ll modificd
version of baited trip snares (Murphy :rnd l.cndley, 1975; Murphy er lll 1983) that wcrc sel
along thc rcceding edge of Par Pond during and shortly after thc cessnrion of drawdown
activities. Snares were set for a total of tive nights and involved a loral of ,{4 rrap nighls. Thcse
sets rcsulled in the capture of 15 aduh nllignlors (trap success = 34.1%). Ninc mrles were
capturcd in snares in the North Arm bctrvccn 28-29 Scp(embcr 1991 (Fieure 2). Ijach was
meisurod, equipped wirh a radio transmilter and rclcascil al the sire of capiure. tle snares
were then moved in ordcr to :rchjeve more complelc covcmge of the reservoir's shorelin€. 'ltis
resulted in the capture of four additional temales on 7 8 Oclober 1991 (Figure 3). Thesc
females were also equipped with radio transmittcn and released, .s was a fifth tcmalc rhar had
been caplurcd from a boat with a snare pole h the Hor Arm on 19 Seprembcr l99l_ Two
addilional adult malcs capiured in snares in thc wrsr Arm were mltrk€d by n.rching (rit scules
(Brandt 1989) and rele6ed without transmitlers.
'fhe ninc mrles equipped with transmitrcrs
rangcd from 2.41 - 3.56 m in total lcngth while the fivc tbmales ranged fron l_91 - 2.50 m.
I{adiotransmitters weighing less than 250g werc altachcd wilh 270 lb tcsr sraintess-sreer
Ieader line to thc dorsal nuchal scutes. Attempts were madc to derermine thc locations of alt
aUigators on 4, 9, 18 rnd 31 October, 8 and 19 November, 13, 23 and 30 Derernber in 1991, and
on 16 January,7 and 19 Iicbruary and 12 .nd 26 March in 1992, producing a lotal of 158
localions of individual animals. TransmitteFequipped Alligators that left the rescNoir were
locatcd :rt more frequent intewals to befler determine rhc extcnl ot their cxcursions and fntcs.
Radio locations wcre deternlined with :l hand,held ^n(enna from ,t smalt boat or airboal or from
the shorc. Although visual observalio.s were occasionally