size: 5036KB - Crocodile Specialist Group

6.1
surface to breathe (Kellogg 1929; Mcllhenny 1935; Chabreck 1966; Goodwin and
Marjon 19?9; Hagan et a], 1983; Chen et al, 1990). Winter locatjons of
telemetered alligators monitored in this study were usually in the water adjacent
to the now bare shoreline of the lowered reservoir and any evidence of den
construction on or near the water's edge would have been obvious.
The winter habital chosen by these adult alljgators was quite similar to that
used by a large adul1 (total length = 2.??m) male alligato. which was studied by
Brisbin et aL (1982) in the Pond B reservoir in 19?7. As described by these
authors, thjs individual endured winter air and water temperatures as low as 0.3
and 4.0-C, respeclively, whjle positioned approximately 2m olfshore along a bare
unvegetated portion of that reservoirrs shoreline. 'lhis alligator was oriented
perpendicular to the reservoirrs shoreline and rested on steeply sloping
unvegetated bottom sediments in water that ranged from 0.802.00m in depth
from the alligator's head to its tail, respectively.
The general characteristics of the reservojr shoreljne and bottom contour of
the West Arm location $/here six of the 13 telemetered alligators spent the winter
months in close proximity to one another during the present study (Fi$rres 2 and
3), were strikingly similar to those of the habitat chosen by the alligator studied
by Brisbin e1 al. (1982), as described above. tsrisbin et al. (1982) described how
behavioral adjustments in the position of the alligator they studied apparently
allow€d that animal to utilize the deeper waters of the reservoir as a heat source
for thermoregllat ion during cold weather, and although such behavior was never
observed for any of the alligators monitored in the present study, the
microhabitat conditions chosen by all of these animals would have allowed such
winter thermor€g!iatory behavior to still take place despite the drawndown state
of the reservoir. Although the winter of 1991-1992 was generally milder than
most in this region, the survivai of all 13 telemelered alligators from November
1991 through the spring of 1992 suggests that the drawdown of the feservoir was
unlikely to have affected the wjnter survival of adults in this population.
Conclusions/Management ImDlications:
Both night eyeshine counts and aerial census surveys suggest that a
considerable number of adult alligators have remained in the Par Pond reservoir
despite its present low€red water levels (Figrres 4 and 5). 1'hese alligators have
most likely subsisted on an increasjngly vulnerable food base including birds,
tufiles, fish and other prey species that no longer have the benefit of protective
vegetative cover along the lakers mar8ins. How long this prey base will continue
to persist under these conditions however, is currently not known, and social
stress/cannibalism will almost certainly increase if prey resources decline, as
would be inevitable if the reseNoir is not refilled within the following year.
Despite the number of alligators still present jn the reservoir, this study has
shown that a number of sdults of both sexes have already emigrated from the Par
Pond population and that this has resulted in the deaths of at least some of these
individuals (Table 2). This will result in a net decrease in the overall breeding.
population of alligators on the SRS as a whol€. The deaths of some smaller males
(eg. aUigator B, Table 2) in this manner might not have a significant impact on
flture population productivity on the site, However the loss of large adult
femaies (eg. auigator D, Table 2) through such emig"ation and territorial conflict
would almost certainly have a negative impact on the population's reproductive
output. The female killed in Pond B for example, represented one of the largest