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6l
However the use of such winter dens has never been documented in any of the
prevjous studies of Par Pond alljgstors (Murphy 1977, 1981t Brisbin et a1. 1982;
Brandl 1989, 1991). Detailed descrjptions of the behavior of altigators dufing cold
winter weather in this reservoir system by Brisbin et al, (1982) rather have shown
adult alligators to submerge in either shallo!,r water in the reservojr's coves or
along steeply-sloping bottom contours near deeper parts of the lake, where they
Iikely exhjbit the "icing behaviorl described by Hagan et aI. (1983) during periods
of particularly lo\^r temperatures.
On 28 January, 1992 however, an adult alligator was observed inside an
extensjve wjnter den that was located at what, before the drawdown, had been
the waterrs edge of a small cove along the eastern shore of par pondrs Main Lake
(Figure 6). Since only the head and forequafters of this alligator coutd be seen
extending from one of the distant branching tunnels of the den (Figure ?), its
length could only be estimated as being approximately 1.5-2.5m. This alligator
was presumed to be a femaie that was known to inhabit and nest in this particular
cove. Further support for the identification of the denned aUigator as being this
female was provided during subsequent exploration of the den on l0 February,
1992 at wbich time a group of at ieast four small juveniles was discovered in a
side chamber of the den, approximately 1.0 1.5m from where the adult alligator
(which $/as not seen at this time) had b€en previously located (Fig1lle 7). Tbe size
of the juveniles suggested that they probably had halched in the falt of 1990 at a
time when the entrance and much of the entrvwav of this den had almost
certajnly been undefwater.
The presence of water in winter dens has been thought to provide alligators
with important thermal buffering during periods of cold temperature (Spotila et
al. 1972; Hagan et aI. 1983). The possibiiity that the drawdown of par pond might
result in cold temperature stress to the juveniles and/or the adult atligator in thjs
now dry winter nursery den was therelore examjned by monitoring it with three
temperature probes! (1) 1.0m inside the den entrance, (2) 5.0m further inside the
den near the point where the juveniles had been located, and (3) 3.0m outside the
den entrance at an elevation of l.om above the dry lake bed (Fig1rre?). These
three probes fecorded temperalures (10.01oC) every 30 min from -18 F'ebruary
through 22 April 1992, During this period, temperatures outside the den showed
much higher variability (CV =63.a%) than did temperatures inside the den
entrance (CV=29.0%), whjch in turn were significantly more vaaiable than
temperatutes further inside the den near the brood chamber (CV=10.6%; F=5.3?;
df-2736, 2830; p1 0.0r), Even on days when outside air temperatures felt
below -5'C and varied throughout the day by nearly 25oC, inside den
temperatures varied by less than 2.0"C and were at times more than 15oC warmer
than the outside air temperatures (eg. 13-14 March 1992; Figure ?). The dates for
which den temperature profiles are provided in Figlre ? were among the coldest
recorded during the period that the probes were in place at the den. Even so,
temperatures within the den r^rhere both the adult and juveniles were seen
remained well above the accepted lower limit of body temperature for this
species (5'Ci Bfisbin et al. 1982). Ahhough the den temperatures were
considerably below the speciesrpreferred body temperature of 32-35oC (Colbert
et al. 1946), the ability of a den such as described in this study to function as a
blackbody cavity would indicate that alligators withjn it, regardless of th€ir body
sizes, should all be well within the limits of their "c.limate space'r (99!Eq Spotila et
al. 1972), and that access to water under such conditions should not be necessary
for thermoregulatory purposes. At some point during the winter, however, access