High Density Hibernacula in Southern Water Skinks (Eulamprus tympanum) (Reptilia:Squamata:Sauria). Originally published in April 2005 in Victorian Naturalist 122(2):119.

On Sunday 5 September 2004, I was seeking cockroaches and other insects for a "bugs party". To that end, I broke into a fallen and decaying log derived from a large Acacia.
The diameter of the log was about 30 cm and it was about 180 cm long (having been cut as a section) and it was not hollow in the sense of a large open air space.
However the log's insides was a mass of generally decayed and easily moved wood material that had been partially decomposed by insects.
This material was easily moved and moist.  It was not however wet in that while damp, there was no evidence of free water or condensation.
The log was situated on the ground, but not embedded in any way.
It received dappled sunlight and was in an area with a strong northerly aspect.
It was on the southern bank of the Yarra River immediately adjacent to a walking track immediately behind the main township of Warrandyte, Victoria.
Inside the log was found numerous beetles, cockroaches, mealworms and some other insects.
Near the log surface (all sides) were Widgety Grubs that had enconsced themselves near the external surfaces of the log.
In the mid section of the log, the consistency was of densely packed but moveable wood shavings.
In this section of the log, I found twelve Southern Water Skinks.
This is a common species in Victoria.
They were not found as a group, but rather individually inside the woody material, having more-or-less burrowed into it.
Some lizards were immediately adjacent to one another, but this did not appear to be a situation of lizards deliberately trying to be with one another.  Instead it was more a case of lizards simply using the one log to hide and others being there as well.
Put another way, the lizards were not aggregating as such to utilize each other's heat or body's for any purpose.  In fact from the positioning of the lizards, it appeared that each lizard was effectively hibernating on it's own.
Five were adults and seven were juveniles (from last summer).  None were sexed.
In my view, the only reason so many turned up in this log was because it provided such an effective hibernation spot in an area of obviously limited sites relative to the high number of these lizards known to inhabit the area (based on how many I see basking in the warmer months).
Under the same log (between it and the dirt) was a single Adult Weasel Skink (Saproscincus mustelina).  None of this species were found in the log and no E. typanum were found under it, indicating distinct microhabitat preferences for the two species.
Due to the destruction of the hibernacula, the skinks were moved to another similar log sited nearby that was not broken open.
The weather at the time had been seasonally mild and mainly sunny that day, with a top temperature in the area of about 17 Degrees C and little wind.  While the log was broken open at about 3 PM, the warmest part of that day, all the lizards appeared to be in a state of torpor and it'd be reasonable to infer that none had been active on that day or any of the cooler days preceding it.

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