Night movement in diurnal skinks
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Originally published in hard copy in Victorian Naturalist (February 2009), 126(1):27.
Lampropholis delicata and Saproscincus mustelina are common small diurnal skinks in urbanised parts of south-east Australia (Hoser 1989).
Nocturnal movement in these reptiles is either unknown or never recorded.
At 9 PM on the evening of Thursday 17 April 2003, I drove a car into the single car garage at the residential house address of 105 Jenkins Road, Carlingford, (a Sydney suburb).
To do this, the roller-door had to be manually opened and then shut again.
Early the following morning (7 AM) the process was repeated, this time to move the car out of the garage.
Found resting were five Saproscincus mustelina and two Lampropholis delicata. All were positioned directly under the narrow lip of the door, more-or-less in line and were exposed as the door was opened.
By virtue of the absence of the lizards the previous evening, it was inferred that these skinks had moved into this position during the intervening night hours.
The same night, there was heavy rain in the area.
It's therefore believed that the lizards had been literally washed out of their resting areas and sought refuge in the nearest area not at risk of flooding.
Both species are common in the area.
Immediately adjacent to the garage door area is a concrete driveway and concrete paths.
Some distance from that is gardens and potential night resting spots (cover) for the lizards.
The general area is well elevated and the garden is sloping with numerous rises and dips created by rock gardens, pots and the like.
It's therefore assumed that the lizards didn't just move to higher ground to avoid rising floodwaters, but instead actually traveled some distance in search of a more suitable resting spot.
While the above case doesn't show that the two species are usually nocturnal, it does indicate that under exceptional circumstances, including something as frequent as heavy rain, nocturnal activity by diurnal species may occur and depending on climatic extremes may occur more often than the published literature may indicate.
In the 1970's and 1980's when I kept Lace Monitors (Varanus varius) and Bluetongues (Tiliqua spp.) in large outdoor "pits", these reptiles were seen active at night during and following heavy rain, as they searched for alternative hiding spots.
At the time, this activity was thought to be a manifestation of the captive situation.
The case documented above involving the Saproscincus mustelina and Lampropholis delicata indicates that my original conclusion may not have been entirely correct. Put differently, the same nocturnal activity may also occur in non-captive monitors and large skinks.
Hoser, R. T. 1989. Australian Reptiles and Frogs. Pierson and Co. Sydney, Australia:238 pp.
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