A mystery solved

One of the ways I try to keep the rabbit population under control is through the use of a cat/possum trap located outside a bunny-lurking spot. It's been pretty successful with about 80 wabbits contributing to the diet  of raptors and corvids by that means.

However on occasion the trap has been tripped but nothing has been inside.  Until today I had attributed that to the trip plate being triggered by the thudding feet of a passing, and large, kangaroo.

This afternoon I glanced at the trap and it had been triggered, but even checking with binoculars I could not see a lagomorph (don't worry, I will soon run out of synonyms for Orytolagus cuniculus) so assumed my usual explanation.  A very few minutes later I glanced out and could see a Common Blue-tongued Lizard clinging to the side of the cage.

So I went out and opened the back of the cage to let it out.  It seemed disinterested in taking the hint but stuck its head into the screen at the front.

I poked with a stick to try to persuade it to back up.  As soon as I removed the prod it charged the front of the cage and with, very little reduction in speed, was through the grid and on its way back under the shed.  My guess it that in normal configuration its head was about 10% wider than the hole while its thorax, at the widest part, was about 20% wider.  I knew snakes can get through seemingly tiny holes but had never before seen a moderate sized lizard do this.

So there is a proven explanation of how the trap gets tripped with nothing left inside.  I will now have to become observant about the seasonality of such events, since the lizards should not be responsible in the cold months.