Snakes (mostly) alive!
by Ron Nagorcka
While most people interested in the observation of wildlife need to make frequent trips away from home 'into the wild', or keep captive animals, Sarah and I have the great advantage of living in a place where wildlife can be observed closely and regularly in its own habitat.
This has always applied to our snake population. Most of our snakes are tigers (Notechis ater), but we have recorded all 3 Tasmanian snakes over the years. Unfortunately, no white-lipped snakes (Drysdalia coronoides) have been observed since a pair of kookaburras nested nearby some years ago. This particular avian invasion also occasioned the disappearance or drastic reduction in the populations of mountain dragons (Rankinia diemensis) and white’s skinks (Egernia whitii). We have also noticed a casuarina skink (Cyclodomorphus casuarinae) being taken off by a kookaburra, a bird which does indeed (as popular opinion would have it) on occasion eat large snakes as the accompanying photo will attest. The knot puzzled us for a while, but observation of basking snakes confirms that a snake coiled up has often tied itself into just the loose sort of knot that a kookaburra might tighten during capture.
The 2010/11 summer has been exceptional for the abundance of tiger snakes, amongst many other things. One day in early summer there were no less than three basking on a hothouse shelf (along with a very brave if not suicidal casuarina skink – but maybe it knew they weren’t hungry?) and outside next to the same hothouse were two more tigers happily coiled up with each other. One day I noticed that the snake on top was making regular jerking motions, and while it was hard to determine through the entanglement what was really going on, the explanation does seem obvious.
I must admit that I find most snake observation to be not all that interesting. After all, they do spend an inordinate amount of time lying quietly in the same spot. On cool sunny days, they flatten their bodies and stretch out to collect as much warmth as possible and look very large, while in cooler weather they will coil into a close spiral and look much smaller (and considerably cuter!). Sometimes even drizzly rain will not drive them into their inevitable nearby bolt-holes as they coil up and wait optimistically for more sunshine.
Things do get a little more interesting when they forage – especially around our many rock walls. This summer I made one fascinating observation as a foraging tiger snake suddenly leapt to pluck an object out of the air. Back on the ground I could see that something was protruding from each side of its mouth, but without binoculars I could not see what it might be, and did not manage to get close enough to confirm my suspicion that it was an insect. Observing the general area over the next few days, I conjectured that it was probably a dragonfly. Not only were they plentiful at the time, but they were the only insect in the area to hover long enough to be captured in such a way.
As the summer waned all but two of our tigers disappeared from their regular basking spots. One surprised me behind a gas bottle in mid-April as I went to change it over, but it disappeared permanently soon thereafter. Another one took up residence in a large old burnt out tree stump. It was not the first over the years to do so as it is a sheltered spot that catches the autumn sun with a black heat-absorbing background and a perfect bolt-hole in the root system. And this snake seemed determined to bask forever. I noted it there on May 4th when the weather seemed reasonable and the thermometer nearby read 10°. After that the weather cooled more seriously, so it was surprising to see it reappear on May 14th after a cold snap with the temperature reading 8° and the radio telling us of snow to 500 metres (we are at 400). At this stage we were beginning to refer to it as 'bonkers' rather than 'snaky' but Sarah conjectured that it may have had a large late meal which it needed to digest before hibernating.
The mystery was solved (or maybe deepened) two days later when I noticed four small snake embryos in the basking spot. I immediately contacted David Bell who has kept tiger snakes since boyhood and who regularly joined CNFN walks in the 1990s. When he came to check the scene the next day we noticed that two more such embryos had appeared. David’s opinion was that these were at least three to four weeks premature and also that this did not preclude the possibility that more mature live young may have been produced. (Tiger snakes generally have a litter of at least twenty.)
Three of the embryos were preserved in alcohol for future reference. The remaining embryos were quickly skeletonised by European wasps but soon even the skeletons disappeared. This attests to the drastic effects these ferocious invertebrate predators are undoubtedly having on the ecology of our forests.
Over the next few days, the snake reappeared to bask whenever the sun was shining. The last we saw of her was during the warm late morning of May 20th. However, after lunch, when it was even warmer and still quite sunny, she had disappeared, and we have not seen her since.
I would be most interested in the reaction of any herpetologists to the observations made in this article.
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