Gravid dragons

Seeing lizards in the bush or in my garden always gives me a lot of pleasure. Where ever I can, I sit still and quiet and observe them as they go about their daily business of living. Dragon lizards are particular favourites of mine.

Dragon lizards (family Agamidae) are more abundant in semi-arid country than damper forests and coastal environments, but they can turn up anywhere.

Of particular interest to me, are the lizards I've seen recently that have obviously been carrying eggs. A gravid lizard will have visible 'lumps' along the flank of the belly in the latter stage of pregnancy.

An unidentified dragon lizard I photographed in the Stirling Range National Park (WA) in November 2009. The plump rounded series of bumps along the side of the belly are the eggs.

Dragon lizards lay soft parchment-shelled eggs. The female will excavate a hole or find a secure place to deposit her eggs, and she may have several clutches throughout the summer. Parchment-shelled eggs lose moisture rapidly when exposed to air, so a protective location must be found for the nest site.

According to reputable records, the sex of dragon lizard hatchlings is temperature-dependent. Both high and low incubation temperatures produce female offspring, while males are produced from intermediate temperatures. The critical period for determining the sex of the hatchling is apparently the middle one-third of incubation. It's all extremely interesting and complex.

I photographed this unidentified dragon in the Pilliga Forests of northwestern NSW. She is also fat with eggs. This could be an Eastern Bearded Dragon.

A close up of the egg bulges

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Once again, I apologise for posting pictures of dead animals on my blog, but I feel these images have scientific value. I had been observing a dragon lizard lounging around in a Callistemon at our campsite by the Gwydir River at Bingara in northwestern NSW in summer last year. A vehicle passed our camp far faster than was sensible, and shortly afterwards, I found this dead dragon lizard on the track.

It was obviously a pregnant female, and when it was squashed by the vehicle, the eggs must have been expelled. Most of the eggs were intact, but unfortunately I didn't have the stomach to investigate the contents of the eggs.

The exact position the lizard was laying after the vehicle's wheel found it....

And I flipped the lizard over.

I found a very interesting article on lizard egg incubation that contains some amazing observations:

Egg size matters for lizard sex.