Water Dragon Research Results

Water Dragons are an excellent species to study for the effect of climate climate as they occur through a huge variety of climates and altitudes, are very common and have nests that are easy to locate.

J.S. Doody and others in 2003-04, from the Institute for Applied Ecology, University of Canberra conducted a study of Water Dragons nest site choices in the Australian National Botanic Gardens in Canberra and at four other locations in eastern Australia. The sites were in Cairns, Brisbane, Sydney, Canberra and the Southern Highlands. The sites vary in climatic conditions from hot tropical to cool temperate and altitudes from sea level to 1200m. The study was to examine the nest site choices and timing made by the Water Dragons over the range of sites, to see how the Water Dragons compensate for differences in climate, and yet produce the necessary mix of sexes for a viable population.

© Nadav Pezaro

The more northern and warm the area, the earlier they nest (Nesting month, Latitudes and Altitudes shown):

• September – Cairns (16.9^oS, 660 m)
• Early October – Brisbane (27.59^oS, 200 m)
• Mid to late October – Sydney (33.9^oS, 40 m)
• Early to mid November – Canberra (35.3^oS, 660 m)
• Early December – Southern Highlands (35.8^oS, 1200 m)

Nest depths: Nest depths did not vary between the sites, except for Canberra in which they were a bit deeper. The upper pivotal temperatures (temperature which contributes to the production of females) did not vary across the sites. Mean nest temperatures also did not significantly change across the sites.

They found the timing of nesting helped with the management of temperature, but not entirely. It was still hotter in Cairns in September, than it was in the Southern Highlands in December.

Nest openess: The main way they compensated for temperature differences was the 'openness' of the nesting site and hence the amount of radiation the nest would receive. This effected the mean daily range in nest temperatures rather than the mean temperature. The canopy openness was much more open at sites in the south, than those in the north. So basically, Water Dragons were compensating for differences in temperatures by selecting how open a nest site is, and to a lesser degree choosing when to nest.

It is hoped by studying animals whose sex are temperature dependant during incubation (TSD), will help scientists model the effects of climate change on these types of animal populations and the adjustments they are likely to make in response to global warming.