Lizards feel climate change

You have to hand it to the pygmy bluetongue – to date, it has quietly survived a barrage of natural hazards and man-made pressures. But the effects of drought brought about by climate change are putting the tiny lizards under unprecedented threat.

A team of Flinders University biologists under Professor Mike Bull has been studying the pygmy bluetongue and its larger cousin, the sleepy lizard, for almost three decades. Professor Bull’s discoveries about the extraordinary life cycle and habits of the sleepy lizard, including its tendency to pair with a mate for life, earned the lizard a major role in David Attenborough’s reptile documentary series, Life in Cold Blood.

At present, it is the conservation of the pygmy bluetongue that is claiming much of Professor Bull’s attention.

The pygmy bluetongue has been driven from much of its habitat on the Adelaide Plains by the pressure of urban development. But the lizards have pulled off an extraordinary conjuring trick. Last sighted on a building site in suburban Marion in the 1950s, the species was thought extinct for 30 years until another individual was discovered in the gut of a dead brown snake some 250 kilometres away, near Burra in SA’s mid-north.

Since then, 24 separate small populations have been found on privately owned land all around Burra. But because the patches of native grassland on which they live are isolated by tracts of cultivated land, the populations are unconnected, meaning that they cannot recolonise naturally when numbers dwindle.

“Lizards do not breed during drought, and if drought years increase as the climate change scenario suggests, the populations will be under threat,” Professor Bull said.

“We know that they’re OK in the short term, but we are really worried about what is going to happen to them in the longer term.”

One response from Professor Bull and his team is an attempt to develop methods for successfully transplanting lizard colonies to managed conservation areas. Experience shows that reptiles seldom respond well to translocation, and tend to move away from new sites.

“What we have to do is find ways to encourage them to stay put,” Professor Bull said.

As well as determining the most appropriate level of land use that will encourage the lizards to flourish – surprisingly, light grazing by sheep appears to be ideal – there is the vexed question of neighbours.

“This group of lizards has very unusual, complex social organization, living in family groups and forming partnerships,” Professor Bull said.

“All of our previous work on sleepy lizards and gidgee skinks will feed into a broad understanding of how an individual lizard interacts with its neighbours, and what we’re working towards is establishing the mix of individuals that is most appropriate to a translocation.”

Questions of genetics will also be crucial in deciding whether lizards should be translocated with family or with strangers. Too little genetic variation results in inbreeding; too wide a gene pool may affect the lizards’ ability to recognise each other.

Professor Bull said that while there is time to work out these variables, climate change is adding a sense of urgency to the research.

“We have had two severe droughts in the last eight years: these events used to be once in 20 years. In dry years the lizards won’t recruit, and a higher frequency of dry years brought about by climate change means that the populations will become much more fragile.”

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