Lizard tails tell environmental tales
A collection of lizard tail tips is playing a key role in the fight against land degradation in rural Australia.
Lizards' habit of dropping the tips of their tails when threatened by a predator is giving CSIRO scientist Dr Don Driscoll a new way to monitor the animals' genetic makeup - an important clue to their long-term survival, and ultimately the survival of the land itself.
Because many of the lizards in outback areas are burrowers, they make a significant contribution to the health of the land. Their burrows help moisture penetration and increase the oxygen content of soils.
But because extensive land clearing has left only fragments of native vegetation in many areas, lizards' long-term survival may depend on being able to travel long distances between suitable habitats.
"A population of any species that is restricted to a small patch of habitat is likely to die out sooner or later," said Dr Driscoll, who works with CSIRO Wildlife and Ecology.
"When it does, the habitat may be recolonised if that species lives nearby. However, if the patches aren't close enough, or if the creature can't move over the land between them, then the patch will always be empty. If that process happens over hundreds of square kilometres, the entire landscape may become bereft of a whole range of species."
Genetic studies can provide some important insights into lizard mobility. Large variations in the genes of lizards from different locations suggest the animals have been unable to move between the locations, and would be unlikely to be able to recolonise new areas if some of the lizard populations died out.
"Species than cannot disperse very well could be at risk of gradually disappearing from a fragmented landscape because they can't recolonise vacant habitat," Dr Driscoll said.
Traditionally, movement in animals is studied by tagging individuals and observing where they go, but rare, long-distance movements are easily missed using this technique.
"By using genetic methods, I can build a picture of movement over a range of distances and over a much longer time scale," Dr Driscoll said.
The tail tips being studied are from lizards in 336 pit traps in remnant mallee in three locations in central NSW. The tails are gently removed at one of a number of naturally-occurring "segmentation points" - a process which causes no pain or bleeding.
The research will help farmers and other land managers concerned about declining biodiversity on their properties.
In areas where extensive clearing has already taken place, it could shape the form and number of replanted shelter points around properties. While in places like Queensland, where clearing is ongoing, it could help determine the best arrangement and conditions for the vegetation strips being created.