INVESTIGATING THE POST-RELEASE SURVIVORSHIP OF REHABILITATED LACE MONITORS

Wildlife rehabilitation is the process of assessing the health of injured or diseased wild animals, and then treating, rehabilitating and releasing them to their natural environment.  The aim is to release these animals in a condition so that they survive as well as other healthy wild individuals. 

Unfortunately, however, the welfare of rehabilitated wildlife can be affected by the stress associated with capturing, handling and proximity to humans.   Rehabilitated wildlife may also have reduced learning opportunities to recognize predators and food sources, and relatively low physical fitness.

Rehabilitated wildlife may therefore not survive well after release due to malnutrition, disease, predation and/or trauma.  These factors appear to vary between species.  

Survivorship post-release needs to be measured on a species-by-species basis.  Dr Rupert Baker and the other veterinarians at Healesville Sanctuary are conducting a project to investigate whether the rehabilitation of Lace Monitors (Varanus varius) is warranted in terms of animal welfare.

AIM

The aim of this project is to provide data to help maximise animal welfare during rehabilitation of Lace Monitors.  There is no literature published on the post-rehabilitation success of Varanids and even a small sample size may result in important knowledge gains. 

METHODS

This study will be conducted opportunistically on Lace Monitors treated at the Australian Wildlife Health Centre at Healesville Sanctuary.  After treatment and rehabilitation, each Lace Monitor will be examined by a veterinarian.  If it is deemed suitable for release, a radio transmitter will be fitted to the animal’s tail.  The Lace Monitor will then be released at the site of capture in early summer (because Lace Monitors are more active and have larger home ranges in summer, they are more likely to find suitable food at this time of year).

The researchers will track the movements of each released Lace Monitor for three months, initially daily and then at bi-weekly intervals.  Animals will be tracked using a hand-held Yagi antenna.  The signal from the radio-transmitter can be detected from 1 km away on flat ground (but less if there are hills and gullies). 

The radio transmitter will fall off when the skin of the Lace Monitor sheds naturally. 

RESULTS

The Lace Monitor “Lex” was found during the Black Saturday fires (February 2009) in Beveridge, 42 km north of Melbourne.  He had burn-wounds on his feet and nose down to the bone. After treatment, he was kept in captivity at the Australian Wildlife Health Centre over winter, and then released at Beveridge in January 2010.

For the first four days after he was released, Lex stayed in the same tree.  On the fifth day, Lex had moved.   The researchers picked up the signal on a nearby hill, but could not find Lex the following day.  In studies of home range, Lace Monitors have travelled up to 1 km a day (on average they move 335 m per day).  Lex was released into hilly country, and it is possible that he has just moved out of range of the receiver.  If he had died, the researchers should still be able to detect the signal from the radio transmitter.  The radio transmitter will fall off naturally in approximately March/April 2010.

The researchers will continue to attempt to monitor the survival of rehabilitated Lace Monitors when appropriate animals are treated at the Australian Wildlife Health Centre, Healesville Sanctuary.

FOR MORE INFORMATION

- on the Australian Wildlife Health Centre – click here.

- on this research project - click here to email Dr Rupert Baker (Principal Investigator).

- on wild Lace Monitors, see:

Guarino, F (2002) Spatial ecology of a large carnivorous lizard, Varanus varius (Squamata: Varanidae).  Journal of Zoology 258(4):449-457.