The second Sunday in September is dedicated to National Bilby Day, so what better reason to tell you of our work on the Greater Bilby in the Arid Recovery Reserve. And it just so happens that last week was a busy week on the reserve fitting radio transmitters to bilby tails as part of a project looking at predator awareness in the Greater Bilby, which is being carried out by Lisa Steindler (a PhD student from UNSW as part of our ARC Project). By fitting a transmitter the bilby’s location can be found, so long as you are in a kilometre range. Knowing where the bilbies are, in particular their burrow, is very useful for Lisa when it comes to setting up her experiments outside the bilby’s home.
However, before a bilby can be radio tracked a transmitter needs to be attached, but only once the animal has been caught -some would say this is the fun part! Here’s also where a team of volunteers comes in handy. Catching a bilby in a cage trap is quite unlikely, instead fast pairs of legs are much more effective. But why does this need a team I hear you ask? Well bilbies come out at night, therefore a person with a powerful torch, called the spotlighter, is important. It is also handy to have a driver to allow a larger area to be searched. Also, when the spotlighter sees a bilby, being able to drive alongside the running animal allows some distance to be gained on the bilby, increasing the likelihood of a catch. When the car stops you need a runner (the final member of the team) to jump out of the car and run after the bilby. Here’s where a fast runner is essential! Believe me, bilbies are surprisingly fast. But they also have the ability to rapidly zig zag from side to side, confusing the best of runners. Therefore to keep track of the bilby two good runners are often better than one! After successfully catching the bilby (using a net or by hand) the animal is then placed into a dark, fleecy bag to keep it calm. All be it fun remember we were catching bilbies for an important reason, so please do not attempt to try this at home.
Unlike the other animals on the Reserve that have radio collars, bilbies have transmitters that are fixed to the base of their tail using Elastoplast. Previous studies have found that bilbies can often get their feet stuck in collars, so tail transmitters are much safer. However, attaching the transmitters directly to the tail fur of the bilbies is not effective -sand is more likely to get stuck in the Elastoplast and cause the transmitter to fall off, so the transmitters must be taped to the skin…This is when hairdresser Lisa comes into action (see the photos below)!
The skilled art of fitting a transmitter to a Greater Bilby's tail! Credit: Ruth Shepherd
After the bilby’s transmitter has been attached other important data such as the animal’s body condition is taken by feeling how much fat the bilby has on the rump area. Some of the fur is also collected to be sent away for analysis for cortisol levels (a measure of stress). This allows Lisa to compare stress levels between bilbies living in the expansion with the cats, and the expansion with no predators.
The final piece of data collected is behavioural data which is done when the animal is released in the place where it was caught. Animals differ in how bold or shy they are, and having one of these qualities may make them better at surviving predation (the ARC project is researching this for bettongs, bilbies and stick-nest rats on the Reserve). Bilby boldness is measured by how long it takes, and how much encouragement it takes (by giving the bilby gentle nudges every 3 seconds), before the bilby leaves the bag.
All of the radio tagged bilbies are monitored by Lisa to see their usual pattern of burrow use and behaviour and then how this changes when the bilbies are presented with a model predator or predator poo outside their burrow. Lisa will compare the responses of bilbies that have been living with cats to those that have not to see if there are any differences. This data will be incredibly useful for Arid Recovery in the long-term to test whether predator awareness of bilbies can be improved if they live with a small number of predators (cats in this case). Lisa will also be able to determine whether there are certain behaviours that we can select for when choosing release animals to make them more likely to survive when faced with real predators in reintroductions outside the reserve.
This article is in honour of the Greater Bilby, once common throughout arid Australia but now only occupies 20% of its former range. We hope through the efforts at Arid Recovery that bilbies will be able to be re-introduced into other areas of arid Australia and their numbers will begin to increase.