If you are a regular visitor of the Arid Recovery blog, you might have read a bit about the ‘bilby business’ that has been happening at the Reserve over the last few months. With the latest experiments on our resident transmitter-equipped bilbies wrapping up at the beginning of November, the final task of retrieving the transmitters has been on the agenda of many of the staff, students and volunteers at Arid Recovery.
For UNSW PhD student Lisa Steindler, removing the remaining tail transmitters from the last 10 of her caught Greater Bilbies (Macrotis lagotis) is just as important as putting them on. Not only are tail transmitters expensive pieces of equipment (retailing at over $200 each), they can be turned off and reused for further research at a later date. Re-catching bilbies can also provide some interesting data on how their weight and body condition has changed over time.
You may be asking “Shouldn’t it be easy to re-catch a bilby, especially if you can track where it is?” Prior to undertaking this task, I would have replied “Sure, we’ll just put a trap in the bilby’s burrow entrance, he’ll waltz on in and gladly hand over his transmitter!” After (finally) retrieving the last transmitter earlier this week, I can safely say that recapturing bilbies is not as easy as one may think. Below I have provided some short explanations of the possible scenarios that I came across during our time recapturing 10 bilbies.
Scenario 1: The tail transmitter falls off.
Transmitters recovered from bilbies: 5 (Romeo, Boomer, Bob, Betsy and Bruno)
Difficulty of retrieval: Varies from pleasantly easy when the bilby conveniently sheds the transmitter above ground on a sand dune (see figure 1), to back-breakingly difficult when it is lost metres down a burrow (see figure 2).
Figure 1: A tail transmitter left on a sand dune by Romeo. The most difficult part of retrieving this transmitter was bending down and picking it up. Credit: Lisa Steindler
Figure 2: Finding a transmitter in a burrow involves 3 steps. 1) Using the radio tracker, find the strongest signal emitting from the ground. 2) Dig, dig and dig some more. 3) Repeat as necessary until the transmitter is found. This process can take as little as 5 minutes or as long as 5 hours. Credit: Lisa Steindler
Scenario 2: The bilby is caught using a trap.
Transmitters recovered from bilbies: 4 (Bellamy, Brian, Bolt, Bullet and Bruce)
Difficulty of retrieval: Depends. The initial set-up of a pen trap can be labour intensive (figure 3), but if a bilby goes into one of the set traps on the first night, all that hard work pays off. On the other hand, trying to catch a bilby hiding in a bettong warren can prove difficult when the only animals you catch for 2 nights are Burrowing Bettongs (Bettongia leuser) and a goanna (Varanus gouldii). Once the bilby’s neighbours have been moved, trapping can be successfully achieved (see figure 4).
Figure 3: A completed pen trap. Constructing a pen trap involves identifying the number of entrances in the warren, building a fence, complete with footnetting around said warren and wiring traps around and inside the fence. Thankfully, with the help of the Green Army, many hands make light work! Credit: Lisa Steindler
Figure 4: When a pen trap is set up around a warren, it is common to trap a neighbour or two instead of the target bilby. In this case, a Sand Goanna is being coaxed out of a trap by Green Army member Jesse. Credit: Adrian Friedel
Scenario 3: Volunteers are led along a 3-week chase by Bill, a cunning escape artist bilby.
Transmitters recovered from bilbies: 1 (Bill)
Difficulty of retrieval: I wouldn’t recommend this scenario to anyone. After 5 days of pen trapping (figure 5), over a week of rain delays, a further 3 days of failed burrow trapping (figure 6) and 1 mornings worth of digging, Bill was finally re-caught the same way he was caught (figure 7). In a net.
Figure 5: Some may think that 6 traps for one bilby might be too much. In this case, it proved to be not enough, with Bill the bilby escaping under the fence from this pen. Credit: Lisa Steindler
Figure 6: Trying a different tact. After residing in a few single-entrance burrows, we thought Bill might fall for a well-baited trap. As you can see, we were wrong. He burrowed straight under instead. Photo Credit: Sam Fischer
Figure 7: Success! After escaping a pen trap, and burrowing around several burrow traps, Bill was caught by digging behind his burrow, flushing him out and into a net. Credit: Bec West
Now, as the last removed tail transmitter is turned off, I’ve had a moment to reflect on the past few weeks. Having the opportunity to work with (arguably) one of Australia’s most iconic endangered animals has been one of the many highlights during my time volunteering with Arid Recovery. The excitement of seeing those distinctive big ears, and the satisfaction of removing the transmitter after weeks of collecting data far outweighs the many early starts, hours behind the shovel, and patience-testing moments.
Written by Sam Fischer, Arid Recovery Volunteer and Roxby Downs Green Army Member.