By Stuart Dawson. Easter is upon us, the holy grail of long weekends (especially when so close to ANZAC Day). Every year in Australia we celebrate this time with chocolate bunnies, inadvertently popularising an invasive and destructive species, the European Rabbit. The reason we use rabbits appears to be due to their famously fecund nature, symbolising Christ-like resurrection. For the moment, let’s just be thankful that we haven’t adopted the Red Fox as the deliverer of eggs, like they do in parts of Germany.
However, in 1991, the Foundation for Rabbit Free Australia developed the Easter Bilby campaign, to raise awareness for native Australia mammals, by replacing the bunnies with bilbies. This campaign has been successful in raising the awareness of the bilby, indeed it appears to be one of the only widely recognisable small marsupials to many Australians. Recent slumps in sales resulted in Cadbury no longer producing chocolate bilbies, but a petition is circulating to pressure them to renew their support.
New research, published last week in the Journal of Zoology, has shed light on the plethora of birds, reptiles, and mammals that use the burrows excavated by bilbies. It appears that the species we give to each other, also gives back to the animals they live with.
Bilbies dig multiple simple burrows, with each animal often using up to 18 burrows at a time, and regularly excavating (and subsequently abandoning) burrows. As a result, each individual bilby is responsible for continually contributing many burrows to often homogenous landscapes.
We deployed camera traps on 127 bilby burrows, for anywhere from 3 to 196 consecutive days, over the 2 years of study. We identified 45 taxa that ‘interacted’ with the mouth of bilby burrows: 22 bird, 16 reptile, and 7 mammal species. The assemblage of these ‘burrow commensals’ was the same whether burrows were maintained or abandoned by bilbies.
After a bushfire swept through one of our sites, there was a change in the assemblage using burrows, although the species richness and frequency of use did not change. Some species used burrows more after fire, indicating that the removal of vegetative cover had made burrows more important for these species.
Burrow commensals fell into three categories:
- The squatters – species that would normally excavate their own burrow, but in this case semi-permanently reside in bilby burrows. This group included native mice (Pseudomys), and Yellow-Spotted Monitors (Varanus panoptes).
- The renovators – species that modify (‘improve’?) the burrow of bilbies to create habitat for themselves. Pardalotes (Pardalotus) often excavated their own burrow into the side of bilby burrows.
- The door knockers – species that use the mouth of the burrow and sand apron, but rarely enter the burrow. These species, including a plethora of birds and reptiles, probably use the depression at the moth for foraging in the collected litter, or for resting in the shade.
Bilbies are considered ‘ecosystem engineers’ due to their improvements in soil condition and vegetation growth. But they are also creating habitat and resources for other species. This elevates their importance to the Australian ecosystem even further.
In a rare case of optimism in Australia conservation, I believe we may have (at least some of) the public support required to bring about careful management of this iconic species. The publication of this article corresponded with Easter this year (by pure chance), and has been reported by multiple news outlets. At Easter, people want bilbies, and they want news of bilbies (which is more than can be said for most native species). Let’s trust that this momentum in public interest can be funnelled into political interest that creates real change.