The secret life of the bilby
Easter bilbies are an increasingly popular alternative to the traditional chocolate rabbit. But the real bilbies are much harder to find - living secretive lives in isolated deserts across Australia, waiting for the right conditions to start a family.
Bilbies once inhabited 70 per cent of Australia. In 1900 rabbit trappers near Adelaide would catch as many bilbies as rabbits. By the 1920s there were none to be found there.
The environmental changes of the last 200 years have resulted in a huge reduction in bilby habitat - damage done by feral foxes and cats; competition with rabbits and grazing animals; land clearing and degradation; and changes to the traditional Aboriginal fire management have all had their toll.
The Greater Bilby (Macrotis lacotis) now only survives in scattered patches amongst the spinifex and mulga of the northern desert areas of Western Australia and the Northern Territory. A tiny isolated group of about 600 hangs on near Birdsville in Queensland.
The fate of their closest relative, the Lesser Bilby (M. leucura) is unknown. It was last seen alive over 70 years ago and is presumed to be extinct.
Cute and weird
With huge rabbit ears and soft grey fur it's easy to see the resemblance to rabbits, but that's where it ends.
"They look like they've been stuck together by a committee," says bilby conservationist, Tony Friend, "Huge ears that belong to a rabbit, soft grey fur, a tail that's stuck out the back like a tufted pencil and they gallop around like a rocking horse. They're so different to any other animals."
Bilby ears are almost naked, which Friend believes may be for temperature regulation, but because the research hasn't been done we don't actually know for sure.
One thing that scientists studying bilbies do agree on is the variability in behaviour between bilby populations living in different conditions around Australia. They've adopted different diets, burrows, breeding habits and social networks, and this adaptability has been the key to their survival.
Bilbies are marsupials and members of the bandicoot family. Opportunistic omnivores, they dig for much of their food, feeding on whatever's around. They have sensitive noses which they use to sniff out bulbs, seeds, fungi, fruit, grubs, termites, insects, spiders and lizards. If the tucker runs out, they're happy to move to where the grub's better. Their resilience even allows them to survive on termites in the height of droughts.
A useful trait for living in arid conditions is their ability to obtain all the water they need from food, which means that bilbies can get by without creeks or waterholes. Combined with their nocturnal lifestyle and deep burrows, their habits have allowed them to survive in arid areas, staying cool in summer and warm in winter, whilst avoiding many predators.
These cautious habits also make bilbies difficult to find and study in the wild. Only emerging in the dark, they stay close to any of a dozen or more burrows they may have in an area, ready to bolt down one if their sensitive ears detect a possible threat. They're also expert excavators, and if caught out in the open they can disappear from sight within three minutes in sandy soil.
In desert areas, bilbies often keep to themselves, digging simple burrows which spiral down up to two metres. Under more favourable conditions, they may live in larger loose groups with more complex warrens.
Females tend to stay in a smallish area around their burrows, while males may wander a few kilometres at night, looking for a bit of "female company".
When: Bilbies are opportunistic breeders waiting until conditions are good, rather than particular seasons.
Where: In the wild, bilbies are now limited to patches of the northern desert areas of NT and WA. and a tiny isolated remnant population in SW QLD. They are also found in sanctuaries and breeding colonies in WA, NSW, SA and QLD.
Other info: The name bilby comes from the Yuwaalaraay people of northern NSW. They are important in Aboriginal culture and were a common food resource. Bilbies live up to 7 years in the wild and 11 years in captivity. They are considered endangered.
Females only come into season under good conditions which, in desert areas, depends on rain and food supply. In breeding colonies established in temperate areas they tend to adapt to seasonal patterns. And when the good times come, the bilbies make the most of them!
"Bilbies are very good at sex," says June Butcher, from the Kanyana Wildlife Rehab Centre, who has bred over 70 bilbies. "Their mating sessions can last 18 hours."
The foetus develops quickly. A fortnight after mating the bean-sized neonate (newborn) wriggles its way to the pouch. The pouch faces backwards, so it doesn't fill with dirt while mum's digging. When it first emerges 11 weeks later, the joey weighs around 200g.
Unlike other marsupials, baby bilbies rarely re-enter the pouch. The female has usually mated again, and the new neonate crawls into the pouch not long after the joey has left. "It wouldn't be good to have this hulking great thing damaging it trying to get into the pouch," explains Butcher.
However, the joey is not yet out on its own, and is still fed by the mother.
"The nipple that the joeys feed on actually hangs out of the pouch," says Butcher, "the one that the little ones latch onto inside the pouch produces a different quality of milk to the outside one that's feeding the young one at heel. It's pretty clever."
A few weeks later, the joeys are left to fend for themselves. Like many animals that produce young quickly to take advantage of good conditions, there's a fairly high attrition rate and only about 25% will survive to breeding age. Foxes and cats will account for many.
The bilby's last main wild stronghold is in Aboriginal lands of the Tanami, Gibson and Great Sandy Deserts area of Western Australia and the Northern Territory. Various communities through the area are working with the Threatened Species Network to carry out survey and monitoring activities, and control feral predators. Warlpiri people from Yuendumu have recently tested an ingenious new fox-baiting device that promises to be safe for dingoes, bilbies, goannas and birds.
Bilbies are also being provided with safe havens such as the Peron Peninsula, WA. This 1000 kmē peninsula forms the west side of Shark Bay and has been fenced off at its neck from the rest of Australia in an attempt to reconstruct an entire ecosystem in the aptly named Project Eden. Alongside the dolphins of Monkey Mia, as many as possible of the original range of native animals - including the bilby - are being successfully re-introduced.
And if you buy a chocolate Easter Bilby you might also be helping with bilby conservation. Proceeds from the sale of some Easter Bilbies are used by the Save the Bilby Fund to publicise and fund breeding projects around Australia.
The fight against ferals
Bilbies can hold their own against natural predators like pythons, raptors, dingoes and quolls. But to give bilbies a fair chance of survival in the wild, it's vital to eliminate as many feral predators as possible before releases into the wild.
While bilby burrows were always important as refuges for a range of natives- reptiles and other small marsupials, they are often taken over by rabbits and cats.
Released bilbies have spread well through the 13,000ha Dryandra Woodland in WA and seem to be coping with predators. Part of their success is due to a local plant which produces a selective poison which kills introduced animals, but not natives. Poison Bush (Gastrolobium microcarpum) occurs throughout the South-West and consequently native mammals are tolerant to the poison. The breeding program is going so well that more releases are planned around the South-West and up into the drier areas.
The Arid Recovery project in the harsh regions around Roxby Downs is trialling another innovative approach to the feral problem. After recently discovering that a group of bilbies released into the wild were killed by predators, they came up with the unusual idea of training the marsupials to avoid cats, with excellent results with bilbies in breeding programs.
"After training, bilbies that encountered cat scents and droppings changed their behaviour - hiding immediately, changing burrows more frequently and selecting burrows with more entrances - all activities that could assist them in avoiding predators," reports Katherine Moseby. "The next steps are to test it in the wild and see if parents can pass it on to their young."
Where to see them?
If you're really lucky you may see a bilby in the wild- but remember, bilbies are nocturnal and extremely shy. Otherwise have a peek at one of these rare creatures at:-
SA - Arid Recovery at Roxby Downs, Venus Bay Conservation Park, Thistle Island, Yookamurra Sanctuary;
WA - Dryandra Woodland SF, Project Eden on Peron Peninsula, Kanyana Wildlife Rehab Centre;
QLD - Currawinya NP, Charleville Breeding Centre;
NT - Alice Springs Desert Park;
NSW - Scotia Sanctuary
Or you could just look out for the Chocolate Bilby this Easter, with the extra bonus that your guilty enjoyment could help fund efforts to save an endangered species.
Further info and credits
With thanks to all the people and groups mentioned through the article and many more, particularly Colleen O'Malley of the WWF Threatened Species Network and Rick Southgate.
Published 06 April 2006