National Bilby Day
13th September 2020
The bilby is the only Australian animal with an official gazetted day of celebration!
This is because the bilby is so incredibly important as a flagship species – if they survive, so do many other threatened species and so they are the perfect critter to front biodiversity month in September.
Bilbies at a glance
The Greater Bilby – Macrotis Lagotis – is a solitary, nocturnal, omnivorous marsupial. It is also known as the rabbit-eared bandicoot.
Bilbies used to cover 70% of Australia but they have been lost from 80% of their former range due to predation by feral cats, foxes & wild dogs.
Bilbies are over 15 million years old and naturally they feature in dreamtime. Bilby is a very important animal for Aboriginal people. Its common name comes from the Yuwaalayaay word, Bilba. Aboriginal languages have different names for Bilby. In one example the bilby is called ‘Ninu’. Unusually, many languages have a separate name for the Ninu’s tail because it was super valuable. Like most Australian animals, Bilby was a meat animal because Aboriginal people needed food. The Ninu tail was made into body decorations that revealed the beauty and virility of women and men. Bilby were also a part of Tjukurrpa stories that connect people to places and people to each other along songlines.
Destruction of habitat
Bilbies habitats are spinifex grasslands and mulga scrublands in the hot, dry, arid and semi-arid areas of Australia. Previously more widespread, the bilby is now only found in remote parts of western Queensland, the Northern Territory and Western Australia.
They live in spiralling burrows which they dig up to 2m deep. This depth helps to keep them safe from predators and also to keep them at a constant temperature of 23°C, as bilbies can become heat stressed. A bilby may have as many as 12 burrows, one for sleeping and the others for escaping from predators.
The bilby digs a lot. This digging breaks up the soil and helps with composting. Their multiple homes mean that other species can use them for shelter too.
Bilbies are a ‘keystone’ species. This means that their protection is even more important because their survival in turn increases the chances of 19 other threatened species who share the same habitats.
Bilbies are one of nature’s eco-engineers. Greater bilbies are important in the restoration of soil and rejuvenation of vegetation in arid Australia. They use their strong front paws to dig deep holes in soil that enables plant material to fall in and decompose. At the same time, soil is aerated which supports seed germination.
Bilbies essentially create numerous compost pits every night.
That’s nature’s perfectly balanced ecosystem at work, but it’s threatened by the decline of bilbies. Where they have disappeared, the soil has become laminated and water, when it comes, reacts in a different way. It changes flood patterns and may cause run off where previously it would soak in due to the soil disturbance.
Bilby habitats also give protection to other endangered species – brush-tailed mulgara, spinifex hopping mice permanently occupy bilby burrows, and a further two species, short-beaked echidnas and sand goannas regularly using bilby burrows for shelter. An additional suite of 16 mammal, bird, reptile, amphibian and invertebrate species were detected interacting with bilby burrows. There was no difference in the number of species using disused or occupied bilby burrows, indicating that even disused bilby burrows are important structures for other species.
Description and behaviour
Australia once had two species of bilby – the greater bilby (Macrotis lagotis) and the lesser bilby (Macrotis leucura) — the lesser bilby is already extinct.
The greater bilby (also known as the ‘rabbit eared bandicoot’) is the largest member of the bandicoot family. This marsupial (pouched animal) measures up to 55cm in body length with a tail of up to 29cm long. Adult males weigh up to 2.5kg and the females average about 1.5kg.
Its coat is silky light grey and white and it has a long black and white crested tail with a naked spur-like tip.
Bilbies have a long pink snout which is hairless at the tip. They have 48 teeth, a long sticky tongue and a well-developed sense of smell to aid in finding food.
Their large, hairless ears are extremely useful for listening for predators as well as prey. These long ears allow a portion of them to remain above ground level when they are digging so they can hear predators approaching. Their eyesight is very poor and they are also sensitive to light.
They have strong forearms and hind legs for digging burrows and manipulating food.
The greater bilby is nocturnal. They don’t emerge from their burrows until an hour after dusk and retreat at least an hour before dawn. A full moon, strong wind, and heavy rain can keep a bilby in its burrow all night.
The bilby is omnivorous and its diet includes bulbs, fruit, seeds, fungi, insects, worms, termites, small lizards and spiders. One of its favourite plant foods is the bush onion or yalka which grows in desert sand plains after fires.
Bilbies don’t need to drink water regularly because, like the koala, they get most of their moisture from their food. This has been essential to their survival over millions of years. However, the fact that feral foxes and cats can now find artificial sources of water or are adapting to the harsh conditions, means that they can now survive in the arid areas where previously the bilbies were untouchable.
The female bilbies tend to associate with males just to mate.
Once pregnant they have the second shortest pregnancy of any mammal – just 12 – 14 days.
When the baby joey is born it looks like a baked bean with legs. (image). It stays in its mother’s pouch for between 75 and 80 days and is independent about two weeks later. Female bilbies have a backward-opening pouch with eight nipples. The pouch opens backward so as not to be filled with earth while digging.
At six months the female bilby can breed and usually has one or two young at a time. Although it is rare, she can have triplets. In a good season in the wild, bilbies can have up to four litters.
They live for about 5 to 7 years in the wild and up to 11 years in captivity.
Bilbies are so much more than just a pretty face.
Today on National Bilby Day, here are a few extra reasons to love these native furry creatures.
They may be small, but the Greater Bilby packs a punch in terms of what it gives back to its environment and how it supports other native animals. They are nationally listed as a vulnerable species, and right now there are only 600-700 of them left on the planet.
Bilbies are eco-engineers. As they dig, they turn the soil, and in the process help to regenerate seeds and restore soil condition, essential work particularly in the driest of regions on our continent. (‘Essential work, but somebody’s got to do it’, did I hear you say?)
Bilbies also provide protection to other endangered native species – in that, their old disused bilby burrows – the bilby burrows left behind after they move to new homes – also provide homes to other mammals, birds, reptiles and amphibians including the Spinifex Hopping Mouse, the Short-beaked Echidna and the Sand Goanna to name a few. One break in the chain has a ripple effect on the entire ecosystem, certain to have a wider, ongoing impact.
In a year when not much has gone right for our native species in the wake of the appalling bushfires, some good news was recently reported that bilbies have been successfully reintroduced in a predator-proof section of the Mallee Cliffs National Park, NSW.
Go you, bilbies, we are backing you all the way.