#AceNewsReport – July.28: “ See!” Rob McLean says in an almost reverential whisper. “I said you’d be hooked!” In my role as AG’s science and environment editor, I see a lot of furry little creatures, and they all seem pretty special to me. But I agree. There’s something about a numbat that draws you in and keeps you transfixed……
AUSTRALIA: The plight of the numbat: Extinction came close twice late last century for Western Australia’s faunal emblem, the numbat. Now this still endangered and enchanting little marsupial is slowly making a comeback, even to parts of eastern Australia where it hasn’t been seen for many decades.
Rob first saw one 10 years ago. He’s since spent a lot of time watching them in this remnant 28,066ha patch of trees at the western edge of the Western Australia wheatbelt. And he’s got some 200GB of photographic and video footage to show for it. When he’s not here you’ll occasionally find him searching at Dragon Rocks Nature Reserve, a declining reintroduced population about 250km to the east. At the time of European colonisation, the species was found right across arid and semi-arid woodland habitat in southern Australia. As well as in WA, there were once natural populations in South Australia, New South Wales, Victoria and the Northern Territory.
“She’s a female,” says John Lawson, sitting next to Rob in our four-wheel-drive. John’s the caretaker of Lions Dryandra Village, a group of historic huts providing woodland holiday and weekend accommodation. “Look, you can see two joeys.” He records the GPS coordinates for this female and makes a few notes, as he and Rob do for every numbat sighting they make.
Females reproduce once a year from about 12 months of age. They live for up to five years, and have up to four young at a time. The babies with this female are hard to miss – they’re spilling out of their mother’s very rudimentary pouch. She would have mated in summer, so these joeys must be almost six months old, close to the age and size when they’ll leave their mother’s pouch. When this happens, she’ll dig a burrow and insulate it with bark and leaves for them, and later move them to other burrows or logs. She’ll join them each night for a further six months, keeping out predators – pythons, goannas and chuditch – by blocking the narrow nest chamber with her thick-skinned rump. Each day she’ll leave them to go off and forage for food.
One of the first of many unusual things you notice about numbats when you set out to look for one is that you’re searching in broad daylight. The numbat is one of very few strictly diurnal – day active – native Australian mammals. Most are either nocturnal – night active – or crepuscular – venturing out only in the dim light of dawn or dusk. It’s highly unusual to see a small Aussie marsupial out in the open like this during the day.
When you do finally see a numbat, it’s hard not to be awestruck by its appearance and behaviour. No other Australian marsupial looks like or could be mistaken for a numbat. It’s stunning, with red-grey fur with black and white bands, a bushy tail and pointy ears. Then there’s the way it moves, with odd little jerky actions. In a moment, this one will be off like a shot, scurrying through the sticks and leaf litter beneath the widely spaced wandoo and powderbark eucalypts, quickly disappearing as if by magic.
Those stripes are a form of camouflage known as disruptive colouration. They stand out when the animal’s still but, in the same way a zebra’s stripes incongruously equip it with an effective way of hiding on the African savannah, a numbat’s stripes quickly meld into the background when the animal is moving.
But for now, this one is staying put, and is moving like a wind-up toy, or a figurine in a stop-go animation. The main natural predators of numbats are birds of prey, which rely on sight to catch their quarry. Those jerky movements numbats display in the open, together with their colouration, are thought to be particularly confusing to visual predators such as hawks and falcons.
Two other significant things about numbats are their size and diet. They’re tiny, weighing only about 500g when fully grown. And they only eat termites. Those two factors, when you’re a mammal, combine to make it hard to maintain body temperature. Size matters, because if your surface area to volume ratio is high it means you’ve got a lot of skin from which to lose heat, compared to your body mass and muscle to retain and generate heat. The termite diet is significant because it has a low energy density. On average, a numbat needs to eat about 20,000 termites a day, and more if, like this female, it’s lactating and trying to sustain growing offspring.
Two things help numbats cope with their low-nutrient diet and small size. First, that coat is special, beyond its gorgeous colouration. On a cold morning such as this, it’s not surprising to see our first numbat of the day with its fur fluffed out, literally catching sunshine. Like any mammal, a numbat will puff its fur when it’s chilly. But the structure of this species’ coat allows it to use the sun to heat up much more productively than most.
This was first revealed in the early 2000s by environmental physiologist Dr Christine Cooper, then at the University of Western Australia. “Solar heat gain by numbats through the pelt to the level of the skin (60–63 per cent) is similar to the highest value measured for any mammal,” she documented at the time.Rob McLean and John Lawson.
We run into Christine later in the forest here. These days she’s at Curtin University, also in Perth, where she’s shifted her research focus from numbats to echidnas, of which there’s a large population in Dryandra. She explains that numbats have a very sparse outer coat and a really dense inner coat, an arrangement that lets the heat in and then retains it close to the skin. It means they’re more efficient at capturing solar energy than any other mammal. “And that’s really good if you want to save energy,” Christine says, “because it means that rather than having to produce your own metabolic heat you can very efficiently exploit solar heat as an avenue for keeping warm.”
The other way numbats save energy is by entering torpor, a short-term hibernation during which an animal reduces its body temperature and metabolic rate. Numbats do this on cold nights, dropping their body temperature to as low as 19°C.
A lot of other small mammals also enter daily torpor, including other small dasyurid species such as antechinus and dunnarts. Dasyurids, native carnivorous marsupials which also include quolls and the Tasmanian devil, are the closest living relatives of numbats. The now-extinct Tasmanian tiger, thylacine, was also in that marsupial group, and it’s hard not to be struck by the similarity of its striped markings with those of numbats. Numbats, however, are so unusual that, taxonomically, they are categorised within their own family, of which they are the sole surviving member.
On the brink
Critical to making sure the numbat doesn’t go the way of its extinct cousin, the thylacine, is a huge network of people across the country working in conservation. Rob and John are a significant part of that, although they dismiss that acknowledgement with embarrassed shrugs.
But it’s likely that without the work of one man – Dr Tony Friend, WA state government ecologist – numbats would have already disappeared forever.
Tony has been instrumental in pulling some of the country’s other most endangered mammals, including the Gilbert’s potoroo, off the path to extinction too. In the early 1980s, he identified foxes as the major cause of the drastic decline of numbats and several other small mammals in the west. He was part of a group of scientists involved in the development of the successful Western Shield wildlife recovery program, which is run by the WA Department of Biodiversity, Conservation and Attractions (DBCA)’s Parks and Wildlife Service. Much of the success of that program is due to the targeted use of the poison 1080 against feral predators in WA. The active constituent in 1080 is a compound called sodium fluoroacetate, developed in Europe in the 1940s for use against rats and mice.
It turns out, coincidentally, to be the same chemical formula as a naturally occurring toxin found in a large number of WA plants in the genus Gastrolobium. Because WA’s native mammal and bird species have evolved in tandem with these plants, they are virtually immune to 1080. But introduced feral predators – foxes and cats – aren’t, and that’s meant 1080 has been able to be used against them in WA to great effect, without harming local species.
Tony established the 1080 program against foxes that initially saw numbat numbers bounce back, peaking in about 1992. They began to drop dramatically again in the late 90s. Tony identified that cats had proliferated as top order predators when foxes were removed. A program that reinvented 1080 as a poison against feral cats, called Eradicat, began in 2012. Now numbat numbers are again climbing at Dryandra, Perup and several other WA sites where the species has been reintroduced.
Unfortunately, 1080 can’t be used against feral predators in the eastern states, because native animals have no natural resistance to the poison. There, private conservation organisation Australian Wildlife Conservancy (AWC) has, since 1991, been using predator-proof fences as its major weapon against foxes and cats and in defence of numbats. It has maintained a protected numbat population at its Yookamurra Sanctuary in SA since the early 1980s, and in 1999 took 19 animals from there and released them behind a predator-proof fence at its Scotia property in south-western NSW. That population has now grown to peak at about 600 animals, depending on local drought conditions. Tony Friend.
In December last year, AWC released 15 numbats from Scotia into Australia’s biggest feral-free exclosure, 9500ha, in Mallee Cliffs National Park. The park is managed in a joint partnership between NSW National Parks and Wildlife Service (NPWS) and AWC. The project represents a ground-breaking joint approach to species recovery that sees private and government conservation teams working closely together.
Dr Laurence Berry, AWC’s senior wildlife ecologist, says another release of animals bred as part of Perth Zoo’s numbat captive breeding program is planned for December. By the end of 2022, it hopes to have released 50 numbats into the exclosure.
For eastern Australia, Laurence says, such exclosures are presently the only way to ensure the survival of a range of native threatened species that have been decimated by cats and foxes. “In the short-term, fenced areas are a critical part of the solution to addressing the impacts of feral predators on these iconic threatened species,” he says.
Whether it’s 1080 in the west or feral-proof fences in the east, Tony points out that these programs developed to support survival of numbats are also benefiting a wider suite of other endangered species. In Dryandra, for example, populations of mardo, chuditch and other mammals preyed on by foxes and cats are bouncing back. Laurence says AWC’s been seeing the same thing happen on their cat- and fox-proof properties.(Image credit: Rob McLean)
How to find numbats
There’s a special way to find numbats; neither complicated nor time-consuming, and unlike any method used to locate any other Australian marsupial species. It can work as readily for a tourist out for a unique encounter with Australian wildlife as it does for a highly trained scientist conducting field research.
First, wait until the day is beginning to warm, when the termites are rising in the soil as it’s hit by the sun’s rays, and numbats are emerging from their night-time nests to lap up these little insects with their long, sticky tongues. Then drive slower than 10km/h along tracks and trails in habitat – woodland with lots of old tree hollows – where these engaging little creatures are likely to appear. On one of the days I’m doing this with Rob and John in Dryandra, we pass at least a dozen other cars doing the same thing.
The two men are proud that people can come to Dryandra to see numbats, and have both fought hard to ensure the experience is possible. The pair were founding members of the conservation group Numbat Task Force, which began for the purpose of raising the profile of numbats via Facebook. Then it focused on fighting a proposal to build a rubbish tip close to Dryandra. “It would have been a haven for cats,” John explains.
In 2016, armed with research about the impact of cats on numbats and proof that the feral predators travel up to 40km looking for prey, Rob and John spent hours, week after week, talking to planners and politicians and fronting council meetings to put forward their case. Ultimately, they won the fight, which brought the task force to the attention of the Australian Geographic Society and earned them the Society’s Conservationist of the Year Award in 2018. These days the group continues to raise awareness about numbats, and also supports research into the species.
Rob still gets emotional when he talks about what might have happened if the tip went ahead where it was planned. “Can you imagine what that would have done to these little guys?” he asks, horrified. Then this burly Bunbury truck driver turns away to hide that he’s wiping away a tear, before continuing.
“We don’t want our grandchildren growing up in a world without numbats. We want them to be able to see and appreciate these extraordinary little creatures,” he says passionately. “That’s how it should be, and that’s why we do this.”
#AceNewsDesk report ………Published: July.28: 2021:
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