Kangaroo Island Dunnart

MammalAustralia

31 Aug

Sminthopsis aitkeni

The Kangaroo Island dunnart lives only on Kangaroo Island, off South Australia. In 2019–2020, catastrophic bushfires swept across the island, burning over 90% of the dunnart’s habitat. The species was feared extinct, but a few were found to have survived — perhaps just 50–100 individuals.

Black Summer

Australia's Black Summer was a series of wildfires that began in June of 2019 and didn't stop until May of 2020. It is considered the most catastrophic bushfire season in Australia's history. An estimated 24.3 million hectares, or 243,000 km² (60 million acres), burned during this season — equivalent to the size of the entire United Kingdom — and around 3,094 homes were destroyed, 33 human lives were lost to the fires, with smoke leading to another 400 deaths.

In addition to the human losses, an estimated 3 billion animals were either displaced or killed by the fires. The majority were lizards; forced to flee, or failed to, as their shelters caught fire. 180 million birds either flew from the flames or burned with the trees around them. 123 million mammals fled or perished. One can be hopeful that the majority of animals escaped with their lives, even if their homes were incinerated, but it's been suggested that over 90% of the impacted animals may have died. This season of successive bushfires, this Black Summer, is considered the worst single event for wildlife in Australia's recorded history. For the dunnarts of Kangaroo Island, it nearly meant the end of their entire species.

Kangaroo Island

Between two peninsulas stretching out from South Australia — near the city of Adelaide — Kangaroo Island leaps into the Southern Ocean. Some 40% of this, Australia's third-largest island, is protected land; limestone cliffs and coves, eucalypt forests and mallee scrub, white dunes, and heaths covered in wildflowers.¹

Left to right: a heath monitor (*Varanus rosenbergi*), painted trilling frog (*Neobatrachus pictus*), ornate cowfish (*Aracana ornata*), glossy black cockatoo (*Calyptorhynchus lathami*), and a tammar wallaby (*Notamacropus eugenii*),

Kangaroo Island is a botanic garden amidst the sea — with 900+ plant species, 50 of them endemic — and a wild menagerie, set afloat like Noah's Ark some 10,000 years ago when it was separated from the mainland by rising sea levels. The island carries 18 reptile species, including predatorial, 1.5-metre (5-ft) heath monitors; 6 frog species, such as trilling and banjo frogs, contributing their croaks to the island's nocturnal soundscape; 231 recorded fish species in the surrounding sea from skinny sea dragons, to pale worm eels, and horned ornate cowfish; and over 200 species of birds, including big grass grazing geese, glossy black cockatoos, colonies of little blue penguins, sea-eagles, honeyeaters, and oystercatchers. Kangaroo Island is also home to 18 species of terrestrial mammals. Among them are two kangaroos, including the western grey kangaroo, common across much of southern Australia, and the tammar wallaby — once common, now rare — with Kangaroo Island one of its last bastions. But only one mammal is endemic to Kangaroo Island, found nowhere else.

The Dunnart

The Kangaroo Island dunnart is rather tiny, less than 10 centimetres (4 inches) long, plus another 10 cm of tail, and about as heavy as an AA battery. With grey fur and a light belly, a naked tapering tail, big round ears and gleaming black eyes, the dunnart very much resembles a mouse. But something about it is off: the digits on its front paws, covered in snow-white sleeves, are a little too long and robust, its snout is a little too pointed, and its mouth contains — not gnawing incisors — but rows of sharp, carnivorous-looking teeth.

While Australia has native rodents, the dunnart (of which there are 19 different species) isn't one of them.² It is a marsupial, more closely related to kangaroos and koalas than mice. And like other marsupials, the dunnart has some unique reproductive quirks. Two marsupial hallmarks are short gestation time (the time between conception and birth) and minuscule newborns — with a red kangaroo's gestation lasting about a month, after which it gives birth to a baby the size of a grape. The gestation period of the Kangaroo Island dunnart is around 12 days, and each newborn in its litter is smaller than a grain of rice.

Most mother marsupials have pouches on their undersides where their tiny joeys can safely grow; the mother dunnart has less a pouch, and more just a fold of skin under which her young (up to 10 per litter) latch onto her nipples and suckle for a month straight. Although we don't know much about the exact parental habits of the Kangaroo Island dunnart, we can reasonably assume that the females are the sole caretakers, given that males don't often live past the breeding season.

The dunnart's closest relatives are other Dasyurids: carnivorous marsupials like ningaui and planigales (also in the same family is the Tasmanian devil). The Kangaroo Island Dunnart is likewise a carnivore, a hunter of small critters — specifically an insectivore, its own size putting an upper limit on the prey it can take. The dunnart emerges from its nest at night, travelling 200-300 metres (650-980 ft) to its hunting grounds where it darts between scrubby grasses in search of spiders, ants, grasshoppers, and even scorpions. After a swift struggle between dunnart and giant arthropod — giant relative to the dunnart — the victorious dunnart crunches its needle teeth into its victim's exoskeleton and tucks in.

An Ark in Flames

It's believed that, in the past, the dunnart hunted across all of Kangaroo Island, across all kinds of habitats, before becoming restricted to a few sites on the western half. While the island is considered a natural haven, the label is relative; half the island has been cleared of natural vegetation for use as farmland. And, with a population of 5,000 people, Kangaroo Island became an exploitable home to feral cats who cared little whether they hunted mice or marsupials. In 2008, the Kangaroo Island dunnart was listed as critically endangered, with an estimated population of 300 to 500 individuals.

Then came the scorching summer of 2019-20. In December of 2019, lightning struck the desiccated island around the north and northeastern coasts, igniting the dry vegetation. Strong winds whipped the flames into an inferno and swept the fiery storm across the island. Over several weeks, nearly one-third of the land area burned, including as much as 68% of the reserve land on the western side of the island. Of the dunnart's habitat, over 90% was scorched. For the Kangaroo Island dunnart, the Black Summer may well have been its last.

This unprecedented level of destruction pushed many threatened and endangered species to the very edge. Not included in the 3 billion affected animals figure were invertebrates — insects, arachnids, slugs, snails, millipedes and centipedes — whose total death toll probably dwarfed the vertebrate figures. It's very likely that some species, maybe some we might not have even known about, were completely wiped out by the bushfires. No vertebrate species — reptiles, amphibians, birds or mammals — are known to have gone extinct as a result of the Black Summer. The Kangaroo Island dunnart came very, very close.

The fires on Kangaroo Island subsided by February of 2020, leaving behind blackened landscapes — natural, agricultural, and residential. 75% of the glossy black cockatoo's feeding sites became char, and fifteen birds unique to the island lost between 30% and 80% of their habitats. The casualties: an estimated 25,000 koalas (50% of the island's population) among thousands of other wild animals, around 32,000 domestic animals, and two humans.

For the Kangaroo Island dunnarts, their namesake island was their only bastion — if they all burned here, they would be gone forever. After the fires, camera traps were deployed across the western part of the island. Over 550 volunteers sorted through nearly 25,000 images of animals in search of survivors.³ Among the gallery were photos of Kangaroo Island dunnarts. Their population was decimated, but the species clung on, occupying a range of just ~24 km² (9 mi²), with a population of 100 individuals, and maybe as few as 50.

A World On Fire

The 'Black Summer' is a harrowing example of how destructive bushfires can be. It also comes with the frightening implication that, if temperature and aridity continue to increase, this 2019-20 season, which scorched an area the equivalent of the UK and affected well over 3 billion souls, might seem quaint compared to the hellscapes of the future.

This isn't limited to Kangaroo Island or Australia; this is an issue with global reach. Satellites watched from space as the bushfires raged. They saw plumes of acrid smoke streaming from the country and circumventing the world, reaching South America over 11,000 kilometres (7,000 miles) away. This single season of burning released an estimated 900 million tonnes of carbon dioxide into the atmosphere, more than Australia's annual emission of greenhouse gases and comparable to the annual emissions from commercial air travel worldwide. But the wildfires are just a symptom.

Islands across the world, each one its own ark of unique flora and fauna, are in danger of catching fire — metaphorically and literally.

On another Australian island, this one more far-flung, lives the Lord Howe Island stick insect. An arthropod giant, known locally as the "tree lobster", it was believed extinct due to an invasion by rats, but was then rediscovered alive in 2001, some 80 years after its supposed extinction. This flightless stick insect had clung onto a patch of vegetation atop Ball’s Pyramid — a sheer tower of rock out at sea, the tallest volcanic sea stack in the world, located some 20 km (12.5 mi) southeast of Lord Howe Island. There are only 20-30 individuals left. Dry conditions, combined with one unfortunate lightning strike, could eliminate the entire species from the wild — for real, this time.

Seychelles magpie-robins, coal-black birds with patches of white along their wings, could once be found across the granitic island of Seychelles. By 1970, just 16 individuals remained, all on Frégate Island. The species pulled through to 1990 with a population of only 21 individuals. Habitat destruction and invasive species drove this bird to the brink, but it was brought back by efforts from BirdLife International, its population climbing steadily over the years with a recent estimate of 190 mature individuals.
In the future, that positive trend may well halt and reverse, as a hotter climate leads to changes in rainfall, prey availability, and vegetation cover, or, more dramatically, an increase in extreme weather events like cyclones. The magpie-robins reintroduction to various islands may prevent a single catastrophe from eliminating the species, but, given the extreme bottleneck it experienced, its genetic diversity is dangerously low.

Low genetic diversity can leave a species dangerously susceptible to disease. On the islands of Hawai'i, it's not fires or cyclones that most threaten its colourful set of endemic birds — 17 remaining species known as honeycreepers — but a plague of mosquitoes (unknown to the archipelago until 1826) and the avian malaria they transmit.
The honeycreepers might have stood a chance by escaping to the cooler highlands where mosquitoes wouldn't usually venture. And they tried. But as the climate warms, the mosquitoes push farther and farther up the slopes, forcing the birds to climb too lest they be swallowed by a swarm of disease. Eventually, the honeycreepers will reach the very peaks, and they'll have nowhere left to flee.

A Lord Howe Island stick insect (*Dryococelus australis*).

A Seychelles magpie-robin (*Copsychus sechellarum*).

A species of Hawaiian honeycreeper, an ʻiʻiwi (*Drepanis coccinea*).

Different species. Different islands. Different threats. But always the same pattern of isolation, rarity, and vulnerability — all worsened by the effects of climate change.

Thanks to their restricted ranges and small populations, island species are particularly vulnerable. For many such species, climate change, and all of its accompanying consequences, are an additional pressure on already threatened populations, rather than the primary threat — habitat destruction and invasive species often take the lead. That is, until the effects of climate change cause an unprecedented catastrophe, like the 2019-20 fires on Kangaroo Island.

It's true that Australia and its islands are particularly prone to fires because of their pyrophytic (fire-loving) plants, but, anywhere else, a dessicated wood- or scrubland would serve just as well as kindling and fuel for a disastrous blaze. Maybe the desiccation, the drought after drought, will do enough damage in itself, causing irreversible change to an ecosystem. Or perhaps the rising temperature makes a habitat more livable for an invasive species, bringing plague in its wake.

The bushfires in Australia serve as a vivid parallel to climate change. Bushfires are a natural part of the Australian ecosystem; many of the plants evolved to tolerate fires or to proliferate in their aftermath.⁴ Likewise, the climate has continuously changed across the history of our planet, and life has evolved accordingly. The problem occurs when life can no longer keep up with the pace of change, when there's one drought after another, fire after fire, with no chance to regenerate in between.

The climate has always changed, just not at the extreme pace it's changing now. Or rather, it has: during the mass extinctions, when supervolcanoes spewed ejecta into the air or an asteroid punched a hole in our planet. There are no volcanoes or asteroids this time to set the world ablaze, just us. The most vulnerable — the giant stick insects on their isolated sea stack, honeycreepers pursued by disease with nowhere to climb, and dunnarts burning on their lone island home — will go first.

The Kangaroo Island dunnarts were resourceful, or lucky, enough to survive the most dire disaster their species has ever faced. If it were worse, they wouldn't be here now. And if it happens again — an inevitability if we keep pushing the climate towards warmer temperatures — we will lose these mouse-like marsupials.

Much of the vegetation across Australia and Kangaroo Island has now returned, sprouting from blackened soil, in many cases richer than before, with some flowers not seen for 70 years blooming across Kangaroo Island. Insects shelter in the new undergrowth. The songs of fairy-wrens, honeyeaters, and rosellas compose the soundscape for scenes of hopping kangaroos, plodding echidnas and dozing koalas. Dunnarts dart around in the dark.

Can this Eden survive another fiery apocalypse?

¹ As National Parks, Conservation Parks, Wilderness Protection Areas, Heritage Areas, and privately owned land.

² Australia is home to between 50 and 60 native species of rodents. A few notables include the bush and swamp rats, common in their respective habitats; the spinifex hopping mouse, with a tiny rotund body and giant legs which it uses to hop across dunes like a kangaroo; and the rakali, or water-rat, which grow to over a 1 kilogram (2.2 lb) and is kind of a national hero for its expertise in killing and dissecting invasive cane toads.

³ "Processing an average of over 350 images every day on DigiVol, a crowdsourcing website created and run by the Australian Museum and Atlas of Living Australia, the virtual volunteers set a record for the largest mobilisation of citizen scientists, contributing to image classifications for a project conducted on the island....The identified animal photos will help draw a picture of the surviving animal populations, assist with feral control and help to inform actions taken for recovery of native species such as the Kangaroo Island dunnart, little pygmy possum, southern brown bandicoot and a range of other species." (CSIRO)

⁴ Learn more about Australia's unique fire regime from the central rock-rat!

**Where Does It Live?**

⛰️ Habitat generalist; mallee woodland in areas with higher rainfall.
📍 Kangaroo Island, South Australia

‘Critically Endangered’ as of 30 Jun, 2008.

IUCN

Size // Tiny
Length // 8 - 9 cm (3 - 3.5 in)
Weight // 10 - 25 g (0.3 - 0.8 oz)
Activity: Nocturnal 🌙
Lifestyle: Solitary 👤
Lifespan: 1 year (males) to 2 years (females)
Diet: Carnivore (Insectivore)
Favourite Food: Ants and spiders 🕷
Class: Mammalia
Order: Dasyuromorphia
Family: Dasyuridae
Genus: Sminthopsis
Species: S. aitkeni

The Kangaroo Island dunnart — endemic to its namesake island in Australia — is a small carnivore that emerges at night to kill and eat ants, spiders, grasshoppers and scorpions.
It's also a marsupial — in the same family as the Tasmanian devil — giving birth after just 12 days of gestation (among the shortest of any mammal) to newborns that are each smaller than a grain of rice.
Prior to 2019–2020, there were thought to be fewer than 500 Kangaroo Island dunnarts, living on their island. Then came the "Black Summer," a catastrophic bushfire season that swept across Australia, burning through an area equal to the size of the entire United Kingdom, and displacing or killing an estimated 3 billion animals (not including invertebrates like insects).
Nearly one-third of Kangaroo Island burned. Of the dunnart's habitat, over 90% was scorched. The species was feared to be extinct.
After the fires, camera traps were deployed across the western part of the island, and over 550 volunteers sorted through nearly 25,000 images of animals in search of survivors. Among them were images of Kangaroo Island dunnarts.
Their population was decimated, but the species clung on — critically endangered — occupying a range of just ~24 km² (9 mi²), with a population of 100 individuals, and maybe as few as 50.