The tropical savannas of Northern Australia are vast, truly epic, and breathtaking in scale. Their immense size – >130,000,000 hectares or ~17% of this continent – is matched by the extraordinary biodiversity and cultural values contained within them. They are recognisable by a dominance of eucalypts and a diverse, largely grassy understory, with tree cover and height varying depending on whether the area is in a higher (~2000mm) or lower (~500mm) rainfall zone, related to the distance from the coastline. Critically, these savannas are the largest and most intact in the world.
The region is dynamic, characterised by a long, protracted dry season (~April-November), when very little rain falls, and a shorter, intense wet season in the summer months (~December-March). Spectacular thunderstorms and lightning are often followed by heavy rainfall events, sometimes hundreds of millimetres of rain pounds down in just hours. As a result, habitats rapidly transform from dry and dusty, and with shrivelled golden and brown grass to a more humid, lush and verdant green splendour. Invertebrate numbers and seed production boom, driving food chains and a pulse of breeding for many species. Across much of the savannas, fire is a significant force of change, burning vegetation often with great regularity, but in recent times much work has been dedicated to managing fire in a more strategic and sustainable way that aims to benefit wildlife and conserve their habitats and homes (e.g. logs and tree hollows).
A multitude of marvellous mammals can be found throughout the savannas. Nabarleks (Petrogale concinna), monjons (Petrogale burbidgei) and black wallaroos (Osphranter bernardus) are among the macropods that can be seen bounding over rocky escarpments and bolting into caves and among boulders when alarmed. Black wallaroos are confined entirely to the west Arnhem Land Plateau, whereas the closely related antilopine wallaroo (Osphranter antilopinus) spans a much larger area, including the Kimberley, Top End, Cape York and Einasleigh Uplands regions.
With an elegant, long black furry tail with a tufted white end, the black-footed tree-rat (Mesembriomys gouldii gouldii – Kimberley and mainland N.T. subspecies) is unarguably one of Australia’s most striking and spectacular native rodents. There are three subspecies, the other two being confined to Melville Island (M. g. melvillensis) and North Queensland (M. g. rattoides). They feed on a range of foods including invertebrates, flowers, hard fruits and seeds, with pandanus being a favourite. Savanna gliders (Petaurus ariel), northern brushtail possums (Trichosurus vulpecula arnhemensis), and brush-tailed rabbit-rats (Conilurus penicillatus) glide, scurry and bounce between and through trees. Ghost bats (Macroderma gigas) fly through the night sky at speed, and with excellent hearing, vision and echolocation, and an impressive set of sharp teeth, they are formidable predators of insects, reptiles, frogs, birds and mammals, sometimes even other bat species.
Other mammals, including the fastidious and obsessive pebble collector and stacker, the eastern pebble-mound mouse (Pseudomys patrius), the reddish-brown and white-spotted northern quoll, and the rather robust (averaging >30kg and growing to more than 1m long!) northern hairy-nosed wombat (Lasiorhinus krefftii), can be found moving their way through the understorey.
Along with northern nail-tail wallabies (Onychogalea unguifera), diminutive long-tailed planigales (Planigale ingrami), and golden bandicoots (Isoodon auratus), these mammals above are just a small fraction of the region’s species. Tragically, many savanna-dwelling mammals are in sharp decline or locally extinct, through a combination of threats that include inappropriate fire regimes, land-clearing, intensified cattle grazing, feral herbivores and feral cats, invasive grasses, cane toads, and increasingly, climate change. Recent proposals for an expanded cotton industry and gas extraction will only place further pressure on this precious region and its mammals.
Show your support for your favourite savanna scurrier!
Meet the nominees:
Antilopine wallaroo (Osphranter antilopinus), northern Australia
This striking macropod comes in his and hers colours, males being large and predominantly reddish whereas as the much smaller-bodied females are greyish with elegant white ear-fringing.
Black-footed tree-rat (Mesembriomys gouldii), northern Australia
With a set of black-gloved feet and a spectacular long tail, these native rodents are among Australia’s most striking.
Common rock rat (Zyzomys argurus), northern Australia
Like some lizards they can shed the skin on their tail, causing it to partially drop off. This increases their chances of escaping predation.
Eastern pebble-mound mouse (Pseudomys patrius), eastern Queensland
They are known for building mounds of pebbles around the entrances of their dens, and as many as 25 individuals have been recorded sharing these underground homes.
Ghost bat (Macroderma gigas), northern Australia
Ghost bats can wait undetected above unsuspecting prey, before swooping down and capturing them with a swift bite to the neck.
Golden bandicoot (Isoodon auratus), north-west Western Australia and a number of off-shore islands
They are distinguished from other bandicoots by the golden-brown fur that covers their back and sides.
Long-tailed planigale (Planigale ingrami), northern Australia
Among the smallest mammal species in the world, weighing less than an average cherry, their flattened heads help them live in tight spaces, including cracking clay soils.
Northern hairy-nosed wombat (Lasiorhinus krefftii), two populations in central and south-west Queensland
They have a hard backside that serves as “armour” when defending against predators.
Northern quoll (Dasyurus hallucatus), northern Australia
Females can carry around up to eight young in their pouch and on their back while traversing rugged country.
Orange diamond-faced bat (Rhinonicteris aurantia), northern Australia
To escape their predator the ghost bat, orange diamond-faced bats exit their roost in an erratic zigzag pattern at speeds up to 26km/hour to take cover in nearby vegetation.
Scaly-tailed possum (Wyulda squamicaudata), far-west Northern Territory to north-west Kimberley coast in WA.
Unlike most others, this possum species with a rat-like tail typically shelters in rocks and boulders and not trees.
Spectacled hare-wallaby (Lagorchestes conspicillatus), northern Australia
While these macropods don’t rock actual bifocals, their distinctive orange eye rings certainly catch one’s attention.
Originally published by Cosmos as Savanna scurriers – who’s winning your hearts and votes?
Euan Ritchie
Euan Ritchie is an applied ecology and conservation researcher at Deakin University. He has been fascinated by Australia’s mammals for as long as he can remember, and has been researching their ecology and conservation across this continent for over two decades. He tweets at @EuanRitchie1.
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