Golden-backed tree-rat: these rodents go nuts for nuts

Name: Golden-backed tree-rat (Mesembriomys macrurus), also known as koorrawal, wunggangbarn or jarri

Group: Rodents

Size: Body length 190-270 mm, plus tail (a whopping 290-350 mm); weight 240g-330g

Diet: Primarily a herbivore, foraging on nuts, leaves and flowers of fruiting trees such as Terminalia, Owenia, and Celtis sp. and boabs (Adamsonia species)

Habitat: Historically, this species was found right across northern parts of the Northern Territory, as well as the east, central and southwest Kimberley around Broome. It’s now only found on a narrow strip of land along the north Kimberley coast from the Yampi peninsula to Kalumburu, as well as a couple of wee offshore islands.

Conservation status: Listed as critically endangered in the Northern Territory

Superpower: Particularly adept at sniffing out the most delicious and tasty nutty snacks

A golden-backed tree-rat sitting on a branch at night and looking back over its shoulder
Credit: Alex Harshorne.

Golden-backed tree-rats are no run-of-the-mill rat that you saw last week raiding your compost. They’re a mysterious and curious rodent native of the north – one that’s a little bit punk, a little bit kung-fu, and definitely has a taste for fine dining. Their movie relative might be some the magical combination of Splinter, the kung-fu rat sensei from Teenage Mutant Ninja Turtles, and Remy, the chef rat from Ratatouille.

These rats’ most distinctive features are their curious dark eyes, the mohawk of golden hair that runs down their back, and their mega-long tail that looks like a giant paintbrush held high in the air behind them as they bounce along. While it’s not prehensile (able to hang onto things like a monkey’s), their tail is used expertly as a counterweight when they’re jumping through the trees, giving them amazing manoeuvrability in the canopy.

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When looking for golden-backed tree-rats at night, it’s sometimes easier to hear them before you see them – sitting high in the tree above you, crunching happily through a tasty boab, Terminalia or Pandanus nut. Despite their size, these rats can travel big distances in a night – up to a kilometre – to visit their favourite trees. During the day they nap in tree hollows, mostly alone but sometimes with buddies or in small family groups.

Their love for fruiting trees – and nutty snacks – is one factor that may in part be responsible for golden-backed tree-rats’ decline in northern Australia. Without traditional Indigenous fire management practices, the tree-rats’ home has experienced an increase in large-scale hot fires occurring late in the dry season, often lit by lightning strikes. These fires can kill fruiting and hollow-bearing trees, causing a decline in the rainforest vegetation that our friendly adventure rats love.

A golden-backed tree-rat running away up a branch, with its long tail prominent
Credit: Alex Harshorne.

These patterns of landscape change may have impacted on dryer areas earlier, leading to the species’ disappearance from large parts of their historic range. Also, feral cats are unfortunately no friend of our tree-rat buddies, as cats are adept at targeting small mammals of the tree-rat’s size and habits.

Luckily, land management practices in the region are improving through landscape-scale collaborations between traditional owners, NGOs and government organisations to reinstate traditional burning practices and protect habitat for our mysterious kung-fu chef punk, the golden-backed tree-rat.

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