Common rock rat: A native rodent with some uncommon features

Name(s): Common rock rat (Zyzomys argurus)

Size: Head and body length 85-140mm, tail usually same length as the body, weight 25-65g

Diet: Omnivore, mostly eating plants, seeds, grasses, fungi, and occasionally insects

Habitat/range: Rocky scree slopes and outcrops across northern Australia, with isolated populations in WA, the NT and QLD

Conservation status: Least Concern

Superpower/fun fact: Like some lizards, common rock rats can shed the skin on their tail, causing it to partially drop off and increasing their chances of escaping predation.

A small, light brown rat under large rocks
A common rock rat on Adolphus Island, Western Australia. Credit: © Russell Palmer, some rights reserved (CC-BY-NC)

If rugged Australian mammals are up your alley, then let me introduce the small, yet mighty, common rock rat (Zyzomys argurus). Despite its somewhat unflattering name, this native rodent has some uncommon traits that make it somewhat of a ‘rock star’ in the animal kingdom.

The common rock rat, the smallest of the rock rat family, lives in the rugged landscapes of Northern Australia. It is a survivor, and true to its name, it is perfectly adapted to living in rocky habitats. With broad hind feet, these acrobats can leap over large gaps between rocks and run up vertical rocky surfaces. To escape extreme heat and other dangers, common rock rats live inside deep, dark crevices within the rocky habitat.

A small rat hidden in a pvc pipe
A common rock rat tucked away in a PVC pipe, used to give them more shelter when caught in a cage trap. Credit: Mitch Cowam

While their nimble feet enable them to run up and down rocks with agility, their long tails provide additional balance. The tail is usually the same length as its body and has many uses, some of which can be lifesaving. For example, in the wet season when resources are abundant, common rock rats can store fat in the base of their tail for use in the leaner dry season when food is scarce. Further, if attacked by a predator they can shed the skin on their tail, causing it to partially drop off – distracting the predator for long enough to allow a quick getaway. Therefore, it is not uncommon to see common rock rats with half a tail in the wild.

Common rock rats must constantly evade large predators to survive. Pythons, venomous snakes, quolls, owls, feral cats and ghost bats all inhabit the rats’ favoured rocky habitats. Fire is also a danger for rock rats, destroying food resources in foraging habitats and further increasing their reliance on the sanctuary of rocky scree where the effects of fire are less extreme.

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The common rock rat’s diet consists mostly of seeds, grasses, and other vegetation. However, in these rugged landscapes, those commodities aren’t always plentiful. So, rock rats aren’t picky. They can and will eat insects, making them an opportunistic omnivore. Like many mammals being studied for conservation, they also have a propensity for loving peanut butter, or in one documented case, custard, and rice pudding. This dietary opportunism or flexibility is a major survival advantage in the unpredictable and often harsh landscapes in which they live.

A hand lowers a small rat among rocks
Be free: A common rock rat being released back into its rocky home. Credit: Judy Dunlop, Nyamal Rangers.

The common rock rat can breed year-round and has a ‘boom and bust’ breeding pattern. This means that they reproduce heavily when resources are abundant, like in wet season. But in low resource conditions, like the end of dry season, their reproductive behaviour slows down. A female will generally give birth to two or three young in one litter, and they are often weaned by four weeks of age.

The common rock rat embodies the principle that no matter how big or small you are, you can adapt and survive in the most challenging of environments. So, the next time you feel like you’re stuck in the ‘rat race’, let your mind wander to the rocky scree slopes of the common rock rat, an unsung mammal of northern Australia.

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