Water mouse population revealed in Cairns

An elusive vulnerable mouse species has been recorded in Cairns for the first time.

The native water mouse (Xeromys myoides) was known to occur in mangroves in Darwin, Arnhem Land as well as in Mackay and south to the Queensland border. 

However researcher Andrew Mitchell recently observed and recorded the rodent in Cairns, more than 500km from the closest known population and 4000km from Darwin.

“There aren’t too many animals in Australia with populations distributed in this manner, which raises even more questions as to how this occurred,” Mr Mitchell said.

The mouse, also known as the false water-rat or yirrkoo, grows up to 12cm with a tail of almost 10cm.

Despite a life in the muddy confines of the mangroves, its sleek fur remains remarkably mud-free.

The find confirms strong biodiversity in the Cairns area’s mangroves, which act as a filter for water entering the Great Barrier Reef and form an important link with the rainforests of the Wet Tropics World Heritage Area.

“The mangroves around Cairns really are special and house many more mammals than people might think, including striped possums and even dingoes,” Mr Mitchell added.

“On an international scale we have these world-class mangroves you can easily access just minutes from Cairns.”

He said the mouse’s mangrove habitat—where tides remove evidence of its activity—had made it difficult to find.

The mouse lives in mud nests, which are often distinguishable from mud mounds created by mud lobsters and sesarmid crabs.

It is a capable swimmer, and has been known to survive major flooding by climbing inside hollow trees.  

The mouse is carnivorous, feeding on small crustaceans including grapsid crabs—the neatly carved remains of which allowed Mr Mitchell to locate the mouse. 

The water mouse is listed as vulnerable by the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and Queensland Nature Conservation Act 2002.

The Wet Tropics World Heritage Area has one of the highest diversity of mangrove trees and shrubs in the world, featuring 34 of the world’s 69 species.

Photo credit: Queensland Department of National Parks, Sport and Racing

Published: 20th Oct 2017