When it comes to native Australian animals, rodents are probably way down the bottom of the popularity list. In fact many Australians think of rats and mice as feral animals. And do not realise that almost a quarter of Australian mammal species alive at the time of European settlement, were actually rodents.
Rodents are successful and adaptable animals which are found throughout the world. The order Rodentia include Capybaras (at 50 kgs the world’s largest rodent), agoutis, porcupines, cavies, squirrels, flying squirrels, beavers, rats and mice. All Australian species belong to the Muridae family and they have evolved arboreal, terrestrial and aquatic habits which have allowed them to occupy virtually every habitat in the continent.
Australian rodents can be thought of as 3 groups:
1) The “old endemics” who belong to the Hydromyinae subfamily, comprising the vast majority of Australian species. They migrated from Indonesia approximately 15 million years ago.
2) The “new endemics” who belong to the Murinae subfamily, comprising 7 species. They migrated approximately 1 million years ago.
3) The introduced species who also belong to the Murinae subfamily, comprising 3 species.
They were introduced by European settlement approximately 200 years ago. The 3 introduced species are the House Mouse (Mus musculus); Brown Rat (Rattus norvegicus) also known as Sewer Rat; Black Rat (Rattus rattus) also known as Roof Rat, Ship Rat and Fruit Rat. The friendly little “fancy rats” that are becoming increasingly popular pets, and the poor old lab rats, are domesticated Brown Rats. In the wild Brown Rats are notoriously aggressive, unlike Black Rats which have a more gentle disposition.
The House Mouse and Black Rat are found on Tamborine Mountain, Brown Rats have a more limited distribution, so fortunately we do not see the Brown Rat here. There are 4 native rodents found on Tamborine Mountain:
Fawn-footed Melomys Melomys cervinipes Body length 95-200mm; Weight 45-110g; Fur short, dense greyish tan to bright orange brown; Habitat rainforest, moist lantana, closed forest, wet sclerophyll forest, dense ground cover; Diet vegetarian; Behaviour nocturnal, arboreal, builds spherical nests in trees; Reproduction may form stable pairs, several litters pa of 2 young.
Bush Rat Rattus fuscipes Body length 120-200mm; Tail length 80-195mm; Weight 55-225g; Fur soft, dense variable colour, upper grey-brown, under grey-cream; Habitat prefers dense ground cover; Diet omnivorous taking insects, plants, fungi and seeds; Behaviour nocturnal, terrestrial, shy, solitary, shelters and nests in shallow burrows and logs; Reproduction several litters pa of 5 young; Similar Species distinguish from the Black Rat by tail proportion, the Black Rat has a tail longer than its body length, whereas the Bush Rat’s tail is shorter than its body length, and the Black Rat has longer ears than the Bush Rat. The Bush Rat is not commensal.
Swamp Rat Rattus lutreolus Body length 120-200mm; Tail length 80-145mm; Weight 55-160g; Fur long, coarse, upper dark brown-grey, under buff grey, dark hind feet; Habitat riverside swamps, heath, fern thickets, ungrazed grassland and sedge-lands; Diet mainly vegetarian, grasses and sedges but some insects taken; Behaviour partly diurnal, nocturnal, terrestrial, tunnels through vegetation and constructs extensive shallow burrows systems, females defend a territory of .5ha males of 4ha; Reproduction several litters pa of 3-5 young.
Water Rat Hydromys chrysogaster Body length 230-390mm; Tail length 230-325mm; Weight 340-1275g; Fur soft, dense, shiny, waterproof, upper black to grey, under cream to orange, white tipped tail; Habitat aquatic environments; Diet crustaceans, frogs, mussels, fish and insects; Behaviour mainly nocturnal, but may forage in daylight, adapted to swimming, territorial, makes nests in waterside burrows; Reproduction several litters pa of 3-4 young ; Notes formerly hunted for its fur.
European settlement has had varying effects upon native rodents depending on the species. A few species have benefited from new food sources and habitat modification, and this may cause some rather strange situations. A north Queensland resident whose home was regularly raided at night by a White-tailed rat (Uromys caudimaculatus) which seemed to particularly enjoy using its considerable incisors to gnaw her telephones. She decided to trap and relocate the offender. The trap was baited with all manner of delicious food, but every morning it was empty, and the destructive rat raids continued. Eventually, out of frustration she threw one of her now useless telephones into the trap. Next morning she found the trap occupied by the telephone gnawer, who had obviously been unable to resist such attractive bait.
However, many, particularly highly specialised species, have suffered reduction in distribution and numbers, several species appear extinct, and many others are at risk. Unfortunately for rodents, especially rats, public perception is that rodents are vermin and there seems to be little interest in, or sympathy for our many species of native rodents.