#rattus

Annandale's Rat Rattus annandalei

It is found in Indonesia (Sumatra), Peninsular Malaysia, and Singapore.

A brown rat (Rattus norvegicus) in Sussex, England

Black Rat (Rattus rattus), family Muridae, order Rodentia, Kerala, India

The black rat is a well known pest that has spread across the world to every continent except Antarctica, causing significant destruction. However, the species likely originates in tropical South Asia.

Despite the name they occur in a variety of shades from black to light brown, like this individual

Above you see the Australian Swamp Rat (Rattus lutreolus), and below you will see information on them. They can reach a body length of up to 20 cm with a tail of 14 cm and are found in eastern mainland Australia and in Tasmania [1].

They were initially described as a water-loving species (and thus given the name lutreolus, meaning little otter), but their main habitat association is actually just dense green vegetation. Ironically the Tasmanian populations even avoid swimming and prefer to keep dry. In this vegetation they will build conspicuous tunnel systems and runways by gnawing and burrowing beneath the surface [2]. They select their habitat by prioritising density, with females occupying the best areas [3]. Females tend to act aggressive towards males outside of the summer mating season [4].

Through the use of these networks, they can protect themselves from aerial predators even during the day [3]. They can then use this advantage to modify what time of day they’re active based on other rodents. While they naturally gravitate to being nocturnal if they’re all alone, their activity patterns shift to twilight and daytime when other, more strictly nocturnal, species of rodents inhabit the same area [5].

Australian Swamp Rats primarily feed on plant stems, however their diet also depends heavily on the availability of other plant materials (and on occasion fungus and insects). For instance, in heath habitats there is little else available for most of the year, but once seeds pop up in spring and early summer, they’ll gladly have those as well (and the additional energy may be why they breed during this time [6], as they can, in theory, breed year round [4]).

There are some threats to them described in the literature. For instance, they do not respond as fearfully to the scent of invasive predator species such as the Red Fox (Vulpes vulpes) or feral cats (Felis catus) as they do to native predator species like the Spotted-tailed Quoll (Dasyurus maculatus) [7]. There has also been some destruction of their habitat “by fire, by grazing by domestic animals, and by the direct hand of man” [2], but overall they are still very common and seem to be surviving quite well as a species, and so are categorised under Least Concern by the IUCN [8].