Invasive, Abundant, Successful… Rats in the Eastern Suburbs

By Keith Hutton on September 4, 2014 in Other

Rats are familiar to just about everybody, and as a group they are represented all over the world. In Australia, introduced Black Rats and Brown Rats are widespread and common wherever there are people. Black Rats have been so successful they are listed among the top one hundred in a Global Invasive Species Database of both animals and plants.

All rats have a pair of chisel-shaped incisor teeth with hard yellow enamel on their front surfaces. Black Rats generally appear slender with elongated bodies. They vary in colour from light brown to black above with cream or white underparts; black individuals are quite rare. They have a sleek smooth coat, a tail much longer than their head and body, and large thin ears, and they are habitual climbers. Brown Rats are sturdy and heavily built, with scruffy brown fur, and thick, often scabby tails that are no longer than their head and body; they have smaller ears. Brown Rats can be aggressive; they too can climb but prefer to be closer to the ground than the more gentle and agile Black Rats.

Black and Brown Rats have spread throughout the world. In Australia, Black Rats probably arrived with the First Fleet and are now established around the entire coast in suitable habitat. Greatest numbers are near human habitation, on agricultural land, along watercourses and at rubbish dumps, but also in relatively unaltered country where they are widespread in forest and woodland. In urban areas, they prefer to live in roofs, cavity walls, trees, and burrows around farms. Brown Rats are seldom far from human habitation and live in sewers, cellars, food warehouses and wharfs, mainly in coastal cities and ports; they also construct extensive burrow systems. Brown Rats and Black Rats are common in the Eastern Suburbs. Native Bush Rats have been recorded in the Eastern Suburbs too, but they are not found often in urban areas. The habitat is largely unsuitable for them and favours the introduced rats. They prefer forested areas and coastal scrub, where they select sites with dense ground cover of shrubs and ferns, and where they remain common.

Both Black and Brown Rats in urban environments eat almost anything that is suitable for people or their pets and livestock. Once they discover a food source they will visit and feed regularly. Bush Rats have a more varied and seasonal diet, different foraging strategy, and are not generally attracted to human modified habitats and food sources.

Humans and rats have interacted since ancient times. Black and Brown Rats have increased dramatically with urbanisation and agriculture, and these exotic species are now recognised as abundant in Australia. Throughout the world both of these species have caused massive economic damage by reducing profitability of primary food production, disrupting ecological systems leading to extinction of species, causing damage by chewing water pipes and power cables, and contributing to the spread of infectious diseases. They are consequently regarded universally as vermin.