Which rat is that?

First published 2017-10-31 09:01
Project The Urban Rat Project

New Zealand has three different rat species – all of which were introduced by humans in the very recent past. This article will tell you how to identify one from the other.

The ship rat Rattus rattus

Also known as the black rat, roof rat or bush rat

This is the most common rat in New Zealand, introduced in the late 1800s. Ship rats are nocturnal and active from dusk until dawn in most weather. They mostly forage in trees, but also on the ground. They are excellent climbers and their habitat reached from the ground to the treetops. They can swim well up to 500 m. The ship rat’s diet is very broad, incorporating plant and animal material, refuse, and stored food. They also predate on eggs and chicks and since they are such agile tree dwellers they pose a big threat to many birds. Ship rats can be wary of new objects and may be initially cautious when a new food is presented.

Identification: To check whether you have caught a ship rat, pull its tail alongside its body. If the tail is longer than the body, it is a ship rat. Also, it will have large ears that are big enough to cover its eyes. The ears are rounded and hairless and the tail is dark.

Image: Ship rat – note the large ears and long slender tail. (Source: Department of Conservation)

The Norway rat Rattus norvegicus

Also known as the brown rat, water rat or sewer rat

This is the largest rat species in New Zealand. It arrived before the ship rat in the late 1700s. Norway rats are able to climb, but they spend most of their time on the ground. They are excellent swimmers capable of over 2 km. They are not as widespread as the ship rat and their distribution is patchy, usually found around waterways (coastal and freshwater), in towns and around farms. They have a very varied diet including plants, seeds, insects, lizards, eggs and chicks as well as molluscs and crustaceans. They are a particular threat to ground nesting coastal and braided-river breeding birds.

Identification: To check whether you have caught a Norway rat, pull its tail alongside its body. If the tail is short than the body, it is a Norway Rat. Also, it will have small ears that are not big enough to cover its eyes. The ears are lightly haired compared to the ship rat and the tail is thick with a pale underside.

Image: Norway rat – note the small ears and shorter tail. (Source: Rod Morris)

The Kiore Rattus exulans

Also known as the Pacific rat

Kiore were the first rat species to arrive in New Zealand, probably in the late 1200s. Since the introduction of the Norway rat and ship rat, Kiore numbers have seriously declined and they are now the least abundant rat species. They are restricted to parts of the South Island and some offshore islands. Kiore are the smallest of the three rat species, are poor swimmers, solitary, nocturnal mostly ground dwelling. They have a varied diet of plant and animal matter, including birds eggs and chicks particularly of burrow nesting species.

Identification: Kiore have brown fur, with white-tipped grey fur on the belly. They have pale feet with dark mark on outer edge of hindfeet. The ears cover the eyes when pulled forward and the thin tail is about the same length as the body.

Image: comparison of the three rat species. (Source: Department of Conservation)

More information

For more information about these species and how to identify them (and their droppings) please go to www.pestdetective.org.nz.

Leave a comment

Join now!

Note that you can choose a Project when you file a report.


© The Urban Rat Project 2019