Rats have starred or appeared in over 400 films and close to one hundred television series – but they’re prime-time villains in the story of New Zealand’s forests.
There are three kinds of rats in New Zealand, the kiore, the Norway rat (also called the brown rat) which is the biggest and the ship rat (also called the common rat) which is the commonest. The Norway rat and ship rat like to live near humans and can be found in houses, waterways and at tips.
The Norway rat has a short, thick tail which is shorter than its body and it has small ears. The ship rat (common rat) has bigger ears and a tail that’s longer than its body. The ship rat is the biggest threat to wildlife because it’s a good climber and can reach nests in trees. The Norway rat is big enough to attack seabirds, but it’s not a tree-climber and can only attack wildlife that lives or nests close to the ground.
Rats are rodents and gnaw their food, wearing down their teeth. That’s why a rat’s teeth keep growing throughout its life. Their front teeth grow 11-14cm in one year, but are constantly being worn away as they eat.
Kiore were introduced by early Maori voyagers from Polynesia to New Zealand, while Norway rats and ship rats travelled to New Zealand on whaling ships and with early settlers. Rats eat weta and other insects, snails, frogs, lizards, tuatara, birds and bats, as well as the flowers, fruits and seeds of plants.
Norway rats can have up to 22 babies in one litter, but usually they have 8 or 9 babies. Newborn baby rats are blind and don’t have any fur. They weigh only 6-8 grams. In theory, if all their babies survived, a pair of Norway rats could have 2000 offspring in 1 year.
Because rats have lots of babies their numbers can increase very quickly. Every 5-7 years, when there is lots of food around, rat numbers will suddenly increase. In these years, rats do a lot more damage to wildlife. As well as attacking native birds, rats also eat the same food as the birds, so when there are lots of rats around there is less food for birds to eat. When the food runs out, the rats eat the birds and other wildlife.
Did you know?
- A group of rats is called a mischief.
In the mid-19th century, Jack Black, the rat catcher for Queen Victoria, found several colour variations of the Norway rat and tamed those he caught. Owners of his pet rats included Queen Victoria.
- A Hindu temple dedicated to the rat goddess, Karni Mata in India, houses more than 20,000 rats. The rats are believed to be reincarnations of Karni Mata and her clansmen and many people travel large distances to the temple to see them. The holy rats are called kabbas.
- Rats use their tails to regulate their temperature, to communicate and for balance. They regulate their temperature by constricting or expanding blood vessels in their tails. They also have glands on the bottom of their feet and will lie on their backs to sweat.
- Rats don’t have gallbladders or tonsils, but they do have belly buttons.
The story of Campbell Island
Campbell Island used to have the highest population density of Norway (brown) rats in the world! Before 2001, about 200,000 rats lived on the 11,300 ha island which is located 700km south of mainland New Zealand. They were descendants of rats accidentally brought to the islands by sealing and whaling boats 200 years earlier.
Rare birds like the flightless Campbell Island teal and tiny Campbell Island snipe had to be removed to other safe islands to save them. These special birds are found no-where else in the world.
It took 2 years and $2.6 million to kill all the rats with tonnes of poison pellets dropped from the air. In 2003 Campbell Island was officially declared rat-free. This meant that the tiny snipe and flightless teal could return from exile to live safely on Campbell Island again.