Two Far North sisters aged 11 and 13 are putting the wildlife-saving efforts of most grown-ups to shame by trapping pests over an area so big they have to patrol it on horseback.
Nina and Jessica Quinlan, who call themselves the Wild Kiwi Girls, have set up a series of traplines over 90ha of bush and rugged farmland just west of Kāeo.
The traps cover eight properties, including 15ha owned by their parents Paul and Katharina, with the sisters checking and re-setting at least some of the traps every day.
They can patrol one trapline on their trusty horses Zahlis and Boxer; another has to be done on foot because the bush is too dense.
Since mid-October they have caught 340 possums, 78 rats and two stoats, with all results logged via the trap.nz website.
Jessica, 13, said their interest in conservation was sparked at a friend's party 18 months ago. They were playing in a stream when someone's dog caught a kiwi. They rushed the injured bird to the nearest DoC office but it died minutes before they arrived.
''After that we wanted to do something for kiwi, and to save out native bush and environment,'' she said.
The sisters heard about an Environment Fund run by the Northland Regional Council so they applied for funding and were granted enough, about $3000, for 30 possum traps and 30 rat and stoat traps.
Nina, 11, said it felt good to be doing something for the environment.
Possums not only killed trees and ate birds' eggs, they could also much their way through 60 giant snails in a night, she said.
The home-schooled sisters are using their trapping operation as an opportunity to learn about statistics, science and even te reo. Their neighbours, who maintain their own traps, send the girls their trapping results in Māori.
It also has led to discussions about the ethics of killing animals.
''I don't like the thought of killing as such, but I feel it's really important if we want to save the environment and native birds,'' Jessica said.
''I hate killing animals, but they are killing kiwi and ruining our environment,'' Nina added.
The sisters are testing a variety of commercial and home-made baits, such as eggs and peanut butter, for a science fair project to find out which is most effective at attracting rats.
Under the funding agreement with the council, the girls have to maintain the traps and log their catches for three years. The Wild Kiwi Girls, however, say they are determined to keep going long after that.