How to fight rats with toilet rolls
When you take on an island heaving with rats, you learn some tricks.
An expert rat catcher shows off a simple and deadly technique
The rats of 1987
which infested Murray Staples’ block of land on Aotea/ Great Barrier Island didn’t know they had bitten off more than they could chew.
He and wife Denise had bought two 6ha (16 acre) blocks and made a nasty discovery.
“We’re about 750m down a track from the main road and the rats had eaten everything, even the insulation off the phone lines. I thought, ‘I’ll get you buggers’.”
The former commercial fisherman wasn’t fazed by a few rampant rodents and started an eradication programme. His first line of attack was traps. The 25 he set were full every night, and some were also catching rats during the day, an indication of how hungry the normally nocturnal rodents were.
“For the first six months I was hard out trapping rats. Then they tailed right off, and there was a very noticeable increase in bird life on the property.
“Every person who starts trapping rats thinks they’re going to kill every last one. Forget it. There’s no big one-time solution. They just take off into the mountains.”
Then he started using brodifacoum poison.
“But it’s pretty non-selective. The rats took it into the chook house and it killed all the chooks.”
That’s a problem on this unique island. There are no possums, goats or mustelids (weasels, stoats) – the pest population is feral cats, rabbits, rats and pigs – but there are a huge number of native birds.
“We’ve got more than our fair share of rare birds,” says Murray. “You don’t want any poison around the place that they can get at.”
Local environmentalist Judy Gilbert had been keeping an eye on Murray’s death-torats operation and she offered to arrange a Heritage Grant for him. This was used to buy another 150 traps. Murray begin rat catching in more earnest, focusing on Judy’s Windy Hill bird sanctuary nearby.
There have been plans to blitz the island’s rugged hinterland with aerial poison drops using 1080 or some other toxin, but Murray says that is the wrong approach for Great Barrier.
“On the mainland, they can hit an area with 1080 or some other broad spectrum poison that will smash everything. But here on the island we haven’t even got half of the pests they’re targeting. I’m not against using 1080 on the mainland, but we’ve got a unique situation here, we’ve got too many rare ground birds.”
That includes the rare banded rail and brown teal (pateke) which are endemic to the island. There are also tui, kererū, kākā,
“Every person who starts trapping rats thinks they’re going to kill every last one. Forget it.”
fantail and fernbirds, eight species of native skink and five types of native gecko.
Murray’s work eventually identified his toxin of choice, diphacinone. It’s the main ingredient in many pest baits you can buy at rural supply stores.
But Murray developed a cost-effective, ecologically-sound method for applying it on the island. He ran ads on the local, solar-powered broadcast radio station Aotea FM and in the Barrier Bulletin newspaper and asked residents for used toilet rolls. This sparked many jokes from the islanders about wiping out the pest population.
However, Murray had discovered a unique way to turn them into an effective rat bait station.
“I dip the rolls in wax to waterproof them, then put about 50g of a peanut butter and poison mix in each one, fold the ends over and staple them to trees in the forest.
“A fit young guy can set 75 baits an hour with about 20m between them,” he says. “Diphacinone is great stuff – it just targets rats and isn’t toxic to most other animals. It won’t even kill mice.”
The bonus: the cardboard rolls are 100% biodegradable.
One 20 litre container of diphacinone holds enough for 400 baits, enough to kill about 1200 rats.
“You can set all your gear in one day and you’re in business.
“Rats are grazers. They only eat twice a night and consume about 10% of their body weight. They will get through about 20g of bait a night, then graze on other foodstuffs. If they have been at the bait on the first night, they’ll have another nibble the next night. On the third night, they don’t turn
He might be a great rat killer, but there’s one pest Murray hates more.
up for work.”
Rats feed in roving packs of 15-20 animals in Murray’s experience.
“We’re lucky. Great Barrier only has ship rats and kiore, not Norway rats. Kiore mostly stay up in the trees – if times are tough the ship rats will eat them if they come down to the ground.”
A mature ship rat can weigh about 300g. They have a four week gestation period and then it’s another four weeks before they reach sexual maturity. “You’ve only got two months to get ‘em,” he says. He might be a great rat killer, but they’re not the pest that Murray hates most. That would be feral cats. Politician Gareth Morgan may be talking the talk in Wellington, but here on the island, Murray is out in the bush walking the walk.
“A couple of days ago I was out one morning and I came across three pairs of ruru (morepork) wings. The cats tear the wings off their prey so that they’re easier to carry.
“In spring, I get a lot of rats and cats just above the high tide mark – they’re there to prey on teal and penguin chicks. You’ve got to keep your thumb on them.
“Lots of people come up with the argument that if you have cats they keep the rats down. It just doesn’t work like that. An adult rat can see a cat off and there are much easier things – like skinks and birds – to eat. I’ve seen plenty of cat chunder, it’s mostly skinks and feathers.”
Murray’s business Rat-a-tack has clients all over the island, mostly householders or bach owners who need rodent control when they’re not in residence. He also keeps a keen eye out for attacks on the local birdlife.
His own block is almost rat-free.
“We’ve got five stock units,” he laughs. “Four pigs and a chook.”
There’s also Rasta the dog. He doesn’t like either.• cats