Trapping success in Kapiti's Whareroa Farm

GOTCHA: Retired Raumati Beach butcher John Rowland with the 100th mustelid caught at Whareroa Farm.

Pest control at Whareroa Farm is proving successful, Shane Cave writes

So you'd like to hear what New Zealand's bush sounded like before Europeans arrived with their accompanying four-legged pests - rats, stoats, weasels, mice, hedgehogs possums and feral cats?

A trip to Kapiti will do it but there's an easier way, just turn off State Highway 1 opposite the Queen Elizabeth Park entrance, and you'll find the Department of Conservation's Whareroa Farm.

A volunteer run trapping programme to control predators began in April 2013 and has now caught 3139 animals, leading to a dramatic rise in native birds in the Whareroa bush.

The biggest cheer from the trappers (and if the birds knew they'd have squawked appreciatively too) came last month when one of the trappers, retired Raumati Beach butcher John Rowland, found the 100th mustelid, a stoat killed in one of over 100 traps supplied by the Department of Conservation.

Mustelids - the family that includes stoats and weasels - are the most aggressive introduced predators of New Zealand's birds, although Raumati veterinarian Sue Blaikie has found that lots of frogs and wetas also get eaten by mustelids.

The biggest catch by numbers has been of rats, 1393 so far.

The significant decline in the rats caught in heavily trapped areas of kohekohe bush, 300m east of the Whareroa car park, means that tui, bellbird, fantail and kereru (wood pigeon) can be seen and heard in unprecedented numbers after only three years of trapping.

The removal of 578 possums has also helped the birds as possums eat eggs and young birds and also accidentally dislodge kereru nests sending eggs and chicks plummeting to the ground. Ten feral cats have also been caught.

The damage is not just done up in the trees either. Mice - 941 - and hedgehogs - 111 - take a significant toll on skinks and lizards, seeds and wetas.

The traps kill pests instantly but need resetting as soon as they've killed something, and the different food lures which attract the animals also need to be renewed regularly, so it's a lot work for the trappers getting around the farm, much of which is very steep and covered in dense bush.

Recent funding from the Ministry for the Environment has allowed the trappers to use automatic resetting gas-powered traps for mustelids, rats and mice.

These fire 24 times before the little carbon dioxide gas bottle needs changing so they are constantly able to catch passing pests in difficult-to-get-to parts of the farm.

New Zealand's birds, lizards and skinks are especially vulnerable to all these predators because, apart from two species of bat, there were no mammals in New Zealand until Maori arrived so they had not evolved to cope with mammalian predators.

Maori brought one species of rat, kiore, but it did little damage compared to the two species of rat, mice, mustelids, hedgehogs and cats which have come since James Cook first landed in 1769.

The Whareroa trapping programme complements long standing predator trapping on neighbouring land by volunteers on Queen Elizabeth Park and from Paekakariki along the escarpment to Pukerua Bay.