Cunning rats plan to protect sanctuary from bird poo
Ship rats are being sent in beyond the wire of a predator-proof fence to try to save a nationally important peat lake network at O¯ haupo¯ from the effects of up to half a million pooping birds.
The Department of Conservation acknowledges the move will seem ‘‘counterintuitive’’ to some, given the rats could threaten native copper skinks and spotless crake birds (pu¯weto) inside the 12 hectare fenced area in the Waikato.
But, after a ‘‘very challenging conversation’’ amongst agencies, DOC sees the introduction of up to 50 rats over three months during a trial as the best option for now to try to scare off the birds.
The trial’s main goal is to protect water quality and plants in the three interconnected Rotopiko lakes from the effects of bird poo.
‘‘It may seem counterintuitive but focusing on lake protection is the key at this point,’’ DOC’s Waikato operations manager Tinaka Mearns said.
The National Wetland Trust has been trying for years to find a way to drive off the massive flocks of roosting starlings, sparrows and pigeons which have found a haven in the rat-free area at Rotopiko since the fence was installed in 2013 around the site’s east lake.
The problem is compounded by the fact that birds feed in local farming areas then come to the comparatively small fenced off area, creating a very concentrated amount of droppings that run off into the lake.
Now the trust has got so desperate it will do a controlled temporary reintroduction of ‘‘locally captured wild ship rats’’ at the site 20 minutes south of Hamilton. The trial starts this week.
The trust’s executive officer, Karen Denyer, said one of the key goals of sending in the rats was for them to climb the trees at night and scare the birds away.
Denyer said it hadn’t been possible to guesstimate the actual effects on native wildlife of introducing rats but it’s hoped the impact on the spotless crakes will be minimised by the fact that they like being in or near water and the ship rats don’t. ‘‘My sense is the crakes are fairly safe.’’
Expert advice suggested the pest birds wouldn’t simply move en masse from the area to another location after rats are brought in
‘‘We believe [the birds] will disperse across the district to different sites, presumably back to where they roosted prior to the eradication of rats from within the reserve,’’ the trust said.
Asked what gave the trust confidence in the rats method, Denyer said ‘‘a lot of talking to experts’’, including bird behaviour scientists.
She wasn’t aware of this method being trialled anywhere else in the world.