A rat plague at Port Taranaki's lee breakwater is posing a serious risk to nesting blue penguins.
Fishermen there say the rats, believed to be rattus norvegicus, or brown rats, have become a common sight as they scavenge for food and bait.
Niwa fisheries researcher Justyn Selby, who has fished off the breakwater since he was a child, said rats were running rampant at the popular fishing spot.
"The rats are just all through the rocks, all the way to the end," Mr Selby said.
"There are tonnes of them - big ones too. They're definitely getting worse."
He said the rats were "cunning" and would steal bait and food when anglers' backs were turned.
"They'll sit there and watch you. They're disgusting."
Murray Chadfield, of Chaddy's Charters, said rats had always been present at the port.
"For every one you see, there's probably 100 you don't," Mr Chadfield said.
New Plymouth District Council has a pest control programme along the coastal walkway but the lee breakwater was part of Port Taranaki, which is the responsibility of its owner, Taranaki Regional Council.
TRC animal pest control manager Steve Ellis said Port Taranaki had carried out pest control on the breakwater in the past.
The port would conduct more now that it was aware of the problem, he said.
Nga Motu Marine Reserve Society ecologist Elise Smith said there were potentially dozens of little blue penguins living in the port.
Several penguin nest sites were dotted around Breakwater Bay and the little blues often used the rocks and concrete akmons on the breakwater to rest, she said.
Although there were no known cases of rats eating penguins, Ms Smith said it was unlikely a big hungry rat would turn its nose up to a meal of little blue penguin. "An increase in rat numbers would mean more competition for food among the population so the animals at the other end of the food chain will cop it," she said.
Rats also attracted cats which were even more likely to kill little blue penguins, she said.
"One small pest brings in another pest to kill it," Ms Smith said.
Stoats had also been seen at the port.
Little blue penguins, which had a nationally vulnerable status, were also easy targets for dogs, Ms Smith said, and she urged dog owners to be extra vigilant when they were walking their pets along the coast.
The breakwater rat plague is reminiscent of a 2008 incident when rats infested the Hobson St car park, colloquially known as Pig-Out Point.
The rats were attracted to fast-food scraps littering the car park, prompting the council to set up bait stations in the area.
Mr Ellis said Port Taranaki would most likely combat the breakwater rat population by laying rat poison.
- © Fairfax NZ News
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