An invasive species of ant have been discovered at the mainland visitor departure point to the nationally important Kāpiti Island.

Department of Conservation has confirmed a colony of the small, honey-coloured Argentine ants was discovered at Paraparaumu Beach on Monday.

The species have been active elsewhere in Kāpiti but this nest is close to where Kāpiti Island tourism providers leave for the island, increasing concerns that these ants could reach the native bird sanctuary.

DOC have support from Kāpiti Coast District Council and Kāpiti Boating Club to poison the nest at the mainland visitor departure point, which is on Council land and leased to the club.

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DOC will continue to monitor the immediate area for reinvasion and do ongoing control if needed.

Jack Mace, operation manager for Kāpiti Wellington said, "We can't afford to let even one of these invasive insects get across to the nature reserve.

"These ants are tiny so we insist that anyone travelling to the island to be very vigilant about checking their gear.

"Our tourism providers have high biosecurity standards but we've asked them to redouble their efforts.

"In fact, it was one of the boat operators who alerted us to the nest, so we know they are on the ball."

The ant is one of the world's most invasive species, DOC said.

They are very aggressive and can combine in large numbers into super-colonies with huge appetites.

They are a threat to our native species because they displace and kill native invertebrates, including native ants.

And they compete with kiwi and other native birds and lizards for food such as insects, worms and nectar.

"With these ants spreading across New Zealand rapidly since the 1990's, it was only a matter of time before they reached the Kāpiti Coast," Mace said.

"We can still prevent them from reaching Kāpiti Island – but we'll need everyone's help to do that."

Mace said DOC will implement a monitoring and response plan on the island to ensure, even if they do reach the reserve, they are picked up quickly.

"We can eradicate them if they get there - that's totally feasible.

"However robust quarantine measures to minimise the risk of them getting there is our first line of defence."

Kāpiti mayor K Gurunathan said the discovery was "a clarion call for a proper best practice bio security facility at Paraparaumu Beach for visitors heading to the highly valued nature reserve".

"For several years we have been repeatedly alerting DOC on the need of such a facility.

"Current practice of undertaking bio security checks on the car park tarmac of at a nearby cafe is not good enough.

"This current pest infestation highlights the continuing lack of such a basic protective shield needed for Kapiti Islands high biodiversity values.

"I take this opportunity to urge DOC to initiate the steps necessary to do this."