Argentine ants: small things causing big problems

Department of Conservation —  07/02/2019

One of the world’s most invasive pests, the Argentine Ant, has a foothold on Ahuahu-Great Mercury Island.

We’re working together with the island’s owners, councils, volunteers and Conservation Dogs to eradicate them but face a difficult battle.

Argentine ant from Entecol. 📷: Richard Toft.

Argentine ant from Entecol. 📷: Richard Toft

Argentine ants are among the 100 most invasive species on Earth. They threaten New Zealand’s native insects, lizards and birds by attacking them directly or competing with them for food.

The ants were discovered here in 2013 and likely arrived via soil or timber. They’re small but they’re aggressive and can form super colonies and kill lizards and chicks.

Pete Corson is a Threats Technical Advisor at DOC and has been working to restore Great Mercury Island for several years, starting with rat and cat eradication project beginning in 2012.

Today he is working to eradicate Argentine ants from the island, advocating for collaboration and volunteers.

Pete talked about this in a recent 1 News at Six story — Impact of Argentine ants as a pest likened to atomic bomb going off in our back yard.

Ahuahu-Great Mercury Island is pest-free, although privately owned. It’s the only island in the Mercury Island archipelago (group) accessible to the public.

The seven Mercury islands are home to a large population of native species including geckos, skinks, giant tusked wētā, tuatara, kākā, kākāriki, New Zealand dotterel, recently arrived pāteke, a plethora of seabirds and 50 species of native land snails.

Pateke have self-reintroduced since the cat and rat eradication in 2014. 📷: Pete Corson.

Pateke have self-reintroduced since the cat and rat eradication in 2014. 📷: Pete Corson

Because Ahuahu-Great Mercury Island is so close to the other islands in the archipelago, DOC and the owners of the other islands are working together to control the ants.

The work of eradicating the ants and keeping the islands free of them also requires an army of volunteers.

The work is ongoing and poses many new challenges. It requires some serious person power as well as constant vigilance.

Collaboration is the key to conservation success, and working with influencers, partners and stakeholders is crucial.

This summer the island has had 45 volunteers giving their time to lay bait, monitor areas and collect data.

Volunteers helping to eradicate Argentine ants from Great Mercury Island. 📷: Pete Corson.

Volunteers helping to eradicate Argentine ants from Great Mercury Island. 📷: Pete Corson

In total this summer there have been 435 volunteer days on the project. Locals are getting involved and encouraging others to do so as well, whether it’s volunteering, treating their properties or spreading awareness of the problem.

Ant eradication also needs Conservation Dogs, who sniff out the ants and sit down when they find them. Veto is an Argentine ant dog in training.

Conservation Dog Veto. 📷: Pete Corson.

Conservation Dog Veto. 📷: Pete Corson

The Conservation Dogs programme is supported by Kiwibank.

Pest-free islands in New Zealand make up 1.2% of New Zealand’s land area but protect more than half of our threatened birds and more than a third of our threatened reptiles. There are strict biosecurity measures in place to make sure pests don’t hitch a ride with visitors.

It’s imperative that visitors check their gear, boats and luggage for pests including ants or rodents. We all have a role to play in staying safe and protecting Aotearoa.

A good tip is to load boats during daylight hours so night time pests don’t sneak in after you have checked the boat and gear.

The goal is to make sure unwanted pests aren’t visiting the island too and our special islands stay safe for the native species living there.

If left untreated Argentine ants have the potential to dominate all of the ecosystem through monopolising food resources, interrupting pollination, and predation by killing reptiles and bird chicks.

New Zealand is the only country that has ever had a successful eradication of Argentine ants – on the 12ha Tiritiri Matangi Island.

Bait is laid for Argentine ants to take back to the queen. 📷: Paul Craddock.

Bait is laid for Argentine ants to take back to the queen. 📷: Paul Craddock

Other projects are underway at Kawau Island and Great Barrier Island. The Ahuahu project is the biggest in New Zealand.

With hard work and persistence, we hope the Argentine ant will become part of the island’s history, not its future.