Canton Zurich beset by a plague of invasive ants

From vampire spiders to invasive mussels and snakes in the lakes, Canton Zurich has been beset with invasive critters in the past few years. Now, local authorities are warning of a new plague of ants, millions of members strong, gripping several towns across the region.

Ant colonies millions of members strong spread across Zurich

In four areas of Canton Zurich, a war involving millions of participants is raging between local councils and an invasive species of ant. The species in question is the Tapinoma ant, which was first discovered in Switzerland in 2018 and has since spread far and wide.

According to reports from SRF, of the 15 areas where the ants have been found, they have only been eradicated from seven of them. Unlike local Swiss species, which only sport colony sizes of a few thousand, Tapinoma ant colonies can sustain several million members at one time.

Tapinoma ants disrupt Swiss public transport

While some may question what impact the two millimetre long ants can have, the species can have a dramatic impact on local energy suppliers by crawling into distribution boxes and damaging them. In addition, last summer in the German city of Kehl, Baden-Württemberg, a playground was closed because the ants had tunnelled underneath and destabilised the site’s foundations.

The largest ant colony is in Volketswil and Schwerzenbach, with experts measuring a community covering a total of 35 football fields. In Oetwil an der Limmat, the ant colony there is now the size of seven football fields. “There were so many ants, you couldn't see the floor anymore," local resident Agnes Wirth told SRF. 

In Switzerland, the ant is also having an impact on public transport. A large ant colony has recently been spotted in Winterthur, exactly where Swiss Federal Railways are planning the Brüttener Tunnel expansion project, designed to increase rail capacity between Zurich and Winterthur.

Another sizeable colony is also expanding in Oberengstringen, and several other cantons have reported their own infestations. Killing the colonies is especially challenging, given that the largest colonies have multiple queens.

Speaking to SRF, Katharina Weber from the Department of Construction of Canton Zurich said that both the canton and local authorities are working together to eradicate the problem. "In areas with large infestations, a coordinated approach by specialists is required. This means a plan is needed, and special pest controllers must be deployed. These can target the nests with insecticide," she explained.