Yellow crazy ants

They’re only a few millimetres long, but their super-colonies can eat entire ecosystems into silence.

Our Work Invasive Insects  |  Photo: David Wilson

Yellow crazy ants are on the list of the world’s 100 worst invasive species

They are a highly aggressive species, and have made their way into Australia through our ports. After first arriving on Christmas island sometime before 1934, yellow crazy ants have since been recorded in Queensland, the Northern Territory and NSW. They now threaten areas like Queensland’s Wet Tropics World Heritage Area, the oldest continuously surviving tropical rainforests on the planet. 

Yellow crazy ants do not bite. Instead, they spray formic acid to blind and kill their prey. And although they’re tiny, they can swarm in great numbers, killing much larger animals like lizards, frogs, small mammals, turtle hatchlings and bird chicks and reshaping entire ecosystems. 

Overseas, in places like the Johnston Atoll National Wildlife Refuge in the middle of the Pacific Ocean, yellow crazy ants have killed and deformed large numbers of chicks in seabird colonies by constantly spraying them with acid. 

But the numbers and impacts of yellow crazy ants fluctuate depending on local environmental conditions. And northern Queensland’s Wet Tropics just happen to be their ideal habitat. If not stopped in their tracks they could threaten Queensland with economic and ecological disaster, putting the state’s sugar cane and tourism industries  at risk and threatening devastating impacts on local communities. 

Impacts of Yellow Crazy Ants

When yellow crazy ant numbers hit super colony levels, they’ve been known to leave entire forests silent and can become a severe threat to people and pets. Yellow crazy ants are also a huge threat to agriculture in Australia’s warmer regions. They farm sugar-secreting scale insects and encourage the growth of sooty moulds that can dramatically reduce the productivity of crops like fruit trees and sugar cane. 

Sugar cane farmers Dino and Stella Zappala have seen first hand how the eradication program has reduced ant numbers on their farms and allowed the sugar industry to continue to operate with little inconvenience: ‘If the ants return to former densities, they will quickly spread and damage sugar cane production and could make the industry unviable’. 

An independent review by Melbourne University found that, without the current eradication program in the Wet Tropics near Cairns, the socio-economic costs in that region alone would exceed $500 million over the next 30 years. They would also jeopardise the tourism values in Queensland’s Wet Tropics World Heritage rainforests region, an industry worth $2 billion a year. 

There are already reports from in and around the Townsville area that some residents can’t sell their properties thanks to the yellow crazy ants that have set up shop in their yards. 

Yellow Crazy Ants on Christmas Island

On Christmas Island, yellow crazy ants have killed millions of the famous red land crabs and robber crabs, both of which play an important role in the island’s forest ecology. The presence of the ants has changed the structure of the forest. 

Following the path paved by yellow crazy ants, sap-sucking bugs and sooty moulds that severely damage plants and trees have proliferated, further degrading the island’s forests.

Unfortunately, the particular biological control agent used on Christmas Island is not likely to help control yellow crazy ant infestations found on Australia’s mainland in the Northern Territory and Queensland. This is because the biocontrol agent being released on Christmas Island targets a particular scale insect which produces the ant’s primary food source on the island but is not a food source for mainland populations.

Yellow Crazy Ants in North and Far North Queensland

While there are a number of yellow crazy ant infestations in Australia, the highest risk infestations to both the environment and the economy are in the Cairns and Townsville regions of northern Queensland. 

The Cairns infestation was first discovered in 2001 and since then has grown to occur in a number of suburbs around Cairns and inside the Wet Tropics World Heritage Area. Thankfully there has been a successful eradication program being run by the Wet Tropics Management Authority to eradicate the infestation around Cairns. In July 2019, we learnt the Queensland and Australian Governments had provided the required $18 million in joint funding to run the Wet Tropics Yellow Crazy Ant Program for three years, ending in June 2022. Since that time this program has been highly successful in reducing the population of yellow crazy ants in the region. The program has so far treated 100% of known infestations and eradicated yellow crazy ants from four sites with projections that most infestations will be eradicated by 2026.

Unfortunately, the program is currently unfunded beyond June 2022.

The yellow crazy ant infestations in the Townsville area are significant and growing. There are now six infestation areas – at Alligator Creek, Nome, Stuart, Douglas, Black River and Mount St John.

These infestations are only 10km from the southern portion of the Wet Tropics World Heritage Area and less than 5km from Bowling Green Bay National Park, which has an exceptionally high number of endemic species that could be wiped out by yellow crazy ants.

Unlike the Cairns infestation, there is no federal or state funded program to manage the Townsville infestation, with management falling to the Townsville City Council.

Without more resources dedicated to eradication there is a significant risks that the Townsville infestations will lead to more widespread of yellow crazy ants across North Queensland

Both the Cairns and Townsville infestations of yellow crazy ants present a significant risk to the environment and economy of northern Queensland.

It is critical that the successful eradication program being run by the Wet Tropics Management Authority is continued. It is estimated this will cost $6 million annually over the next 6 years.

It is also vital that an equivalent program, with state and federal support, is established in Townsville. It is estimated that this would cost $3.5 million annually over the next 6 years.

When the costs of inaction on this dangerous pest run into the billions, we know this is a smart investment in Queensland’s and Australia’s future!

What You Can Do


Learn what yellow crazy ants look like and how to report potential sightings.

If you live in the Cairns region and think you have yellow crazy ants call the Wet Tropics Management Authority on (07) 4241 0525.

If you live in Townsville and want to report potential yellow crazy ants contact Townsville City Council here or email us at:


Take action by communicating with your local, state and federal members of parliament that you would like funding for an eradication plan to be implemented. Speak to neighbours about this dangerous, invasive species so they can be educated too!


Yellow crazy ants are a serious threat to native wildlife in tropical and sub-tropical Australia. We need to secure enough funding to rid the Townsville area of yellow crazy ants and the only way we can do that is with your help.

You can also donate your time by getting involved with the Townsville Yellow Crazy Ant Community Taskforce.

What We Do

Since 2018, our Queensland yellow crazy ant team have been quietly working away with localsin the Townsville region to eradicate yellow crazy ants. It’s vital work if we want to secure Queensland from the march of these invasive ants.

Right now we are running a community surveillance citizen science program around Townsville, helping educate the local community about the risk of yellow crazy ants and equipping them with the knowledge and tools to identify and take action on this dangerous invasive species.

Current infestation sites of yellow crazy ants in Townsville include:

  • The Black River site is 8km from the southern end of the Wet Tropics World Heritage Area and just 5km from the only known population of the critically endangered Gulbaru gecko.
  • The Mount St John site is close to Townsville Common, important wetlands that are home to 11 frog species and 280 recorded bird species, including magpie geese and brolgas.
  • The Douglas site is adjacent to residential areas and the banks of the Ross River, which leads to mangrove areas and enters the coast near Magnetic Island.
  • The Alligator River site is less than 5km from the Mt Elliot section of Bowling Green Bay National Park, an area of exceptional species endemism and a climate refuge with many species found only on Mt Elliot, including the Saxicoline sunskink, the Mt Elliot crayfish and the critically endangered Mt Elliot nursery frog. If the ants were to reach Mt Elliot, it is likely they would extinguish these ground-dwelling endemic species and trigger a multi-species extinction event.
  • The Stuart site is a new discovery, where yellow crazy ants have been found in the industrial area.

While we are making good progress in Townsville, there is only so much we can do on our own. Unlike the infestation in Cairns, there is no dedicated program for the eradication of yellow crazy ants in and around Townsville. This is why we are pushing for a more systematic approach, including establishing an eradication program with matching funding from the Queensland and Australian Governments.

FAQs - Yellow Crazy Ants

They earned their name thanks to their colour and their quick, frantic movements, especially when disturbed. They walk in short spurts, often changing direction as if they can’t decide where to go.

Identifying ants is a tricky business! Luckily, our Insect Watch program has compiled some resources to help you identify yellow crazy ants.

If you’re in or around the Townsville region, you can use this guide to help distinguish yellow crazy ants from other types of local ants. 

Please see the contact list compiled under our Insect Watch program to find the relevant body to contact based on where you think you’ve found yellow crazy ants.

More Info