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Media Release
Commonwealth Minister for the Environment and Heritage
The Hon. Dr David Kemp

28 February 2003

Aerial Campaign Defeats Devastating Crazy Ants On Christmas Island

A combination of Federal funding, hard work and academic know-how has defeated Christmas Island's biggest environmental threat - yellow crazy ants - which had the potential to wipe out the world-renowned red crab population and devastate Christmas Island's unique environment.

Minister for Environment and Heritage, Dr David Kemp, today congratulated a team from Environment Australia's Parks Australia North branch and Monash University for successfully controlling the exotic and highly destructive yellow crazy ant super-colonies through an aerial baiting program - the first of its kind and of international significance.

"This highly effective aerial baiting program involved distributing some 12 tonnes of fish-based bait over 2143 ha by helicopter. After the baiting, each site was systematically surveyed and at no site were there any super-colonies or large numbers of crazy ants - in fact they had virtually disappeared. This operation was funded by the Commonwealth and was overseen and managed by our agency, Parks Australia," Dr Kemp said.

"These ants were having a devastating effect on Christmas Island's unique environment including the world-renowned red crab population which makes a spectacular annual migration to the sea to spawn."

The crazy ants devastate the island's rainforest ecosystem by killing the crabs and also pose a threat to reptiles and birds, including some EPBC (Environment Protection and Biodiversity Conservation Act) listed seabirds such as the Abbotts Booby.

Robber crabs, red crabs and blue crabs have been completely wiped out from crazy ant infested areas. Studies show the ant has displaced an estimated 15-20 million crabs by occupying their burrows, killing and eating resident crabs, and using their burrows as nest sites. The crabs are overwhelmed by high levels of formic acid secreted by the ants which blinds and leaves them vulnerable to attack.

The super-colonies have also devastated crabs migrating to the coast. This has seen a rapid depletion of land crab numbers which are vital to Christmas Island's biodiversity. They are a keystone species in the forest ecology by digging burrows, turning over the soil, and fertilising it with their droppings.

"The red crabs are unique to Christmas Island. It is believed at least half of the existing population of some 43,000,000 crabs migrate over Christmas Island each year at the onset of the first rains, usually in October," Dr Kemp said.

"The yellow crazy ant was accidentally introduced to Christmas Island between 1915 and 1934, but has only in recent years exploded in population - forming high density super-colonies, each comprising hundreds of millions of ants. These super-colonies have affected some 2500 hectares or 25% of the island's forest.

"Once a super-colony is established, it can expand rapidly, in some cases doubling in size in 12 months. To put it in context, the edge of a super-colony can expand at around three metres per day or around one kilometre per year.

"It is probable that, without the Commonwealth-funded control program, crazy ant super-colonies would have invaded the entire island, very likely eliminating the red crab and other important species. It is hoped that this risk has now been averted."

The Federal Government has spent more than $1.5 million on controlling yellow crazy ants, $200,000 of which was funded under the Natural Heritage Trust. The control program took place over the last five years, starting with ground baiting in the first two years, followed by extensive - and highly effective - aerial baiting annually towards the end of the dry season.

"The control of crazy ants on Christmas Island is an excellent example of how government and scientific partnerships can work together to protect Australia's unique biodiversity from pests," Dr Kemp said.

"This project has been both unique and is of international significance with conservationists and foreign media taking an avid interest in the protection of seabirds, such as the Abbotts Booby, and Christmas Island's unique rainforest ecology.

"It has also be widely recognised for its many elements of 'best practice' for managing an invasive species and is a model for controlling invasive species on oceanic islands.

"I thank and congratulate the team for their efforts. The government officers, scientists and research students involved worked day, night and weekends surveying the ant invasion, developing successful chemical control methods, and undertaking an intensive ground and aerial baiting effort with minimum impact on other island species.

"Despite the program's enormous success, crazy ants are still present in low numbers on Christmas Island. Parks Australia staff will continue to monitor any formation of new super-colonies and control these with hand baiting over the next few years."

For further information visit

Photos and visual on Betacam are available by contacting the Minister's office on (02) 6277 7640.

Media contacts:
Parks Australia Peter Cochrane, Director of National Parks 0419 125 137
Dr Kemp Catherine Job (02) 6277640 or 0408 648 400

Commonwealth of Australia