Maui News

Eradication of “Yellow Crazy Ants” at Johnston Atoll Protects Seabird Colony

June 23, 2021, 12:14 PM HST
* Updated June 23, 12:21 PM
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Red-tailed tropic bird chick swarmed by red ants. Photo credit: Sheldon Plentovich/USFWS.

The US Fish and Wildlife Service has eradicated the yellow crazy ant from Johnston Atoll NWR. Yellow crazy ants are non-native ant species that cause harm to seabirds, disrupting their ability to reproduce. These ants no longer exist at Johnston Atoll NWR thanks to the great work of staff and volunteers who lived at Johnston for half a year at a time, to exterminate the ants.

After combating “yellow crazy ants” for a decade, the US Fish and Wildlife Service has eradicated the invasive species, protecting vital seabird colonies at Johnston Atoll National Wildlife Refuge, part of the Pacific Remote Islands Marine National Monument. This is the first time the species has been eradicated from such a large area in the US.    

The refuge is one of the most isolated atoll formations in the world, providing essential habitat for tens of thousands of seabirds, including the world’s largest colony of red-tailed tropicbirds. It is the only seabird habitat in more than 570,000 square miles of open ocean, sustaining fifteen species of breeding seabirds that rely on the emergent land protected by the refuge. 

For more than 10 years, these ground nesting seabirds were severely threatened by yellow crazy ants. “The infestation increased in such density that  they swarmed anything on the ground, spraying formic acid on seabird chicks and adults – causing blindness, injury and death. The arrival and rapid spread of the invasive ants prevented red-tailed tropicbird nesting in the 70 acres infestation area and put the entire seabird colony at risk,” according to the FWS.

Following a long decade of combating a menacing invader detrimental to seabird colonies, the U.S. Fish and Wildlife Service has achieved another invasive species success – the eradication of yellow crazy ants (YCA) from Johnston Atoll National Wildlife Refuge. Photo (left) A flock of sooty terns gather near the only building left standing on Johnston Atoll National Wildlife Refuge, March 24, 2019. Photo by Eric Baker/USFWS. Photo (right) YCA Bait Testing Efficacy Trial at Johnston Atoll NWR. Photo by Robert Peck, HCSU/USGS

The presence of the ants and their threat to the seabirds on Johnston Island was discovered in 2010 by USFWS biologists. Nearly 100 staff and volunteers devoted over 130,000 field hours as a part of Crazy Ant Strike Teams – specialized invasive species control teams that worked to combat the island invaders over the last 10 years. The last known sighting of yellow crazy ants on the refuge was in December 2017.  

Tern Colony. PC: USFWS – Pacific Region.

“Thanks to the brilliant work of these volunteers and staff, as well as the help of our partners, this is the first time an invasive ant species has been eradicated on such a large land area in the US,” said Kate Toniolo, Superintendent for the Pacific Remote Islands Marine National Monument. “To ensure the eradication was successful, the teams have been monitoring, searching, and surveying for yellow crazy ants. Their hard work, dedication, and scientific rigor have helped us ensure a safer future for the tens of thousands of seabirds that rely on Johnston Atoll National Wildlife Refuge.” 

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The battle against yellow crazy ants at Johnston Atoll required creativity and ingenuity as crews experimented to find the best way to bait and eradicate the ants. After these bait treatments the crews hand-searched the island multiple times to find remove any remaining ants. 

Guinness (far right) and the detection dog trainer, Kyoko Johnson, pose for a shot before conducting a dog detection survey on Johnston Atoll, along with Solo (far left) and dog detection assistant, Michelle Reynolds. Photo by Tor Johnson / US Fish & Wildlife Service.
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Two conservation detection dogs trained to sniff out the ants were brought to the refuge in December 2020 to help with this process. The dogs surveyed 118 total miles without detecting a single ant, providing greater confidence that the ant has indeed been eradicated. The success at Johnston Atoll National Wildlife Refuge could provide a roadmap for other conservation managers dealing with invasions of yellow crazy ants in other protected areas.  

“While the mission of the Crazy Ant Strike Team is complete, the Service will continue to focus on habitat restoration, preventing the spread of other invasive species, and the conservation of the wildlife and habitat protected by Johnston Atoll National Wildlife Refuge,” said Stefan Kropidlowski, Deputy Superintendent for the Pacific Remote Islands Marine National Monument. “For now, we celebrate that the refuge is once again a safe haven for the amazing seabirds that call this incredible place home.” 

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