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  • By Pacific island Times News Staff

Endangered species on Cocos Island facing threat from brown tree snakes

A bunch of brown tree snakes have been removed from Cocos Island but officials said the population count of this invasive species on the tiny atoll was not known at this time.

Surveys to better understand the number of brown treesnakes on the island are ongoing and the Rapid Response Team is also capturing and removing any snakes they find, according to the Guam Department of Agriculture Division of Aquatic and Wildlife Resources.

Four adult browntree snakes capable of breeding, as well as five juveniles, have been taken out of Cocos Island, an 83.1 acre atoll located 1.5 miles off the southwest coast of Guam. This was the first time an invasive brown tree snake population has been discovered on the uninhabited atoll, following a report from a local fisherman in September.

The brown treesnake was a major contributor to the loss of nine of 11 native forest birds and significant population declines of several native lizards, bats and other bird species on Guam. They now pose a threat to the wildlife of Cocos Island.

Guam Department of Agriculture Division of Aquatic and Wildlife Resources is working with partners to better understand how many brown treesnakes are on the island and the best way to remove them.

“Thanks to the diligence of the members of the public who reported the brown treesnake sighting, we were able to quickly respond to the threat that the brown treesnake poses to the wildlife on Cocos Island,” said DAWR Wildlife Supervisor Diane Vice.

DAWR worked with the U.S. Geological Survey’s (USGS) Brown Treesnake Rapid Response Team to take quick action.

The department said the browntree snake population on Cocos Island would have remained unknown and its expansion unchecked if it were not for the careful attention and reporting of local residents.

DAWR is working with USGS, the U.S. Fish and Wildlife Service and the U.S. Department of Agriculture’s Animal Plant Health Inspection Service Wildlife Services to develop a long-term plan for controlling and eradicating brown treesnakes on Cocos Island.

These territorial and federal agencies, along with the private and territorial landowners, have a long history of collaboration that will be vital to the successful eradication of brown treesnakes from Cocos Island.

Cocos Island is a special area of wildlife conservation for DAWR because it is home to the only wild population of the endangered ko’ko’ (Guam rail) on Guam.

One of the few remaining bird species endemic to Guam, ko’ko’ were successfully introduced on the island in 2010 by DAWR to save the species from extinction in the wild. Like many native bird species, the ko’ko’ was once abundant across Guam before the introduction of brown treesnakes contributed to their disappearance.​

Other native wildlife have survived and thrived on the island, creating a natural home for animals that Guam residents and tourists enjoy. Cocos Island is a diversity hotspot for Mariana lizards, including the endangered Mariana skink.

The island also provides habitat for såli (Micronesian starlings), fahang (brown noddy), chunge (white terns) and nesting beaches for endangered haggan (green sea turtles). The presence of invasive brown treesnakes could negatively impact all wildlife that call the island home. Many animals are prey for the snakes and their presence threatens Guam’s endemic ko’ko’ once again.


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