Dan Vice, a Wildlife Services biologist with the U.S. Department of Agriculture, yesterday holds one of the brown tree snake traps that can be seen along fences around Guam. Vice said this is one of a few ways federal agencies control the invasive species population on Guam, in addition to the aerial bait drops. (Michelle Conerly / (Hagatna, Guam) Pacific Daily N)
Representatives from several federal agencies watched yesterday as a crew dropped dead mice filled with mild toxins onto two test sites on Andersen Air Force Base, for the fourth official aerial bait drop event.
Dan Vice, a Wildlife Services biologist with the U.S. Department of Agriculture who has worked on the project for more than a decade, said the mice filled with 80 mg of acetaminophen are used to kill the invasive brown tree snake population that was accidentally introduced to the island around 60 years ago.
A pilot project involving 280 mice dropped in a similar manner was conducted in 2010, and the success of that project allowed for the official aerial bait drops that began in September 2013.
The drops, including research, cost a total of $1.5 million, with funding coming from the Department of the Interior and the Department of Defense.
The total budget nationally for the project is $8 million.
An estimated one to two million snakes live around the island, Vice said, making the aerial bait drops the most effective and efficient way of controlling the population while not affecting other animals on Guam like deer and pigs.
“The risk to non-targets is slight,” Vice said. “It would take 500 baits to kill a pig (or dog and) 15 baits to kill a cat.”
Crews yesterday afternoon combed the two 136-acre areas — equaling the size of about 210 football fields combined — to locate tiny radios also implanted in some of the mice. These radios help the USDA track the snakes’ activity — whether or not they’ve eaten the mice or if the mice decompose on their own.
They also track the abundance of small animal and rodent populations, as these would increase if the brown tree snake populations were to decrease.
“If it proves to be successful then we may potentially start ramping up the efforts and doing this on a larger basis across more of Guam,” Vice said.
Vice said this technique is for non-human habituated areas only and would never be done in villages.
Although no one has ever died from the venomous bite of a brown tree snake, according to Vice, most bites to adults result in nothing more than a bee sting-like sore.
According to USDA documents, the brown tree snake has caused extensive economic damage to the island’s economy, specifically the Guam Power Authority’s electrical grid, costing about $1 million to $4 million a year in lost productivity due to power outages.
That’s why facilities like major substations, the A. B. Won Pat Guam International Airport and other areas are surrounded by special fences that keep out brown tree snakes.
Vice said about 4,000 snake traps attached to these fences catch about 8,000 brown tree snakes a year.
Threat to other islands
The threat of these snakes becoming established on another island is a reality, said Vice, noting that a stable population of brown tree snakes could be disastrous to the island of Hawaii, costing anywhere from $400 million to $2 billion a year to mitigate.
Snake-sniffing dogs also are used at major ports on Guam to detect any critters that could have made it on ships or planes and repopulate on other islands.
Vice said the goal of the project is to find the right technologies and tools to eradicate the brown tree snake and eventually reintroduce native species of animals that became prey to the snake population.
And although they can show up on fences outside of houses or wrapped around side-view car mirrors, Vice said a person could live many years on Guam and never encounter this type of snake.