Poison-Laced Mice Airdropped into Guam to Kill Tree Snakes (Video)
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The above headline may seem to describe an overly imaginative kid's overly ambitious idea for a science fair project. But no, it's a plan conjured up and carried out by working conservationists in Guam. So when do poison-laced mice need to be parachuted from helicopters into natural forest under any circumstances? When you have a rampant, invasive species of tree snake to kill off, of course.The brown tree snakes arrived in Guam in the 1940s, where they immediately began asserting dominance over the ecosystem. The Guardian describes how scientists have found that the snakes have "eaten to near extinction some native birds, lizards and fruit bats; preyed on poultry; bitten small children; and 'cause[d] power outages by climbing on electrical transmission wires'."
So a remedy was sought for the menace. The tree snakes, however, turned out to inhabit a tough-to-reach part of the forest canopy, thus making extermination efforts more complicated. See, conservationists decided that a good way to get rid of the snakes would be to entice them with poison-laced mice -- the problem was delivering them to the intended target. Getting a dead, poison-coated mouse snagged in the forest canopy is harder than it seems.
Furthermore, if the mice missed their mark, and instead found their way to the ground, they could be eaten by unintended targets. All this was documented in a 2007 report by Colorado biologists, called Flotation Materials for Aerial Delivery of Acetaminophen Toxic Baits to Brown Treesnakes (pdf)
The Guardian parses the report, and summarizes the plan contained there:
get dead mice, "treat" them with acetaminophen, stuff the tempting acetaminophen/mouse treats in PVC tubes, and put those where the snakes are. "However," complains the report, "PVC tubes are not practical for delivery of baits to remote areas of jungle or the forest canopy. Further, it is important that baits entangle in the canopy and not fall to the ground, where they can be scavenged by non-target animals such as crabs."Which brings us to the parachutes. Recently, an innovation was stumbled upon -- graft the dead mice to parachutes that will get caught in the dense forest canopy. The biologists attempted different combinations of materials in building the ideal dead mouse parachute: biodegradable Ecofilm, paper cups, and paper plates. The researchers attached tiny radios to the bodies of the mice in order to track the efficacy of the various methods. The streamers won out, as the Guardian wryly notes: "The best arrangement for dropping thawed, frozen, poisoned, dead, radio-equipped mice from a helicopter into a tree, they indicate, is to attach a paper streamer to some cardboard, and hot-glue the cardboard to a rear leg of the mouse."
This video sums up the story, and provides another look at the quandary posed by the tree snakes in Guam:
Invasive species are becoming an ever-greater threat as globalization continues to better link disparate habitats through trade and transportation -- we're going to need a lot more creative thinking of this sort this if we hope to preserve the planet's diverse and unique ecosystems further down the line.