This Guardian piece, tucked away in the Education section, has such an eye-catching title that I decided I was going to blog about it even before I read the article. Seriously, compliments to the editor (or the author?): “Why dead mice need parachutes in the forest”. The facts reported in the piece are even funnier than the title might suggest.
Why would dead mice need parachutes, you may ask? The answer is, possibly, odder than the question: to deliver poison to tree snakes. Guam is an island in the Pacific Ocean, an unincorporated territory of the United States, which is infested by brown tree snakes (Boiga irregularis). They are thought to have been a stowaway on a US military cargo back in the days of World War II. Having no natural predators on Guam, they quickly became numerous and troublesome. They prey on domesticated birds, they occasionally cause power outages by climbing on transmission wires, and they even bite small children mildly affecting them with their venom. Besides being a nuisance to humans, they have also eaten to near extinction some native birds and lizards posing a serious ecological threat to the island.
The solution to this problem passes for reducing the tree snake population, and this is how the mice and their parachutes get into this story. The principle is simple: snakes that eat poisoned mice die. But you can’t simply drop poisoned mice on Guam rain forests because other species, such as the coconut crab (a protected species), can become victims of this non-targeted approach to the problem. The solution? Parachutes. If you parachute the mice from an aircraft, they get entangled in the forest canopy where only the tree snakes can reach them!
The funniest thing is that this is not even what the Guardian article and the scientific paper it refers to are about. The key issue of the scientific study is the parachute itself. About 10 years ago people tried plastic and cornstarch parachutes but the former take long to degrade and the latter dissolve too quickly in the rain dropping the mice to the ground. It is important to test different materials and types of parachute to make sure the mice get entangled in the forest canopy for long enough for the snakes to eat them, but do not pose an environmental problem. This is what scientists did.
Scientists attached various parachute-like objects – the list included paper plates, paper cups and paper streamers, amongst others – to dead mice and then thrown them from a US Navy helicopter into the forest. They also radio-equipped the rodents to track their fall. The results of the study indicate (you’ll be glad to know) that all of the easily degradable materials tested work well. However, certain parachutes, such as the paper cups and paper plates, are not practical because they need to be secured to the dead mice with threads, which is a time-consuming process. The best method appears to be attaching paper streamers to cardboard which is then glued to one of the mouse’s rear legs.
I know this is a serious and environmentally conscious scientific study. Yet, I cannot help laughing every time I picture the face of that US Navy pilot looking at the crazy people gluing stuff to dead mice before throwing them out of his chopper: “WTF!?”