Today’s factismal: Rodents have invaded Saddle Island three times in the past century.
Look almost anywhere on the globe and you will see the footprints of mankind. We’ve moved into the mountains, conquered the prairies, sailed the oceans, and even put a few outposts in places like Antarctica. But where man goes, other critters follow. Sometimes, those critters are intentionally brought along to serve as companions or food (or both). Dogs followed man to Australia and turned into the invasive species known as the dingo. Horses followed man to North America and became the invasive species known as the mustang. Chickens followed man to Hawai’i (and Key West) and became feral chickens. However, no other invasive species, not the fly, not the mosquito, and not the cat, has done nearly as much damage as the humble mouse.
The reason that mice do so much damage is because they are terrific survivors that breed faster than comments on a viral video. A typical female mouse can start having babies by the time she’s two months old and can have a litter of up to six babies every month. Given that they live for about 18 months, any single mouse mom could have as many as 100 babies. And each of those babies can contribute to the general population explosion. In theory, if you started with a single pair 0f mice, you could have as many as 20,000 mice by the end of the year!
To test that idea, scientists turned to a little island off of New Zealand. Known as Saddle Island, thanks to its shape, this little 15 acre rock of grass and sand was a haven for sea birds until rodents invaded it. The rodents ate so many of the native birds that the population was crashing. In order to prevent that, scientists exterminated the invading rats in 1989. But just after the rats were eradicated, mice were found on the island. They, too, were killed, giving the local sea birds a chance to recover. But that set scientists to thinking – just how fast could rodents fill up an island?
The scientists took a male mouse and let it go free at the north end of the island. Twelve hundred feet away, they let the female mouse loose and then let nature take its course. Once the mice had found each other, they settled down to the serious business of making more mice. In two months, the population had swelled to 14. In five months, it had grown to 68. But the most amazing thing of all was that when the scientists did genetic analysis on the mice, they found that another female had somehow made her way to the island; they suspect that she had stowed away on a boat before escaping to the island. Once the experiment was over, the scientists made Saddle Island rodent-free once more – but for how long?
Invasive species are an amazing thing. They are found in every continent and every clime and cost us more than $120 billion in damage every year! If you’d like to join the fight against invasive species (or just learn more about the topic), head over to the Texas Invasives web site. Just don’t bring any mice along with you (unless it is the one on your computer!)!