A study published last week in the journal Royal Society Open Science described everyone’s worst nightmare: rats that appeared to be too smart to eat poison put out by exterminators on Henderson Island, a Pacific islet where survivors from the whaleship Essex landed in 1820.
Researchers described a case report in which a project to eradicate invasive rats failed spectacularly. An extermination campaign dropped poisoned bait on the island from a helicopter. Initially, the population decreased to a handful of rats. But after a few months, the rats had fully recovered to an estimated 50,000 to 100,000 individuals. They showed no resistance to the poison, suggesting that the rats had never tried it. The researchers concluded that there was enough food on the island to satisfy the rats so that they didn’t need to take the bait. Continue reading