National Geographic News has an interesting story about the early detection and not-so-rapid response to a rat invasion. To test how they would deal with the introduction of rats on an island, researchers released a single Norway rat (Rattus norvegicus) on New Zealand's Motuhoropapa Island. Then they tried to recapture it. And tried. And kept trying, for more than 10 weeks.
It was a lot harder to capture that single rat than they'd imagined, even with the rat wearing a radio tag. Part of the reason was that the rat wasn't on Motuhoropapa Island anymore - it swam to Otata Island, which was 400 meters away! The researchers have concluded that traditional management methods, like trapping and the use of dogs, are likely not the best response to rat introductions. The results of the study will be published in the next issue of the journal Nature (link forthcoming).