The rat race

A single Norway rat released on to a rat-free island was not caught for more than four months, despite intensive efforts to trap it. The rat first explored the 9.5-hectare island and then swam 400 metres across open water to another rat-free island, evading capture for 18 weeks until an aggressive combination of detection and trapping methods were deployed simultaneously.

Apparently, it is quite hard to clear islands of rats and once they are cleared they often get reinfested. Now we know why. Above is part of the abstract of and article from this week's Nature (not free access)

An extended account is here:

Despite being weighed down by a tiny radio transmitter collar, Razza eluded intensive efforts to trap him during his 10-week sojourn on New Zealand's uninhabited and forested Motuhoropapa Island.

During that time, the rat evaded an arsenal of traps and poisoned baits that included peanut butter. He even continued to stay one step ahead of sniffer dogs sent in to track him down.

Then he disappeared only to turn up on neighboring Otata Island after his dip, apparently motivated by primordial urges during the spring-summer mating season

Only a cynic would note that by not catching the rat they got a paper in Nature, and wonder how hard they really tried.