LONDON, England (Reuters) -- A rat released on a deserted island off New Zealand outsmarted scientists and evaded traps, baits and sniffer dogs before being captured four months later on a neighboring island, researchers have said.Scientists from the University of Auckland in New Zealand released the Norway rat on the 23.5-acre island of Motuhoropapa to find out why rats are so difficult to eradicate.They got more than they bargained for."Our findings confirm that eliminating a single invading rat is disproportionately difficult," James Russell and his colleagues said in a report in the science journal Nature.Despite all their efforts, including fitting the rat with a radio collar, they couldn't catch the crafty creature.After 10 weeks on the island the rodent decided it had had enough. It swam 400 meters, the longest distance recorded for a rat across open sea, to another rat-free island where it was eventually captured in a trap baited with penguin meat several weeks later.The Norway rat, which is also called the brown or sewer rat, is a husky rodent that weighs about 11 ounces and has a long tail.Invading rats on remote islands off the coast of New Zealand have been a recurring problem. Norway rats have invaded the uninhabited Noises Islands at least six times between 1981 and 2002."Our results may help in the design of conservation strategies to keep islands free of invasive rodents," Russell and team added.Copyright 2005 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.