Saturday, October 22, 2005

The ultimate escape

Razza swam from one island to another 400m away

The ultimate escape by an island-hopping rat
By Richard Macey
October 20, 2005 - 10:19AM

Razza was the Susie Maroney of the rodent world.
A wild rat, captured and then released on a deserted New Zealand island as part of an experiment, he amazed scientists by taking to the sea to escape.
No one knows why, but Razza swam 400 metres through treacherous open water to reach another island.
His feat, loosely billed as a record, has also alarmed the scientists, who say it shows that coastal islands cleared of rats can easily be reoccupied. Mick Clout, Professor of Conservation Ecology at the University of Auckland, said yesterday Razza was taken to Motuhoropapa, a flyspot east of Auckland, for a study on how a rat behaves when alone on an island.
"We assume most rat invasions begin with one or two rats coming ashore, probably from ships," Professor Clout said.
Researchers wanted to know how hard it would be to spot a single invader, and how difficult it would be to capture.
Razza had a small radio transmitter attached and was set free on the island. Scientists intended to recapture him within eight weeks, but Razza gave a new meaning to "rat cunning".
He avoided all the scientists' traps, and after 10 weeks his radio signal failed. "It would be fair to say that at that point we were worried," Professor Clout said. The Conservation Department was also worried, as the island had been cleared of rats.
Two weeks after the transmitter failed a woman reported finding rat droppings on Otata, a rat-free island 400 metres from Motuhoropapa. DNA tests confirmed they were Razza's.
"To our knowledge this is the first record of a rat swimming across open sea, and it's often quite rough water," Professor Clout said. "We assume he did it deliberately, but who knows what was in his mind?"
He speculated that Razza may have wanted female company.
A trap on Otata finally ended Razza's four months of freedom, and his life. His adventures are detailed in today's Nature.

Experiment ends in wild rat chase

Scientists got more than they bargained for when they released a single rat named Razza in an experiment into why rats are so hard to eradicate.
Razza avoided traps, escaped dogs, and ultimately swam a record distance from one uninhabited island to another.
Researchers from the University of Auckland in New Zealand had problems catching him even though they had fitted him with a radio transmitter.
He was finally killed by a trap 18 weeks after the experiment began.
The researchers released Razza to study "the problem of rats reinvading islands that have been cleared", author Mick Clout told the Associated Press news agency.
The research was reported in the scientific journal Nature.
Let loose on the uninhabited New Zealand island of Motuhoropapa, Razza ran free for 10 weeks before swimming 400m (1300ft) to a nearby island which was also deserted.
It is thought to be the longest swim across open water ever recorded for a rat.
Just lucky?
It then took the scientists another eight weeks to find and catch him once he arrived on Otata island.
"We were literally tearing our hair out at times trying to find this animal," Mr Clout said.
He said it was fortunate they had used a lone male rat in the experiment.
"If this had been a pregnant female rat it would have been a problem. It takes only one to establish a population."
Scientists have released a new male rat in a follow-up experiment to see if Razza was unusually clever or lucky.
"We want to check whether this was normal behaviour," Mr Clout said.

Cunning rat outsmarts scientists
Rodent eludes capture for 4 months
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.

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