Wednesday 6 June 2012

Rat found on key ‘rat free’ island in New Zealand

Rat found on Ulva Island
May 2012. New Zealand Department of Conservation (DOC) staff ran a final check of the trap network on Ulva Island in the hope of declaring the island rat free again. Unfortunately, a rat was found in one of the traps during this check.

Rats established on Ulva Island in 2010 and DOC attempted to eradicate these rats in August 2011. Since that date, extensive trapping, tracking tunnels and two checks with a rodent detecting dog have not found any sign of rats on Ulva Island. Therefore, this capture of a male Norway rat was unexpected.
Caught on small islet
DOC's biodiversity manager, Brent Beaven said: "the rat was caught on one of the small islets off Ulva Island. This islet has two traps on that have been checked regularly since the eradication. This suggests to us that it is likely that the eradication was successful and that this is a rat that has just recently invaded. Ulva Island is prone to reinvasion, with an average of one rat per year managing to get to the island. If this is a "re-invader" then our biosecurity trap network has been successful in killing it on arrival."
A sample of the rat has been sent away for genetic profiling. DOC has been building up a library of genetic profiles of rats from the 2010 Ulva invasion as well as of mainland populations surrounding Ulva Island. By comparing this latest profile against the library, we should be able to determine if the rat was a re-invader or a survivor from the eradication attempt. Results should be available next week.

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