Biosecurity increased on Ulva Island
A lone rat has been found dead in a trap on Ulva Island/Te Wharawhara, one of the few pest-free open sanctuaries in New Zealand, sparking increased biosecurity on the island.
“Our response will include having more rangers on the ground completing more trap and trail camera checking, as well as additional rat detection dog survey work,” Department of Conservation (DOC) Rakiura operations manager Jennifer Ross said.
“A technical advisory group will also be appointed to support the operation and provide expert advice.”
The island is located 780m off Rakiura Stewart Island. With numerous visitors, Ross said incursions were frequent on the island, averaging between one and two events each year.
“Catching rats in traps is a key way we detect invaders and protect the island from rat populations becoming established.”
DOC undertook an eradication programme on Ulva Island/Te Wharawhara last winter after a breeding population of rats established on the island.
In the months since the eradication took place, Ross said monitoring, including trap checks, motion sensitive camera surveillance, and the use of rodent detection dogs, had not shown any sign of rats remaining on the island.
“Since the last incursion, we’ve upgraded the island’s biosecurity system with new tools like trail cameras, more frequent trap checks, and a rearranged grid increasing detection and control devices in the coastal areas where the pests typically first arrive.”
Genetic analysis would determine whether the dead rat had remained on the island undetected since the eradication, or if it was a new arrival.
“As long as rats are present on Rakiura, re-invasion to Ulva is a high risk,” Ross said.
“Ulva Island is our best local example of Aotearoa as it used to be, and it’s absolutely worth defending.”