Ulva Island rodent free once more

Date:  26 March 2024

The pest-free open sanctuary has been the subject of a month-long incursion response after a rat was found dead in a trap in February.

DOC Rakiura Operations Manager Jennifer Ross says that after more than four weeks of increased surveillance, intensive trap checks and comprehensive monitoring work across the island, there have been no further rodent detections.

“This means we’re winding down our incursion response and returning to normal surveillance measures. Normal surveillance doesn’t mean we’re taking our foot off the pedal; far from it. Having an intensive network in place round the clock means when we do get a detection – like we did in February – we can act quickly and scale up.”

Ulva Island is one of the few pest-free open sanctuaries in New Zealand. It is home to vulnerable native species like tieke/South Island saddleback, mohua/yellowhead, titipounamu/rifleman, and South Island kākā.

Since 20 February DOC staff have checked over 225,000 trail camera images, walked more than 110 km of trap lines, travelled more than 180 km by dinghy, and completed over 2,750 trap checks. Two rodent detection dogs also scoured the island multiple times. 

“Given how close Ulva is to mainland Rakiura – just 780 m at its closest point, and how many people visit it, incursions are frequent, averaging between 1 and 2 incursion events each year,” says Jennifer.

“Catching rats in traps is a key way we detect and remove invaders and protect the island from rat populations becoming established.”

The island was first declared pest free in 1997. In winter 2023 a breeding population of rats established on the island sparking an intensive re-eradication programme. In the months since the eradication took place, 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, until one was found in February.

As part of last year’s re-eradication response, the island’s biosecurity system was upgraded with more trail cameras, more frequent trap checks and a rearranged grid increasing detection control devices in the coastal area where rodents usually arrive.

However, Jennifer says keeping Ulva Island pest free will continue to be a challenge as long as there are pests on mainland Rakiura.

“That’s why initiatives such as Predator Free Rakiura are so important, and everyone has their part to play.

“We’d like to extend our thanks to everyone for doing their part and continuing to be extra vigilant when visiting Ulva Island. Special mention to the Ulva Island Charitable Trust who have offered to donate $5,000 to the response.”

If you see anything suspicious on Ulva Island – please take photos, record the location accurately and report it to the DOC Rakiura Office.

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