The Department of Conservation (DOC) has set out a network of new traps and monitoring systems after live motion sensors set up to monitor shore plover nests detected a rat on Mana Island in the early hours of Saturday morning.
“Keeping pests off our island nature sanctuaries is a constant battle,” said DOC spokesperson Kerry Swadling.
“While offshore islands are important for our native wildlife recovery they are, by no means, invulnerable and these types of incursions do occur.”
As a result of the incursion DOC is implementing a biosecurity response plan that involves setting out and closely monitoring a network of 140 traps and 130 tracking tunnels. These measures will be supplemented with additional traps in the next day or two, weather permitting. A rodent detection dog may also used in the future.
“Mana Island is a top ecological restoration site and an important sanctuary for endangered wildlife – including takahe, rare lizards, North Island robin and shore plover – and we are doing everything we can to protect it.
“A rodent audit of the island in April, using rodent detection dogs, found no rat sign. While the extent of the problem is unknown at this stage, we are monitoring the situation closely and are hopeful that a significant population has not become established.
Ms Swadling also confirmed that a shore plover and nest were predated last week. DOC is awaiting the results of DNA tests to ascertain whether they were killed by a rat or by a natural predator such as a harrier hawk.”
While it is unknown how the rat may have arrived on the island, the most likely scenario is that it arrived on the island on a log or swam from a boat.
“We are confident that this incursion will be eradicated – we have successfully eradicated pests from other islands in the past, including rat invasions on Rangitoto Island in the Hauraki Gulf Marine Reserve and the Hen and Chicken Islands in 2009.”
Surveillance and trapping will continue on Mana Island for two years following no additional evidence of rat presence on the island. This is required for the island to be classed as pest free.