"Any feral deer are an issue for us because they're selective browsers, targeting particular forest species over others which can substantially alter a forest's make-up, along with associated negative impacts on the fauna that rely on those plants," McKenzie explained.
As well as destroying the understorey of native forest by browsing, grazing, bark-stripping and trampling, feral deer can also damage crops and exotic forests, and have been implicated in the transmission of bovine tuberculosis.
McKenzie says the sika deer were targeted with local landowners' permission after sightings throughout the year by members of the local community.
Four deer had been spotted and one shot during the recent operation.
Meanwhile, in two other incidents, the regional council had received reports of feral red and fallow deer wandering in the Kaiwaka and Topuni area – close to the southern edge of the NRC's boundary – just before central government had imposed alert level 4.
McKenzie said subsequent investigations revealed a landowner with more than a dozen animals illegally inside a large fenced area.
Several animals had been tracked and shot by NRC's deer response team in nearby regenerating bush. There was evidence a number of animals may still be in the area and the hunt for them is ongoing.
The Department of Conservation has legal responsibility for deer farms and is considering what action might be taken against the landowner involved in the Kaipara incident and what would become of the animals themselves.
The landowner had been co-operative with officials but claimed he had been unaware it was illegal for him to keep the animals, which he had reportedly held for several years.
The regional council is urging anyone who sees wild deer to immediately call a 24/7 Deer Hotline 0800 FIND DEER (0800 346 333).
