The council was urging anyone who saw or heard wild deer to call a 24/7 Deer Hotline (0800 FIND DEER - 0800 346-333) without delay.
"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 said.
As well as destroying the understorey of native forest by browsing, grazing, bark stripping and trampling (which could all increase soil erosion), feral deer could also damage crops and exotic forests, and had been implicated in the transmission of bovine tuberculosis.
"Similarly, our kauri forests are already at risk from kauri dieback, and wild goats and pigs, and in some places wild cattle, are adding to that pressure. We don't want another large-hooved animal like deer spreading soil and disease through our forests."
The council had also received reports of feral red and fallow deer wandering in the Kaiwaka / Topuni area, just before the government imposed the Covid-19 alert level 4 lockdown. Investigations revealed that a land owner had more than a dozen animals inside a large fenced area.
Several had been tracked and shot in nearby regenerating bush. There was evidence that more might still be in the area, and the hunt for them was ongoing.
McKenzie said DOC was considering what action might be taken against the Kaipara land owner, and what would become of the animals. The land owner had been co-operative, but claimed to have been unaware that it was illegal to keep the deer, which he had reportedly had for several years.
Meanwhile samples were taken from all culled deer in Northland for DNA testing in a bid to shed more light on where they were originally from, and whether they had established breeding populations.