Northland residents are being urged to report feral deer sightings after several animals were spotted in the area.
Four deer were recently seen - and one shot - from a helicopter in the Bay of Islands.
Wild deer are classed as an 'eradication species' in the north and it is illegal to release or move wild deer in or around the region.
Northland Regional Council biosecurity manager Don McKenzie said Northland is one of the few regions in New Zealand that has no established wild populations of deer and it would be "disastrous" for the area's kauri forest if this changed.
"Deer would really graze the understorey right out so it would be very, very damaging for our kauri forests in terms of the kinds of vegetation that makes Northland iconic," McKenzie said.
He said hooved animals, such as deer, also spread soil-borne disease, like kauri dieback.
Red and fallow deer are farmed legally in the region but have escaped from farms or have been illegally released, while sika deer are in the region through illegal release alone.
McKenzie asked hunters to refrain from illegally releasing deer and risking the destruction of native forests and possible spread of disease, such as tuberculosis.
Anyone who sees or hears wild deer in the Northland area is urged to call a 24/7 hotline immediately - 0800 FIND DEER (0800 346 333).