Contract goat culling combats kauri dieback in Northland forests

Contract hunters have killed thousands of goats in Northland forests since the discovery of kauri dieback disease.

In the battle against the spread of kauri dieback disease, most people know the importance of cleaning their shoes before and after going bush.

Far fewer people know about another important measure being taken to curb the disease - contract goat culling.

Like humans, feral mammals - goats, deer, and pigs - can easily transport soil containing spores of the disease from one precious kauri tree to another.

While humans can be barred from entering areas of major concern - several public walking tracks in Puketi Forest are currently closed - there’s no way of keeping wild animals out.

If a site within a forest is infected by kauri dieback disease, pest animals such as goats and pigs can spread it further as they move into different catchments. Goats particularly, are highly mobile.

The Department of Conservation (DoC) has long-running regional goat control programmes across the country, covering about a million hectares of conservation land.

Goats are agile and cover large areas of bush in a day, making them perfect vectors for soil disease spores.

The aim is to prevent the spread of wild goats into new areas, remove wild goats from areas with high biodiversity values, and keep numbers low enough in other areas to ensure forest health is not compromised, DoC says.

In Northland, hunters contracted by the DoC have killed thousands of wild goats since kauri dieback disease was formally identified in about 2007.

Among those contract hunters working hard on the ground to keep the goat and other ungulate (large hoofed animal) numbers in check is a team of six from Dylan Hogg’s Bushcraft Contracting.

Hogg said teamwork and new technology are keys to controlling pest numbers.

He estimated that together, contract hunters have removed 3000 to 4000 goats from Northland’s forests in the last few years.

He and his crew regularly team up on projects with other service providers, making the most of opportunities to share knowledge and resources.

Contract hunter Dylan Hogg says returning to an area where the forest understory is beginning to regenerate after control work is hugely satisfying.

Kauri dieback disease has highlighted the poor health of New Zealand’s forests generally and the need to take greater care of them, Hogg said.

Accordingly, demand for pest management services has grown - as had funding from local and central government agencies. There was still plenty of room for other keen, motivated people to join the industry.

DoC said goats and other browsing animals can decimate the forest understory, leaving it no chance to regenerate and soils exposed. The animals trample undergrowth and compact the soil. Steep countryside becomes more vulnerable to slips and erosion.

Pigs disturb the ground by rooting up the soil, accelerating erosion and damaging the delicate feeder roots of kauri trees.

Goats are prolific breeders. They strip bark from trees, and devour any new seedlings.

“This all contributes to a loss of biodiversity and can prevent forest regeneration. These changes will threaten the function of ecosystems, and have long-term consequences for forest health.

“If left unmanaged the increased impacts of wild goats on our ecosystems will further compound issues with water flows/catchments and climate change,” DoC said.

Bushcraft’s work in Northland is centred on forests around Hokianga and the Bay of Islands, including Puketi and Omahuta forests - one of the largest contiguous tracts of native forest in Northland and home to magnificent stands of kauri tree that are sadly under threat from kauri dieback disease.

Returning to an area after control work can be hugely satisfying, Hogg said.

The understory is the first thing to respond to reduced browsing pressure.

Hunters tracking goats and other feral animals through the bush follow strict cleaning protocols to ensure they don't transfer disease spores from tree to tree.

Contract hunters sometimes cover 20km or more in a day, often in steep terrain.

“Noticing [the return of] palatable plant species such as coprosma, hangi hangi and young canopy trees such as puriri and kohekohe with new growth is very rewarding and reflects on the overall health of the forest.”

Good lower canopy cover meant less exposed soils and less potential for kauri dieback disease spread.

Hogg’s team spends up to 10 days in the bush at a time, often in remote locations, he said.

Being away from home that long can be tough and the work is physically challenging - a big day includes walking up to 20km, often in steep terrain - but the results are rewarding and backcountry life is enjoyable.

Dogs specially trained to detect and track goats and pigs are an integral part of the team.

Over the last few years thermal technology has also become a highly effective tool for managing pests, Hogg said.

“In the right setting, thermal drones allow us to view animals from above. An area that might take a hunter a whole day to cover, can be surveyed by a drone in 20 minutes.

Specially trained dogs are crucial in tracking down feral animals.

“This allows us to quickly identify where animals are located and move in on them on the ground more efficiently. It’s particularly useful for farmland and bush edges.”

Trail cameras are also a useful tool for monitoring goat numbers.

The work is largely carried out over the summer when drier weather and less mud helps to reduce the risk of kauri dieback spread.

Following animals through potentially infected forest areas means pest control workers are also at risk of spreading the disease. Stringent hygiene processes have to be followed, Hogg said.

“When we are in the bush, we take great care not to spread soil from one area to another. We thoroughly clean our boots, vehicles, and gear. It is particularly important to clean our boots when moving between catchments within a forest, also when working in one forest and then another.”

Hogg recognises that goats and pigs are important food sources in some communities so does not want to see them fully eradicated.

He believed these animals can be managed to a level where they don’t put pressure on the forest - where it can regenerate and be healthy despite their presence.

Sarah Curtis is a news reporter for the Northern Advocate, focusing on a wide range of issues. She has nearly 20 years’ experience in journalism, much of which she spent court reporting. She is passionate about covering stories that make a difference.