health & science

A last-ditch attempt at rabbit control

A Korean virus developed to curb our rampant rabbit population won't work long-term unless landowners spend winter killing off survivors of the disease.

The strain of the rabbit haemorrhagic virus, which was recently approved for release in New Zealand, is not as strong as the Czechoslovakian virus illegally released in 1997, which 40-90 percent of rabbits are now immune to.

Rabbits are estimated to cost $100 million in lost agricultural production every year and are a food source for predators of native wildlife.

The Korean strain of the virus is expected to kill approximately 35 percent of rabbits when it is released over autumn.

Otago rabbiter, Stephen Dickson, said unless follow-up methods are used after the virus is released, rabbit numbers could be back to current levels within three years.

“This is basically their last shot at the title. Everyone needs to get stuck into it. They need to get on top of the rabbits.”

He said a lack of follow-up after the 1997 release of the Czechoslovakian virus strain has led to current numbers.

“When they first released the virus, everyone went out and bought new utes and new houses and didn’t do any control, they just stopped spending money on control.”

Dickson said some of the bigger station owners are already making plans for post-virus release control activity after the “balls-up they made last time”. But ensuring all property owners do enough follow-up work is a big issue.

“This is basically their last shot at the title. Everyone needs to get stuck into it. They need to get on top of the rabbits.”

Rabbit populations have been an ongoing issue since the dissolution of government-subsidised rabbit boards in 1980.

Land-owners are responsible for controlling rabbits on their own land, which can cost tens of thousands of dollars.

The Otago Regional Council (ORC) inspected 154 properties in the year to February 2017 and found 62 had higher levels of rabbits than permitted.

Dickson said he thinks councils don’t have laws available to them to enforce compliance.

“The council doesn’t really seem to be able to do much about it. They can put an enforcement notice on, but it’s got no weight to it. It seems to come down to 'Nah, I don’t want to do anything, I’m not spending that kind of money' so they just don’t.”

ORC’s director of environmental monitoring and operations, Scott MacLean, said the council is currently reviewing their Pest Management Plan and may change the rules around non-compliance.

Currently properties that are not sufficiently controlling rabbit numbers are required to submit a three-year property plan on reducing rabbit numbers. They are then re-inspected annually to see if they are sticking to that plan.

“It’s quite a process to follow up with every single property plan. We have several hundred property plans in various stages across Otago at the moment.”

One option under consideration is to eliminate the requirement for a property plan. Non-compliant properties would be served a notice and control work would be have to be done right away. If the property occupier doesn’t comply, the council can organise for the work to be done and on-charge it to the property.

"If you’ve got a lot of land, you just can’t afford to spend the money to have rabbiters come in over a huge amount of property. That’s why the virus is so popular.”

MacLean said the ORC is spending around $60,000 on the release of the virus. This is a significant increase from the $15,000 it spent on pest management in the previous year and a deviation from the stance land-owners take responsibility for their own properties.

Some of the 100 doses they plan to release will be on private land, all at no cost to the land-owner.

Follow-up activity will fall to land-owners.

“This [virus] will just assist, but it’s not the panacea, it’s a tool in the toolbox and it’s not going to eradicate rabbits by any stretch. Our preference is for communities to take ownership of this problem and work together. The thing about rabbit control is it's really essential that everybody works together.

“You only need one property owner to not do their bit and everyone can go backwards really quickly.”

Gibbston vineyard owner, Terry Stevens, said rabbits were a continual problem.

“When they get hungry they’ll ringbark the vines. They’ll also chew the ends off any shoots hanging down.”

Stevens has rabbit-proof fencing he has recently raised to a higher level as he believed rabbits were jumping over it. He also has a rabbiter visit regularly. Control costs him $10,000 annually.

Stevens leases some of his vineyard and said the company leasing it could be doing more to control the rabbits.

“I think they fall into the category that a huge number of farmers do. If you’ve got a lot of land, you just can’t afford to spend the money to have rabbiters come in over a huge amount of property. That’s why the virus is so popular.”

Stevens said he hadn’t seen much information from the ORC regarding follow-up activity aside from reading a news story.

“The virus will be a big help. Is it going to stop it? No. If we didn’t have to have a rabbiter out say every month, and we could do it every two months that would certainly be a big cost savings to us. Maybe if the people who work the vineyards saw they were getting a 40 percent knock-off then that would give them more incentive to get the rest of the numbers down.”

If follow-up activity is not undertaken by property owners, it’s hard to know how effective the $60,000 the ORC is spending will be.

Landcare Research scientist, Janine Duckworth, said currently there is no data, or thoughts on how long it would take rabbits to develop immunity to the Korean virus strain.

New Zealand is not researching whether any other strains of the virus would be able to be imported once immunity to the Korean strain develops. Hopes for effective new strains lie with Australian researchers.

Dickson, the rabbiter, doesn’t think rabbit control should be as hard as it has become.

“It’s not rocket science, it’s just a case of going around, and around. Because it’s so fragmented at the moment - that neighbour’s doing something and that one is not – it’s where the problem lies. That’s why I think they should just go back to the rabbit boards and everyone pays on their rates.”

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