New Zealand Rabbit Control
Effort Showing Side-Effect

WELLINGTON, New Zealand — Talk about your unintended consequences — not to mention just plain weird ...

Folks in the down-under countries of Australia and New Zealand should be keenly aware of what can happen when strange new organisms are introduced into a habitat where they didn’t exist before, especially when the introduction has anything to do with rabbits.

After all, the introduction of rabbits for sporting purposes a century or so ago is the classic example cited worldwide for unintended biological consequences. The furry, voracious and avid procreators proliferated to the point where today their control is a critical issue for landowners and land managers.

Now one prong of that control effort has gone awry — though, so far, with consequences that appear more strange than serious.

An anti-rabbit virus that ranchers and farmers introduced in New Zealand to kill the animals has just left many with deformed ears, scientists said recently.

The calicivirus disease — illegally smuggled in from Australia a year ago to control a surge in rabbit populations — has produced a mysterious side effect: rabbit ears that don't stand upright, remain stunted, or fall off, the scientists said.

The disease is causing excessive cartilage growth that cuts blood supply to parts of the ears and removes hair, said Peter Kettle, the Ministry of Agriculture's director of science policy.

The ear deformities have been found in five parts of New Zealand's South Island where the virus was released, but nowhere in Australia where it was imported from, he said.

"Unfortunate though it is, there is this unexpected side effect. Nobody anticipated the ears dropping off," Kettle said.

Gary Clark, manager of Dunedin's Invermay animal health laboratory, said some rabbit ears remain folded down, become withered, develop scabs, or end up with missing portions.

The virus is spread by using a kitchen blender to mix an infected rabbit's innards into a brew that is then sprayed onto carrots and left for other rabbits to eat.

Kettle said his ministry lacks the funding for the kind of research needed to discover what is causing the side effect among the infected rabbits.