Weather reins in rabbits
A wet spring for the third year in a row has driven rabbit numbers down in Canterbury with the main exception being the semi-arid eastern side of the Mackenzie Basin.
Rabbit populations are up to concerning levels on some farms in this rabbit-prone area and are also marginally up from last year in the Amuri, Ashley and Kaikoura areas of the 11 districts that Environment Canterbury monitors.
Outside of these districts rabbit numbers are down and across the province are low because of a wet and warm spring.
Environment Canterbury (ECan) biosecurity team leader Brent Glentworth said the early spring breeding "recruitment" of the initial newborns, known as kittens, had been hampered by wet early spring conditions the past three years.
"This reduces the ability of many of the population to show the exponential rate of increase as the early kittens sexually mature and breed themselves prior to December."
The low survival rates of the early newborns is partly because of rabbit haemorrhagic disease (RHD) outbreaks naturally occurring in early summer and contributing to capping numbers in many areas.
"The other thing with a wet spring is we get more burrow drownings of the kittens and the young ones are prone to pneumonia," said Glentworth.
He said young rabbits get wet from passing wet grass and catch pneumonia or coccidiosis - a liver disease often found in warm and wet weather.
Young rabbits are also susceptible to predators such as ferrets, cats and hawks.
"All these factors mean rabbit populations are not booming."
Glentworth said farmers were being encouraged to not let up with rabbit control despite numbers being low and the temptation to ease off.
Rabbit problems in prone areas had not changed and it was only climatic conditions which had altered rabbit recruitment, he said.
Eastern Mackenzie is one of the lowest rainfall areas in Canterbury, with its semi- arid conditions favoured by rabbits.
Farmers under notice in the district to reduce numbers have been identified with 20 rabbits a kilometre during night counts in strips of one kilometre long and 50 metres wide.
At one property numbers are up to 26 rabbits a kilometre - and ECan starts to get concerned when they reach above the 10-rabbit threshold. Notices were delivered to landowners after daytime inspections.
Compounding the problem was the late snow interrupting the poison programme last year.
While numbers are up in eastern Mackenzie, the other districts of Pukaki and Tekapo in the Mackenzie Basin are down. However, rabbit increases in the eastern basin around Haldon Rd have brought the entire basin average up.
- The Press