(Kim) 28 - Mustelid pest control failure on rabbits

Question 1

Catastrophic rabbit damage of 1870-80s

-Main rabbit invasion moved North from Southland affecting sheep paddocks and losing farmers $$$$ and paddocks that depleted by rabbits farmer abandoned them.

• Traditional methods of killing rabbits totally ineffective.
• Use of poisoned grain killed many birds

They believed this was down to the rabbits being imported without their natural predators, therefore.. they bought in mustelids (except fox’s which were known for killing lambs)

Question 2

Ferrets from Australia and UK

Aus has foxes and no stoats/NZ has stoats but not foxes

• 75,000 ferrets bred in south island after imported from AUS.
• Ferrets did not do well when released in high country as they are not used to cold climate and are more domesticated.
• Stoats now imported from UK (Maybe 7,838)

Question 3

Ferrets from Aus & UK

Long established use of ferrets against Rats, rabbits.

But

Couldn’t cover vast areas needed in NZ

-Ferrets tame and easy to buy

BUT

• Susceptible to canine distemper
• Bred for release on pastoral runs in tens of thousands

BUT

-High mortality rate in mountain country

Question 4

Did mustelids (stoats and ferrets) save Colonial economy?

They killed alot of rabbits but they did not save the wool industry

Simply because they removed so much of the grazing the ewes couldn’t produce so many lambs

• As rabbits began to increase wool production went down
• Rabbit numbers not affected by arrival of mustelids

-

Question 5

The difference between substitute and additive mortality

• Rabbits breeding at normal rate were unaffected by mustelids or trappers substituting for normal pest losses, reducing their density from B to A
• Only when pest breeding is reduced for other reason (drought/1080), mustelids and/or trappers can add to their normal losses, so achieve a real effect.

Answer 5

Question 6

Bullens Success was not just about killing rabbits

• Managed land very carefuly to maximise hunting preferences of ferret.
• Produced extra ferrert predation at the right time
• Spring - to target young rabbits
• Limited re-invasions by fencing off his paddocks

Question 7

MOST IMPORTANT SLIDE

Reasons for failure of mustelids to control NZ

• North and South Islands to big
• NOT ALL RABBITS AT RISK

(mustelids searching on and under ground inefficent; rabbits alert and pose risk of injury during attack)

• Mustelids stop hunting when full
• Mustelids much lower density and reproductive rates, short breeding season, can’t match rabbits numbers.