The 12-member Tuturau Titty Ticklers blasted 712 rabbits to win the 24-hour, 25-team killing contest this year, as shooters griped of an alleged paucity of targets caused by the unauthorized release last summer of rabbit calicivirus (RCD). The bag fell to 5,290, from nearly 24,000 in 1997.
"A group called the Waihou Virus shot more geese than rabbits," reported the New Zealand Press Association. "Eight teams bagged fewer than 100 each."
That left organizer Martin McPherson to pick among ending the event, opposing RCD use, or targeting captive animals, like the Labor Day pigeon shoot at Hegins, Pennsylvania. Any of the options would belie the purported higher purpose, in combatting the depredations of feral rabbits. But, though rabbit proliferation in New Zealand and Australia has long been problematic, it has never been clear that they do a fraction as much ecological harm as sheep, the agricultural staple species in both nations. Mainly, sheep ranchers blame rabbits for their problems, much as U.S. cattle ranchers blame coyotes and Atlantic Canadian fishers blame seals.
RCD, the latest anti-rabbit weapon, was found among European rabbits in China in 1984, and in Mexico in 1990, apparently imported with a frozen rabbit carcass from Korea. As RCD appeared to be species-specific, Australia began investigating possible deliberate deployment at a test site on Wardong Island. In 1995, however, either insects or birds took RCD prematurely to the mainland.
After sweeping Australia, RCD was bootlegged to New Zealand in 1998, and soon afterward was released officially, as officials argued that delay would mean further use of homemade versions, which in the long run might tend to immunize more rabbits than were killed. A suspected benign form of RCD is already suspected of immunizing up to a third of the exposed Australian rabbit population, but whether the immunity is maternally conferred remains unclear.
Data from the Otago peninsula of New Zealand??the locale of the Easter bunny shoot??indicates that RCD released there afflicted 82% of the resident rabbits, killing 68%. Fourteen percent became ill but recovered, developing immunity, while 18% were apparently already immune. Massey University epidemiologist Dirk Pfeiffer in February began a $50,000 radio collaring study to find out why RCD is reportedly killing virtually all the rabbits in some areas, even as populations rebound in others. The New Zealand health ministry meanwhile asked the Wellington School of Medicine to investigate the possibility that RCD might be crossing over into humans. That notion first surfaced in Mexico, where one human was reportedly infected. A South Australian Health Commission study in January held that humans cannot get RCD, but a re-analysis of the South Australian data by U.S. epidemiologist Alvin Smith and pediatrician David Matson, of the Eastern Virginia Medical School, found that many of the study subjects had developed antibodies to RCD, suggesting some infection. Since March 28, 1998, Zenith Technology of Dunedin has been selling RCD to anyone who wants it, expecting sales volume this year of about $750,000.
The Australian National Parks and Wildlife Service in March claimed success in using a combination of RCD and poisoning to extirpate rabbits from Cabbage Tree Island, the only known breeding habitat of the endangered Gould's petrel. Rabbits had inhabited the island from 1906 until the last reported dead rabbit on September 16, 1997.
According to Sydney Morning Herald reporter Honey Webb, the rabbits had "destroyed the vines, shrubs, seedlings and leaf litter which once covered the rainforest floor and protected the petrels' breeding grounds." As of 1992, the island supported 500 rabbits but only 150 petrels.
"Without the rainforest undergrowth," Webb continued, the petrels "were easy prey for currawongs and ravens. As well, gluey fruits from the island's bird-lime trees immobilized the petrels by sticking to their feathers, instead of dropping onto leaves higher in the canopy."
An estimated 316 Gould's petrel chicks hatched this year. They will roam the Pacific Ocean for five years before the survivors return to Cabbage Tree Island to mate.
But rabbit foes are finding that RCD is not quite the boon for native species that they anticipated.
First, it often doesn't work. In the Sydney area, Rural Lands Protection Board managing director Andrew Glover announced on April 29, rabbit numbers are at an all-time high despite RCD use.
Second, Sydney Morning Herald rural editor Anthony Hoy reported in February, where RCD has killed most rabbits, biologists have also seen "the decimation of marsupials of all sizes, as foxes and feral cats are deprived of their rabbit kill. Studies in New South Wales," Hoy wrote, "show that foxes have learned to take joey grey kangaroos from their mothers. Scientists are also concerned that brushtail possums may not survive the change in the predatory order."
That wouldn't disturb New Zealand conservationists, who are trying to exterminate brushtail possums almost as avidly as rabbits. Native to Australia, where they now are scarce, brushtail possums were introduced to New Zealand by fur trappers as a potential prey species, proliferated, and are??like rabbits??accused of destroying bird habitat.
But New Zealand Forest and Bird Society field officer Basil Graeme did predict ecodisaster as a probable result of the January 1998 formation of the New Zealand Ferret Association, by owners of pet ferrets. Graeme argued that pet ferrets, if encouraged, would soon escape and go feral, as closely related stoats and weasels already have. The stoats, however, were imported for use in attempted rabbit control.
"A surge in ferret numbers as rabbits collapse is a lethal combination for native wildlife," he said. "The last thing we need are escaped and released ferrets. Penguins, kiwi, weka, dotterel, and stilts are just some of our native birds being killed by mustelids," the family including ferrets, stoats, and weasels. "It seems idiotic to us," Graeme continued, "to have the government requiring the Department of Conservation to issue [exotic pet] permits which boost ferret distribution and numbers, when taxpayers are also funding the department to stop mustelids killing native wildlife."
The November 1997 find of a dead Bennett's wallaby near Nelson, New Zealand, raised the possibility that killing rabbits might open habitat to other feral herbivores. At least two wallaby species were at some point introduced to New Zealand from Australia, but were believed to have been limited to the vicinities of Rotorua and Canterbury. Bennett's wallabies, Christchurch Landcare Research staff scientist John Parkes said, could be "as devastating on the environment as rabbits."