Rabbit virus worries

Forest and Bird, Issue 279, 1 February 1996, Page 10

Rabbit virus worries

WHILE NEW ZEALANDERS are understandably concerned about the possible effects of the escaped rabbit calicivirus on our own wildlife, many Australians, after the initial excitement of seeing piles of dead rabbits, are asking whether the whole exercise is going to provide a net plus for the natural environment. Unlike New Zealand where the rabbit is largely an agricultural problem, in Australia it is one of the country’s worst environmental pests. Rabbits are responsible for the decline of many native plant species and have displaced many small marsupial grazers such as bettongs and bilbies. Many native herbs and shrubs, long suppressed by rabbit grazing, will flourish in the new rabbit-depleted environment, and the benefits

will also flow through to herbivores such as wombats and kangaroos. But the success of RCD still spreading across the continent — is causing concerns about small native animals which are likely to come under greater threat from predators such as foxes and cats. The ravages of cats — there are up to 18 million feral cats in the country — and foxes on native wildlife have been mitigated to a degree by the supply (until now) of up to 200 million rabbits. A quarter of the world’s mammal extinctions of the past 200 years have been in Australia, and foxes and cats are thought to have played a large part in these. The worry is that increased predation pressure will tip the balance for many local populations of endangered animals including species of wallaby, potoroo and native mice. Another problem is that a number of native species have become dependent on rabbits as prey. Rabbits make up 90 percent of the diet of wedgetailed eagles, for example, and the birds are likely to experience a population crash. Overall, the lives of rabbits, cats, foxes and native mammals have become so interwoven, that the demise of large rabbit populations is likely to have unpredictable effects. Environmentalists have warned that if the gap produced by the fall in rabbit grazing pressure is merely filled by increases in sheep stocking levels, then very little will have been gained for the natural environment.