Big rabbit kill, but warnings remain

The rabbit-killing virus RHD has this year in Otago taken its biggest toll on the animal in at least five years.

Its effectiveness during the past summer has puzzled the industry because the Otago Regional Council's two-yearly tests for the disease's presence in Otago show high levels of immunity to the virus.

Test results show the average immunity across the 10 sites was 68%, similar to 2009 levels, council regional services technical field adviser Don Robson says in a report to be presented to its regulatory committee tomorrow.

"Interpreting this year's serum results has been difficult, with most monitoring sites showing high immunity levels, yet the virus has been the most effective and widespread for many years."

The virus displayed its greatest activity in the Alexandra basin, Ida Valley, Upper Clutha and Strath Taieri.

"In fact, most of Otago appears to have received the benefits of good kills from the virus."

As well as good death rates, observations showed deaths due to the virus continued to occur longer than normal, which meant the antibodies were still present during testing - unlike in other years.

"This observation clearly indicates high immunity levels do not necessarily mean the virus is no longer effective.""Exceptional" conditions in Central Otago had seen grass growth throughout most of summer because of frequent rain, which meant more young rabbits survived, he said. It also meant more flies, which were thought to be an important vector of the virus.

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Deadly Rabbit Disease May Have Doomed Iberian Lynx

The 1988 arrival of viral hemorrhagic disease (VHD) in Spain devastated that country's European rabbit (Oryctolagus cuniculus) population and, in the process, possibly doomed the local species most adapted to hunt rabbit, the Iberian lynx(Lynx pardinus).

The wildcat is now critically endangered, with an estimated 100 to 200 animals remaining in the wild. That makes them the world's most endangered feline species. The species numbered 4,000 animals in 1960.

One of the few areas where Iberian lynx still reside is Spain's Doñana National Park. According to research published in the March 2011 issue of Basic and Applied Ecology, the lynx was the only predator in the park not able to adapt to eating other prey when the rabbit population crashed.


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Baiting Complete for Macquarie Island Pest Eradication

“It is fantastic to see that this first stage is now complete and that our efforts to restore Macquarie Island to an ecosystem free of introduced pests is well underway.”

 

The number of non-target species impacted by baiting has been minimised, with a total of 855 birds affected to date.  The introduction of Rabbit Haemorrhagic Disease Virus on the island earlier this year drastically cut rabbit numbers which resulted in fewer carcasses on the ground and a reduction in secondary poisoning among non-target species.

 

Another key factor in reducing non-target species mortality has been an increased effort by specially dedicated ground crews collecting and burying poisoned carcasses after baiting.

 

Mr Wightman said that while the impact on non-target species was unfortunate, if the pests continued to cause damage it was likely that some seabirds and unique plant species would no longer exist on the island.

 

“This short-term impact will be balanced out by the long-term protection to the island’s ecosystems achieved through the pest eradication.”

 

The team involved in the baiting operation is expected to return to Hobart in late July.

 

Twelve trained hunting dogs are already on the island ready to begin the next phase of the operation, hunting down the rabbits that survived the baiting project.  Hunters will work with the dogs and their handlers to dispatch any rabbits found. This is expected to take up to five years.

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Rabbit resistance plagues Coorong

THERE appears to be a gradual resurgence in rabbit populations in the Coorong area, according to Biosecurity SA's natural resource management-biosecurity senior research officer Greg Mutze.

In many sites where rabbit numbers had been low for 10 years there was substantial recovery during the past five years. The trend was widely reported in arid and semi-arid Australia.

Evidence from studies on wild rabbits collected from 10 sites stretching from South Australia to Queensland indicated that rabbits at many places had developed some level of genetic resistance to rabbit haemorrhagic disease virus.

Current research seeks to determine whether the virus itself has weakened or if it is co-evolving with rabbits to maintain virulence.

from here.