Australia’s redbacks invade New Zealand

By Amanda James with AFP 12 November 2010
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One of Australia’s deadliest spiders has set up home across the Tasman.

AUSTRALIA’S DEADLY REDBACK SPIDER has shown its stripes in New Zealand, threatening to colonise major cities, researchers have found.

The venomous redback, a relative of the black widow, may have hitched a ride to New Zealand on imported goods from Australia and has established itself at sites on both the North and South Islands, says Dr Cor Vink of Lincoln University in Canterbury.

Redback spiders (Latrodectus hasseltii) are common in dry, urban areas in Australia, and first made their way to New Zealand’s South Island in the 1980s. But it was believed that the climate in urban parts of the country was too wet to support the spiders, says Cor, who is the New Zealand spokesperson for the International Society of Arachnology.

Few fatalities

Now, a study co-authored by Cor and published in the journal Biological Invasions, shows that the spiders have the ability to thrive in New Zealand’s urban areas, just as they’ve survived in large cities in Japan.

This isn’t necessarily a reason for concern, however; the Australian Venom Research Unit reports that only 14 people have died from redback bites in Australia since records began, and there have been no fatalities since an anti-venom was developed in the 1950s.

Cor says that people needn’t to worry about safety if they are careful, but they should be aware of the spiders’ presence and know what they look like. “The spiders keep to themselves and you have to go looking for them,” he says.

Threat to natives

Redbacks do, however, pose a threat for native New Zealand species, including other spiders and insects. In the Otago region of the South Island redbacks have been recorded preying on a threatened species of beetle present only around Alexandra, 100 km east of Queenstown. There are also concerns the redbacks could out-compete the protected katipo spider found by the coast on both islands.

The redback is not the only insect pest from Australia that’s travelled to New Zealand. Other Australian invaders include the white tail spider, the Australian paper wasp, and various insect pests of gum trees.

Along with a team of researchers, Cor is part of Better Border Biosecurity – a program to tighten the borders around the country, which aims to keep harmful species out of New Zealand.