Redback spiders established in New Zealand

L to R: Dr Craig Phillips and Dr Cor Vink

Australian redback spiders (Latrodectus hasseltii), which are already established in Central Otago and New Plymouth, could become established in many other parts of New Zealand, particularly urban areas around major ports.

AgResearch scientists Dr Cor Vink and Dr Craig Phillips are developing new approaches and tools to ensure harmful organisms are kept out of New Zealand. As part of this work they recorded sightings of redback spiders in New Zealand, then used biological and climatic information to reveal where redbacks could establish.

Warm, dry conditions in some eastern areas of New Zealand are suitable for redback spiders to become established, and the spider is likely to spread further than previously expected. It was originally thought the spiders couldn’t establish in even moderately wet climates, but the research strongly suggests that where there is shelter from rain, particularly in urban areas, redbacks can establish and survive.

Spread of redbacks is likely to arise from the establishment of new invasions, rather than the spread of existing populations which have been here for some years. However, currently the distribution of redback spiders in New Zealand is still very limited, they are not aggressive, and eradication of geographically-limited populations may be possible.

Redbacks could have negative impacts on endemic insects and spiders as well as on public health, as they have the potential to become established in a number of areas that are close to urban populations.

This research is part of Better Border Biosecurity, a large multi-partner 12 year science programme funded by the Foundation for Research, Science and Technology, and is published in the international journal Biological Invasions.