Climate change threat to native spider

Climate change threat to native spider

Climate change may threaten one of our more reclusive native animals, according to Lincoln University research.

Trapdoor spiders are found throughout New Zealand, springing out from their concealed burrows to capture prey.

Dr Vikki Smith, while carrying out her PhD Research at Lincoln, has found current models of future climate change in New Zealand do not bode well for trapdoor spider populations on the West Coast, and in Tasman, Central Otago, and Southland.

The regions are all predicted to see increased rainfall, which makes an area less suitable as a habitat for trapdoor spiders.

“The spiders were more likely to be present where the rainfall was below 1000mm per year, and no populations were found in areas with more than 3000mm per year,” Dr Smith said.

She could only speculate about why the spiders don’t like a lot of rain.

“They can cope with brief periods of intense rainfall, but constant high levels may cause harmful fungus to grow quickly in their burrows, or it may affect their ability to catch prey. I have noticed that trapdoor spiders will not catch prey on rainy nights,” she said.

The full extent of the impacts of losing trapdoor spiders cannot be predicted, due to their many complex and unknown interactions with the environment.

“They are vital parts of their ecosystems: they control insect populations, provide food for birds and lizards, and are hosts for at least three different parasites (wasps, fungi, and worms).

“Losing trapdoor spiders would remove a food source for native animals, which may put increased pressure on their other food sources, particularly spiders,” Dr Smith said.

Insect populations could increase due to the removal of a major predator, which may put more pressure on their food sources, such as native plants.

“Parasitic wasps, fungi, and worms would be particularly badly affected. Some may rely entirely on trapdoor spiders for reproduction, and may therefore become locally extinct, while others will have to use alternative hosts, including other native spiders.”

Climate change could also threaten other species.

“It’s hard to tell what effect climate change will have on our native species, but marine and coastal species are most likely to be affected due to changes in sea level and temperature, according to climate models.

“Tuatara may be affected badly as the sex of an embryo is determined by incubation temperature, and tuatara have long generation times and little genetic diversity so their adaptability is limited.”

However, invasive species and habitat loss remain the greatest threats to native New Zealand species in general, Dr Smith said.
People could help trapdoor spiders by checking clay banks for burrows before landscaping, and putting any unwanted spider visitors outside rather than killing them.

“If you like trapdoor spiders, spread the word – try to discourage any of your neighbours from using insect or spider control services by talking to them about how interesting and important the animals are,” Dr Smith added.

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