Spiders in the city are bigger

By Karl Gruber 21 August 2014
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Orb-weaving spiders in urban areas are larger than spiders in less developed regions

THE RICHES OF city life apparently plumps up spiders, according to a new Australian study.

The orb-weaving spider (Nephila plumipes), a common inhabitant of natural and urban landscapes, grows bigger and produces more eggs when found in highly urbanised places.

“They were larger when living in areas with human structures, less leaf litter and less vegetation,” says lead author Dr Elizabeth Lowe from the University of Sydney.

Urban spiders fatter

Researchers collected more than 200 spiders from various locations in Sydney and measured different physical attributes, such as body size, fat reserves and ovary weight.

They then compared these measurements with the degree of urbanisation found at each sampled sites. Reporting this week in PLoS ONE, researchers found a clear trend: spiders thrive in the most urbanised areas.

“The spiders are probably larger in the urban areas as a result of more food, warmer temperatures (that is, the urban heat island effect) and a relaxation of predation,” Elizabeth says. With fewer birds around, there are fewer threats to spiders.

The study was published this week in the journal PLoS One.

Spiders thrive on warmer city habitats with more food

Conventional wisdom about urban wildlife holds that development is harmful to their survival. But the new findings suggest the picture is more complex, and that some creatures may thrive in cities. “These spiders actually do better in urban areas, so no, urbanisation is not bad for them. “[It] is important to manage and maintain biodiversity in urban areas,” she says.

The findings come as no surprise, according to Dr Fritz Vollrath, a zoologist at the University of Oxford in the U.K. Urban spiders are likely larger from a “lack of pesticides coupled with the city lights that attract insects”, he says.

Future work will focus on whether urban spiders also live longer.