Uh-Oh: City Spiders Are Getting Bigger and Fatter

They’re also having more babies as temperatures rise.
A golden orb-weaving spider. (Photo: Mrowka/Flickr)
Aug 22, 2014· 0 MIN READ
Kristina Bravo is Assistant Editor at TakePart.

Do spiders creep you out? You might want to consider moving to the countryside. Scientists have found that urban living makes arachnids bigger, fatter, and more fertile.

A new study published in PLOS ONE discovered that the golden orb-weaver spider that’s indigenous to the Australian countryside has been thriving in cities. Thanks to more food, the spiders are packing more body fat. Females are also growing heavier ovaries in well-off neighborhoods and therefore spawn more eggs.

“The increased expenditure and management of parks in wealthy suburbs could result in healthier vegetation patches,” the authors wrote, “which would increase prey abundance and allow spiders to grow larger and build up fat reserves.”

Higher temperatures—buildings and concrete surfaces absorb heat—are linked to growth in invertebrates, according to Elizabeth Lowe, coauthor of the study.

The average tibia of the 222 spiders studied measured 0.42 inches, but the city spiders had tibiae as long as 0.55 inches. The urban spiders’ ovaries accounted for about 39 percent of their body weight, the highest ovary-to-body ratio of all the arachnids in the group’s research. Although the study doesn’t specify how many eggs urban dwellers carry, on average a single egg sac contains about 380 eggs.

More likely than not, this doesn’t just happen Down Under. The researchers looked only at golden orb-weavers, the spiders most familiar to Australians, but Lowe thinks other arachnids enjoy the perks of city living too.

“Other web-weaving spiders are also known to thrive in urban environments, and it is likely they are responding to similar modifications to the natural environment,” she told City Lab.