Spiders In Cities Are Getting Bigger – A LOT Bigger

Scientists say spiders in urban areas are getting much, much larger. According to a new study published yesterday in PLOS One, specific species of spiders in urban Sydney, Australia are getting bigger and reproducing at much higher rates than the same spider species’ in rural areas.

The suggestion from the data in the study is that a combination of hotter temperatures combined with more abundant food sources are definitely having an effect on the spider species Nephila plumipes, a member of the orb-weaver family found mostly in the Asia Pacific region and across eastern Australia.

You might be thinking, well, okay – but that spider only lives on the other side of the world. But here’s the thing: the Nephila plumipes is only one of over 10,000 orb-weaver species. Orb-weavers make up over 25% of all the known spiders in the world. Orb-weaving spiders are known for their circular webs and are found on almost every continent.

To conduct their study, scientists caught exactly 222 orb-weaver spiders from all different environments across Sydney. They then studied the spiders’ different physical characteristics – such as leg size, ovary size and overall body weight – with respect to increased urbanization. Urbanization was in turn measured by a set of data that included factors such as paved surfaces and distance from the city center.

Country Spider/City Spider Urban spiders are growing much larger than other spiders.
Country Spider/City Spider
Urban spiders are growing much larger than other spiders.

The PhD student that led the spider size study, Elizabeth Lowe, says the increased size of the spiders is actually a good thing – whether you have a fondness for our eight-legged friends or not. Web slinging spiders in urban areas make sure that insect populations don’t get out of hand. The larger spiders are also a vital food source for birds, and lastly, the spiders’ ability to not only live – but thrive – in cities shows us that urban animals are a lot more resilient than we thought.

Lowe told the Conversation:

“The fact that some spiders are loving cities is cause for hope. In fact, in order to maintain biodiversity in cities we need to be able to support more diverse populations and other invertebrates.”

One of the interesting reasons for the increased food supplies for urban spiders is nighttime lighting. The lighting attracts the spider’s food, making the urban landscape a veritable smorgasbord for spiders. There are also fewer predators of spiders in urban areas. Whereas spiders can continue through their lives highly undetected by humans, their predators – snakes, birds, etc.- have a tougher time evading the human landscape without interaction.

Spiders are quickly being added to an animal group that scientists call City Exploiters. This group includes other animals that have adapted to take advantage of urban areas rather than avoid them. The group includes pigeons, crows and crickets.

image via The Conversation