Urbanization making Spiders Bigger

Golden orb-weaving spiders living in Sydney are larger than their country cousins, a new study has found.

Urbanization and habitat encroaching are known to negatively affect plants and animals. However, a study by researchers at the University of Sydney has found that city life helps a certain species of spiders to grow large and produce more offspring.

"Our findings show the impact urbanisation can have on local wildlife. While many species do not survive encroaching urbanisation and the consequent loss of native habitat, others have a more complex relationship with man-made changes to the landscape," said Elizabeth Lowe, a PhD candidate in the University's School of Biological Sciences and lead author of a study.

For the study, the researchers collected golden orb-weaving spiders (Nephila plumipes) from different sites in Sydney and from the countryside too. These spiders are abundant in Australia and can be found both in cities as well as in the countryside. These eight-legged creatures tend to stay at the same location.

The researchers found that spiders that lived in areas with natural vegetation had smaller bodies when compared to those living in the city.

Urban spiders also had higher ovary weight, which indicated an increase in reproductive abilities.

"City-dwelling orb-weaving spiders grow larger and could produce more offspring than their country cousins our research shows," said Lowe in a news release.

The researchers say that there are two possible reasons for large size. One reason is that cities have 'urban heat islands' due to lack of vegetation and hard floors; and heat is known to drive the size of creatures. The second reason might be that city lights attract more insects and provide spiders with more prey. Abundant food supplies lead to spiders becoming larger and fatter.

The study is published in the journal PLOS One.

Spiders in Australia aren't the only organisms benefiting from city lifestyle. A recent research had shown that frogs in Taiwan were using drain pipes in cities to amplify mating calls.