Australian Golden Orb Weaving Spiders Grow Bigger And Have More Offspring In Urban Areas

City-dwelling Sydney orb spider. Image: University of Sydney

Golden orb weaving spiders (Nephila plumipes) grow bigger and have more offspring when they live in the city compared to their country cousins, according to Australian research.

Elizabeth Lowe from the University of Sydney says urbanisation may drastically alter the landscape, local climate, and consequently the organisms which inhabit it.

Some will no longer have the resources they need to survive in the urban environment while others may thrive, possibly more so than in their native habitat.

The authors of this study investigated changes in the physical attributes of the orb-weaving spider which are abundant on Australia’s coast in both urban and natural environments and, once matured, remain in the same location for the rest of their lives.

The spiders were collected from 20 sites across Sydney checked for body size, fat reserves and ovary weight.

Results show that the spiders had smaller bodies in areas with more vegetation cover and larger bodies in areas associated with urban development, indicated by the presence of hard surfaces.

The spiders’ reproductive ability, measured by increased ovary weight, may have increased in higher socioeconomic areas, such as in areas with hard surfaces or leaf litter.

“Two reasons likely to explain the differences between these spiders in urban and non-urban environments are temperature and prey availability. Hard surfaces and lack of vegetation lead to the well-known ‘urban heat island’ effect with more heat retained than in areas with continuous vegetation,” says researcher Elizabeth Lowe.

“Higher temperature is associated with increased growth and size in invertebrates.

“Urban lighting also may be a contributing factor as it attracts insects and means more food for spiders in those environments. This increase in prey would result in bigger, heavier, more
fecund spiders.”

The study is published in the journal PLOS ONE.

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