Bright lights, big spiders: Researchers say city life is breeding giant arachnids

  • The research was conducted by PhD student Lizzie Lowe from the University of Sydney
  • Her study revealed golden orb weaving spiders are fatter and more fertile at Tamarama Beach, Sydney's eastern suburbs
  • She said this will help control pest like flies, mosquitoes and other insects
  • The findings were published in science journal POS ONE on Wednesday

Spiders are growing far larger in the city than in rural environments, researchers have said.

They found that rather than thriving in areas with lots of vegetation, golden orb weaver spiders living in urban areas of Sydney, Australia, were larger and had more babies.

The say city an abundance of food and city lights could be to blame.

City-dwelling orb-weaving spiders grow larger and could produce more offspring than their country cousins, researchers say.

City-dwelling orb-weaving spiders grow larger and could produce more offspring than their country cousins, researchers say.

THE GOLDEN ORB WEAVER SPIDERS

 Golden orb weaver spiders, known as Nephila plumipes, are found in Queensland in Australia, Indonesia and some Pacific islands.

They are characterised by bright, vibrantly coloured abdomens and produce webs up to one metre, which appear a golden colour.

Females are often three or four times larger than males and, although they do have venom. they are usually harmless.

'City-dwelling orb-weaving spiders grow larger and could produce more offspring than their country cousins our research shows,' said Elizabeth Lowe of the University of Sydney, who led the research.

This study shows invertebrates are sensitive to urbanisation but that not all species are negatively affected by living in cities.

'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.'

The researchers collected golden orb-weaving spiders (Nephila plumipes) from across the Sydney city region.

The spiders 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.

'We quantified the degree of urbanisation of 20 sites then looked at changes in the spiders' body size, fat reserves and ovary weight,' Ms Lowe said.

The results show spiders in areas with more vegetation cover had smaller bodies and larger bodies when located in urbanised areas, characterised by increased housing and population density and hard surfaces such as roads and buildings.

The authors also found that the spiders' reproductive ability, measured by increased ovary weight, appeared to increase in urban areas.

The spiders are particularly fond of Tamarama Beach, Sydney's eastern suburbs, just a km away from Bondi

The spiders are particularly fond of Tamarama Beach, Sydney's eastern suburbs, just a km away from Bondi

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

University of Sydney ecologist Lizzy Lowe found that spiders thrive in Sydney's rich suburbs

University of Sydney ecologist Lizzy Lowe found that spiders thrive in Sydney's rich suburbs

'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, published in the journal PLOS One, examined 222 spiders collected between April and June 2012.

Researchers wrote: 'Habitat modifications significantly alter species distributions and can result in increased abundance of select species which are able to exploit novel ecosystems.

'Spider size was negatively associated with vegetation cover at a landscape level, and positively associated with hard surfaces and anthropogenic disturbance on a local and microhabitat scale.

'The larger size and increased reproductive capacity of the spider in urban areas show that some species benefit from the habitat changes associated with urbanisation.'

The research found the largest golden orb weighed three grams, and their webs can measure up to three metres.

The smaller spiders were found in rural sites such as the Brisbane Waters National Park, near the Central Coast - north of Sydney, where the smallest measured 0.5 grams.