Spider haters, run for the hills! Like a plot ripped straight from the screenplay of a B-movie, it turns out that some spiders thrive wonderfully when their habitat has been degraded and replaced with a manmade environment. While most wildlife species aren’t so lucky, orb-weaving spiders love city life.
For the study, authors looked at differences in the physical attributes of orb-weaving spiders, which are commonly found in both urban and rural environments. The researchers quantified the degree of urbanization at a number of sites in Sydney, Australia, and then measured and compared spiders’ body size, fat reserves, and ovary weight (as an indication of fertility).
Lead author Elizabeth Lowe, from the School of Biological Sciences at the University of Sydney, and her team found that spiders living in more natural environments were smaller, while their city slicker counterparts had larger, fatter bodies. They also found that the metropolitan spiders' reproductive ability was improved in higher socioeconomic areas, as evidenced by more hard surfaces or leaf litter. Meaning that city and suburban spiders are not only larger, but also bring baby spiders into the world more quickly.
Among the urban elements that make the spiders tick, lawns and “heat islands” (the increased heat created in cityscapes) seem to make a difference — as well as street lamps, which present a buffet of bugs for hungry spiders.
“Artificial night lighting has many implications for spider fitness as it leads to local increases in insect abundance, and increased prey capture for spiders in lit habitats,” wrote Lowe.
Another advantage city spiders have over their bumpkin kin is that they have fewer parasites to contend with. The city’s heat and hard surfaces are tough on the parasites that prey on spiders, paving the way for healthier urban spiders with fewer pests.
Lowe and her colleagues concluded, “By identifying the elements of cities that influence the success of urban exploiters, we gain a better understanding of what drives changes in the biodiversity of urban systems.” (And in doing so, bring new terrors to the nightmare landscape of arachnophobes in cities everywhere.)
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