Itsy, bitsy spiders — with a ginormous appetite for bugs
They eat up to 880M tons of insects a year
All the spiders in the world combined eat about 440 million to 880 million tons of insects and other pests a year — equal to the weight of more than 85 million elephants, a new study says. That’s a lot of bugs. In comparison, all humans combined consume about 440 million tons of meat and fish annually. Whales feed on 300 million to 550 million tons of seafood, and the world’s seabird population eats about 77 million tons of fish and other seafood.
Most spiders, of which there are about 45,000 species, are found in forests, grasslands and shrublands. Their ravenous appetites keep countless insect pests in check.
The spiders serve to protect plants and trees by eating the bugs that would feed on them, especially in forests and grassland areas, says the study’s lead author, Martin Nyffeler of the University of Basel in Switzerland.
“Our calculations let us quantify for the first time on a global scale that spiders are major natural enemies of insects,” Nyffeler says. “In concert with other insectivorous animals such as ants and birds, they help to reduce the population densities of insects significantly.”
All spiders are carnivorous, feeding predominantly on insects and to a lesser extent on other spiders, the study says. Larger species of spiders are known to chow down on frogs, lizards, snakes, fish, birds and bats.
It’s hard to estimate the number of spiders in the world. A British scientist speculated in 1947 that there were about 2.2 trillion spiders — in England and Wales alone, Nyffeler told LiveScience.
Sometimes just being a spider is scary enough: Researchers have shown spiders can intimidate insects to the point where they eat less in the presence of spiders.
Nyffeler has been studying spiders for 40 years and used data from 65 studies in his findings.
“We hope that these estimates and their significant magnitude raise public awareness and increase the level of appreciation for the important global role of spiders in terrestrial food webs,” says the study, which appeared in The Science of Nature.