The team used two calculation techniques based on varying models, finding that the global spider population weighs around 25 million metric tons and wipes out up to 800 million tons of prey annually.
"Our estimates of the global annual prey kill imply that spiders exert considerable predation pressure on insect populations, especially in forests and grasslands", wrote Nyffeler and Birkhofer.
In comparison, all the humans on Earth consumed about 400 million tons of meat and fish each year, according to the UN Food and Agriculture Organisation. "Spiders make an essential contribution to maintaining the ecological balance of nature", Nyffeler said, USA Today reported. Large tropical spiders also occasionally devour plants and small vertebrates such as lizards, frogs, fish, snakes, birds, and bats. Zoologists at the University of Basel and Lund University in Sweden have now shown just how true this is - spiders kill astronomical numbers of insects on a global scale.
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Spiders are considered to be one of the world's most species-rich and widespread groups of predators. The spider's eating habits can even be compared to those of the whales (Cetacea) in the world's oceans, which eat an estimated 280-500 million tons of prey a year. Most spiders are found in forests, grasslands and shrublands, followed by croplands, deserts, urban areas and tundra areas. These eight-legged creeps have a population density of up to 1,000 individuals per square meter.
This showed just how big a role spiders play in keeping pests and disease-carriers at bay - especially in forests and grasslands where majority live. Some 8,000 to 10,000 other predators and parasites consume spiders exclusively, while up to 5,000 bird species have made these crawlies a part of their diet.