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Researchers find spiders eat up to 800 million tons of prey annually

Researchers find spiders eat up to 800 million tons of prey annually

According to further calculations, spiders in forests and grasslands account for more than 95% of the annual prey kill of the global spider community. Most of their victims are insects and springtails, small insect-like arthropods, but they occasionally make a meal of vertebrates such as frogs, lizards, fish and small mammals. Seabirds pick off a relatively paltry 70 million tons.

A gargantuan figure at least equivalent to the quantities of meat and fish consumed each year by humans (400 million tons), according to data from the Food and Agriculture Organization of the United Nations ( FAO ).

"Our calculations let us quantify for the first time on a global scale that spiders are major natural enemies of insects", says one of the researchers, biologist Martin Nyffeler, from the University of Basel in Switzerland.

Together with ecologist Klaus Birkhofer from Lund University in Sweden, Nyffeler analysed data from previous studies to find out how much food spiders chomp through annually. 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.

Each year spiders eat an estimated 400 to 800 million metric tons of insects. "Spiders thus make an essential contribution to maintaining the ecological balance of nature", he adds.

Spiders are found everywhere from the Arctic to the most arid of deserts, in caves, on ocean shores, sand dunes and flood plains, the study authors said.

Jumping spider Phidippus mystaceus feeding on a nematoceran prey.

In some parts of the world, spiders have a population density of 1,000 individuals per square meter.

"These estimates emphasize the important role that spider predation plays in semi-natural and natural habitats, as many economically important pests and disease vectors breed in those forest and grassland biomes", Dr. Nyffeler said. Between 8,000 to 10,000 predators eat only spiders, and another 3,000 to 5,000 bird species eat them frequently, USA Today reported.

But these numbers are not meant to terrify anyone, the scientists hope their study will raise awareness of the importance of spiders in the global food web.

The findings are reported in The Science of Nature.

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