Spiders Eat Up to 800 Million Tons of Prey Each Year

For comparison, whales eat up to 500 million tons annually

A spider munches on its prey. Pavel Kirillov/Wikimedia Commons

The itsy bitsy spider has a pretty voracious appetite, according to a new study. A team of Swiss and Swedish researchers has calculated that the world’s spiders eat between 400 and 800 million metric tons per year, the Associated France-Presse reports.

Researchers used data from 65 existing studies to estimate that the Earth is home to 25 million metric tons of spiders. They then applied that number to the amount of food spiders need to consume for survival. Their findings, published in journal The Science of Nature, that the total spider population eats up to 800 million metric tons of animal prey annually.

To put that number in perspective, researchers compared the spiders’ smorgasbord to the amount of prey consumed by other, much larger species. Spiders fall in “the same order of magnitude” as whales, which eat 280-500 million tons per year, the researchers write in the study. Spiders may also exceed humans’ total animal consumption, which tallies to about 400 tons of meat and fish annually.

As Ryan F. Mandelbaum writes for Gizmodo, the total mass of the spiders’ diet is roughly equal to the mass of humans on Earth. There are 7.4 billion people living in the world today, with an average weight of 130 pounds per person. “Converted to metric tons, that’s a bit over 400 million,” Mandelbaum explains.

According to the AFP, there are approximately 45,000 known spiders species, all of them carnivores. For the most part, the critters eat insects and collembolans, a soft-bodied hexapod. As they pursue these tasty snacks, spiders can travel up to 19 miles per day on delicate strands of web.

The image of swinging, rapacious spiders is unlikely to soothe the arachnophobes among us, but there is an important benefit to spiders’ vast appetite. As the authors of the study note, spiders play a significant role in controlling pests and disease-carrying insects. The impact of forest and grassland spiders, which kill up to 95 percent of the total population’s prey, is particularly high. In these environments, Stephanie Pappas of Live Science explains, spiders do not have to contend with human activity that disrupts their habitats.

“[M]any economically important pests and disease vectors breed in those forest and grassland biomes,” the study’s authors write, adding that they hope their findings “raise public awareness and increase the level of appreciation for the important global role of spiders in terrestrial food webs.”

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