Spiders are already horrifying, with their eight beady little eyes and spindly legs and sticky webs. They also probably eat more meat than your mind can wrap your head around — more meat than humans eat, even.
Spider meal specialist Martin Nyffeler of the University of Basel, Switzerland decided, hey, let’s try and estimate the total weight of all of the food spiders around the world eat per year. Some data crunching resulted in a number so bafflingly high you’ll either squirm or thank the spiders for keeping us safe from all the other bugs. Maybe both.
Image: David E. Hill, Peckham Society, Simpsonville, South Carolina
That number: The world’s estimated 25 million metric tonnes of spiders eat between 300 and 800 million metric tonnes of food per year, according to estimates published today in the very silly-sounding journal The Science of Nature. (That almost feels like calling something the Ferrari of Lamborghinis in academic journal speak). That food consists mainly of insects, little non-insect bugs called springtails, and even small vertebrates. The researchers make several assessments, using the amount of food individual spiders need to eat, the number of insects they catch in their webs, and the number of insects they kill on the hunt.
The 300 to 800 million metric tonne figure is pretty close to the mass of meat and fish humans eat per year — around 400 metric tonnes, according to the paper. It’s also equal to the mass of humans: There are 7.4 billion people on earth, and the average human’s weight is around 130 pounds. Converted to metric tonnes, that’s a bit over 400 million.
The idea to do this eye-opening calculation came from a book Nyffeler read 40 years ago, The World of Spiders by arachnologist William Bristowe in 1958, according to a prepared statement he passed along to Gizmodo. “In this book, Bristowe speculated that the weight of insects annually killed by the British spider population would exceed the combined weight of the British human population,” wrote Nyffeler. “This statement fascinated me very much. I decided that I would like to find out if Bristowe was correct with his speculation.”
Image: David E. Hill, Peckham Society, Simpsonville, South Carolina)
You might think this means spiders are helping our crops by eating all of the pests, but that doesn’t seem to be the case. “Instead spiders appear to play a significant ecological role as predators of insects in forests and undisturbed grasslands,” Nyffeler wrote. Very generally speaking, spiders don’t seem to eat as many bugs in agricultural areas because these heavily managed systems don’t have as many or as good an assortment of prey.
Our apologies for that horrible image. But hey, at least they aren’t eating you. Yet. [The Science of Nature]