CREEPY, CRAWLY STUDY
Spiders could, theoretically, eat every human on Earth in one year — and still be hungry. Theoretically.
Spiders are quite literally all around us. A recent entomological survey of North Carolina homes turned up spiders in 100 per cent of them, including 68 per cent of bathrooms and more than three-quarters of bedrooms. There’s a good chance at least one spider is staring at you right now, sizing you up from a darkened corner of the room, eight eyes glistening in the shadows.
Spiders mostly eat insects, though some have been known to snack on lizards, birds and even small mam- mals. Given their abundance and the voraciousness of their appetites, two European biologists recently wondered: If you were to tally up all the food eaten by the world’s entire spider population in a single year, how much would it be?
Martin Nyffeler and Klaus Birkhofer published their estimate in the journal the Science of Nature earlier this month and the number they arrived at is frankly shocking: The world’s spiders consume between 360-million and 725-million tonnes of prey in any given year. That means spiders eat at least as much meat as all seven billion humans on the planet combined, the latter whom consume about 360-million tonnes of meat and fish each year.
In other words: The total biomass of all adult humans on Earth is estimated to be 260-million tonnes. Even if you tack on another 64-million-ish tonnes to account for the weight of kids, it’s still not equal to the total amount of food eaten by spiders in a given year, exceeding the total weight of humanity.
To arrive at this number, Nyffler and Birkhofer did a lot of sophisticated estimation based on existing research into A) how many spiders live in a square meter of land for all the main habitat types on Earth, and B) the average amount of food consumed by spiders of different sizes in a given year.
These numbers yielded some interesting factoids. For instance, one study estimated that global average spider density stands at about-131-spi-- ders per square meter. If you gathered up all the spiders on the planet and placed them on a very large scale, together they’d weigh about 23million tonnes, according to Nyffler and Birkhofer. For comparison, the Titanic weighed about 47,000 tonnes. The mass of every spider on Earth today, in other words, is equivalent to 478 Titanics.
Spider biologists have also generally found that spiders consume approximately 10 per cent of their body weigh in food per day. That’s equivalent to a 200-pound person eating nine kilograms of meat each day.
In the end, spiders’ voracity actually works out to our benefit. Since they primarily feast on bugs, their hunger means fewer pests in the garden and fewer flies in the house.