75CFDA33-4183-4D54-9393-81C6E28FAAD9 Created with sketchtool. Weird Science: Spiders Could Eat Everyone and Still Want Dessert

Our spider friends do a pretty great job of clearing up the environment for us, getting rid of all sorts of pesky bugs and insects. This makes life more comfortable for us, less pests, less flies, and less bugs inside the house. But how much do they really eat? Do they make that much of a difference?

Two biologists took up the question and came out with a staggering answer. They calculated the world’s spiders eat somewhere between 400 and 800 million tons of prey every year. If you’re wondering, humans eat about 400 million tons of meat and fish – so the spiders are eating at least the same amount as us.

To come to this conclusion they considered how many spiders there are estimated to be in the world, and the average amount of food spiders of different sizes consume. The average density of spiders is thought to be around 131 per square metre, which is terrifying itself when you realise that must mean that there are some areas where the number is far higher. According to the study if you weighed all those spiders it would come to approximately 25-30 million tons. That’s the equivalent of nearly 500 Titanics. Of spiders.



They then averaged that spiders eat around 10% of their body weight every day (that’s like a person eating 8kg of meat every day). Do the maths and you realise the horrifying reality that spiders eat much more than 400 million tons every year.

As well as their efforts reducing insect numbers, they also do a pretty great job of scaring the living bejeezus out of us by hiding behind doors or on car mirrors. So what would happen if they decided to turn their attention to eating the 7 billion humans instead?

Spoiler: it doesn’t end well. The total mass of all adults on Earth is estimated to be 287 million tons. If we add another 25% to allow for the weight of children it would bring the weight of humans up to around 350 million tons. So if the spiders turned their attention to us they could easily eat everyone on Earth and still be hungry.

With that knowledge on board, have a great sleep tonight everyone!

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About the Author

Ben Lewis
Ben Lewis is a Producer at Australia’s Science Channel, and Editor of the Space, and Innovation and Tech channels. He has worked with scientists and science storytellers including Brian Cox, Chris Hadfield, Robert Llewellyn, elite athletes, Antarctic explorers, chefs and comedians. Ben has also been involved in public events around Australia and was co-writer, producer and director of The Science of Doctor Who, which toured nationally in 2014 in association with BBC Worldwide Australia & New Zealand. Want more Ben? You can hear him on commercial radio in Adelaide, ABC radio around Queensland and regional SA, and community radio stations around Australia, plus as a guest speaker at universities around Australia on communicating science to the public. Around the office he makes the worst jokes known to mankind.


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