By Dr. Karen Shaw Becker
Some find spiders fascinating. Others have phobias that range from recurring dreams to constantly looking under pillows and in dark corners to see if one might be hiding. (You might be one who can relate.)
But whether you think spiders are interesting or wonder why this particular creature had to be included as part of the animal world, here’s a fact that will probably make you sit up and take notice: All combined, the spiders of the world eat anywhere from 440 million to 880 million tons of insects, from flies to moths to butterflies, as well as ants, beetles and other diminutive critters, every year.
That’s equal to the weight of about 85 million elephants, USA Today1 reports, and yes, that’s a lot of bugs. In fact, humans are said to eat the lower end of that scale — 440 million tons — in meat and fish in the same length of time. Even whales ingest less than that at 300 million to 550 million tons of seafood, as do all the seabirds on the planet, which scientists say take care of 77 million tons of fish and other types of seafood.
Your first reaction might be “That’s good — they’re getting rid of mosquitoes.” That’s certainly true, but they’re helping with a few other things, too, such as protecting plants and trees by chowing down on the bugs that would otherwise harm the foliage. In fact, spiders usually live where they eat:
“Most spiders, of which there are some 45,000 species, are found in forests, grasslands and shrublands, followed by croplands, deserts, urban areas and tundra areas. And their ravenous appetite keeps countless insect pests in check.”2
While that is no doubt a good thing, it’s still a little sobering to find that, according to research by Martin Nyffeler, Ph.D., from the University of Basel in Switzerland, there’s something like 25 million metric tons of spiders throughout the world.
Spiders Eat More Than Insects
If you have a natural aversion to spiders, you might find it rather unnerving that spiders, being inherently carnivorous, are not so selective as to limit their palate to insects. The fact is, there are arachnid species around the world that regularly include larger animals, such as lizards, snakes, frogs, bats, birds and even fish. They also feed on other spiders.
According to a study published in The Science of Nature,3 led by Nyffeler along with Klaus Birkhofer, Ph.D., of Lund University in Sweden and the Brandenburg University of Technology Cottbus-Senftenberg in Germany:
“Our calculations let us quantify for the first time on a global scale that spiders are major natural enemies of insects. In concert with other insectivorous animals such as ants and birds, they help to reduce the population densities of insects significantly. Spiders thus make an essential contribution to maintaining the ecological balance of nature."4
CNN relates that spiders also have “uncanny” survival mechanisms, thriving quite nicely in the coldest climes of the Arctic as easily as the hottest deserts. You’ll find them in high altitudes where other organisms are unable to survive, and in every bog, jungle, steppe and sand dune.
"There is hardly any terrestrial area on this globe where spiders would be missing,” says Nyffeler, who’s been so enamored with spiders for the past 40 years that his research uses data from around 65 studies on the topic. “Essentially, they'll go wherever they can find food.”5
While spiders have been known to make a meal of a bird, as mentioned earlier, spiders are also a very important part of the food chain, as an estimated 3,000 to 5,000 bird species are happy to return the favor. As such, spiders are the delectable meal of as many as 10,000 predators that spend their time concentrating solely on getting their fill of the eight-legged arachnids, a family to which mites, ticks and scorpions are also members.
More Interesting Spider Statistics
Humans aren’t the only ones reluctant to relax in the presence of a spider. The study revealed that even insects are so intimidated when there’s a spider in the area that they eat measurably less. Additional factoids observed in Nyffeler’s spider studies include:
- Cursorial spiders are similar to wolves, which move around to hunt prey, and horses, which graze while walking, in that they move around to find their food.
- Spider communities in warmer areas of the world (“often dominated by cursorial hunters”) contain a higher percentage of spiders in their diets than spider communities in colder climates, and cursorial spiders eat other spiders more often than web-building types.
- Spiders are carnivorous, but they’ve been known to resort to plant materials from time to time.
- Forests, grasslands and tropical and subtropical savannas, covering approximately 87 million square kilometers, contain more spiders simply because those areas are disturbed by activity less often, so their numbers can thrive.
- Honey bees in large numbers are also prey for spiders in forest and grassland habitats.
Want more creepy-crawly facts? Try these:
- The largest spider, hands down, is the bulky Goliath birdeater, with a leg span of 11 inches and weighing around 6 ounces, which Dogo News6 compares to the weight of a newborn puppy. It belongs to the tarantula family and lives in rainforest areas of Guyana, Suriname, northern Brazil and southern Venezuela. They can take up to six years to mature, after which the males die soon after. Females, however, can live for around 25 years.
- A much lankier specimen is the Giant Huntsman spider with a leg span of 12 inches, earning it the size comparison of a dinner plate. They’re said to be common in wooded areas of Australia, Asia, India, Pakistan, China and Japan. They don’t build webs but they do forage for food, and while they eat mainly insects, they’ve been known to eat dead mice and small reptiles.7
- Earning the gold star for deadliest spider, The Conversation contends that the funnel-web spiders of Australia can kill a small child within minutes and adults within hours. However, there’s an antivenom, as there is for the infamous widow spider, which inspires far less trepidation than it once did.
- The brown recluse, found in many areas of the U.S., may cause pain and require “minimal intervention,” but there’s also “significant skin necrosis” in 10 percent of the population when bites occur.8