It can be startling to look at a world population counter. There are eight billion (and counting — fast) humans on Earth. That’s a lot. And humans, of course, have an enormous impact. However, we are far from the most abundant animal on the planet. In fact, mammals are at the bottom of the list, with only about 5,500 or so named species.
On the other hand, scientists have identified about a million species of insects, and there are many insects that haven’t yet been identified, explains Scott Hoffman Black, entomologist and executive director of the Xerces Society, an organization dedicated to the conservation of invertebrates. Experts estimate that anywhere from a conservative four million to possibly as many as seven million species are yet to be identified.
So yes, the most abundant land animal is definitely an insect. But which one?
The Most Populated Animal in the World
According to an oft-told anecdote, the British evolutionary biologist J.B.S. Haldane was once asked what he could say about the nature of God based on his study of the natural world. Haldane responded dryly that the creator has “an inordinate fondness for beetles.” The story is most likely apocryphal but so delightful that it has been repeated for decades.
And indeed, there are a lot of beetles on the planet — by some estimates, approximately 350,000 described species. But they aren’t the most abundant land animals. There are a lot of ways to break this down, but if you go by either individual animals or biomass, which is basically weight, the honor almost certainly goes to ants.
The authors of a widely cited 2022 study estimated that there were 20 quadrillion (that’s 20 followed by 15 zeros) ants on Earth — and they were being conservative. Or if this helps you get your mind around the sheer number of ants, the total biomass of ants is greater than the combined biomass of all wild birds and mammals and is about 20 percent of the biomass of all humans on the planet, according to the study.
Read More: An Ancient Ant Army Once Raided Europe 35 Million Years Ago
Why Are There So Many Ants in the World?
Phillip Barden studies ants (and other social insects) at the New Jersey Institute of Technology. He says the amazing success of ants is likely due to the fact that ants are social animals.
“Once you get out of this unitary system where it’s one individual collecting and foraging on its own, the race is on, and you get these massive colonies, some with tens of millions of workers,” he says.
Black adds that ants have adapted to almost all environments, from the high mountains to deserts, and have many different strategies for survival. They also have a very adaptable diet. Many ants are predators, eating other animals — and they’re good at it because they cooperate in getting food. Some ants eat seeds, and some grow a fungus they eat, basically practicing agriculture, as Barden puts it.
This ability to adapt to whatever conditions they find themselves in is probably the reason ants have survived. Ants were present in the Cretaceous period, says Barden, but they made up no more than one percent of all the insects researchers have found in amber or fossil deposits. But after the K-T extinction at the end of the Cretaceous, some 65 million years ago, ants made up at least 10 percent and maybe as much as 30 percent of all insects.
And he adds, “If you go to a rainforest, the biomass of ants and termites today is greater than not only all insects, but all insects plus all vertebrates combined.”
Read More: 6 Unusual Traits of Animal Evolution
Could Ants Outlast Humans in a Mass Extinction?
Many experts argue that we’re in the midst of the sixth mass extinction. If that’s the case, how will ants fare? Almost certainly better than humans, says Black. In previous extinctions, insects have survived when many other groups didn’t, he says. And ants specifically?
Barden points out that many types of ants do exceptionally well in places that humans have disturbed, such as golf courses and lawns.
“I think we’re going to see, and will continue to see, that a handful of ant species that are really well suited to disturbed habitats are going to continue to be really successful. And so instead of finding many dozens or hundreds of species in certain places, we might find just a few, but in those places, those species will be highly abundant,” says Barden.
So have some respect the next time you come across an ant in your cupboard.
Read More: What Happens If a Tiny Insect Goes Extinct? Should We Even Care?
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Avery Hurt is a freelance science journalist. In addition to writing for Discover, she writes regularly for a variety of outlets, both print and online, including National Geographic, Science News Explores, Medscape, and WebMD. She’s the author of Bullet With Your Name on It: What You Will Probably Die From and What You Can Do About It, Clerisy Press 2007, as well as several books for young readers. Avery got her start in journalism while attending university, writing for the school newspaper and editing the student non-fiction magazine. Though she writes about all areas of science, she is particularly interested in neuroscience, the science of consciousness, and AI–interests she developed while earning a degree in philosophy.
