What is the world’s most populous animal?

There are now over 8 billion humans on the planet, which puts us in a pretty exclusive club. Even 1 billion is rare for a species. We’re the most populous mammal, with rats the only other species that come remotely close. We are not, however, the most common animal in the world. That title goes to the magnificent little ant.

most populous animal in the world

We’re ignoring bacteria, because that seems like cheating. It’s also worth noting the cyclothone, a genus of deep sea-dwelling fish believed to be the most abundant fish on earth. Estimates put the number of cyclothones at a quadrillion individuals – this is 1015, or one million billion. In other words, there’s a lot of them. Scientists believe they are the most common vertebrate on earth. 

But even they cannot compete with the mighty ant. If one quadrillion individuals of one fish seems like a lot, there are roughly 20 quadrillion ants on our planet – so 20 million billion. Counting this volume of something is impossible to conceive. It would take a human some 635 million years to eventually count to 20 quadrillion. 

most populous animal in the world
A cyclothone fish.

This is the latest estimate from a French study, conducted in 2022. They studied over 450 different regions of ant population, measuring the number of local ants via two standardized techniques: setting traps that captured ants passing by during a certain period, or analyzing the number of ants on a given patch of leaves on the ground.

There is, of course, a lot of guesswork involved, and the study was unable to record extensive data in major areas, such as central Africa and central Asia. Yet even giving a ballpark figure for the number of ants on our planet is important in tracking their impact on the planet. 

most populous animal in the world

One ant is a small thing. A colony of ants is another, and 20 quadrillion is a different proposition entirely. They play a significant role in the earth’s biosystems, involved in dispersing seeds, hosting organisms and serving as either predators or prey. 

“The true abundance of ants globally is likely to be considerably higher” than estimated, the study says. “It is of utmost importance that we fill these remaining gaps to achieve a comprehensive picture of insect diversity.”

Read More: Silky anteater | Meet the smallest anteater in the world

For the sake of this, we’re grouping some 15,700 named species and subspecies of ants together. These are just the species we already know about, but considering how many unknown species there remain in the world, it’s likely the number of different ants is far higher.

Almost two-thirds of the world’s ants live in only two of the world’s ecosystems: tropical forests and savannahs. Based on their estimated total, the global biomass of ants is believed to be 12 megatons of dry carbon – more than that of wild birds and all non-human mammals combined.

most populous animal in the world

It is estimated that there are some 10 quintillion (10,000,000,000,000,000,000) individual insects alive at any given moment. The New York Times estimated that the world holds 300 pounds of insects for every pound of humans. The biomass of every ant is about 12 megatons of dry carbon, which is more than the total of every single bird and every non-human mammal combined. 

Over 99% of species to have ever existed (amounting to over five billion) on earth are now believed extinct. Of the species currently living here, it is estimated that we know of only 10-15%. In other words: 90% of the species living today could be unknown to us. It’s pretty remarkable, considering how well-documented our planet now is.

According to one study, these estimates are generous. One analysis of microbial data suggested that 99.999 percent of all species remain undiscovered, meaning we’d identified only one-thousandth of species.

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