People love a party. But as populous as our species is, the headcounts at our gatherings don\u2019t match those of other species.<\/p>\n
The Maha Kumbh Mela, a Hindu pilgrimage in Prayagraj, India, drew more than 660 million people in January 2025. But this horde \u2013 thought to be the largest in human history \u2013 pales in comparison to the groups formed by our animal relatives.<\/p>\n
The largest animal gatherings in the world likely occur in the chilly depths surrounding Antarctica<\/a>. The Southern Ocean is home to Antarctic krill<\/a> \u2013 tiny crustaceans that form swarms more than 20km long. A single swarm may contain trillions of individuals. Krill are a crucial food source for other organisms, including fish, penguins and whales.<\/p>\n The largest recorded terrestrial gathering is believed to be the so-called Albert\u2019s swarm of 1875. Recorded by physician Albert Child, it constituted an estimated 12.5 trillion Rocky Mountain locusts, a now-extinct species of grasshopper<\/a>. The cloud of insects covered some 512,800km\u00b2 of the Midwestern USA. Even if Child\u2019s methodology for estimating the numbers was likely to be off, locusts do form some of the largest animal gatherings on the planet. A locust plague in East Africa and parts of Asia that lasted from 2019\u201322 saw swarms of up to 70 billion individuals.<\/p>\n Other animal gatherings are comparatively modest. Vertebrate animals generally reproduce more slowly and thus do not match the astonishing population surges of their spineless relatives. Still, their numbers can be impressive.<\/p>\n A 482km-long flock of now-extinct passenger pigeons<\/a> observed in 1866 comprised some 3.5 billion birds. And red-billed queleas, the most numerous species of bird on Earth, form flocks that number in the millions, which earn them the nickname \u2018feathered locust\u2019.<\/p>\n