As we mourn the decline of many species, let us take heart, for animal abundance still surrounds us – sometimes to an astonishing degree.

In these pages we’ve discussed how careful management can revive stocks of wild fish, such as our beloved sockeye salmon. But overall on this still-teeming planet, which species gathers in the grandest numbers?

Let’s look – and watch your step!

Gatherings in the billions and trillions

The biggest animal assemblies are at our expense, and caused in part by human activity. The Argentine ant, a stowaway on ships to Europe, built a continuous colony along the Mediterranean coast that runs 3,700 miles underground. Each nest contains billions of ants; the entire colony is home to trillions (Bryce, 2020).

How did this happen? Far from the other aggressive ants back home, this species has tended to conquer and decimate the natives it encounters wherever it goes. Genetically similar ants also have super-colonies in California and on the Japanese west coast (Sood, 2021).

swarm of locust
The 2020 African locust swarm covered an area almost the size of Moscow and contained some 200 billion locusts, by United Nations estimates.

Climate change is a boon to the desert locust. The Horn of Africa has become more arid, with bouts of heavy rain, and both help the locust breed (Bryce, 2020). Last year, dense clouds of locusts flew from Ethiopia and Somalia into Kenya, which saw its biggest swarm in 70 years.

In a year of drought and floods, this locust visitation was another calamity for human beings, consuming crops and pasture (Al Jazeera, 2020).

And those swarms may get bigger, with the right conditions such as sudden rainfall leading to overcrowding, inspiring the bugs to find new habitat. The largest known locust swarm came in 1875, when the Rocky Mountain locust, now extinct, covered nearly 200,000 square miles – from the eastern slope of the Rockies into Iowa, Minnesota and Missouri, and from the Canadian Prairie provinces to central Texas. “Albert’s swarm,” named for amateur meteorologist Albert Child, is estimated at three and a half trillion locusts (Lauterborn, 2016).

The sparrow-sized bird known as the red-billed quelea, sometimes called the “feathered locust,” feeds on barley, buckwheat and sorghum as well as seed grass in the sub-Sahara. When farmers began devoting more land to cereal crops, the quelea population may have grown a hundred-fold in the savannah and grassland. The males weave oval balls of grass for nests, sharing a tree; one tree has been seen bearing 6,000 nests. Peak post-breeding population is estimated at 1.5 billion (CABI, 2021).

Red-Billed queleas forming a living cloud.

People who see a large flock of the quelea rise from the ground often insist that they’ve spied the smoke of an oncoming grass fire. As the “smoke” approaches, the synchronized wing-beats sound like high wind. (Greij, 2018). A flock might take five hours to pass overhead.

As with the desert locust, the quelea is rivalled only by an American species that is now gone: the passenger pigeon, which once darkened American skies for days. In 1866, one flock was estimated at more than 3 billion (Bryce, 2020). Easy prey, they were hunted by early settlers into extinction.

sardines fish underwater
Herring swirl, swarm and rise in vertical clusters to find better currents, escape predators, and perhaps just for fun.

In the sea, the Atlantic herring may hold the biggest (and most transcendent) parties. Some schools approach four billion fish. As the afternoon light begins to fade, scattered herring spread out in a thin layer near the ocean floor, then, just before sunset, small vertical clusters rise up and merge horizontally. From several starting points, the school gathers in a series of waves that merge, collectively moving ten times as fast as any one fish can swim (Yong, 2009). Rock on!

Gatherings in the mere millions

Near San Antonio, Texas, more than 20 million Mexican free-tailed bats pack themselves into a single cave, creating an interior that looks like a writhing mass (Bracken Cave Preserve, 2020).

antarctic chinstrap penguin
A chinstrap penguin in a rare moment of solitude.

Imagine seeing two million chinstrap penguins in a cluster on the South Sandwich islands off Antarctica (That’s about twice as many starlings as you might see in one flock). These cute birds, white-breasted with blue-black backs, are named for the thin curved line of black feathers under the chin. Their feathers are so thick they’re waterproof. At about 8 million, the chinstripe is the most abundant penguin on the continent of Antarctica (Strycker, 2020).

It is not the most abundant penguin, however. That honor goes to Macaroni penguins, which have yellow feathers sticking up from their heads and number almost 24 million but are spread out in colonies across South America and Australia as well as Antarctica and Marion Island, (Bryce, 2020).

Look back to Africa for the biggest gathering of hoofed creatures: the Great Migration in Tanzania and Kenya. As many as 1.5 million wildebeest, 350,000 Thomson’s gazelle, 200,000 zebra, and thousands of eland and other hoofed animals, all seeking lush seasonal pastures, make a huge loop each year in nature’s “Greatest Show on Earth” (Asilia Africa, 2021).

No circus could ever compare.

Animal gatherings remind us that we share the earth with magnificent creatures. Individually, each may impress us. In these large groups, they inspire awe, and help keep us humble. After all, as for human beings, we number just shy of eight billion - about as many as two or three of those shimmering schools of herring.