| 1 | Common garter snake |
Maximum length: 137.2cm.
Snakes are generally solitary creatures, from the carpet pythons of suburban Sydney, to the white-lipped pitvipers of Bangkok. But there’s more than a decent handful of snakes worldwide which break this rule, and one is the common garter snake, the most widespread snake in the USA, as well as southern Canada.
Common garter snakes are regularly found writhing together in vast underground dens, usually with the goal of preserving warmth. In their coldest territories, the numbers can be colossal. One common garter snake den in the Interlake region of Manitoba contained over 20,000 snakes. This den was a 15 metre deep sinkhole, the former limestone roof of an underground stream, which had collapsed to allow the garter snake swarms access to the caverns below.
Common garter snakes can hibernate in vast numbers in caves, beneath railways, or in the foundations of houses. In the south, their hibernation sites tend to be simpler, like a rotting log or rock pile. But in Canada or Maine, it’s vital that they’re below the frost line, and optimal sites are rarer – hence why they all end up in the same place.
Common garter snakes (Thamnophis sirtalis) can slither up to a mile in order to return to winter hibernation sites they’re familiar with. A small gathering can rapidly mutate into a pulsating, writhing snake mass, like a northerly version of an Egyptian tomb. The species also breeds while in these communal gatherings, sometimes with so many males jumping on a single female that she gets crushed and dies.
| 2 | Prairie rattlesnake |
Maximum length: 151.5cm.
Defying their devilish reputation, the Crotalus genus of rattlesnakes might be the most social group of any snake worldwide. Not all rattlesnake species huddle together in communal formation, but a large proportion do, particularly those in the western USA.
The prairie rattlesnake is one of the most social members, and one of the most social snakes on Earth. This species inhabits New Mexico, Wyoming, Colorado and more, and is faithful to the same hibernation sites its entire life, returning to the same mammal burrows for over 2 decades. After journeying up to 20 miles to their summer feeding grounds, they slither all the way back in November, using scent alone. When they arrive, they gather together with dozens, hundreds, or even thousands of fellow prairie rattlesnakes.
In 2020, for example, a project launched in Routt County, Colorado, to record a prairie rattlesnake colony consisting of over 1000 individuals. These were crammed into a space just half the size of a tennis court, on a slice of private ranch land west of Elk Mountain (AKA Sleeping Giant).
The rattlesnakes assisted each other, as females would guard the newborns of fellow mothers while they went on excursions underground. They would also leave the den at the same time, in order to catch rainwater on their backs, which they then drank off each other.
Prairie rattlesnakes can hibernate together in many spots, including vacant prairie dog burrows, fissures in canyon walls, scree slopes, caves, or intricate underground burrow networks.
| 3 | Ring-necked snake |
Maximum length: 85.7cm.
The ring-necked snake (Diadophis punctatus) is a widespread species of the USA, covering at least 45 of 48 lower states. This a species of forests, but also paths between forests, and sparser woodlands. Ring-necked snakes are totally harmless, and their communal tendencies are one of their most interesting features.
You can wander around a forest in Arkansas, pulling up old logs and tearing off pieces of rotting bark as you go, and find hundreds of ring-necked snakes in an hour if you’re lucky. This species gathers together not just during hibernation, but throughout the entire year. Ringneck snakes feel uncomfortable when exposed, and instantly gravitate towards shelter. With certain logs or rock piles being optimal, this inevitable brings them into a huddle with fellow members of their species.
For example, Henry Fitch once spent 30 minutes ripping up sheet metal on a hilltop in eastern Kansas. In that short time, he managed to find 279 ringneck snakes. In Douglas County, Kansas, researchers Dundee and Miller discovered 300 ringneck snakes in under an hour.
Ringneck snakes follow the scent trails of their fellow species members, meaning that if one finds an excellent shelter, dozens more can be hot on its heels. Ring-necked snakes also gather together during hibernation, sometimes slithering hundreds of metres to find the optimal dark rock crevice.
| 4 | Eastern brown snake |
Maximum length: 240cm.
The second most toxic land snake in the world, as judged by LD50 venom potency. Eastern brown snakes are growing more common in Australia, not less, thanks to agricultural sprawl which has created the perfect open habitat for them. There’s no need to huddle together for warmth in Australia, yet this species has been witnessed in communal gatherings several times.
In July 1991, a Mr Reeve was digging a trench at Melton airport, 40km west of Sydney. As he scooped out a dirt block, he unearthed a secret underground hollow, where 6 adult eastern brown snakes were resting. It was winter, and the snakes were extremely lethargic.
In October 1976, Gary Stephenson found a den of 10 eastern brown snakes, including 4 adults and 6 younglings, in a den in New South Wales. They were resting beneath a piece of tin sheet metal, partially embedded in the ground.
In autumn 1972, a resting group was found near a demolished house, beneath large slabs of concrete where a building had once stood. There were 13 eastern brown snakes, plus a blue-tongued lizard. After moving smaller slabs of concrete nearby, Mr Webb found another 17 eastern brown snakes.
Exactly why this species congregates in groups is a mystery. They could be arriving at decent shelters independently of each other, or there could be a secret snake code at play.
| 5 | Yellow-faced whipsnake |
Maximum length: 100cm.
Another species of eastern Australia, which is only mildly venomous, mainly causing local swelling in humans. The yellow-faced whipsnake is often mistaken for an eastern brown snake, but is easily identifiable by its far larger eyes.
Yellow-faced whipsnakes can be extremely common in the suburbs of Sydney and Brisbane, due to the abundance of skink lizards which they prey on. They’re quick to flee when threatened, dashing for cover, where they happily nestle alongside several other species members.
In Goodna, 9 yellow-faced whipsnakes were found lurking under one piece of plastic, with one eastern brown snake accompanying them. Likewise, 16 yellow-faced whipsnakes were once found on a single stone wall 3 metres high at Chapel Hill. In towns, they often lurk beneath mounds of litter, sheet metal and timber piles.
Away from towns, 5 yellow-faced whipsnakes were once found resting together on a sandstone rock outcrop, and another 5 beneath sandstone rocks on a rocky hill near a forest. Both batches were found in mid-winter, barely moving. Yellow-faced whipsnakes also lay their eggs communally, with piles of 500-600 sometimes being discovered in one hollow.
| 6 | Blackish blind snake |
Maximum length: 75cm.
Yet another species of Australia’s east coast, this time a totally harmless burrowing snake which closely resembles an earthworm. Blackish blind snakes (Anilios nigrescens) are found in abundance near Sydney and mainly prey on ants, finding them by enlarging subterranean tunnels made by insects.
This species lives largely underground, and is completely harmless to humans. Their eyesight is atrocious, with their pupils looking like the dots of a biro pen. However, blackish blind snakes are excellent at flecking their tongues to detect scents, and this seems to allow them to gather together in groups, by tracking each others’ hotspots.
35 blackish blind snakes were once found resting together beneath sandstone rocks on a hillside. Another batch was found below a heavy log in dry, open woodland. A batch of 7 blackish blind snakes was found resting together on a valley floor, again below sandstone rocks. This included 6 adults and 1 youngling, and they tried to flee when the rock was lifted up. Again, it’s unknown exactly why blackish blind snakes gather together in groups, with Australia’s climate being so warm.
| 7 | Green tree snake (Aus) |
Maximum length: 164cm.
Australian snakes have a particular tendency to congregate for some reason, despite the various families diverging tens of millions of years ago. Green tree snakes (Dendrelaphis punctulatus) differ from other communal snakes in that they gather together not under rocks or in burrows, but in trees.
This snake has excellent homing abilities, which allow it return to the same favourable vantage points annually, using scents and landmarks which guide them through the dry bushland. Green tree snakes particularly like high, overlapping branches disguised with leaves, which can be up to 25 metres above ground.
In 2002, Brendan Schembri found 9 green tree snakes resting on a small section of a forest red gum tree, with 4 occupying the same branch. He returned to the same tree every month after June 2002, and the congregating snakes always greeted him in the same period each year, beginning in March and ending in September.
In May 2005, the tree hosted 17 common tree snakes at once. Like a freakish haunted house decoration, dozens of shed skins hung from the tree’s branches, which had probably accumulated over many months. This tree was like the green tree snake’s unofficial capital, and who knows how many similar trees are out there in eastern Australia.
| 8 | Sharp-tailed snake |
Maximum length: 48.3cm.
A strangely similar species to the ring-necked snake, in habits and personality. The sharp-tailed snake (Contia tenuis) is found in California, Washington and Oregon, and averages at just 30cm. Like the ring-necked snake, they inhabit mulchy forest floors, and have a tendency to lurk beneath logs and rotting tree bark in groups of up to 20.
Sharp-tailed snakes are harmless to humans, except for their spiky tail. This is mostly designed for skewering slugs, but can cause a painful pinprick if you overconfidently pick them up. In California, 7 sharp-tailed snakes were once found resting under a pile of boards, while in Washington state, 22 were found together beneath cobblestones on a river embankment.
Their favourite spot to rest together is under rotting bark on fallen tree logs, where they craftily disguise themselves as millipedes, using an alternating black and white colour scheme on their underside. In the areas where they overlap, sharp-tailed snakes have actually been found resting in forests alongside ring-necked snakes.
| 9 | Queen snake |
Maximum length: 93.3cm.
A river snake of the northern US, which preys on freshly molted crayfish, avoiding the hard-shelled adults which would break their teeth. Queen snakes have been witnessed congregating in huge numbers in their riverside homes. A Mr Neill spotted “dozens upon dozens” gathering together along a creek in Georgia, and believed that the entire population of the creek may have flocked together.
In October 1947, a Mr Wood observed 47 queen snakes gathered on a single sapling tree overhanging the Miami river in Ohio. A 1946 survey from Ohio found 125 queen snakes along a 100 yard stretch of rocky creek, and 24 in one spot.
Scientists have unearthed 16 queen snakes lurking under a single limestone rock formation, and found 10 within a 6 metre stretch of riverbank on the Thames River near London (Ontario). While queen snakes might not be social exactly, they clearly don’t mind each other’s company.
Unlike garter snakes, the exact purpose of these gatherings is unknown, but huddling for warmth is likely further north. Their hibernation dens include hollows in bedrock, old bridge abutments, and cracks in manmade dams.
| 10 | Arizona black rattlesnake |
Maximum length: around 120cm.
This rattlesnake lives solely on mountainous sky islands in Arizona. The Arizona black rattlesnake (Crotalus cerberus) is found only at 900 metres or higher, usually at over 1500 metres, and often lives near hiking trails, lurking in rocky outcrops within cool pine forests.
This species was originally considered to be a prairie rattlesnake subspecies, before being made independent in 2009. One feature the two share is a communal lifestyle. Arizona black rattlesnakes are incredibly social, as they can gather together in their dozens, or even hundreds, forming entire snake communities high in the mountains.
Mother black rattlers particularly cling to one another, and reside in their dens year round, not just during hibernation. Arizona black rattlesnakes seem to make friends, as they have fellow snakes which they strongly associate with, particularly as adults. They live in subgroups within communities, which vary in size from 4 to several dozen.
The rattlesnakes had individual personalities, as a few preferred to stay alone. Adults will also form groups with younglings – for example, 2 adults and 2 hatchlings. However, no mating takes place at these communal sites, as they prefer secretive spots in the woods instead. Like prairie rattlesnakes, female Arizona black rattlesnakes often entrust their hatchlings to fellow mothers while they leave the communal den on missions.