Why Some US States Have No Venomous Snakes

There aren’t many animals with less glowing reputations than snakes. They’re popularly associated with danger, deception, and the need for constant vigilance, but our aversion to the slithering denizens of our planet is more than cultural: many species, including humans, have been shown to possess a biological predisposition to be wary of them. So for many people, the perfect place to live is the one where the odds of finding a snake in the grass are slimmest.

But in the United States, there are some places you’re just a lot less likely to hear about snake sightings than others. There are a total of four U.S. states without venomous snakes, and barring the introduction of non-native species, geography and climate make it seem likely things will stay that way.

Of the fifty U.S. states, two of them - unsurprisingly, Alaska and Hawaii — have no native snake populations at all. (Hawaii’s waters are home to venomous sea snakes, but for the sake of continuity, let’s stick to terrestrial species here.) And while Maine and Rhode Island do have native snake species, none of them are venomous. These four states are some of the best places to be if you can’t stand the thought of something slithering through your garden.

But why?

Again, the short answer is a simple one: geography and climate. But what makes these four states so unappealing to venomous snake populations? That one will take a little more digging to explain.

Reason #1: Snakes Don’t Thrive in Cold Climates

It may not be too surprising that Alaska is not very rich in snakes for the same reason that it’s so sparsely populated by people. There’s no state with a more extreme climate, and cold-blooded snakes don’t do very well in the freezing Alaskan winter. While Alaska is the most obvious example of a state that’s just too cold for snakes, climate also explains the lack of venomous snakes in Maine and Rhode Island.

But why are snakes so averse to cold? The short answer is that they can’t internally regulate their body temperature. That’s what it means to say that snakes are cold-blooded: their internal temperature relies largely on external conditions. And when snakes get too cold, their metabolism gets a little out of whack. They tend to become lethargic, and basic bodily functions like digestion and locomotion become much more difficult. This is why some species of snakes in temperate states with cold winters will go into a form of hibernation called brumation.

While snakes have strategies for toughing out the coldest months of the year, there are some places that are just too chilly to be worth the risk. Alaska, stretching all the way to the Arctic Circle, is the most obvious example of this - it’s got no established snake populations at all. But in New England, winters get just harsh enough that Maine and Rhode Island aren’t very snakey, either.

Reason #2: Some Populations Have Gone Locally Extinct

Alaska and Hawaii haven’t been home to native snake populations at any point in human history, let alone venomous ones. The influence of climate and isolation made sure of that without any human help. But in Maine and Rhode Island, the absence of venomous snakes is actually a direct result of human efforts to eradicate a much-loathed species frm the area.

Although cultural associations with snakes vary worldwide, it’s long been common in many cultures to believe that the only good snake is a dead snake. This was certainly the case among European settlers who moved into Maine and Rhode Island in the early 19th century. Faced with all the dangers of the wilderness, these settlers were more than eager to take one such danger out of the picture: the timber rattlesnake, once Maine and Rhode Island’s only venomous snake species.

Timber rattlers aren’t a woodland creature most of us want to run across: some individuals have been known to measure over four feet in length. But New England’s earliest European inhabitants took it one step further than that. With no understanding of the benefit the snakes provided their ecosystem, settlers saw only a threat to human safety, often killing them on sight. Coupled with the destruction of snake habitats, this ensured that timber rattlesnakes were extinct in Maine by 1860.

While timber rattlesnakes are still found in small numbers throughout much of their former range in the eastern United States, they’re endangered just about everywhere. And while the Rhode Island population hung on about a century longer, not a single one has been sighted in the smallest U.S. state since the 1970s.

So, while cold winters in Maine and Rhode Island ensure that the snake populations of both states are smaller and less diverse than those of warmer states, it’s actually human intervention that’s kept both — for better or for worse — free of venomous snakes.

Reason #3: Snakes Can’t Swim That Far

Hawaii’s ecosystems are like no other in the U.S. Its tropical climate, its extreme isolation, and its unusual volcanic origins have given rise to ecosystems and species that are found nowhere else on earth. And while Hawaiian species’ daptations to island isolation make for some truly unique wildlife, all of those critters had to make it halfway across the Pacific Ocean to get there in the first place.

As a result, every terrestrial species in Hawaii had to get there in one of three ways. The first and most obvious option is flight: birds and even bats are abundant in Hawaii thanks to their ability to cross vast swaths of ocean in the air. Many plant species also arrived via air mail thanks to wind currents that brought a couple of lucky spores or seeds across from other landmasses. And, of course, the final option is to float or swim.

Are you seeing where this is going? Most snakes are a little too heavy to blow in on the wind, and they usually aren’t up for a swim across thousands of miles of rough open ocean. Sure, many species can swim, but not that far! So while Hawaii sees the occasional sea snake, there aren’t any terrestrial species to speak of.

And even if snakes had managed to reach the Hawaiian Islands on their own, they quickly would have starved. Snakes usually rely on small terrestrial species, especially mammals, that just don’t exist in Hawaii.

So, while you might assume that a densely forested archipelago of tropical islands would be crawling with snakes, it’s actually near-totally free of them. The only snake you’ll find on land is the invasive Brahminy Blind Snake, a tiny, non-venomous species that sometimes sneaks in via crop imports and poses no threat to anyone. But that’s not an accident: Hawaii’s government has gone to great lengths to keep snakes out.

To prevent non-native species from disrupting the state’s incredibly delicate island ecosystem, it’s imperative that snakes never enter the islands. Other Pacific islands have seen devastating impacts on their native wildlife when the notorious Brown Tree Snake was introduced, and though the species hasn’t colonized Hawaii, preventing that outcome is one of the state’s highest wildlife conservation priorities. Hawaiian customs authorities rigorously inspect imports, and it’s illegal to import or even own a pet snake because of the damage it could do if it were to escape.

This hasn’t always stopped Hawaii residents from owning snakes anyway — several illegally-imported pet boa constrictors have been found and confiscated in the past decade — but these strict laws have kept Hawaii free of snakes so far.

Predictable Population Patterns

If your idea of paradise is a place where a venomous snakebite is never a potential risk, these four U.S. states are the only ones where you’ll never have to worry about encountering something nasty in the grass. But the geographical, climatological, and human factors that keep snakes out of these states are applicable worldwide.

No matter where in the world you wander, you can be sure that a cold climate or an extremely isolated location keep venomous snake numbers at a minimum. And while venomous snakes serve an undeniable ecological purpose, anybody who would rather not live with them needs only to seek out those two key accidents of geography.