Being reptiles, snakes are cold-blooded. That doesn’t mean they’re out to kill you with nary a pang of guilt (though of course that could happen!), but it does mean that they need a climate that affords at least enough ambient heat to get themselves up and running for a sufficient portion of their day, season, or year. They do best in deserts, where it’s plenty hot much of the time, or in tropical settings where it’s pretty hot almost all of the time, and in temperate areas where there’s enough heat to take care of life’s necessities even if winters get downright cold. They can always put on some pounds and then sleep through that.
The places that just won’t do for snakes are the really cold locales, like Antarctica, Canada’s far north, the tundra of Asia or the southern tip of South America. There are also places in the world really well-suited for serpents climatically, but which are inaccessible by slithering. These would include tropical or temperate islands. Snakes are known to swim, but not for hundreds of miles (and sea snakes stay in the ocean) so it is thanks to the inadvertently helpful hand of humans that snakes have been carried to such hospitable places, and where certain species have thrived. Sometimes that hand of man releases snakes on purpose, usually as unwanted pets, but whether by accident or design, snakes will find a way to survive if the weather’s right and there is prey. Unfortunately, where snakes have not been part of the biological community as it evolved, certain species may be quite defenseless against their appetites. The accidental introduction of the brown tree snake from the southwestern Pacific region to the island of Guam resulted in the decimation of local bird and lizard life, as well as other disasters. That’s a fascinating story, but we’ll save it for another day. New Zealand is famously snakeless, but reports have come in over the years (going back 150 years, actually) of snake sightings. The gold mining areas along the west coast of NZ’s South Island may be the adopted home of Australia’s Victorian copperhead. Though deadly, they are reclusive, and if they have indeed established a population, they haven’t caused trouble for anyone yet.
There are islands which have their own native snakes. We know these residents have been there for quite some time, because they had to have arrived across land bridges exposed during historic periods of low sea level. Such is the case with Great Britain, which has three scaled species: the adder (or common viper), the grass snake (or water snake), and the smooth snake. Only the adder is venomous, and they’re not aggressive, so England doesn’t require a lot of caution while out hiking. Great Britain’s land bridge connection to Europe became submerged under the waters of what is now the Straits of Dover somewhere between 7 and 8 thousand years ago, so snakes had their last chance to board back then. However, the land bridge thought to have linked Great Britain to Ireland was covered over much earlier. Some claim a land bridge never formed. If there was one, it was open for too few years for snakes to get established so far west. Or maybe it was just too chilly too much of the time, because Ireland has no snakes now, nor did it ever, judging by the fossil record. So no offense to fans of St. Patrick, but there never were any snakes for him to drive out of the Emerald Isle. More likely, the “snakes” he sent away were a metaphor for the evils of paganism, which he was much more successful at banishing.
Poor snakes. From the Garden of Eden to St. Patrick to the House of Slytherin and Snakes on a Plane, they get the bad rap for being “evil.” Any invasive species can seem to be inherently troublesome, and they do often wreak havoc on the local ecology, but it’s not their fault. Nature is programmed to survive, and wherever a plant or animal finds itself, it looks for a way to feed and reproduce. But if you still don’t like them, it’s probably a comfort to know that you can retreat to Greenland, or Alaska, or Patagonia to find a reliably snake-free zone.