|Global distribution of all snake species combined|
Public domain from Wikipedia
Terrestrial data from Ernst & Ernst (2011) and Cogger et al. (1998)
Sea snake data based on Campbell & Lamar (2004), Phillips (2002),
Ernst & Ernst (2011), and Spawls & Branch (1995)
hot-spring snakes of Tibet (genus Thermophis) have done. However, Iceland has never been connected to any continent—instead, it was formed about 20 million years ago by a series of volcanic eruptions in the Mid-Atlantic Ridge, which separates the Eurasian and North American plates. It's been at about its current latitude the entire time, and, as far as anyone knows, has never been colonized by snakes. Today, the closest snakes are adders (Vipera berus) in both Scotland (470 mi away) and Norway (600 mi away), both of which are separated by a great deal of very cold ocean.
by the time snakes evolved (150 million years ago, in the late Jurassic-early Cretaceous) Ireland had separated from any other land mass, and has been connected on and off to this day. There is some debate over how recently a land bridge connected Ireland with Great Britain and, by extension, mainland Europe, with the consensus resting on the idea that Ireland was isolated by ocean by 16,000 years ago, at which time the climate was still quite cold and there was a lot more ice in Ireland than there is now. Although it's not insane to think that snakes might have colonized Ireland from Europe sometime during the 90 million years that preceded the Pleistocene Ice Ages, as they have since re-colonized Great Britain, so far no one has found any snake fossils in Ireland. But, viviparous lizards, natterjack toads, and common frogs have managed to make it to Ireland, and the slowworm has been introduced there, so it could happen one day. Likely successful colonists include adders (Vipera berus), grass snakes (Natrix natrix), or smooth snakes (Coronella austriaca) from Great Britain, France, or Scandinavia. The Irish climate is highly moderated by the gulf stream, with much milder winters than expected for such a northerly area, so snakes could do quite well there.
in a 1951 paper that, according to the authors, was an accidental introduction from Guinea-Bissau. Neither this snake nor any other has ever been recorded again from Cape Verde, although the archipelago is home to 31 endemic lizard species, more than any other island chain in the Macaronesian region.
summarized in 1997, at which time an amazing 69 records of 2 species were known, dating back to 1837 (more records and a third species have been added since). About 90% are of pelagic sea snakes (Hydrophis platurus; formerly Pelamis platurus, also known as yellow-bellied sea snakes), a very widespread species that is infamous for vagrancy and recently made headlines when one washed ashore in Ventura County, California. The remaining 10% of records are of banded sea snakes (Laticauda colubrina), a species that normally sticks more closely to shores, and judging by their morphology most of these have likely come to New Zealand from Fiji or Tonga. In 1995, one specimen in the British Museum collected in New Zealand in 1925 and formerly classified as L. colubrina was re-identified as a new species from New Caledonia, L. saintgironsi, by herpetologists revising the widespread Laticauda colubrina complex.
|Map of pelagic sea snake records from New Zealand|
From Gill 1997
New Zealand also owns the Chatham Islands 560 miles to the east, the Kermadec Islands 620 miles to the north, and Tokelau 2000 miles to the northeast3, but no sea snakes have been reported from these islands, probably because so few people live there. Like vagrant birds, even the records from mainland New Zealand surely represent just a small percentage of the total number of marine reptiles that have reached New Zealand over the years. However, New Zealand is still widely considered to have no native snakes, since H. platurus stop feeding at sea temperatures below 18°C and die at temperatures between 14.5 and 17°C (the average sea temperature in the coldest month in northern New Zealand is 16°C).
the most up-to-date and authoritative guide to the reptiles of the Pacific Islands. This guide takes a conservative approach in listing only species that are confirmed by a museum specimen or literature record, so it's possible that at least pelagic sea snakes are found in the waters of eastern Kiribati. What is certain is that the western half of Kiribati (Banaba and the Gilbert Islands) is home to breeding populations of banded sea snakes (Laticauda colubrina), and possibly pelagic sea snakes as well. Additionally, there is a single record of an ornate reef seasnake (Hydrophis ornatus), a species that is normally found much farther west, from the Gilbert Islands. This might represent a vagrant, but more likely it is a misidentified or mislabeled specimen. So, Kiribati has no terrestrial snakes, unless you count banded sea snakes, which mate, lay eggs, and sometimes digest food on land, but hunt, catch prey, and spend much of their time in the ocean.
on one of its coins! It's a commemorative coin rather than a coin that's actually part of normal circulation, but still, it's pretty cool to have a snake on your money. Tuvalu is also home to at least 9 species of lizards and the introduced cane toad, so it's possible that snakes could show up there one day. In fact, it's even possible that a native, endemic blindsnake could have escaped detection on Tuvalu (or any other Pacific island) to this day. The only reason the Federated States of Micronesia aren't on this list is because of two unexpected species of endemic blindsnakes, Ramphotyphlops adocetus and R. hatmaliyeb, described in 2012 from two small islands, one in the eastern part of FSM and the other in the western part.
Brahminy Blindsnake, the only unisexual species of snake. It's actually amazing to me that we're on the seventh entry and haven't encountered this species yet, considering how widespread it is globally. The original native range of I. braminus is unknown, but it probably evolved in continental Asia. Because a single individual constitutes a reproductively-competent population, it has since spread all over the world, and it's unclear how long it has been established on Nauru or elsewhere in the Pacific. Many similarly-widespread species in the Pacific owe their distribution to human-assisted transport, the precise timeline of which is difficult to determine. Given the harm done to Nauru's environment by phosphate mining during the 20th century, it's unlikely that any native terrestrial snake would have survived.
The Marshall Islands (see above map) have close political ties with the USA, but they are self-governing. They are located north of Kiribati, west of the FSM, and south of Wake Island. The authoritative guide to the reptiles of the Pacific Islands lists only I. braminus from the Marshall Islands, but other sources suggest that at least a few brown treesnakes (Boiga irregularis), infamously introduced to Guam, have been found there as well, and it's possible that H. platurus and possibly other sea snakes are found off its shores. Both the Gilbert Islands in Kiribati to the south and Pohnpei and Kosrae in FSM to the west have L. colubrina, although an official page states that the Marshall Islands have no sea snakes. So, as far as we know the Marshall Islands have no snakes that are native and terrestrial (unless you count I. braminus as native, considering that we don't know how long it's been there).
The Vatican is a walled enclave within the city of Rome, Italy, with an area of 110 acres and a population of 842, making it the smallest internationally-recognized independent state in the world, both by area and population. I couldn't find any references confirming or denying the presence of wild snakes in the Vatican, but other wildlife seem to be pretty minimal, which makes sense considering that Rome has been a large city for thousands of years. But, snakes and other wildlife can hang on in some amazingly urbanized places, so I wouldn't completely rule out the presence of a few of the eight species of snakes that can surely be found in the surrounding Italian countryside. Monaco, another European microstate with a very dense population and a high degree of urbanization, is another possibility for a snake-less nation, although, given Monaco's reputation as a playground for the rich and famous (30% percent of its population are millionaires), there are certainly some who meet an alternate definition of the word "snake" within its walls.
|Cover of a joke book that's blank inside|
In the course of the research I did for this post, I found many travel articles promoting the snakelessness of some of these places as overwhelmingly positive, as I'm sure it is for many ophidiophobic travelers. But, the risk that snakes pose is way, way smaller than the fear we have of them, and in my mind the real danger is that many people see eradication of snakes as a positive thing, despite the fact that many of them are in real danger of extinction. Mauritius barely made it off this list, with one of two native species extinct and the other hanging on thanks only to captive breeding and reintroduction efforts. St. Kitts & Nevis could lose its only native snake, the Saba or orange-bellied Racer (Alsophis rufiventris), and native snakes have gone extinct or become critically endangered on many other islands throughout the Pacific and Caribbean due to centuries of forest clearance, overgrazing, development, and the introduction of invasive species, not to mention the many continental snake species threatened by sprawling development and habitat fragmentation. So, please, let's keep this list from growing.
1 Given the growing popularity of herpetoculture, I'd be willing to bet that there are captive snakes in every country, although a few countries have stringent laws banning any captive snakes, including as pets as well as in zoos and research facilities.↩
2 Studies have shown that, although many Pacific birds avoid pelagic sea snakes, naive Atlantic birds will try eat them (only to throw them up, since they are apparently poisonous as well as venomous). New Zealand's birds might be sufficiently naive to try to eat one.↩
3 Zug's Reptiles and Amphibians of the Pacific Islands lists Tokelau as having no snakes, not even sea snakes, but does not cover the Chatham or Kermadec Islands.↩
4 Hawaii has introduced Brahminy Blindsnakes and, unlike many Pacific Islands, it is known that these colonized the island chain more recently, in 1930, when they were imported from the Philippines in potted palm trees. Hawaii also has pelagic sea snakes and there are a few records of introduced brown treesnakes and boa constrictors, but neither species has established a breeding population (yet).↩
5 A study evaluating the probability that pelagic sea snakes could enter the Caribbean and Atlantic through the Panama canal, as lionfish have, concluded that there were no real barriers to their colonization of the eastern side of the Americas, but so far this has not happened.↩
Thanks to Kerry Nelson for doing some of the background research for this post as part of a discussion in the Wild Snakes: Education & Discussion Facebook group.
Edwards, R. J., and A. J. Brooks. 2008. The Island of Ireland: Drowning the Myth of an Irish Land-bridge? Pages 19-34 in J. J. Davenport, D. P. Sleeman, and P. C. Woodman, editors. Mind the Gap: Postglacial Colonisation of Ireland. Special Supplement to The Irish Naturalists’ Journal <link>
Gill, B. J. 1997. Records of turtles and sea snakes in New Zealand, 1837-1996. New Zealand Journal of Marine and Freshwater Research 31:477-486 <link>
Heatwole, H., S. Busack, and H. Cogger. 2005. Geographic variation in sea kraits of the Laticauda colubrina complex (Serpentes: Elapidae: Hydrophiinae: Laticaudini). Herpetological Monographs 19:1-136 <link>
Hecht, M. K., C. Kropach, and B. M. Hecht. 1974. Distribution of the yellow-bellied sea snake, Pelamis platurus, and its significance in relation to the fossil record. Herpetologica 30:387-396 <link>
McKeown, S. 1996. A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing.
Vasconcelos, R., J. C. Brito, S. Carranza, and D. J. Harris. 2013. Review of the distribution and conservation status of the terrestrial reptiles of the Cape Verde Islands. Oryx 47:77-87 <link>
Wynn, A. H., R. P. Reynolds, D. W. Buden, M. Falanruw, and B. Lynch. 2012. The unexpected discovery of blind snakes (Serpentes: Typhlopidae) in Micronesia: two new species of Ramphotyphlops from the Caroline Islands. Zootaxa 3172:39–54 <link>
Zug, G. R. 2013. Reptiles and Amphibians of the Pacific Islands: A Comprehensive Guide. University of California Press, Berkeley, California, USA <link>
Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.