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Wednesday, June 26, 2013

What the State Snakes Should Be: Part I

The 50 United States have various state symbols, including state trees, flowers, songs, drinks, and even fossils. Just over half the states have a state reptile, and none have a state snake (although a few of the state reptiles are snakes). This post was inspired by the witty and spot-on post 'The State Birds: What They SHOULD Befrom thebirdist.com, which struck a chord with me because I've always been underwhelmed by the state birds, many of which are uncreative and absurd. The selection of state reptiles has been characterized by the same lack-of-creativity, bordering on willful ignorance of a state’s unique and endemic biodiversity, as the selection of state birds. In fact, it's probably worse, since most people can at least name several different kinds of birds whereas even distinguishing reptiles from amphibians or fishes (or worms) is apparently beyond many. Perhaps having a state snake would help remedy this problem as well as improve upon the massive and undeserved PR problem faced by snakes in general.

At the risk of catalyzing a scandal on par with my home state of North Carolina's State Fruit Fiasco of 2001, which in an effort not to alienate any of several fruit growing lobbies resulted in an official state red berry (the strawberry), state blue berry (wait for it…the blueberry), and state fruit (the scuppernong grape), I've taken the liberty of choosing a state snake for each of the 50 U. S. states, 44 of which I've been to and almost half of which I've caught snakes in. This was surprisingly hard to do, because some snakes have too many good choices and others have too few. I used the same rules as thebirdist: I didn't repeat any species. Feel free to chime in with your opinion about what your state's snake should be, if it differs from my choice.

1. Alabama. Eastern Diamond-backed Rattlesnake (Crotalus adamanteus)

Crotalus adamanteus
The Eastern Diamondback is iconic in the southeast, appearing on America's first flag, the Gadsden flag (better known as the 'Don't Tread on Me' flag) and in the first political cartoon appearing in an American newspaper (Ben Franklin's 'Join, or Die'). State symbolism of the world's largest rattlesnake might help abate pressure from rattlesnake roundups in Alabama and other states, which have caused declines so serious that this species has been considered for listing under the Endangered Species Act.

2. Alaska. Northwestern Gartersnake (Thamnophis ordinoides)

Thamnophis ordinoides
Alaska's only got one snake, and I do mean one: a road-killed juvenile gartersnake was found outside of Haines, Alaska, in August of 2005. The poor condition of the specimen prevented a positive identification based on morphology alone, so some of my colleagues including my fellow USU graduate student Lori Neuman-Lee sequenced genes from the snake and identified it as a T. ordinoides. This highly variable species eats mostly slugs. Because the closest known population of Northwestern Gartersnakes is over 600 miles south of Haines, the snake might have been transported there accidentally. However, reports of gartersnakes on the banks of the Taku and Stikine rivers in Alaska, including one ostensibly vouchered (now lost) specimen, keep the door open for future discovery of a naturally occurring population of snakes in The Last Frontier. Don't lose hope, Alaska! If nothing else, gartersnakes from British Columbia will probably disperse there eventually if climate change keeps up the way it's been going.

3. Arizona. Arizona Ridge-nosed Rattlesnake (Crotalus willardi)

Crotalus willardi
This actually is the state reptile of Arizona! Way to go, Arizona! This snake is a phenomenal choice for its beauty and uniqueness. Principally a Mexican species, it is found in scattered, isolated "Sky Island" mountain ranges separated by uncrossable desert. Former Staten Island Zoo reptile curator and herping godfather Carl Kauffeld, in his classic 1957 memoir Snakes and Snake Hunting, called this species "sublime" and said of finding one that "no greater triumph is possible". It was the last rattlesnake species discovered in the United States, in  1905 (just as the "Baby State," as it was once known, was one of the last states to enter the union, seven years after C. willardi was discovered). These small rattlesnakes grow to be only one to two feet long and as a result are relatively unthreatening. Few bites have been recorded, none serious, although I wouldn't go picking one up. Runner up: Glossy Snake (Arizona elegans), which shares its genus name with the state.

4. Arkansas. Cottonmouth (Agkistrodon piscivorus)

Agkistrodon piscivorus
When I asked my colleague Geoff Smith, a native Arkansan, about snakes iconic to Arkansas, he first informed me that, as someone born above the Arkansas River, he was an Arkansawyer rather than an Arkansan. He went on to suggest that the Cottonmouth was a good choice because every snake someone sees in Arkansas is identified as a Cottonmouth (a joke that is all too true, poor Nerodia). He also suggested some similarities between Arkansans and Cottonmouths: they stink1, they're fat, they like to eat fish. I decided not to contradict him because 1. I haven't been to Arkansas, and 2. he's from there so he can say that. In the end, we decided that a generalist state needed a generalist snake. Because Arkansas' diverse landscapes encompass the range edges of many species that are more characteristic of other places (for example, Queensnakes, Coralsnakes, and Western Diamond-backed Rattlesnakes can all be found in the state), choosing a widespread generalist is appropriate. I know of few better examples than the Cottonmouth, a denizen of river swamps that eats a variety of other vertebrates. Furthermore, Cottonmouths might have the worst PR problem of any snake: in addition to being misidentified, they suffer from exaggerated accounts of their aggression, size, breeding habits and even basking behavior ("A Water Moccasin tried to get in my boat!"). State snakehood might help with that.

5. California. Giant Gartersnake (Thamnophis gigas)

Thamnophis gigas
This largest of gartersnakes is endemic to California's Central Valley, where it historically occupied tule marshes but today persists mostly in rice fields and their associated canals and drains, where it mostly eats introduced fishes and Bullfrogs. Because of the massive agricultural use of this area, this species has lostmuch of its habitat and is on the edge of extinction, so it could use some positive PR. It is highly aquatic, with habits more similar to eastern Nerodia watersnakes than to its  western congeners - the same could be said of many Golden State residents in terms of their political opinions and attitudes.

6. Colorado. Great Plains Ratsnake (Pantherophis emoryi)

Pantherophis emoryi
Once considered a western subspecies of the Cornsnake, Great Plains Ratsnakes were re-elevated to full species status in 2002 by College of Staten Island snake taxonomist Frank Burbrink. Although Colorado's majestic landscapes are home to many beautiful snakes, not one but two geographically-separated forms of Great Plains Ratsnakes are found in the state: the larger, more brightly colored nominate subspecies in the high plains and tablelands of southeastern Colorado, and the smaller, drabber Intermountain Ratsnake (P. e. intermontanus) on the Colorado Plateau in the west-central part of the state. Originally named by Baird & Girard for surveyor and U.S. Army officer William H. Emory, these large constrictors are more subtly colored than other ratsnakes but just as harmless and beautiful.

7. Connecticut. Northern Watersnake (Nerodia sipedon)

Nerodia sipedon
Northern Watersnakes are some of the most common snakes in eastern North America. Found in almost every aquatic habitat, they are frequently seen basking on fallen logs, from which they will drop into the water at the slightest provocation. Leo Finneran reported this species from the Branford area in the 1940s, saying that it was "a very common snake occurring along water bodies in all parts of the town" and noting that some carried heavy loads of parasites, which is common in watersnakes. You can remember how to tell this species from its southern counterpart because the bands across its back fail to connect near the tail. OK, I'm stretching a bit for this one. Keep reading, it gets better.

8. Delaware. Copperhead (Agkistrodon contortrix)

Agkistrodon contortrix
Delaware was the first state, and the Copperhead is the first snake you should learn to identify if you live within its range. Delaware's Brandywine Valley is reminiscent of New England, whereas its middle and lower parts resemble the tidewater South. Both regions are inhabited by Copperheads, which are found from New York to Texas, where they are the most common venomous snakes in many suburban areas. Due to the high encounter rate, more than a third of U. S. venomous snakebites are from Copperheads. Fortunately, they seldom require antivenin, because they have the least potent venom of any North American viper, and the fatality rate is negligible. Furthermore, the vast majority occur when someone deliberately attempts to handle or kill the snake. In this way, Copperheads and their relatives are distinctly "antiwar," eponymous as they are of the vocal antebellum Democrats that once represented Delaware and other Union states in Congress.

9. Florida. Eastern Coralsnake (Micrurus fulvius)

Micrurus fulvius
Florida as a state is unlike any other U. S. state. Coralsnakes are unlike any other North American snakes - they are more closely related to cobras and sea snakes, which live on other continents or in the oceans. They're also brightly colored, like the iconic pink flamingos often seen on Sunshine State lawns. Coralsnakes spend most of their time underground and are difficult to find. When asked how to see one in the wild, most herpers reply: "Go to Florida." Although Coralsnakes are quite venomous, they are secretive and non-aggressive, so very few Coralsnake bites ever occur. Runners up: Short-tailed Snake (Lampropeltis [Stilosoma] extenuatum) or Rim Rock Crowned Snake (Tantilla oolitica), both endemic to the state.

10. Georgia. Eastern Indigo Snake (Drymarchon couperi)

Drymarchon couperi
The largest snakes in North America and literal "lords of the forest" (from the Greek drymos: forest and archos: commander), Eastern Indigo Snakes are in decline due to habitat loss and fragmentation. Georgia boasts some of the best remaining indigo habitat (both Fort Stewart and Fort Benning harbor large, unfragmented tracts of longleaf pine savanna with healthy populations of Gopher Tortoises, the actual Peach State reptile and the burrows of which these snakes depend upon) and the headquarters of the Orianne Society, a non-profit formed to help conserve indigo snakes and other rare reptiles.

11. Hawaii. Yellow-bellied Sea Snake (Pelamis platura)

Pelamis platura
This is the Aloha State's only native snake, making it a pretty easy choice. It's also awesome! Yellow-bellied Sea Snakes are the only pelagic snakes, and the most widely distributed and specialized of the sea snakes. They are most commonly seen in Hawaiian waters in El Niño years, when average water temperatures are in the upper 70s. Pelamis have fast-acting venom that they use to kill fishes. They shed their skin often to remove barnacles, using a knotting behavior to compensate for the absence of objects to brush against in the open ocean. Paying homage, a Scottish tidal energy company adopted the genus name of this snake for both their company and the offshore wave energy converter itself, although the company closed its doors in 2014.

12. Idaho. Rubber Boa (Charina bottae)

Charina bottae
I've written about Rubber Boas before, but man are they cool. Some of the best research on Rubber Boa thermal biology and behavior was conducted in southeastern Idaho, and Craters of the Moon National Monument is a great place to see them. Incredibly, these snakes are active at temperatures as low as 40°F, which is good news for them given that they live in Idaho's mountains. Roughly the same color as a potato, Rubber Boas mostly eat small mammals, which they kill by constriction similar to their larger relatives, which include Anacondas and Boa Constrictors. As is fitting for the Gem State, their small, smooth scales have a rubbery shine.

13. Illinois. Prairie Kingsnake (Lampropeltis calligaster)

Lampropeltis calligaster
Illinois, like Arkansas, contains many ecoregions but is not dominated by any one that isn't more iconic of elsewhere. There are actually more species of snakes in Illinois than in many southern and eastern states, due to its mixture of northern, southern, eastern, and western ecosystems. I lived here for a while, but it was hard to pick a snake for Illinois because its habitats are so varied. Prairie Kingsnakes are common along Illinois roads and lake shores in spring. Unfortunately, many are run over by vehicles during this time, and still more are mistaken for venomous snakes are maliciously killed. In fact, these large and harmless constrictors are highly beneficial, consuming mice and voles that would otherwise overrun farms, gardens, and homes. In the agricultural desert of the Prairie State, Prairie Kingsnakes are one species that seems to do reasonably well.

14. Indiana. Eastern Ribbonsnake (Thamnophis sauritus)

Thamnophis sauritus
The slender, long-tailed ribbonsnakes share a genus with gartersnakes, from which they are not terribly different. Ribbonsnakes show a preference for wetter habitats and eat predominantly fishes and amphibians. Indiana harbors two subspecies of Eastern Ribbonsnakes, which together are found essentially throughout the state where suitable habitat still exists. Because of the Hoosier State's intensive agricultural land use, a state snake that requires intact wetlands with healthy prey populations could encourage a shift towards sustainable agricultural practices that use minimal pesticide and fertilizer and promote healthy waterways.

15. Iowa. Western Foxsnake (Pantherophis ramspotti)

Pantherophis ramspotti
These large constrictors used to be considered the same species as Eastern Foxsnakes, Pantherophis vulpinus, but were elevated to full species status by Brian Crother and colleagues in 2011. Rapid northward expansion by Foxsnakes from refugia in various southern states following the last glacial maximum has resulted in their odd modern distribution: two species apparently separated not by the gap in the range of the eastern in Michigan but by the Mississippi River. Because they no longer occupy any of the habitat where their fossils are found, it seems that Foxsnakes simply filled in the new habitat made available by the retreat of the glaciers. They had few barriers since the glaciers flattened the topography, and few states beat the Hawkeye State for flat.

16. Kansas. Milksnake (Lampropeltis triangulum)

Lampropeltis triangulum
The Red Milksnakes of Kansas are like jewels. Essentially fancy kingsnakes, these beauties are easy to find underneath large, flat rocks in prairies and fields almost throughout the state. They eat lizards as well as small mammals and other snakes, which should be easy for them to find since they all live under the same rocks. The late herpetologist extraordinaire Henry Fitch undertook detailed natural history studies of nearly every Kansas snake during his long and productive career, publishing hundreds of articles of the highest caliber, and his 1970 paper on milksnake ecology and natural history is no exception. About as popular as a snake can get, the Red Milksnake (L. t. syspila) is an easy choice for the state snake of the Sunflower State. All those states within the range of the Scarlet Kingsnake (L. t. elapsoides) only wish they weren't also home to so many other strong contenders.

17. Kentucky. Plain-bellied Watersnake (Nerodia erythrogaster)

Nerodia erythrogaster
Common elsewhere, a threatened subspecies of Plain-bellied Watersnake, the Copper-bellied (N. e. neglecta), is found in isolated spots in the western part of the Bluegrass State, as well as in adjacent areas in Illinois and Indiana. It is the most terrestrial of the ten species of watersnakes in the US, in part because it prefers frogs and toads to the other, more aquatic prey of its congeners. Uniquely among watersnakes, this species may possess resistance to toad toxin. It has been found that, atypically for a watersnake, these snakes tend to choose hibernacula close to wetlands, such as crayfish burrows and muskrat lodges. During spring floods, they are often submerged, but somehow are not drowned or swept away. The presence of these amazing snakes helps justify wetland buffers and adjacent upland conservation as part of the innovative Copperbelly Watersnake Conservation Agreement made between coal mining companies and state environmental groups within the range of the snake, particularly in Kentucky.

18. Louisiana. Louisiana Pinesnake (Pituophis ruthveni)

Pituophis ruthveni
Notable for its large eggs and small clutch sizes, the Louisiana Pinesnake is indigenous to west-central Louisiana and eastern Texas, where it relies strongly on Baird's pocket gophers for burrows and food. The Louisiana Pinesnake is rarely seen in the wild and is considered to be one of the rarest snakes in North America. The demise of the species is due to its low fecundity coupled with the extensive loss and degradation of suitable habitat, the longleaf pine savannas of the Gulf coastal plain. Now nearly a lost cause, some positive PR could help ensure that the last fragments of longleaf pine are preserved in perpetuity, for Louisiana Pinesnakes as well as their other unique flora and fauna.

19. Maine. Smooth Greensnake (Opheodrys vernalis)

Opheodrys vernalis
Although the Pine Tree State has a reputation for being snowy and cold, it is actually replete with snakes, at least in summer along its rocky coast. In the crumbling foundations of homes in old fields live many Smooth Greensnakes, a species that is a good example of the ecosystem services that snakes provide because it eats so many insects and spiders. Only a few species of snakes eat insects, this one chief among them. Less arboreal than their rough-scaled congeners, Smooth Greensnakes are quite beautiful and most people seem to know that they are harmless. A ranger in Acadia National Park found them "common" from sea level to above 1000 feet in 1938. Smooth Greensnakes are even found on Isle au Haut, a remote island in the outer reaches of Maine's Penobscot Bay first settled by Europeans in 1792, so it is likely that this is one of the first North American snakes ever seen by Europeans. Isle au Haut is home to Microneta bowditchiae, an endemic spider, which is undoubtedly eaten by the local O. vernalis.

20. Maryland. Queensnake (Regina septemvittata)

Regina septemvittata
Named for Queen Henrietta Maria of France and crisscrossed by myriad freshwater habitats, including the cool crayfish-filled streams preferred by Queensnakes, Maryland is a beautiful but densely-populated state. From the Central Appalachians in the west to the tidal marshes and barrier islands of the Delmarva peninsula and Chesapeake Bay, Maryland seems to represent the entire gamut of eastern North American habitats. Queensnakes inhabit most of these, although they are absent from the lowest and highest elevations and from brackish water. Research has shown that Queensnakes are exquisitely sensitive to the crayfish molting hormone ecdysone. Because numerous stream contaminants are known to imitate ecdysone and disrupt the arthropod molting cycle, this finding may have important implications for the conservation of Queensnakes and their conegners.

21. Massachusetts. Red-bellied Snake (Storeria occipitomaculata)

Storeria occipitomaculata
These little slug-eaters are named for a Massachusetts herpetologist, David Humphreys Storer, who wrote Report on the fishes, reptiles and birds of Massachusetts in 1839. Being one of the original 13 colonies, Massachusetts should show a little appreciation for its herpetological history. In my experience, these snakes are more common in New England's forests than they are throughout the rest of their range, particularly in Maine, which was once a part of Massachusetts. The Bay State gets kudos for actually selecting a group of snakes as their state reptile: the genus Thamnophis, the gartersnakes, is not an inapt choice, although it is a little vague.

22. Michigan: Eastern Massasauga (Sistrurus catenatus)

Sistrurus catenatus
The Eastern Massasauga Rattlesnake has declined dramatically over the last century and is critically endangered in nearly every state where it occurs. Due to human persecution and the nearly complete conversion of native wet prairie habitats to agriculture, this formerly widespread and abundant species is seemingly relegated to just a few viable populations within its historic range in Wisconsin and Illinois. Michigan is its stronghold, and state snakehood might help keep it that way.


23. Minnesota. Plains Gartersnake (Thamnophis radix)

Thamnophis radix
These beautiful gartersnakes are common in the plains of southern Minnesota. In northwestern part of the Land of 10,000 Lakes, the prairie-forest ecotone is characterized by the westward extension of the forests, which terminate roughly along the Big Stone Moraine, from which scattered areas of relict prairie form "fingers" that extend eastward into the woodland. Both Plains and Common (T. sirtalis) Gartersnakes co-occur there, but are not usually found together in high densities, perhaps because the diets of both species consist essentially of the same items: earthworms, minnows, and frogs. Unfortunately, Minnesota's many lakes (the combined shorelines of which exceed those of California, Florida, and Hawaii combined) are too cold, young, and oligotrophic to support any endemic snakes.

24. Mississippi. Mudsnake (Farancia abacura)

Farancia abacura
The Mississippi Mudsnakes has a good ring to it. Found in swamps, which abound in the western part of Mississippi, these gorgeous snakes eat mostly giant aquatic salamanders such as sirens and amphiumas. Seldom seen, their name belies their fabulous coloration, which more than compensates for their clandestine nature. Any state in their range would be proud to honor the Mudsnake with a state snakehood. Mudsnakes prefer still, acidic waters with aquatic vegetation and bottom debris. They also occur along small, acidic streams with swampy edges. Runner up: The Mississippi Green Watersnake (Nerodia cyclopion) shares its name with the state.

25. Missouri. Lined Snake (Tropidoclonion lineatum)

Tropidoclonion lineatum
Little is known about the tiny Lined Snake, a small relative of watersnakes and gartersnakes whose scientific name is longer than it is. Little is left of their original habitat, wet prairies, now mostly converted to agriculture. Lined Snakes, often incongruously misheard as "lion snakes," are secretive and semifossorial. The Forest Park neighborhood of St. Louis, south of the zoo and near the wonderful Turtle Park, was built on a hill during the 1920s and harbors a dense population due to the relatively light disturbance to the area's soil, so many urban residents of this city and others in the Show-Me State could show themselves their state snake by turning over paving stones or garden gnomes in their yard or garden.

Stay tuned, faithful reader, for Part II!



1 Life is Short but Snakes are Long does not officially endorse the views of interviewed persons.




Creative Commons License

Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, May 28, 2013

Basics of Snake Taxonomy


A while back, medical-doctor-turned-snake-blog-post-translator-extraordinaire1 Alvaro Pemartin asked me to write an article covering basic snake taxonomy. Taxonomy is the branch of biology that deals with naming and classifying organisms. Biologists still use the Linnean hierarchical system for taxonomy, which is convenient for grouping organisms, but there is a move towards using phylogenetic systematics and the evolutionary species concept in taxonomy, particularly in the sense that recognizing and giving names to non-monophyletic groups is discouraged.2 We'll primarily stick with the Linnean system in this article, which uses particular suffixes to denote the taxonomic level (for example, all animal families end in '-idae' and all subfamilies end in '-inae'). However, I've also included some cladograms, which are the most useful figures for understanding evolutionary relationships. If you haven't read one before, you can read up on them here, here, or here, but just know that they essentially work just like a family tree.

Snake Diversity

My only criticism of this film:
not enough snakes
There are about 3,400 species of snakes in the world. All are placed in the suborder Serpentes (aka Ophidia) of the order Squamata, which also includes lizards, from which snakes evolved about 190 million years ago during the Jurassic Period. Extant (modern or living) snakes are divided into two major groups, the blindsnakes (aka threadsnakes or scolecophidians) and the advanced or true snakes (alethinophidians). Advanced snakes are also divided into two non-monophyletic groups, the "older snakes" (henophidians) and the "recent snakes" (caenophidians). The vast majority of all living snakes, about 77% or 2,650 species, are caenophidians, including most of the snakes you've probably heard of: rattlesnakes, cobras, kingsnakes, and many others. A few well-known snakes are henophidians, namely boas and pythons. Most scolecophidians are poorly known. Let's break down each of these groups in slightly more detail.

Scolecophidians

Ramphotyphlops braminus,
a parthenogenetic blindsnake
There are about 400 species of scolecophidians, divided into five families and found mostly in the tropics. They are commonly called blindsnakes, because many have vestigial eyes as a result of their fossorial lifestyle, or threadsnakes, because most are very thin. Most have unspecialized ventral scales, shed in thick rubbery rings, and have a spine at their tail tip. Many eat termites and ants. Most are probably oviparous, or egg-laying, but their reproductive biology is poorly known. Scolecophidians diverged from alethinophidians about 125 million years ago during the Cretaceous Period. You can read more about a fascinating mutualism between a blindsnake and an owl here, or about basic blindsnake biology here.


Phylogenetic tree showing currently accepted hypotheses of snake relationships. Figure from Lee et al 2007.
Thick lines are supported by both morphological and molecular studies, thin solid lines are supported
primarily by similarity of morphology, dotted lines are supported primarily by molecular analyses.




"Henophidians"

Anilius scytale
Red Pipesnake
"Henophidians" are a diverse, if species-poor, group of snakes. I mentioned earlier that they are non-monophyletic, meaning that some henophidians are more closely related to caenophidians than others, which is why the name of their group is in quotation marks. All henophidians shared a common ancestor about 98 million years ago, during the Cretaceous Period. There is some pretty major uncertainty about how henophidians are related to one another, but many taxonomies divide them into four superfamilies (which end in '-oidea' under the Linnean system). The most primitive, the Uropeltoidea, is comprised of five families (Aniliidae, Tropidophiidae, Anomochilidae, Cylindrophiidae, and Uropeltidae) that lack the ability to open their mouths very widely. These snakes have stout skulls with few lizard-like teeth, short tails, and poorly developed ventral scales. Most are viviparous, meaning that they give birth to live young, except the anomochilids, which are oviparous. There is better evidence linking the former two and latter three groups than there is for combining all five families together into a single superfamily. Also, two enigmatic species in the genus Xenophidion might belong somewhere in here.

Calabaria reinhardtii,
the Cameroon Burrowing Boa,
the only oviparous booid
The rest of the henophidians together with the caenophidians are often called the macrostomatans, because they have the ability to open their mouths (Greek: stomata) very wide and consume very large (Greek: macro) prey items. The most primitive of these are the oviparous Pythonoidea, a superfamily including true pythons (Pythonidae) as well as two small lesser-known groups respectively known as the Asian and Neotropical sunbeam snakes, the xenopeltids and the loxocemids. Pythonoids and a superficially similar but surprisingly unrelated group, the  viviparous booids (consisting of true boas and their less well-known relatives, the ungaliophine dwarf boas and the erycine sand boas),  diverged from other henophidians about 75 million years ago. Finally, the most advanced henophidians, the oviparous splitjaw snakes (aka Round Island "boas" or bolyeriids), diverged just slightly later than or around the same time as the true boas. Because the splitjaw snakes constitute only a single family and were historically considered boas, you don't usually hear them referred to as a fourth superfamily.

Caenophidians


Acrochordus granulatus
Little Filesnake
This huge group is divided into two superfamilies, called Acrochordoidea and Colubroidea. The first is small, containing only three species of Acrochordus, the filesnakes of southeast Asia and north Australia. These diverged from other caenophidians about 60 million years ago. The second is huge and there is some uncertainty about the relationships therein, although thanks to recent work by Alex Pyron and his colleagues, the picture is becoming more clear. Traditionally, colubroids have been divided into groups based on their tooth morphology: those with fixed fangs were placed into Elapidae, those with folding fangs into Viperidae, and those without fangs lumped into Colubridae. The first two of these groups have proven to be for the most part monophyletic, certain exceptions notwithstanding. However, a more nuanced and accurate view of colubroid snake taxonomy is emerging thanks to a combination of molecular tools and decades of careful work by snake morphologists. Ready for it? Here it is:

Figure from Pyron et al. 2011
These snakes are exciting! These snakes have venom, excellent color vision, and sophisticated chemosensory, prey acquisition, and antipredator abilities. Also they have spines on their hemipenes. Also they are awesome. Can you tell which group is my favorite?

Dendrelaphis punctulatus
Common Treesnake
The traditional three-family tooth-morphology arrangement of colubroids has been replaced by the seven family arrangement seen above.3 Three of those seven families include several subfamilies. The most primitive colubroids are the xenodermatids, or odd-scaled snakes, which diverged from the others about 47 mya. The snail-eating pareatids are next, a group you'll be familiar with if you've been following this blog since the beginning. Next diverged the viperids or vipers, about 35 million years ago. There are three subfamilies of vipers: the old world viperines, the widespread crotalines (or pit vipers), and the monotypic Azemiopsinae, or Fea's Viper. True colubrids are still a large group, even though many species have been removed to the "new" families. The subfamilies are large and diverse, although most lack dangerous venom (a few species notwithstanding). You can read the story of the evolution of some of the subfamilies here. There are many well-known colubrids, including ratsnakes, kingsnakes, racers, hog-nosed snakes, and many others. Homalopsids, including some that chew their food, are a small but interesting group of semi-aquatic snakes found in southeast Asia. The front-fanged elapids (including cobras and coral snakes) have retained their monophyly, and little support has been found for recognizing the sea snakes as a separate family. Finally, we have the Lamprophiidae, a new family erected to contain former colubrids that turned out to be closer relatives of elapids. Lamprophiids also represent several interesting subfamilies, including the side-stabbing atractaspines, scale-polishing psammophines, and Malagasy pseudoxyrhophiines. I think Darren Naish would agree that there's plenty of fodder for future articles in these groups.

One a closing note, some non-snakes that are commonly mistaken for snakes, primarily because they have no legs, include:
  • Legless lizards: There are several groups of legless lizards. The North American glass lizards are among the most familiar. All have external ear openings and most have eyelids. In one sense, snakes are but one very diverse group of legless lizards.
  • Amphisbaenians: These are also technically lizards, but under some older taxonomies they are referred to as a separate group of reptiles, because they have a vestigial right lung and have a unique skeletal structure.
  • Caecilians: These most primitive of amphibians have slimy skin and are found underground in the world's tropics. Many are common prey of coral snakes.
  • Eels: Elongate fishes that actually do have limbs in the form of fins. There are several groups of fishes that are all colloquially called eels, including spiny eels, fire eels, electric eels, and true eels (Anguilliformes). Some amphibians are also sometimes called eels, including amphiumas or conger eels, sirens or mud eels, and rubber eels, a kind of caecilian.
  • Worms: There are several different major groups of worms, including roundworms (nematodes), flatworms (platyhelminths), and segmented worms (annelids).
Snake taxonomy is a complicated field and there is still much disagreement among experts. I have made several oversimplifications above, so if this is your area of expertise feel free to chime in with a comment or two. I hope you're looking as forward to reading more about many of these groups as I am looking forward to writing about them.




1 His wife tells me that mediocre is actually more accurate




2 A monophyletic group is one that contains a common ancestor and all of its descendants. Examples include groups like animals, vertebrates, mammals, birds, amphibians, primates, and snakes. A non-monophyletic group is one that either omits some descendants (e.g., "reptiles", which does not include birds, or "fishes", which does not include tetrapods) or omits the common ancestor (e.g., warm-blooded vertebrates, which includes mammals and birds but not their cold-blooded common ancestor).


ACKNOWLEDGMENTS

Thanks to ptrick127, Gary Nafis, Tein-Shin Tsai, and Stephen Zozaya for use of their photos.

REFERENCES

Lee, M. S. Y., A. F. Hugall, R. Lawson, and J. D. Scanlon. 2007. Phylogeny of snakes (Serpentes): combining morphological and molecular data in likelihood, Bayesian and parsimony analyses. Systematics and Biodiversity 5:371-389 <link>

Pyron, R. A., F. Burbrink, and J. J. Wiens. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Biology 13. DOI: 10.1186/1471-2148-13-93 <link>

Pyron, R. A., F. T. Burbrink, G. R. Colli, A. N. M. de Oca, L. J. Vitt, C. A. Kuczynski, and J. J. Wiens. 2011. The phylogeny of advanced snakes (Colubroidea), with discovery of a new subfamily and comparison of support methods for likelihood trees. Molecular Phylogenetics and Evolution 58:329-342 <link>

Zaher, H., F. G. Grazziotin, J. E. Cadle, R. W. Murphy, J. C. Moura-Leite, and S. L. Bonatto. 2009. Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: A revised classification and descriptions of new taxa. Papeis Avulsos de Zoologia (Sao Paulo) 49:115-153. <link>



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Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Wednesday, May 15, 2013

Tibetan Hot-spring Snakes


Everyone likes a good soak in a hot spring now and again, but imagine spending your whole life in one! Now imagine being the size of a pencil and unable to regulate your own body temperature, and you're doing a pretty good approximation of a Tibetan Hot-spring Snake (Thermophis). These tiny snakes reach only 2.5 feet in length and are found at fewer than ten sites on the Tibetan plateau in the Himalayan Mountains of south-central China, all above 14,000 feet elevation. For comparison, that's at least as tall as Mt. Rainier in Washington, Pike's Peak in Colorado, or Mont Blanc in the Alps. To cope with the cold, hot-spring snakes inhabit marshes, rivers, and rocky areas around sulfur-free hot springs, where they eat amphibians and fishes, including the dicroglossid frog Nanorana parkeri, the minnow Schizothorax oconnori, and elongate stone loaches in the genus Triplophysa. As you can see from this video, these are highly charismatic snakes.

Frank Wall
Hot-spring Snakes were first described in 1907 by a physician and herpetologist living in India named Frank Wall. Wall received specimens of this snake sent  from Tibet by Lieutenant F. M. Bailey, who reported that local people familiar with the snake told him that it could be found within half a mile of certain hot springs at any time of the year (although he stated that they did not enter the spring water, which has since been shown to be false). Wall was impressed by the altitude at which the snakes were found, which to date is still higher than any other snake known! Wall named the snake Natrix baileyi after Bailey, and in 1953 herpetologist Edmond Malnate moved it into a newly erected genus, Thermophis, meaning "heat snake" in Greek, giving it the name is has today: Thermophis baileyi. In 2008 a second species of Thermophis was discovered which differs slightly in scale characters and body proportions. Peng Guo of Yibin University named it Thermophis zhaoermii for preeminent Chinese herpetologist Zhao Ermi.

Just how remarkable these snakes are was not fully realized until recently. In the past, analyses of evolutionary relationships were limited to comparisons of morphological characteristics (for snakes, early taxonomists primarily relied on features of the scales and of the male reproductive organs, called hemipenes, to inform their hypotheses on how snakes were related to one another). Modern advances in molecular biology have enabled taxonomists to compare genetic sequences of related organisms and discover the intricate branching pattern of the evolutionary tree of life, essentially the family tree of all life on Earth. Although molecular phylogenetics, as this branch of science is called, is not flawless, it can provide incredible insight into the ancestry of species that have no close living relatives and therefore are very unique morphologically, making them difficult to compare with other organisms. Hot-spring Snakes are in this very situation, and although to a non-specialist they look pretty much like any other snake, their evolutionary history remained a mystery until 2009, when a group of biologists led by Zhao Ermi published two papers on the evolutionary origins of Thermophis.

Thermophis baileyi
As it turns out, Hot-spring Snakes are most closely related to South American snakes called xenodontines. Xenodontinae is one of the largest subfamilies of colubrid snakes, with about 90 genera and more than 500 species known. They are primarily tropical snakes previously thought to be restricted to the Americas, and they include several well-known (and many poorly-known) species, among them the South American Hog-nosed Snakes (genus Xenodon). Similarities of hemipenal morphology had hinted at a relationship between these taxa, but who would have guessed that the closest relatives of Hot-spring Snakes lived nearly 10,000 miles away on the tropical other side of the world? Not I, for one.

Thermophis baileyi
Hot-spring Snakes probably diverged from their "nearest" relatives about 28 million years ago. Despite the strengths of molecular phylogenetics, there is still some uncertainty about the position of Thermophis relative to other colubrid snakes because their branch of the tree arises near the base of a major clade (Xenodontinae), meaning that, as suspected, they have no close living relatives. In some phylogenies, Hot-spring Snakes are clustered with the "relict snakes of North America": CarphophisContia, Diadophis, Farancia, and Heterodon. Some of my favorite snakes, these are thought to have dispersed from Asia into North America during the Miocene, about 16 million years ago. (Diligent readers will recall that I've told this story before in my post on Rainbow Snakes, although I didn't know then about the involvement of Thermophis.)

Reproduced with permission from
Story in the Stone: The Formation of a Tropical Land Bridge
by Tom Gidwitz, illustration by David Stevenson & Greg Wenzel
Probably the common ancestor of all modern colubrids (Thermophis and NA relicts included) lived in Asia more than 30 million years ago. When the Bering Land Bridge connected North America and Asia, some of these snakes dispersed eastward across it, just like the ancestors of sabre-toothed tigers, woolly mammoths, and even Tyrannosaurus rex1. These evolved into a North American snake fauna, now largely extinct except for the few aforementioned relicts, and a hugely successful South American snake fauna, which was isolated from North America for a 5 million year period during the late Miocene-early Pliocene when the Isthmus of Panama was submerged by the ocean. One reason for this disparity is that two other groups of colubrid snakes, which are today the dominant colubrids of North America, the colubrines and the natricines, dispersed from Asia to North America around the same time as the xenodontines. Apparently ancestral colubrines and natricines dispersed more slowly than xenodontines, because they didn't reach South America before it separated. Instead, they only moved into South America following the most recent closing of the Isthmus of Panama in the late Pliocene, in an event known as the Great American Biotic Interchange. The GABI was responsible for allowing toads, treefrogs, opossums, armadillos, hummingbirds, and vampire bats to colonize North America, and salamanders, pit vipers, rabbits, squirrels, raccoons, deer, and jaguars (and colubrine and natricine snakes) to colonize South America. Assuming that Thermophis are all that's left of the original Asian proto-xenodontine snake stock, this pattern explains the evolutionary and biogeographic relationships of the Hot-spring Snakes and their relatives. However, given other recent discoveries in Asia, I wouldn't rule out the future discovery of another Asian proto-xenodontine more closely related to Thermophis than to any other known snake.

One reason we know only a little about Thermophis is its high mountain habitat. Most of the mountain ranges in China run east-west, but the Hengduan Mountains, where Hot-spring Snakes are found, stretch north-south (the name "Hengduan" means "to transect" and "cut downward" in Chinese). Parallel north-south sub-ranges of the Hengduans are separated by deep river valleys through which flow the famous Three Parallel Rivers: the Nujiang (Salween), Lantsang (Mekong), and Jinshajiang (Upper Changjiang or Yangtze). Thermophis baileyi is distributed west of the Salween, whereas T. zhaoermii is distributed east of the Changjiang. Geologic uplift of the intervening region of southern Tibet has lasted for about the last 20 million years, about the same age as the divergence between the two extant species of Thermophis. It is hypothesized that refuges in the Kyi Chu/Lhasa and Yarlung Zhangbo valleys during the last glacial maximum probably allowed T. baileyi to persist in the west, alongside such glacial relicts as neo-endemic ground beetles, juniper trees, and even humans. Following the end of the last Ice Age, they dispersed to other hot spring sites, and today connectivity among these sites is maintained when male snakes make rare movements among them, probably facilitated by the rivers and streams that connect the sites. Female snakes are less likely to disperse, because the plateau's short summers necessitate highly seasonal reproduction. Whether Thermophis are oviparous or viviparous is still unknown.

Sylvia Hofmann's photo of T. baileyi
made the cover of  the
Herpetological Bulletin
in 2007
Although the advantages of living around hot springs at high altitudes, where the temperature is relatively cold, are pretty obvious, recent surveys by Ding-qi Rao found that Hot-spring Snakes also live in fields and other areas far from hot springs, suggesting that the species' ecological niche may be wider than previously thought. This is fortunate, both because the growing exploitation of geothermal energy has led to destruction and degradation of hot spring habitats, and because global climate change will likely continue to cause mountaintop habitats around the world to shrink, necessitating a shift upward in elevation by high-altitude species in order to follow their habitat. This problem has been documented for pikas and for birds and will likely affect Hot-spring Snakes too. Because the ability of mountaintop species to disperse across intervening areas to higher mountain ranges is limited, many may go extinct. Will we one day see the top of Mount Everest as the last foothold for Hot-spring Snakes? Let's hope not.



1 Not all of these dispersal events happened at the same time. Evidence suggests that the Bering Land Bridge has connected North America with Asia several times over the last seventy million years: at least once during the time of the dinosaurs, again about 55 million years ago, another 20-16 mya, and more recently both 35,000 and 22-7,000 years ago. The ancestors of the New World xenodontines probably came across 20-16 million years ago.


ACKNOWLEDGMENTS

Thanks to photographers Kai Wang, Daniel Winkler, Sylvia Hofmann, Brian McDiarmant, and Gavin Maxwell for use of their photographs, and to Tom Gidwitz, David Stevenson, and Greg Wenzel for allowing me to reproduce their artwork.
REFERENCES

Guo, P, Liu S, Feng J, He M (2008) The description of a new species of Thermophis (Serpentes: Colubridae). Sichuan Journal of Zoology 27:321 <link>

Guo, P., S. Y. Liu, S. Huang, M. He, Z. Y. Sun, J. C. Feng, and E. M. Zhao. 2009. Morphological variation in Thermophis Malnate (Serpentes: Colubridae), with an expanded description of T. zhaoermii. Zootaxa 1973:51-60 <link>

He M, Feng J, Zhao E (2010) The complete mitochondrial genome of the Sichuan hot-spring keel-back (Thermophis zhaoermii; Serpentes: Colubridae) and a mitogenomic phylogeny of the snakes. Mitochondrial DNA 21:8-18 <link>

Hofmann S (2012) Population genetic structure and geographic differentiation in the hot spring snake Thermophis baileyi (Serpentes, Colubridae): indications for glacial refuges in southern-central Tibet. Molecular Phylogenetics and Evolution 63:396-406 <link>

Hofmann S, Fritzsche P, Solhøy T, Dorge T, Miehe G (2012) Evidence of sex-biased dispersal in Thermophis baileyi inferred from microsatellite markers. Herpetologica 68:514-522 <link>

Huang S, Liu S, Guo P, Zhang Y, Zhao E (2009) What are the closest relatives of the hot-spring snakes (Colubridae, Thermophis), the relict species endemic to the Tibetan Plateau? Molecular Phylogenetics and Evolution 51:438-446 <link>

Pinou, T., S. Vicario, M. Marschner, and A. Caccone. 2004. Relict snakes of North America and their relationships within Caenophidia, using likelihood-based Bayesian methods on mitochondrial sequences. Molecular Phylogenetics and Evolution 32:563-574 <link>

Sekercioglu, C. H., S. H. Schneider, J. P. Fay, and S. R. Loarie. 2008. Climate change, elevational range shifts, and bird extinctions. Conservation Biology 22:140-150 <link>

Wall, F. 1907. Some new Asian snakes. The Journal of the Bombay Natural History Society 17:612-618 <link>

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Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Tuesday, April 30, 2013

Spider-tailed Adders


This species was brought to my attention about two years ago by a friend who, like me, was working on completing her Master's thesis at that time. In the post-script of her message, titled 'Probably the coolest thing I've learned in weeks', she wrote "PS I swear this started out as a legitimate search for information for my thesis." In addition to being a welcome distraction from my writing, the story of the Spider-tailed Horned Viper, Pseudocerastes urarachnoides, is, in my opinion, one of the most interesting recent discoveries in herpetology.

The tail in question
The first specimen of P. urarachnoides was collected in 1968 by the Second Street Expedition, mounted on behalf of Chicago's Field Museum of Natural History by a retired businessman and activist couple, William and Janice Street. The primary purpose of the expedition was to collect mammal specimens, but reptiles were also collected, including the first specimen (also known as a type specimen or holotype) of P. urarachnoides. Because only a single specimen was collected, its unusual tail morphology was thought at first to be a solfugid clinging to the tail. Solfugids (also called solpugids, camel spiders, wind scorpions, or sun spiders) are members of the same arthropod class, the Arachnida, as spiders and scorpions, although they are neither spiders nor scorpions. Upon closer examination, the Field Museum's Steven Anderson found that the tail of the snake bore a peculiar structure with an uncanny resemblance to a solfugid that could have been a tumor, congenital defect, or growth caused by a parasite. The snake was identified as Pseudocerastes persicus, the Persian Horned Viper, and entered into the Field Museum collection, where it was almost, but not quite, forgotten.

Egyptian Giant Solfugid (Galeodes arabs)
The story ended there, until 2001, when Hamid Bostanchi collected a second specimen with identical tail morphology to the first. A third specimen was later discovered in the collection of the Poisonous Animal Section of the Razi Institute in Karaj, Iran, in 2008; it had been misidentified as a Desert Horned Viper, Cerastes cerastes. Together with Anderson, who had described the first specimen, and their colleagues Haji Gholi Kami of Gorgan University and Ted Papenfuss of the Berkeley Museum of Vertebrate Zoology, they described the new species in 2006, naming it Pseudocerastes urarachnoides, from the Greek ura (tail), arachno (spider) and ides (similar to). In their paper, Bostanchi et al. described the structure of the tail, which is formed of the last pair of subcaudal scales, much enlarged, and a single enlarged dorsal scale. The elongated components are modified lateral scales. X-rays taken by the team showed that the caudal vertebrae extend well into this structure and are not deformed or modified. Bostanchi et al. also speculated that the function of the modified tail might be to augment caudal luring behavior exhibited by many vipers. By mimicking a solfugid, birds or other would-be solfugid predators could be enticed to approach within the viper's striking distance.

Behavioral observations made in 2008 of a live P. urarachnoides captured in western Iran and maintained in captivity confirm these ideas. Closed-circuit video was used to record behavior, and the results published in the Russian Journal of Herpetology by Behzad Fathinia of Razi University and his colleagues. They observed the snake, a juvenile male that regurgitated a Crested Lark, using its caudal lure to attract sparrows and baby chickens that they introduced into its enclosure. When the birds approached and pecked the tail, the snake struck and envenomated the birds, a process taking less than one half second. A bird was also found in the stomach of the paratype specimen, further evidence that this species might feed heavily on birds in the wild with the aid of its spectacular caudal lure. The tail of P. urarachnoides probably represents the most elaborate morphological caudal ornamentation known in any snake, with the possible exception of the sound-producing rattles of rattlesnakes.



Within its restricted range in the mountainous terrain of western Iran, P. urarachnoides inhabits rock crevices in the gypsum formations that comprise its hilly, arid habitat. Adaptations of the genus Pseudocerastes to desert life include supralabials (upper lip scales) with a serrated lower margin and a groove to accommodate the lower lip, which provide complete closure of the mouth and prevent sand from entering. The nostrils also have a valvular prominence to the same effect. The other two species of Pseudocerastes, P. persicus and P. fieldi, share these characteristics. These two species are sometimes combined, although differences in venom chemistry and scalation, along with the fact that their ranges are separated by the Zagros Mountains, suggest that they are probably distinct species (and they are certainly distinct morphologically from P. urarachnoides). Both overlap in range with P. urarachnoides in places.

P. urarachnoides

Two other recent and noteworthy discoveries of Old World pitvipers are worth a mention. One, Protobothrops mangshanensis, is a large and beautiful pitviper discovered in 1990 in mountainous regions in southern Hunan and reputed to be the only non-cobra capable of spitting venom. The other, Atheris matildae, discovered in 2011, is a member of an especially popular genus in the pet trade (although this could be said of many of the most beautiful vipers). The exact type locality of A. matildae, in the southern highlands of Tanzania, was concealed in order to limit collection for the pet trade. In addition, a novel strategy is being tested: A. matildae is being bred at a facility in Tanzania and the first few dozen offspring are being given away to collectors in order to reduce the market for illegally collected specimens. Whether this strategy will succeed remains to be seen, but hopefully A. matildae can be saved from the same sad fate as the Lao Newt, Roti Island Snake-necked Turtle, Chinese Leopard Gecko, coelacanth, and other species that have been overcollected almost as soon as they were described.

Atheris matildae
Protobothrops mangshanensis













Check out another amazing new snake discovery at Greg Laden's blog: once thought to be a single deadly sea snake, Enhyrina schistosa is actually two!


Update 1/16/2015: Check out this video of a P. urarachnoides actually caudal luring and catching a bird!

ACKNOWLEDGMENTS


Thanks to Heather Heinz for bringing P. urarachnoides to my attention, and to photographers and videographers Michael Kern, Behzad Fathinia, Michael & Patricia Fogden, Omid Mozaffari, and Alireza Shahrdari.

REFERENCES

Bostanchi H, Anderson SC, Kami HG, Papenfuss TJ (2006) A new species of Pseudocerastes with elaborate tail ornamentation from western Iran (Squamata: Viperidae). Proceedings of the California Academy of Sciences 57:443-450 <link>

David P, Tong H (1997) Translations of recent descriptions of Chinese pitvipers of the Trimeresurus-complex (Serpentes, Viperidae), with a key to the complex in China and adjacent areas. Smithsonian Herpetological Information Service 112:1-31 <link>

Fathinia B, Anderson SC, Rastegar-Pouyani N, Jahani H, Mohamadi H (2009) Notes on the natural history of Pseudocerastes urarachnoides (Squamata: Viperidae). Russian Journal of Herpetology 16:134-138 <link>

Fathinia B, Rastegar-Pouyani N (2010) On the Species of Pseudocerastes (Ophidia: Viperidae) in Iran. Russian Journal of Herpetology 17:275-279 <link>

Menegon M, Davenport T, Howell K (2011) Description of a new and critically endangered species of Atheris (Serpentes: Viperidae) from the Southern Highlands of Tanzania, with an overview of the country’s tree viper fauna. Zootaxa 3120:43-54 <link>

Stuart BL, Rhodin AGJ, Grismer LL, Hansel T (2006) Scientific description can imperil species. Science 312:1137 <link>



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Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Wednesday, April 10, 2013

Fea's Pitless Pitvipers


Leonardo Fea
Late one spring night in 1887 in the Kakhyen Hills of Burma, 35-year-old Italian explorer Leonardo Fea crested a karst outcrop and entered a bamboo thicket. He barely noticed the rain, because before him lay a two-foot long snake of indescribable beauty. It was shiny, dark purplish-black and marked with thin, widely-spaced neon orange bands so bright they almost  looked white. The head bore a striking symmetrical pattern of orange, gold, and black. When Fea picked the snake up, he saw that it had a plain purple belly. It appeared to be a harmless colubrid, and luckily for Fea, he wasn't bitten, so he had no opportunity to find out that it wasn't.

Fea was among the many European explorers and natural historians who were pouring into the newly-annexed nation of Burma, whose cultural roots date back to the 2nd century BCE. He collected thousands of vertebrates there for the Genoa Civic Museum, but perhaps none so unique or amazing as that snake. When Belgian-British herpetologist George Boulenger received a loan of Fea's reptiles from the museum, he declared of the single specimen "I may well say that Azemiops is the most interesting ophiological discovery made since that of Dinodipsas [Causus]1". Boulenger described it as a new genus and species in his 1888 report on Fea's expedition, writing "it affords me great pleasure to connect with [this snake] the name of the courageous and highly successful explorer to whom science is indebted for this and so many other additions." Azemiops feae was the first species named for Fea, who was soon to also receive the honors of an eponymous petrel, tree rat, and muntjac, collected with his "untiring zeal" in southeast Asia and the Cape Verde islands.

Azemiops feae. Notice the enlarged head scales
and the absence of a heat-sensing facial pit.
The enigmatic “pitless pitviper,” Azemiops feae or Fea's Viper looks almost nothing like other vipers, with its elliptical head, enlarged head scales, and smooth dorsal scales. In fact, it is so unusual that at times it has been classified as an elapid or a colubrid instead, of which its enlarged head scales in particular are reminiscent. Morphological and molecular evidence point to an ancient relationship between Fea's viper and other old world vipers ("viperines"), which last shared a common ancestor over 56 million years ago. Rather, Fea's viper is more closely related to the crotaline vipers, or "pit vipers", a predominantly New World clade that includes rattlesnakes, copperheads, and bushmasters (although even from these it is distinct, having diverged over 32 million years ago). Although there are a few other Asian crotalines, such as Hypnale and Trimeresurus, even these are more closely related to their New World counterparts than they are to Fea's viper, all sharing an infrared-sensitive facial pit. Indeed, Azemiops occupies a lonely branch of the snake family tree.

We know a little of the natural history of Fea's viper. It is found primarily in karst systems in the tropical uplands of northern Burma, northern Vietnam, and south-central China. Adults are active predominantly during cool, rainy summer nights, when they move slowly through deep leaf-litter in bamboo and tree fern thickets interspersed with well-lit clearings. They spend much of their lives in the holes and crevices of karst outcrops and in open and underground streams. Juveniles are most active on cool, wet fall nights. Like other vipers, Fea's viper hibernates in winter, so presumably they are fairly predictable in space and time when entering and leaving their hibernacula. Only a few prey items have been recorded, all of which have been rodents and shrews abundant in karst outcrops associated with swift mountain streams, although these snakes will also eat geckos in captivity.

This specimen's head shows more than the usual amount
of white. In preservative, the head turns completely white,
causing some to call them "White-headed Vipers".
Fea's vipers are rare and difficult to keep in captivity. In 1986, the price list for Scales & Tails Trading Company in Hong Kong offered five Azemiops feae as "White Head Vipers" for $300 a piece, the most expensive item on the list. Observations of captive individuals indicate that these snakes do not tolerate dry conditions, and develop skin problems when maintained at less than 100% humidity. Ideal temperatures are between 60 and 68°F, surprisingly cool for a reptile (but a little warmer than those preferred by Rubber Boas). In the words of one reptile keeper, they are "so boring & difficult to keep" that he sent his off to a zoo. If widely held, this sentiment may actually bode well for Fea's vipers if it renders them unlikely to become overcollected for the pet trade, especially if the low demand can be met by captive breeding. Mating behavior involves courtship of females by males and is similar to that of other vipers in most respects. Fea's vipers lay small clutches of eggs, a characteristic they share with most viperines but not their closer relatives, the crotalines.

Plate from Boulenger's 1888 Account of the Reptilia obtained in Burma,
north of Tenasserim, by M. L. Fea, of the Genova Civic Museum
Skull of a Fea's Viper, showing the solenoglyphous fang,
the definitive viper characteristic.
How dangerous are Fea's vipers? Few bites have been reported, but these are described as "mild", causing few serious consequences. There are similarities between Fea's viper venom and that of viperines, especially Wagler's Temple Viper, except that Azemiops venom has no blood clotting, hemorrhagic, or muscle-destroying activity. The venom gland itself is similar to a viperine's, but Fea's viper fangs possess a ridge at the tip and a blade on the back seen only in some opisthoglyphous and atractaspid snakes. One venom component, dubbed azemiopsin, has been identified as a potential model in neurotransmitter research, adding to the pharmacopoeia of medicinally-useful compounds found in snake venom. Although discovered 125 years ago, Fea's viper has much still to teach us about evolution, neurology, and much else. Let us hope we can learn from it.




1 The genus Causus consists of six species of viper from sub-Saharan Africa commonly known as night adders. Night adders were once considered the most primitive vipers due to their round pupils and enlarged head scales, which is why Boulenger found them remarkable. They are oviparous and are now known to be more closely related to viperines than to Azemiops and crotaline vipers. Look out for an article on them up here one day!


ACKNOWLEDGMENTS

Thanks to Gernot Vogel, David Nixon, and Michael and Patricia Fogden for use of their photographs.

REFERENCES

Andreone, F. 2000. Herpetological observations on Cape Verde: a tribute to the Italian naturalist Leonardo Fea, with complimentary notes on Macroscincus coctei (Duméril & Bibron, 1839) (Squamata: Scincidae). Herpetozoa 13:15-26

Boulenger, G. A. 1888. An account of the Reptilia obtained in Burma, north of Tenasserim, by M. L. Fea, of the Genova Civic Museum. Annali del museo civico di storia naturale di Genova, Seria 2 6:593-604

Fry BG, Wuster W, Ryan Ramjan SF, Jackson T, Martelli P, Kini RM, 2003. Analysis of Colubroidea snake venoms by liquid chromatography with mass spectrometry: evolutionary and toxinological implications. Rapid Commun Mass Spectrom 17:2047-2062 <link>

Kardong, K. V. 1986. Observations on live Azemiops feae, Fea's Viper. Herpetological Review 17:81-82

Liem, K., H. Marx, and G. B. Rabb. 1971. The viperid snake Azemiops: its comparative cephalic anatomy and phylogenetic position in relation to Viperinae and Crotalinae. Fieldiana: Zoology 34:189-196

Mebs, D., U. Kuch, and J. Meier. 1994. Studies on venom and venom apparatus of Fea's viper Azemiops feae. Toxicon 32:1275-1278 <link>

Orlov N, Ananjeva N, Khalikov R (2002) Natural history of pitvipers in eastern and southeastern Asia. In: Schuett GW, Höggren M, Douglas ME, Greene HW (eds) Biology of the Vipers. Eagle Mountain Publishers, Eagle Mountain, UT, pp 345-360 <link>

Utkin, Y. N., C. Weise, I. E. Kasheverov, T. V. Andreeva, E. V. Kryukova, M. N. Zhmak, V. G. Starkov, N. A. Hoang, D. Bertrand, J. Ramerstorfer, W. Sieghart, A. J. Thompson, S. C. R. Lummis, and V. I. Tsetlin. 2012. Azemiopsin from Azemiops feae viper venom, a novel polypeptide ligand of nicotinic acetylcholine receptor. Journal of Biological Chemistry 287:27079-27086 <link>

Wüster, W., L. Peppin, C. Pook, and D. Walker. 2008. A nesting of vipers: Phylogeny and historical biogeography of the Viperidae (Squamata: Serpentes). Molecular Phylogenetics and Evolution 49:445-459 <link>

Zhao, E.-M. and G. Zhao. 1981. Notes on Fea's Viper (Azemiops feae Boulenger) from China. Acta Herpetologica Sinica 5:66-71


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Life is Short, but Snakes are Long by Andrew M. Durso is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.