Galápagos Racers: answers to your questions about the BBC Planet Earth II iguana chase scene

This post will soon become available in Spanish

Galápagos Racers (Pseudalsophis occidentalis)
on Fernandina Island, from the BBC's Planet Earth II footage

If you haven't seen the incredible footage of the "iguana chase scene" from the BBC's Planet Earth II Islands episode, I encourage you to watch it right away. In addition to being a highly dramatic cinematographic masterpiece, it raises a number of interesting questions about the biology of the snakes in the clip. For a few days after it aired, the Internet was buzzing with these questions, and I've cataloged the answers to some of the most popular ones below. If you have one that isn't listed, feel free to ask it in the comments! And, if you want to know more about the process I used to dig up some of this information, check out my tutorial for teaching oneself about obscure snakes.

What kind of snakes are they?

Throughout the clip, Attenborough calls them "racer snakes"¹, but herpetologists would normally call the snakes on the screen Galápagos Racers. Although these snakes are called "racers", they're not closely related to North American racers (genus Coluber); it's been about 45 million years since these two snakes last shared a common ancestor.

Galápagos Racers belong to the genus Pseudalsophis. Depending on which sources you consult, there are between 4 and 7 species of Pseudalsophis in the Galápagos, as well as one in mainland South America.

Pseudalsophis slevini eating a gecko on Pinzón Island

Just like Galápagos tortoises, finches, and many other organisms, there are different species of Galápagos Racers on the different Galápagos Islands (one of the concepts that sparked Darwin's theory of evolution by natural selection). The film was made on Fernandina, the youngest, westernmost, and most volcanically-active island in the Galápagos. Fernandina has two species of snakes, Pseudalsophis slevini and Pseudalsophis occidentalis. The snakes in the film must be Pseudalsophis occidentalis, because they are too large and not boldly banded enough to be P. slevini. You can read the original descriptions of both species here.

None of the sources reporting which species is shown in the film are authoritative, but without exception when the species is given it is given as Pseudalsophis biserialis. This is not correct under any modern taxonomy, although there is also a good explanation for why it is mistakenly being used—P. occidentalis was briefly a subspecies of P. biserialis, but has mostly been and is now treated either as a subspecies of P. dorsalis or as its own species. See below for much more (probably too much) detail.

Why are there so many of them?

Galápagos Racer (P. dorsalis) among adult Marine Iguanas
on Santa Cruz, which are much too large for it to eat

Most snakes are not social, and because they must swallow their food whole they cannot share prey. These snakes are not found at such high densities year-round, but rather aggregate around consistent Marine Iguana nesting sites in May when the eggs are hatching.

Just as when baby sea turtles emerge from their nests, predators congregate at the temporary buffet, returning afterwards to their usual densities. Around the world, there are numerous examples of avian and snake predators exploiting emerging hatchling iguanas. Researchers working at other iguana nesting sites in the Bahamas, the West Indies, and Venezuela have hypothesized that snakes and other predators also converge on the nesting sites of these other iguanas to exploit the temporary food source. Another example of snakes congregating around abundant prey resources is that of Puerto Rican and Cuban boas, which aggregate around the openings of massive bat caves.

The rest of the year, Galápagos Racers eat lava lizards, geckos, insects, marine fishes, and hatchling birds, as well as introduced rats and mice.

Are they really hunting in a pack?

Almost certainly not. Again, most snakes are not social, and because they must swallow their food whole they cannot share prey. Pack-hunting behavior is unknown in snakes.

Two P. occidentalis trying to eat the same iguana
Jaw-walking is a fixed action pattern in snakes and they
may eat things that only vaguely resemble their food
once they start jaw-walking them.
From Planet Earth II Behind the Scenes

Some species have surprisingly social behaviors. It would be really interesting to examine social behavior in these snakes. To my knowledge no one has done so. Although they obviously cannot share a single food item, but if they are foraging in the same time and place on a limited resource, there might be an opportunity for the evolution of social cues. At least one paper suggested that this might be the case with a pit viper. Even though the BBC videographers saw snakes actively fighting over the same prey items and in some cases eating one another, it's possible that more closely-related snakes are less likely to fight over food or eat one another, or that males are less likely to compete with or try to eat females. These are testable hypotheses. However, these are not well-studied snakes. I don't think they are helping each other, but there's a lot that we don't know about snakes. Some snakes exhibit dominance hierarchies, and one study suggested that individual recognition occurs and persists over time in gartersnakes.

Few scientists are currently studying these snakes. It's a testament to the BBC that they are consistently able to film natural phenomena that are still unknown to science. Hopefully this tape will stimulate some research on this exact question, and on the ecology of Galápagos Racers. When I wrote about Galápagos Racers in 2013, not much was known about their ecology, and that's still the case. It's amazing that so little research has been done on these snakes, particularly in contrast to Galápagos tortoises and marine iguanas (not to mention finches and other non-avian reptiles).

Why don't the female Marine Iguanas just lay their eggs somewhere else, closer to the ocean maybe?

Fates of rock iguana hatchlings, over half of which were
eaten by Cubophis and Epicrates snake predators in their
first month of life. From Knapp et al. 2010

Marine Iguanas have to dig nests and lay their eggs in soft sand, away from the rocky, tidal foraging grounds of the adults. They choose protected lava reefs for this purpose, which are in short supply on most islands. One estimate suggested that the cost of migrating to their nesting sites represented half the reproductive effort of female Galápagos land iguanas.

Many species of reptiles nest in areas where they otherwise do not spend much time, especially aquatic species (reptile eggs need to "breathe" air and cannot be laid underwater). Female Marine Iguanas may all use the same nesting sites because those are the only sites available, or they may choose to nest near one another because, just like with sea turtles, synchronous hatching of the young increases their probability of survival.

In a study of Bahamian rock iguanas (Cyclura cychlura), snake predation was the most likely cause of mortality for newborn iguanas dispersing away from their nests. They estimated that about 20-30% of hatchling iguanas survived their first month, and those that moved quickly and linearly away from their nests were the most likely to survive, perhaps because predators had learned to hang around the nesting area. Another study of Galápagos land iguanas showed that predation attempts by Galápagos hawks were more than three times as likely to be successful when the body temperature of the iguana hatchlings was below 90°F. And, baby Galápagos marine iguanas that hung around their hatching area had about a 10% lower survival rate than those that moved to the coast, which the researchers attribute mostly to higher risk of predation at the nesting area.

Studies on the population biology of Marine Iguanas have shown that most of their mortality is caused by "predation, starvation (sometimes as a result of being trapped by a rock), crushing by a rock, being beaten against rocks by the sea, and suffocation in collapsed nest burrows. Animals may also die after being swept out to sea by offshore currents". So, actually, predation may be the best way for them to go. Besides Galápagos Racers, their other predators include Galápagos Hawks, Short-eared Owls, crabs, and Giant Hawk-fish.

Are they venomous/dangerous to humans?

No. Like many snakes, Galápagos Racers are rear-fanged. This means that, although technically they are venomous, they don't pose a danger to humans. Rear-fanged snakes mostly have grooved teeth (rather than hollow fangs) on the back of their upper jaw (as opposed to the front); they can use these teeth to get venom into their prey once they are biting it, but they cannot strike out and deliver venom the way a viper can. A small minority of rear-fanged snakes have delivered medically-significant bites to humans, but almost all of these take place in a captive setting. You can read more about the different types of snake fangs here.

I didn't know there were snakes in the Galápagos. How did they get there?

Map showing the estimated age of each of the
Galápagos Islands. From Ali & Aitchison 2014

Galápagos Racers colonized the Galápagos Islands from mainland South America, just like all of the other Galápagos fauna and flora. The modern Galápagos Islands formed from volcanoes over the past 4 to 5 million years, although some of them have been building beneath the ocean surface for up to 15 million years. It is thought that there have been islands in the Galápagos for at least 8 million years, but the oldest islands have eroded and are now back beneath the ocean surface.

Because the Galápagos Islands are located only six hundred miles off the coast of Ecuador, it is easier for them to be colonized by plants and animals from the mainland than for a more remote island chain such as Hawaii (which is >2,500 miles away from the nearest snake-inhabited landmass).

Molecular dating of the divergence time between Galápagos Racers and their closest mainland relative, Pseudalsophis elegans, suggests that it has been about 15 million years since they last shared a common ancestor. This suggests that the mainland ancestor of Galápagos Racers probably went extinct sometime over the last 15 million years, and that the ancestors of Galápagos Racers probably colonized the Galápagos Islands before any of the current islands existed (as is also the case for the Marine Iguanas). Until genetic work is done, we won't know how many times snakes colonized the Galápagos archipelago or how many distinct lineages there are. [Edit 12/30/2016: I have recently learned that Massey University ecologist Luis Ortiz-Catedral and his colleagues are working to understand the evolution of all the species in the genus Pseudalsophis and definitively answer this question.]

Could the film have been staged?

Obviously the scenes are spliced together, but in my opinion there's no chance the Galápagos National Park would allow something like this to be staged. They are among the strictest places in the world for researchers to conduct scientific work. However, more recent episodes of Planet Earth II have been criticized for incorporating fake sound effects.

I want more detail on the complicated taxonomic history of these snakes (said almost no one ever).

One of the few phylogenies to include Galápagos Racers

From Pyron et al. 2013

Broadly, Pseudalsophis is nested within a large clade of Caribbean, Central, and South American xenodontine snakes including, among numerous others, the genus Alsophis, which once contained Galápagos Racers and after which their current genus is named. They have been in a variety of genera since their description, especially Dromicus, which is no longer in use, from 1876 to 1997.

In 1973, herpetologist Charles Myers wrote: "The classification of colubrid snakes in general, and of South American colubrids in particular, is in a notoriously unsatisfactory state." Unfortunately, we are not that much better off today when it comes to Galápagos Racers. It seems pretty clear that the nearest relative of P. biserialis, P. dorsalis, and P. occidentalis is Pseudalsophis elegans, the only species in the genus found on the mainland (in Ecuador, Peru, and extreme northern Chile). Beyond that, there isn't a lot of clarity about their next-closest relatives. They are possibly most closely related to obscure South American "groundsnakes" in the genus Psomophis, or to the even more obscure genus Saphenophis, which was described by Myers as "quite lacking in peculiar or unique features" and so named "in allusion to one incontrovertible fact about these snakes...from the Greek saphenes (evident truth, clear) + ophis (a serpent), meaning 'clearly a snake'". We don't really have a great hypothesis about how the different lineages of Galápagos Racers are related to one another, or even if they are all descended from a single common ancestor, because we only have DNA from one of them so far.

Hypothesized scenario for the evolution of Pseudalsophis snakes
So far, we have no DNA evidence that would support or refute this model
From Ali & Aitchison 2014

Two reviews based on morphology addressed this question in the late 1990s. The first (Thomas 1997) focused exclusively on Galápagos Racers and suggested that P. biserialis, P. dorsalis, and P. occidentalis are descended from a shared common ancestor with P. elegans, but that P. hoodensis is more closely related to the mainland species Philodryas chammissonis, and that P. slevini and P. steindachneri are most closely related to Caribbean species. The other study (Zaher 1999), which looked at hemipene morphology over a much larger group of snakes, disagreed, finding a shared derived character—an inflated papillate ridge, placed far medially, on the medial surface of the lobes—linking the Galápagos Racers together with the mainland species P. elegans. Statements that Galápagos Racers have “very similar hemipenes” notwithstanding, Zaher was criticized for not describing the specific characters uniting the Galápagos species to the exclusion of others.

Maglio (1970) noted that the tooth counts and arrangement and the and shape of the premaxilla bone was most similar among the three Galápagos species that he examined (P. biserialis, P. dorsalis, and P. slevini), and different from the West Indian species that Taylor later suggested are P. slevini's closest relatives. More recently, a study led by Grazziotin claimed that they "unequivocally support...Zaher's (1999) hypothesis based on morphology that continental Pseudalsophis elegans is closely related to the Galápagos Island species of Xenodontinae (herein represented by Pseudalsophis dorsalis), rather than to West Indian Alsophis and Antillophis, and mainland Philodryas (Thomas, 1997)." However, they obviously didn't read Thomas's paper very carefully, because he also hypothesizes that P. dorsalis is closely related to P. elegans, and the Grazziotin paper didn't sequence any DNA from P. slevini, P. steindachneri, or P. hoodensis, and therefore didn't test any hypotheses about them.

As for whether or not the snakes in Planet Earth II should be called P. occidentalis or P. dorsalis occidentalis, that's really a lumper/splitter question. But, both the IUCN and the 2014 edition of Snakes of the World recognize P. occidentalis as a full species; it was originally described as such by Van Denburgh in 1912, sunk to a subspecies of P. dorsalis by Mertens in 1960, and re-elevated to a full species in a 1999 paper by Zaher that was not primarily concerned with taxonomy and appears to have subsequently been neglected. The Reptile Database is currently a holdout for the subspecies designation, which has not been disputed but which is also not explicitly supported by unambiguous data. Perhaps wisely, the official webpage of Galápagos National Park chooses not to use scientific names and refers to the Fernandina racers as the "western subspecies". The truth is that, until more research is done, we won't be able to settle on an accurate taxonomy for these snakes.

---

1 This sounds a bit redundant to a snake biologist, but it isn't incorrect. The one thing that I wish BBC programs would do is identify the species in them more precisely. I'm advocating for a "biologist mode" that can be activated which would show the location and identity of species in all clips, similar to the old MTV show Pop-up Video.^↩

ACKNOWLEDGMENTS

Thanks to Andy Kraemer and Jim Moulton for the use of their photographs.

REFERENCES

Ali, J. R. and J. C. Aitchison. 2014. Exploring the combined role of eustasy and oceanic island thermal subsidence in shaping biodiversity on the Galápagos. Journal of Biogeography 41:1227-1241 <full-text>

Bisconti, M., W. Landini, G. Bianucci, G. Cantalamessa, G. Carnevale, L. Ragaini, and G. Valleri. 2001. Biogeographic relationships of the Galapagos terrestrial biota: parsimony analyses of endemicity based on reptiles, land birds and Scalesia land plants. Journal of Biogeography 28:495-510 <full-text>

Carpenter, C. C. 1966. The marine iguana of the Galapagos Islands, its behavior and ecology. Proceedings of the California Academy of Sciences (Series 4) 34:329-376 <full-text>

Carpenter, C. C. 1984. Dominance in snakes. Special Publication, University of Kansas Museum of Natural History 10:195-202 <full-text>

Christian, K. A. and C. R. Tracy. 1981. The effect of the thermal environment on the ability of hatchling Galapagos land iguanas to avoid predation during dispersal. Oecologia 49:218-223 <abstract>

Geist, D., H. Snell, H. Snell, C. Goddard, and M. Kurz. 2014. A paleogeographic model of the Galápagos Islands and biogeographical and evolutionary implications. The Galápagos: a natural laboratory for the Earth Sciences. American Geophysical Union, Washington DC, USA:145-166 <full-text>

Grazziotin, F. G., H. Zaher, R. W. Murphy, G. Scrocchi, M. A. Benavides, Y.-P. Zhang, and S. L. Bonattoh. 2012. Molecular phylogeny of the New World Dipsadidae (Serpentes: Colubroidea): a reappraisal. Cladistics 28:437-459 <full-text>

Grehan, J. 2001. Biogeography and evolution of the Galápagos: integration of the biological and geological evidence. Biological Journal of the Linnean Society 74:267-287 <full-text>

Günther, A. 1860. On a new snake from the Galápagos islands. The Annals and Magazine of Natural History 3:78-79 <full-text>

Hedges, S. B., A. Couloux, and N. Vidal. 2009. Molecular phylogeny, classification, and biogeography of West Indian racer snakes of the Tribe Alsophiini (Squamata, Dipsadidae, Xenodontinae). Zootaxa 2067:1-28 <full-text>

Knapp, C. R., S. Alvarez-Clare, and C. Perez-Heydrich. 2010. The influence of landscape heterogeneity and dispersal on survival of neonate insular iguanas. Copeia 2010:62-70 <full-text>

Laurie, W. and D. Brown. 1990. Population biology of marine iguanas (Amblyrhynchus cristatus). II. Changes in annual survival rates and the effects of size, sex, age and fecundity in a population crash. Journal of Animal Ecology 59:529-544 <full-text>

Maglio, V. J. 1970. West Indian xenodontine colubrid snakes: their probable origin, phylogeny, and zoogeography. Bulletin of the Museum of Comparative Zoology 141:1-54 <full-text>

Merlen, G. and R. A. Thomas. 2013. A Galapagos ectothermic terrestrial snake gambles a potential chilly bath for a protein-rich dish of fish. Herpetological Review 44:415-417 <full-text>

Mertens, R. 1960. Über die schlangen der Galápagos. Senckenbergiana Biologica 41:133-141 <not available online>

Myers, C. W. 1973. A new genus for Andean snakes related to Lygophis boursieri and a new species (Colubridae). American Museum Novitates 2522 <full-text>

Parent, C. E., A. Caccone, and K. Petren. 2008. Colonization and diversification of Galápagos terrestrial fauna: a phylogenetic and biogeographical synthesis. Philosophical Transactions of the Royal Society B: Biological Sciences 363:3347-3361 <full-text>

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 Evolutionary Biology 13:93 <full-text>

Pyron, R. A., J. Guayasamin, N. Peñafiel, L. Bustamante, and A. Arteaga. 2015. Systematics of Nothopsini (Serpentes, Dipsadidae), with a new species of Synophis from the Pacific Andean slopes of southwestern Ecuador. ZooKeys 541:109-147 <full-text>

Radder, R. S. and R. Shine. 2007. Why do female lizards lay their eggs in communal nests? Journal of Animal Ecology 76:881-887 <full-text>

Rassmann, K. 1997. Evolutionary age of the Galápagos iguanas predates the age of the present Galápagos Islands. Molecular Phylogenetics and Evolution 7:158-172 <full-text>

Rodríguez-Durán, A. 1996. Foraging ecology of the Puerto Rican boa (Epicrates inornatus): bat predation, carrion feeding, and piracy. Journal of Herpetology 30:533-536<full-text>

Shine, R., L. X. Sun, M. Fitzgerald, and M. Kearney. 2002. Accidental altruism in insular pit-vipers (Gloydius shedaoensis, Viperidae). Evolutionary Ecology 16:541-548 <full-text>

Steindachner, F. 1876. Die schlangen und eidechsen der Galapagos-inseln. Zoologisch-botanischen Gesellschaft, Wien, Germany <Google book>

Swash, A. and R. Still. 2000. Birds, Mammals and Reptiles of the Galapagos Islands. Pica Press <Amazon>

Thomas, R. 1997. Galapagos terrestrial snakes: biogeography and systematics. Herpetological Natural History 5:19-40 <full-text>

Van Denburgh, J. 1912. Expedition of the California Academy of Sciences to the Galápagos Islands, 1905-1906. IV. The snakes of the Galapagos Islands. Proceedings of the California Academy of Sciences (Series 4) 1:323-374 <full-text>

Wallach, V. W., Kenneth J. and J. Boundy. 2014. Snakes of the World: A Catalogue of Living and Extinct Species. CRC Press, Boca Raton, Florida, USA <Google book>

Weinstein, S. A., D. A. Warrell, J. White, and D. E. Keyler. 2011. "Venomous" Bites from Non-Venomous Snakes: A Critical Analysis of Risk and Management of "Colubrid" Snake Bites. Elsevier, Amsterdam <Google book>

Werner, D. I. 1983. Reproduction in the iguana Conolophus subcristatus on Fernandina Island, Galapagos: clutch size and migration costs. American Naturalist 121:757-775 <abstract>

Yeager, C. P. and G. M. Burghardt. 1991. Effect of food competition on aggregation: evidence for social recognition in the plains garter snake (Thamnophis radix). Journal of Comparative Psychology 105:380-386 <abstract>

Zaher, H. 1999. Hemipenial morphology of the South American xenodontine snakes, with a proposal for a monophyletic Xenodontinae and a reappraisal of colubroid hemipenes. Bulletin of the American Museum of Natural History 240:1-168 <full-text>

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 <full-text>

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

The 9,999th Reptile

Click here to view this post in Spanish
Haga clic aquí para ver este mensaje en Español

Number of new snake species by decade, with highlights
Data from The Reptile Database

Linnaeus's 1758 Systema Naturae, the starting point of zoological nomenclature, described 118 species of reptiles, including 74 snakes (not counting the limbless lizards and amphibians he included in the same group). It took over 100 years for the number of described species of snakes to reach 1000, an event that probably passed without much notice amid the American Civil War. Since that time, new snake species descriptions have been added at the rate of about 15 a year, although molecular taxonomy has increased this pace over the last few decades. The trends for snakes and for reptiles as a whole have been similar, and on July 9th, 2014, a team of American, German, Lao, and Vietnamese scientists described a new species of gecko from Laos, which the journal Herpetological Review reported as the 10,000th reptile species. Needless to say, I was excited, but I was also extremely disappointed because I had been so hoping that it would be a snake! Rather than admit defeat and scrap this planned post, I emailed Peter Uetz at The Reptile Database, an incredible resource that I've praised before, to confirm that this gecko was indeed #10,000. As usual for taxonomy and as I should have suspected, the reality was a bit more complicated.

Although Cyrtodactylus vilaphongi was the 10,000th reptile species for a while, the order and position of entries in The Reptile Database is constantly changing. Although new species get added to the end of the list, it's common for two or more existing species to get synonymized or merged, which moves the position of all subsequent species up. Furthermore, sometimes species that were described long ago and subsequently synonymized are revalidated, leading to 'new' species that aren't really new in the sense that they have existed before. Finally, often existing species get split up, leading to additions that aren't as dramatic as legitimate new discoveries. This last complication is on the rise now that molecular systematics has enabled us to describe the cryptic diversity of some lineages, which are not all that morphologically distinct but may contain considerable genetic diversity.

At the time of my email to Peter last month, C. vilaphongi was the 9988th species, and (happily), a new snake, Siphlophis ayauma, was #10,000. Although this has probably changed again by now, I'm going to operate under the assumption that, since we can't really say with certainty that any particular species was #10,000, if it was a snake, it was probably one of the 11 brand new snake species that have been described so far this year. You can read about many of these on the blog 'Species New to Science', but I'm going to highlight them in a little more detail here.

Rhabdophis guangdongensis
From Zhu et al. 2014

The first new snake described this year, Rhabdophis guangdongensis, was collected by a team of Chinese herpetologists in Guangdong Province in 2008. The reason it wasn't described until the February 20th issue of the journal Zootaxa is because, as is often the case, it takes a couple of years to compare both the anatomy and the DNA of a suspected new species to reference specimens of known similar species and establish that the species really is new. In the past, particularly prior to the internet, the difficulty of doing this was a huge problem, resulting in close to half of all 'new' species later being invalidated as duplicates. The genus Rhabdophis  is distributed in southern and eastern Asia, and this is the 21st species. It's an extremely interesting genus from a chemical ecology perspective, because at least one species sequesters defensive chemicals from its prey and provisions them to its young (which I wrote about for Scientific American shortly after I started this blog). A recent paper by Yosuke Kojima and Akira Mori on the Japanese species R. tigrinus showed that females periodically leave wetlands for forest streams where they forage on toads, likely to obtain the necessary toxins for provisioning their offspring. The new species also has specialized structures, known as nuchal glands, on the back of its neck, so presumably it stores bufotoxins there as well, although this has yet to be verified.

Opisthotropis durandi
From Teynié et al. 2014

On March 3rd, a team of French, German, and Vietnamese scientists published a description of Opisthotropis durandi, a highly aquatic snake collected from the base of a waterfall in northern Laos. This is the seventh species of Opisthotropis described in the past 20 years, and the first from Laos (although other species are likely to occur there based on their occurrence in surrounding countries). Like the new Rhabdophis, it is also the 21st species in its genus. It is important to realize that, like most species new to science, this snake was already known by local people. It is called Ngou Koung or Ngou Kung, meaning “shrimp snake”, suggesting that it may eat shrimp. The pools at the base of the waterfall where the first specimen was found contained many small shrimp.

Eutrachelophis bassleri and its weird penis
From Myers & McDowell 2014
A color photo of E. bassleri was published in Echevarría & Venegas 2015

Harvey Bassler, a petroleum geologist, explored many of the Amazon's upper tributaries for his work during the 1920s and 30s, during which time he collected over 4,200 snakes on the side. Bassler deposited his magnificent collection in the American Museum of Natural History in 1934, and on March 6th this year Charles Myers and Samuel McDowell published a monograph in the Bulletin of the American Museum of Natural History describing a species of snake collected by Bassler in 1927, for which they erected a new genus, Eutrachelophis (‘beautiful-necked snakes’’). They also placed in this genus a species originally described by Boulenger in 1905, Rhadinaea steinbachi, which they renamed Eutrachelophis steinbachi. Although the two species (and a third, yet undescribed) have very similar skeletons, muscles, glands, viscera, and markings, they probably would have been placed in separate genera had they been described in the 19th or early 20th century because their hemipenes are so different. E. steinbachi has long but relatively normal-looking hemipenes, whereas E. bassleri  has extremely unusual heimpenes tipped with a dome-like structure so strange (at least within the world of snake hemipenes) that the authors wrote "we have seen nothing quite like [it]." Hemipenes were traditionally considered one of the most taxonomically-important structures in snakes¹ because they were considered to be evolutionarily neutral (that is, unlikely to change in response to selection), but a growing awareness that evolution by both natural and especially sexual selection can influence the morphology of male genitalia led these authors to recognize that these two snakes were in fact close relatives. Although we await molecular confirmation, the authors propose a mechanism by which differential expression of Hox genes² could cause such a rapid divergence in hemipenal morphology between two sister species.

Siphlophis ayauma
From Sheehy et al. 2014

On January 12th, 2008, a group of American and Ecuadorian herpetologists stopped for lunch at a grilled-chicken restaurant in Paute, Azuay province, Ecuador. They noticed a peculiar sun-faded snake on display in a jar of alcohol that they couldn't quite put a name to. Following negotiation with the restaurant owner, the specimen was acquired and determined to belong to the genus Siphlophis, but could not be identified to any known species. A few months later, another specimen was found alive about 100 miles to the north, and two more were discovered in 2011 about the same distance to the south. A fifth individual is now recognized to have been hiding out unnoticed in the collection of the Museo de Zoología, Pontificia Universidad Católica del Ecuador. Because of its red-banded head and its occurrence in the mountains near cold (achachay) streams, the new species was named Siphlophis ayauma after the Kichwa spirit Aya Uma, a good spirit devil who derives strength from nature, particularly from cold mountain pacchas (cascades) and is represented in Kichwa folklore as having a colorful red-banded head. This is the seventh species in the genus, the third species known from Ecuador, and the first new species of Siphlophis since 1940. The results are published in the April 1st issue of the South American Journal of Herpetology.

Philodryas amaru
From Zaher et al. 2014

In a montane grassland high in the Andes Mountains of southern Ecuador, another genus gained its 21st species this year: Philodryas amaru. Known to the Ecuadorian and Brazilian authors since 2005, a small population of these striped racers was formally described in Zootaxa on April 4th this year. The new species resembles Philodryas simonsii in color pattern, but differs noticeably in its hemipenis morphology. "Amaru" means "snake" in Kichwa, and is also the name of a snake deity who influences water and the economy. This diurnal snake lays clutches of 9-13 eggs underground in galleries and under decaying logs, and probably eats frogs and lizards. It is a close relative of the Galapagos racers that I've written about before.

Causus rasmusseni
From Broadley 2014; photo by Paul L. Lloyd

Night adders (genus Causus) are a small and unusual group of vipers found in sub-Saharan Africa. They were once thought to be the most primitive vipers and were placed in their own subfamily, but they are now grouped with the viperines even though they have a plethora of unusual features: platelike head scales, round pupils, a different hinge mechanism for their erectile fangs, incomplete fang canal closure, and elongate venom glands in most species. On April 25th of this year, Don Broadley³ described the first new species of Causus since 1905. He named it Causus rasmusseni after the late Jens Rasmussen, a Dutch expert on African snakes who died in 2005. This species is found only in the watershed between the Congo and Zambezi basins, where it co-occurs with three other species of Causus. Broadley first became aware that there might be a new species of night adder in this region in 1991, when he noticed pale gray C. rhombetaus from northwestern Zambia with black markings and low ventral scale counts. In 2013, someone sent him a picture of one eating a toad (another unusual adaptation that night adders share with several other snakes), which prompted him to look again at the unusual specimens and describe them as a new species. Few molecular data are available for Causus, so this diagnosis is based on morphology alone.

Micrurus potyguaraFrom Pires et al. 2014

Brazil is graced with nearly 400 species of snakes, including 30 of the world's ~80 species of coralsnakes. The morphology of coralsnakes is highly variable, and there are many misidentified specimens in museum collections, so it is often difficult to recognize new species. A group of Brazilian herpetologists working on the tri-colored coralsnakes from the endangered northeastern coastal forests discovered a new species, which they described in the June 5th issue of Zootaxa (if any of these dates are your birthday, then you share a birthday with that of a new species of snake!).

Top: Jaw of Lycodon aulicus
From Jackson & Fritts 2004
Middle: Lycodon zoosvictoriae
From Neang et al. 2014
Bottom: Lycodon cavernicolus
From Grismer et al. 2014

Wolfsnakes (genus Lycodon) are named for their fearsome-looking fang-like anterior maxillary teeth. Unlike the true fangs of vipers, elapids, and atractaspidids, wolfsnake teeth are not grooved or hollow and they have no venom. Instead, their strongly arched upper jaw helps them feed on skinks, whose hard, cylindrical bodies fit snugly into their diastema, or the gap between their anterior and posterior teeth. The wolf-like anterior teeth keep the skink from being squeezed out of the mouth, while the posterior teeth slice through the skink's cycloid scales. At least 16 of the nearly 60 species of Lycodon have been described since the 1990s, including two this June: Lycodon zoosvictoriae from the Cardamom Mountains of southwestern Cambodia, and L. cavernicolus from a limestone cave in peninsular Malaysia. The latter is a cave-adapted species, both specimens of which were found climbing several feet above the cave floor, in total darkness. It's likely that they eat a cave-adapted gecko. Many of the caves in this region are in immediate danger of being quarried for cement before their endemic fauna and flora can be fully documented. Both of these species were also described in Zootaxa, which is a relatively new journal dedicated almost exclusively to rapid publication of new species descriptions, with the stated goal of aiding conservation efforts by circumventing the lengthy delays normally associated with publication of new science. Since its inception in 2001, Zootaxa has become a daily journal that has published nearly one quarter of all new animal taxa and nomenclatural acts in the last five years, including over 400 new species of reptiles and the 7000th species of amphibian.

"Cloudogram" of Crotalus triseriatus species group
showing the new nine-species arrangement
From Bryson et al. 2014

Just three days before the new gecko, a team of scientists from Mexico, the USA, and Canada published a genetic analysis of the Crotalus triseriatus species group, which contains small montane rattlesnakes found in Mexico and the southwestern USA. Although five species were historically recognized within the group, an analysis of seven nuclear genes revealed that there are at least nine species, including two that were previously recognized as subspecies and two more that have not heretofore been formally recognized. The paper described the two new species: Crotalus tlaloci, named for Tláloc, the Aztec god of rain, and Crotalus campbelli, named for herpetologist Jonathan Campbell. The authors of this paper suggest that these rattlesnakes speciated rapidly from a single common ancestor during the uplifting of the Trans-Mexican Volcanic Belt near the end of the Neogene period 2.6 million years ago, which makes sense because they are not very mobile and populations of their common ancestor likely would have become isolated from one another  on various "Sky Islands" of suitable habitat during the genesis of this new mountain range. Many species are endemic to the high-altitude pine-oak forests and grasslands of this region, which has become famous as the overwintering grounds of the Monarch Butterfly.

Chironius diamantina
From Fernandes & Hamdan 2014

Surprise! Just when you thought we were through, at press time the description of four more new species of snake had just been published, all from relatively recent issues of Zootaxa. One is a Brazilian species of Chironius, one of my favorite genera. Chironius diamantina is the 16th species in the genus, which is unusual is having a very low, even number of dorsal scale rows (10 or 12), the central pair of which are strongly keeled, giving the snake a distinctly flat-backed appearance. This species is found in riparian forests along rocky streams in coastal Brazil, not too far south of the new coralsnake (above). Chironius are diurnal and generally eat birds and mammals. Another is a new Asian keelback, Herpetoreas burbrinki, from near the border of China, India, and Burma. which is relatively closely related to the Rhabdophis above. Finally, two new species from the large ground-dwelling Latin American genus Atractus, both small and described from single specimens collected decades ago in Colombia (perhaps they will one day be rediscovered). More new species from both of these groups will likely follow, given the taxonomic untidiness of their genera. [Update: shortly after publication David Salazar-Valenzuela alerted me to the fact that I had missed his description, with colleagues, of a third new Atractus from the cloud forests of northern Ecuador earlier this year, in the journal Herpetologica. They mention that some of the specimens were collected from under logs alongside an undescribed species of slender blindsnake of the genus Trilepida, so it seems we are at 3,500 this year without a doubt!] [[Update II: It seems I missed more than I thought - a new species of Trimeresurus from Sumatra was described in September from specimens collected in 1899, and a new Ninia from Trinidad was described in August from a 1988 specimen.]]

In addition to these 15 species, there are a couple of species of snake which were described long ago but that were revalidated recently, including several scolecophidians (Typhlops silus, first described in 1959; Afrotyphlops angeli, first described in 1952; and Letheobia acutirostrata, first described in 1916) and a rattlesnake (Crotalus armstrongi, originally described as a subspecies in 1979 and elevated by the same group that described C. tlaloci and C. campbelli). These are typically announced with less fanfare than the truly new descriptions that I've highlighted above.

Although it's actually been the slowest year for new snakes since 1997⁴, we have 15 new snakes this year, bringing snakes to a total of 3,499 (and 2014 isn't over yet!). We could make it to 3,500 snakes in the same year that we hit 10,000 reptiles. I think these milestones in taxonomy emphasize the importance of reptiles and how much we have left to learn about them. I doubt that the pace of new species descriptions will slow down anytime soon, as experts estimate that less than 15% of the species on Earth have yet been described. Increasingly, reptiles, and snakes in particular, are becoming poster-children for biodiversity and conservation, a welcome change from their history of being overlooked and maligned. Soon, we will have high-quality global range maps for all species of reptiles, an achievement reached some time ago by amphibians, mammals, and birds, which will enable their incorporation into global assessments of vertebrate diversity and conservation planning. It's an exciting time.

For a complete list of all 24 snake species eventually described in 2014, click here.

ACKNOWLEDGMENTS

Thanks to Peter Uetz at The Reptile Database for sharing with me some inside information, and to the authors of these papers for their photos.

REFERENCES

Newspaper clipping from 10 January 1960
showing Broadley with his amputated finger.
You can see more at the finger's Facebook page
or listen to Broadley describe the experience here.

Angarita-Sierra, T. 2014. Hemipenial Morphology in the Semifossorial Snakes of the Genus Ninia and a New Species from Trinidad, West Indies (Serpentes: Dipsadidae). South American Journal of Herpetology 9:114-130 <link>

Broadley, D. G. 2014. A new species of Causus Lichtenstein from the Congo/Zambezi watershed in north-western Zambia (Reptilia: Squamata: Viperidae). Arnoldia Zimbabwe 10:341-350 <link>

Bryson, R. J., C. W. Linkem, M. E. Dorcas, A. Lathrop, J. M. Jones, J. Alvarado-Diaz, C. I. Grunwald, and R. W. Murphy. 2014. Multilocus species delimitation in the Crotalus triseriatus species group (Serpentes: Viperidae: Crotalinae), with the description of two new species. Zootaxa 3826:475-496 <link>

Cope, E. D. 1895. The classification of the Ophidia. Transactions of the American Philosophical Society 18:186-219 <link>

Dowling, H. G. 1967. Hemipenes and other characters in colubrid classification. Herpetologica 23:138–142 <link>

Grismer, L. L., E. S. H. Quah, S. Anuar, M. A. Muin, P. L. Wood Jr, and S. A. M. Nor. 2014. A diminutive new species of cave-dwelling Wolf Snake (Colubridae: Lycodon Boie, 1826) from Peninsular Malaysia. Zootaxa 3815:51-67 <link>

Guo, P., Q. Liu, L. Zhang, J. X. Li, Y. Huang, and R. A. Pyron. 2014. A taxonomic revision of the Asian keelback snakes, genus Amphiesma (Serpentes: Colubridae: Natricinae), with description of a new species. Zootaxa 3873:425-440 <link>

Fernandes, D. and B. Hamdan. 2014. A new species of Chironius Fitzinger, 1826 from the state of Bahia, Northeastern Brazil (Serpentes: Colubridae). Zootaxa 3881:563-575 <link>

Trimeresurus gunaleni
From Vogel et al 2014

Jackson, K. and T. H. Fritts. 2004. Dentitional specialisations for durophagy in the Common Wolf snake, Lycodon aulicus capucinus. Amphibia-Reptilia 25:247-254 <link>

Köhler, G. and M. Kieckbusch. 2014. Two new species of Atractus from Colombia (Reptilia, Squamata, Dipsadidae). Zootaxa 3872:291-300 <link>

Linnaeus, C. 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. [10th ed.]. Laurentii Salvii, Holmiae, Stockholm, Sweden <link>

Myers, C. W. and S. B. McDowell. 2014. New Taxa and Cryptic Species of Neotropical Snakes (Xenodontinae), with Commentary on Hemipenes as Generic and Specific Characters. Bulletin of the American Museum of Natural History 385:1-112 <link>

Neang, T., T. Hartmann, S. Hun, N. J. Souter, and N. M. Furey. 2014. A new species of wolf snake (Colubridae: Lycodon Fitzinger, 1826) from Phnom Samkos Wildlife Sanctuary, Cardamom Mountains, southwest Cambodia. Zootaxa 3814:68-80 <link>

Pires, M. G., N. J. da Silva Jr., D. T. Feitosa, A. L. d. C. Prudente, G. A. P. Filho, and H. Zaher. 2014. A new species of triadal coral snake of the genus Micrurus Wagler, 1824 (Serpentes: Elapidae) from northeastern Brazil. Zootaxa 3811:569-585 <link>

Atractus savagei
From Salazar-Valenzuela et al. 2014

Salazar-Valenzuela, D., O. Torres-Carvajal, and P. Passos. 2014. A New Species of Atractus (Serpentes: Dipsadidae) from the Andes of Ecuador. Herpetologica 70:350-363 <link>

Schneider, N., T. Q. Nguyen, M. D. Le, L. Nophaseud, M. Bonkowski, and T. Ziegler. 2014. A new species of Cyrtodactylus (Squamata: Gekkonidae) from the karst forest of northern Laos. Zootaxa 3835:80-97 <link>

Sheehy, C. M., M. H. Yánez-Muñoz, J. H. Valencia, and E. N. Smith. 2014. A new species of Siphlophis (Serpentes: Dipsadidae: Xenodontinae) from the eastern Andean slopes of Ecuador. South American Journal of Herpetology 9:30-45 <link>

Teynié, A., A. Lottier, P. David, T. Q. Nguyen, and G. Vogel. 2014. A new species of the genus Opisthotropis Günther, 1872 from northern Laos (Squamata: Natricidae). Zootaxa 3774:165-183 <link>

Uetz, P. 2010. The original descriptions of reptiles. Zootaxa 2334:59-68 <link>

Vogel, G., P. David, and I. Sidik. 2014. On Trimeresurus sumatranus (Raffles, 1822), with the designation of a neotype and the description of a new species of pitviper from Sumatra (Squamata: Viperidae: Crotalinae). Amphibian and Reptile Conservation 8:1–29 <link>

Zaher, H., J. C. Arredondo, J. H. Valencia, E. Arbeláez, M. T. Rodrigues, and M. Altamirano-Benavides. 2014. A new Andean species of Philodryas (Dipsadidae, Xenodontinae) from Ecuador. Zootaxa 3785:469–480 <link>

Zhu, G.-X., Y.-Y. Wang, H. Takeuchi, and E.-M. Zhao. 2014. A new species of the genus Rhabdophis Fitzinger, 1843 (Squamata: Colubridae) from Guangdong Province, southern China. Zootaxa 3765:469-481 <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.