Dragonsnakes and Filesnakes Revisited

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I've written about both filesnakes (family Acrochordidae) and dragonsnakes (part of the family Xenodermidae¹) before. Traditional snake taxonomy suggests that, although they branch off from the main stem of the snake family tree at about the same time, they're not very closely related. But, new evidence emphasizes the uniqueness of dragonsnakes and thickens the plot in the unfolding story of the evolution of snakes.

Two hypotheses about the relationships of the major groups of snakes.
Left: tree based on nuclear genes, showing Acrochordidae and Xenodermidae
as successive outgroups to core Colubroidea
Right: tree based on mitochondrial genes, showing a sister relationship
between Acrochordidae and Xenodermidae
From Oguiura et al. 2009

Most phylogenetic analyses are pretty consistent in classifying both filesnakes and dragonsnakes as caenophidians, or "advanced" snakes. But, they differ in their placement of dragonsnakes and other xenodermids, including the truly strange and obscure odd-scaled snakes (Achalinus), bearded snakes (Fimbrios), stream, earth, or red snakes (Stoliczkia²), wood, mountain, or narrow-headed snakes (Xylophis), and a new genus, just described in 2015 and still without a common name, Parafimbrios. Most analyses group xenodermids with the colubroids (pareids¹, vipers, homalopsids, colubrids, lamprophiids, and elapids), albeit as the most basal branch. Many textbooks actually define Caenophidia as Colubroidea + Acrochordidae (aka Acrochordoidea), distinctly separating the colubroids from the filesnakes on the basis of shared, derived characteristics such as wide ventral scales, as well as features of the skull, hemipenes, and the muscles, cartilages, and arteries between the ribs. However, several recent trees based on DNA sequences suggest instead that filesnakes and dragonsnakes might be one another's closest living relatives.

Study	Acrochordid-Xenodermid Relationship	Support	How many species?	What data were used?
Boulenger 1893	X&A	-	-	Morphology
Kraus & Brown 1998	X+A	8%	37	ND4
Kelly et al. 2003	X+A	98%	98	4 mitochondrial genes
Vidal et al. 2007	A,X	not reported	25	7 nuclear genes
Wiens et al. 2008	A,X	>95%	50	20 nuclear genes
Wang et al. 2009	A,X*	100%	30	12 nuclear genes
Zaher et al. 2009	A,X	94%	131	2 mitochondrial genes + 1 nuclear gene
Pyron et al. 2011	A,X	97-100%	761	3 mitochondrial genes + 2 nuclear genes
Gauthier et al. 2012	X,A	95-100%	141 extant + 51 extinct	610 morphological characters
Wiens et al. 2012	A,X	100%	161	44 nuclear genes
Pyron et al. 2013	X+A	95%	4,161	5 mitochondrial genes + 7 nuclear genes
Pyron et al. 2014	A,X*	99%	32	333 nuclear loci with 100% coverage
Zheng & Wiens 2016	A,X	91%	4,162	5 mitochondrial genes + 47 nuclear genes

A selection of studies that have examined the relationship between acrochordids and xenodermids.

X+A means that the two are each other's closest relatives; A,X means that acrochordids are more distantly
related to colubroids than xenodermids; X,A means that xenodermids are more distant
*Relationships differed depending on which methods were used

Arafura Filesnake (Acrochordus arafurae)

For example, the first study to use DNA to examine the relationships of these two groups of snakes found some support for each hypothesis, concluding that the "potential sister-taxon relationship of acrochordids and xenodermines [is] a reasonable hypothesis requiring future testing." In 2003, data from three more mitochondrial genes resulted in the same relationship, causing the authors to suggest that xenodermids should be excluded from Colubroidea. However, since that time, numerous studies have not repeated this result. In 2009, one research group predicted that "these differences...are due to taxonomic sampling issues", predicting that as DNA was collected from more species of snakes, the basal position of Acrochordus would be confirmed.

Dragonsnake (Xenodermus javanicus)

So, it was a real surprise when a 2013 analysis, the largest yet, including samples from 80% of all snake genera, placed Acrochordidae and Xenodermidae as sister groups. Neither a follow-up analysis combining that dataset with one containing data from many more genes nor an analysis using only the most complete data have settled the issue. The latter study compared several methods for generating phylogenetic trees and found that the relationship between acrochordids and xenodermids depended a lot on which methods were used. Part of the problem is that, even if they are each others' closest relatives, they still diverged between 70 and 80 million years ago, making them susceptible to a problem in phylogenetics known as long-branch attraction, which happens when the amount of evolutionary change within a lineage causes that lineage to appear similar (and thus closely related) to another long-branched lineage, solely because they have both undergone a lot of change, rather than because they are actually related.

Bearded Snake (Fimbrios klossi)

The truth is that both acrochordids and xenodermids are obscure snakes, and we don't have that much data on either one of them. They are both found in areas of the world that are hard to get to. Morphologically, they appear superficially similar, and an association between them was first hypothesized in 1893. But, even the most comprehensive morphological trait database for snakes is missing crucial data on their anatomy, such as whether or not their hemipenial spines are mineralized. This would be helpful to know because  the hemipenial spines of basal snakes such as boas and pythons are not mineralized, whereas those of definitive colubroids are heavily mineralized.

Parafimbrios lao
From Teynié et al. 2015

Within the past year, two new studies on the chromosomes of dragonsnakes (Xenodermus javanicus) have been published. In the first, the karyotype (the number of chromosomes and their shape) of dragonsnakes was reported for the first time. In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. In most snakes, each cell normally contains 18 pairs of chromosomes, for a total of 36. Usually, eight of these pairs are relatively large (called macrochromosomes), and the other ten are somewhat small (called microchromosomes). Dragonsnakes have 16 pairs of chromosomes, for a total of 32, of which seven are large and nine are small. The dragonsnake karyotype probably evolved by two fusion events, one of two macrochromosomes and the other between a macrochromosome with a microchromosome. There are some other exceptions to the 18-pair pattern; some snakes have as few as 12 or as many as 25 pairs, including the only other xenodermid to have been karyotyped, the Sichuan Odd-scaled Snake (Achalinus meiguensis), which has just 12 pairs of chromosomes.

Amami Odd-scaled Snake (Achalinus werneri)

From the 1960s to the 1980s, before DNA sequencing became cheap and easy, scientists invested heavily in collecting karyotypes from a diversity of species for comparative purposes, so we can say with pretty good certainty that the ancestral state for all snakes is 36 (18 pairs). That's the number in filesnakes, pareids, most vipers, homalopsids, and many colubrids, lamprophiids, and elapids, although there are lots of exceptions in the latter three groups.  The fusions in xenodermids emphasize their uniqueness, but unfortunately don't shed any new light on their phylogenetic placement.

Stoliczkia borneensis

The other study focused on the sex chromosomes. In humans, sex is determined by which combination of sex chromosomes a baby receives from its parents: two X chromosomes make a female, whereas an X and a Y chromosome make a male. It's pretty similar in snakes, with a twist: the sex chromosomes are called Z and W instead of X any Y, and females are the heterogametic sex (meaning that a Z and a W chromosome make a female, and two Z chromosomes make a male). Birds and many other reptiles also have ZW sex determination. In many colubroid snakes, the W chromosome is about twice the size of the Z,  and it is often unusual in other ways as well, such as having sections of highly condensed chromatin or a different centromere position. In contrast, filesnakes, boids, and other more basal snakes have morphologically indistinguishable Z and W chromosomes, although they still contain different genes and perform different functions.

Perrotet's Narrow-headed Snake (Xylophis perroteti)
Are members of this genus really xenodermids? Or, like the
former xenodermids Oxyrhabdium and Nothopsis, will they
prove to be more closely related to something else?

One reason the W chromosome looks so different from the Z in colubroids is that it contains repetitive elements called Bkm ('banded krait minorsatellite') repeats, which consist of the sequence "GATA" (sometimes "GACA") repeated thousands of times. Mammalian X chromosomes and avian W chromosomes also have these repeats. Cell biologists think that these repeats function to inactivate all the genes on the W chromosome except for those that determine sex³. Both mammalian X chromosomes and snake W chromosomes become very dense in body cells, so that none of the genes on them can be expressed. They only decondense and plays their brief, female-determining roles, in maturing eggs that are destined to become females. Unlike in mammals, the sex chromosomes of snakes span the gamut from completely identical to markedly differentiated, allowing biologists to study the evolution of chromosomal sex determination. The new study showed that female dragonsnakes have two different-looking sex chromosomes, with many Bkm repeats in the W, whereas the two Z sex chromosomes of male dragonsnakes look similar and lacked Bkm repeats, bolstering the relationship between xenodermids and other colubroids and diminishing the relationship between xenodermids and filesnakes.

The other major finding of the new study is the documentation that at least part of the sex chromosomes are homologous across all families of caenophidian snakes, suggesting that snake sex chromosomes emerged in the common ancestor of Caenophidia some 60-80 million years ago. One gene that is only on the Z chromosome in all caenophidians, including dragonsnakes, is also found on the W chromosome in filesnakes. The Z-chromosome-specific genes in caenophidians were on both the Z and W chromosomes in boas, pythons, and sunbeam snakes (Xenopeltidae), as well as in bearded dragons and anoles. Other toxicoferan lizards with ZW sex chromosomes, including chameleons and monitor lizards, seem to have evolved them independently.

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1 A recent article in the journal Herpetological Review pointed out that the grammatical rules for structuring family and subfamily names from genus names have recently been incorrectly applied in two cases involving snakes which concern this article: 1) Xenodermatidae/inae for the family/subfamily containing Xenodermus, the root of which is "dermus", a masculine noun with which the masculine specific epithet javanicus is correctly coupled (not the neuter javanicum; in contrast think of the neuter Heloderma horridum in family Helodermatidae). The correct family or subfamily name is thus Xenodermidae/inae. 2) Pareatidae or Pareatinae for the family containing Pareas, which is also masculine, making the correct family/subfamily name Pareidae/inae.^↩

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2 Don't confuse this snake genus (Stoliczkia) with a genus of extinct ammonite (Stoliczkaia), both named for Czech biologist Ferdinand Stoliczka. The extra "a" was added to the original spelling of the snake genus by Boulenger in 1899, probably by accident, and this genus is still widely misspelled today (e.g., on GenBank and on Wikipedia before I fixed it while writing this article).^↩

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3 It's also thought that "GATA" is a particularly potent regulatory sequence, with the power to turn nearby genes on and off. In a way, the sex genes have essentially 'hijacked' the W chromosome, turning off all its other genes, and simultaneously creating a concentrated source of mutation-causing elements. Chromosomal sex determination may therefore constitute a unique and potentially very powerful genotypic mechanism for abruptly enhancing evolutionary rates, which might have contributed to the explosive radiations of species in clades with chromosomal sex determination, such as mammals, birds, squamates, and certain groups of insects.^↩

ACKNOWLEDGMENTS

Thanks to Thomas Calame, Sam Howard, Konrad Mebert, Zeeshan Mirza, Takehito Sato, and Stephen Zozaya for the use of their photos.

REFERENCES

Boulenger, G. A. 1893. Catalogue of the Snakes in the British Museum (Natural History). Volume I., containing the families Typhlopidae, Glauconiidae, Boidae, Ilysiidae, Uropeltidae, Xenopeltidae, and Colubridae Aglyphae, Part. Trustees of the British Museum, London. <link>

Boulenger, G. A. 1899. Description of three new reptiles and a new batrachian from Mt. Kina Balu, North Borneo. Annals and Magazine of Natural History 7:451-453 <link>

Gauthier, J. A., M. Kearney, J. A. Maisano, O. Rieppel, and A. D. B. Behlke. 2012. Assembling the squamate Tree of Life: perspectives from the phenotype and the fossil record. Bulletin of the Peabody Museum of Natural History 53:3-308 <link>

Jerdon, T. C. 1870. Notes on Indian Herpetology. Proceedings of the Asiatic Society of Bengal 1870:66-85 <link>

Jones, K., and L. Singh. 1985. Snakes and the evolution of sex chromosomes. Trends in Genetics 1:55-61 <link>

Lawson, R., J. B. Slowinski, B. I. Crother, and F. T. Burbrink. 2005. Phylogeny of the Colubroidea (Serpentes): new evidence from mitochondrial and nuclear genes. Molecular Phylogenetics and Evolution 37:581-601 <link>

Kelly, C. M. R., N. P. Barker, and M. H. Villet. 2003. Phylogenetics of advanced snakes (Caenophidia) based on four mitochondrial genes. Systematic Biology 52:439-459 <link>

Kraus, F., and W. M. Brown. 1998. Phylogenetic relationships of colubroid snakes based on mitochondrial DNA sequences. Zoological Journal of the Linnean Society 122:455-487 <link>

Oguiura, N., H. Ferrarezzi, and R. Batistic. 2009. Cytogenetics and molecular data in snakes: a phylogenetic approach. Cytogenetic and Genome Research 127:128-142 <link>

O’Meally, D., H. R. Patel, R. Stiglec, S. D. Sarre, A. Georges, J. A. M. Graves, and T. Ezaz. 2010. Non-homologous sex chromosomes of birds and snakes share repetitive sequences. Chromosome Research 18:787-800 <link>

Pokorna, M., and L. Kratochvíl. 2009. Phylogeny of sex‐determining mechanisms in squamate reptiles: are sex chromosomes an evolutionary trap? Zoological Journal of the Linnean Society 156:168-183 <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>

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 13:53 <link>

Pyron, R. A., C. R. Hendry, V. M. Chou, E. M. Lemmon, A. R. Lemmon, and F. T. Burbrink. 2014. Effectiveness of phylogenomic data and coalescent species-tree methods for resolving difficult nodes in the phylogeny of advanced snakes (Serpentes: Caenophidia). Molecular Phylogenetics and Evolution 81:221-231 <link>

Rovatsos, M., M. Johnson Pokorná, and L. Kratochvíl. 2015. Differentiation of sex chromosomes and karyotype characterisation in the Dragonsnake Xenodermus javanicus (Squamata: Xenodermatidae). Cytogenetic and Genome Research 147:48-54 <link>

Rovatsos, M., J. Vukić, P. Lymberakis, and L. Kratochvíl. 2015. Evolutionary stability of sex chromosomes in snakes. Proceedings of the Royal Society B: Biological Sciences 282:20151992 <link>

Savage, J. M. 2015. What are the correct family names for the taxa that include the snake genera Xenodermus, Pareas, and Calamaria? Herpetological Review 46:664-665 <link>

Sharma, G., and U. Nakhasi. 1980. Karyological studies on six species of Indian snakes (Colubridae: Reptilia). Cytobios 27:177-192 link>

Teynié, A., P. David, A. Lottier, M. D. Le, N. Visal, and T. Q. Nguyan. 2015. A new genus and species of xenodermatid snake (Squamata: Caenophidia: Xenodermatidae) from northern Lao People’s Democratic Republic. Zootaxa 3926:523-540 <link>

Vicoso, B., J. Emerson, Y. Zektser, S. Mahajan, and D. Bachtrog. 2013. Comparative sex chromosome genomics in snakes: differentiation, evolutionary strata, and lack of global dosage compensation. PLoS Biology 11:e1001643 <link>

Vidal, N., A. S. Delmas, P. David, C. Cruaud, A. Couloux, and S. B. Hedges. 2007. The phylogeny and classification of caenophidian snakes inferred from seven nuclear protein-coding genes. Comptes Rendus Biologies 330:182-187 <link>

Wang, G., S. He, S. Huang, M. He, and E. Zhao. 2009. The complete mitochondrial DNA sequence and the phylogenetic position of Achalinus meiguensis (Reptilia: Squamata). Chinese Science Bulletin 54:1713-1724 <link>

Wiens, J. J., C. A. Kuczynski, S. A. Smith, D. G. Mulcahy, J. W. Sites, T. M. Townsend, and T. W. Reeder. 2008. Branch lengths, support, and congruence: testing the phylogenomic approach with 20 nuclear loci in snakes. Systematic Biology 57:420-431 <link>

Wiens, J. J., C. R. Hutter, D. G. Mulcahy, B. P. Noonan, T. M. Townsend, J. W. Sites, and T. W. Reeder. 2012. Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species. Biology Letters 8:1043-1046 <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>

Zheng, Y., and J. J. Wiens. 2016. Combining phylogenomic and supermatrix approaches, and a time-calibrated phylogeny for squamate reptiles (lizards and snakes) based on 52 genes and 4162 species. Molecular Phylogenetics and Evolution 94:537-547 <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.

Book Review: Bushmaster by Dan Eatherley

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Bushmaster (Lachesis muta) from Peru

Lachesis is the name of one of the three Greek Moirai or Fates, sister-deities who determined the destiny of every human life by spinning each life as a thread on a loom. Her role in the process was to determine the length of a mortal's life, and so she is appropriately immortalized¹ in modern biology in the genus name of Bushmasters, huge Latin American pitvipers that occasionally play the same role and are herpetologically mythical in their own right. Her sisters, Clotho (who spun the threads of life) and Atropos (who did the actual thread-cutting), are similarly honored in the Latin name of vipers of the genus Atropoides and in Clotho, an old synonym for some members of the African viper genus Bitis.

Ditmars filming the Bushmaster "Lecky" at the Bronx Zoo in 1934
©WCS. Courtesy of the WCS Archives

If you're interested in Bushmasters and herpetological history, check out Dan Eatherley's new book, "Bushmaster: Raymond Ditmars and the Hunt for the World's Largest Viper", which chronicles the life and times of the Bronx Zoo's first reptile curator and one of America's first and most successful popular herpetological writers. Ditmars authored 24 books, >200 articles, and pioneered nature films in an era when video technology was still in its infancy. Eighty years ago, he was a household name in New York, enjoying a celebrity attained by few herpetologists. President Theodore Roosevelt praised Ditmars's The Reptile Book and invited him to the White House. One of the reasons for his popularity was his "obsession" with keeping large, exotic, sexy, venomous snakes—such as Bushmasters—in captivity, an endeavor on which the press regularly reported. Ditmars was reporter for New York Times when he was young, and the paper published 12-15 stories a year on his exploits between 1899 and 1942. Such was the popularity drummed up for snakes that, when a short-lived Bushmaster named "Lecky" was exhibited at the Bronx Zoo in 1934, it was credited with attracting an estimated 100,000 additional guests at the zoo and a 60% increase in visitors at the nearby American Museum of Natural History’s reptile hall.

The first photograph of a female Bushmaster guarding her eggs,
taken by C.S. Rogers in Trinidad, was published in Ditmars (1910),
and subsequently as a postcard sold at the Bronx Zoo.
The snake was a captive in the possession of R.R. Mole.

Bushmasters are unique among New World vipers, with the possible exception of the rare Bothrops colombianus, in laying eggs rather than giving birth to live young. Because they guard their eggs, a phenomenon that Ditmars and his correspondent R.R. Mole first described, they may offer insight into the complex evolution of parental care in pitvipers. In Ditmars's time, there was a single, widespread species of bushmaster, with four subspecies separated by tropical mountain ranges; we now recognize those four subspecies as species on the basis of morphological, behavioral, and molecular differences. Bushmasters are also the only pitvipers where the venom of juveniles appears to lack the chemical potency of adults, at least towards mammals. Many vipers feed on amphibians or other reptiles when they are young and switch to mammals as they grow up², which might explain this observation. Bushmasters are the world's longest vipers³ (Gaboon Vipers exceed them in weight) and the longest venomous snakes in the Americas (King Cobras exceed them in length).

Ditmars wears a snake fang tie pin
on the book's cover

Eatherley's book is well-researched and accurate. I found it to be an exciting read with an excellent historical perspective. My biggest criticism was that it was a little sensational at times, as are most popular accounts dealing with venomous snakes. I particularly enjoyed the author's description of his experiences meeting up with some New York City herpers to seek Gartersnakes (Thamnophis sirtalis), Brownsnakes (Storeria dekayi), and other snakes that could still be found in the northern part of Central Park in the 1880s, when Ditmars was cutting his herpetological teeth. I was also interested to learn that Ditmars supplied snake venom to early antivenom producers and set a precedent, still in place today, of zoos stocking exotic snake antivenoms for the dual purpose of protecting their keepers and providing them to the medical community when bites from exotic species occur elsewhere.

In his writing, Ditmars often portrayed Bushmasters as aggressive, in contrast to many other herpetologists who have described their manner as relatively gentle, even timid. In reality, they are, like most venomous snakes, cowards first, then bluffers, and lastly warriors, and their large size has earned them a reputation as formidable warriors as well as a prominent position in folklore throughout Latin America⁴. Their mystique and biology effectively drive Eatherley's book, only the second biography of Ditmars ever written (the first, by Laura Newbold Wood, was written for children and published in 1944, just two years after Ditmars's death). Throughout the book, Eatherley goes from stating that negative responses towards reptiles are “of course, the norm for most of us” (p. 11) to tracing a rapid path from ecstasy to palpable disappointment, familiar to any snake enthusiast, when informed during his search for a wild Bushmaster in Trinidad that a nearby farmer has found one, but killed it (p. 255). I think that Ditmars would be pleased with his abiding influence, nearly 75 years after his death, in inspiring passion for and love of snakes.

You can read two other reviews of Eatherley's book, published last month in Copeia and Herpetological Review.

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1 I suppose she was already immortal, since she's a Greek Goddess.^↩

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2 Strangely, bushmasters seem to be one of the only vipers where this shift is not well-documented. Collecting data on young snakes is hard, and the venom study found that venom chemistry became more adult-like after just one year, so perhaps we've just missed the shift. Another hypothesis is that bushmasters tend to hold onto their prey after striking it, unlike other vipers which strike, release, and relocate, so perhaps the rapid immobilizing venom components have been replaced by a mechanical means of immobilization.^↩

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3 Regarding their maximum length, Campbell & Lamar's authoritative reference on venomous reptiles of the western hemisphere says: "Documented reports of measured specimens are scarce, however, and the maximum length has been the subject of some hyperbole. Hoge and Lancini (1962) claimed 4.5 m, Abalos (1977) claimed 3.5 m, Ditmars (1937) mentioned specimens of 11 feet (3.35 m) but apparently never saw one exceeding 3m, Bellairs (1969) gave the maximum length as between 3.05 and 3.36m, Dunn (1951) gave the maximum length as 14 feet (4.27 m), and Mertens (1960) listed 13 feet (3.96 m) as the maximum size. Sandner-Montilla (1994) claimed a record of 5.28 m for a Venezuelan specimen of L. muta (with 6-cm fangs!), but such records must be placed in the same realm as 20-m anacondas and other legendary monsters.", and concludes "The great majority of adult specimens of all species of Lachesis measure less than 2.5 m, and 3.5 m is likely near the maximum size."^↩

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4 Bushmasters play other roles in human culture as well—as food. Bora and Yagua Indians in eastern Peru consider them a delicacy. They are certainly one of the few snakes large enough to make a filling meal for a family.^↩

ACKNOWLEDGMENTS

Thanks to Dan Eatherley and Arcade Publishing for producing such a wonderful book, of which they kindly provided me a copy, to Drew Foster for sharing an advance copy of his review of this book for Copeia, to Marisa Ishimatsu and the Wildlife Conservation Society for the use of their photographs, and to Harry Greene for shedding a little more light on the diets of juvenile bushmasters.

REFERENCES

Adler, K. 1989. Contributions to the History of Herpetology. Volume 1. Society for the Study of Amphibians and Reptiles, Oxford, Ohio <link>

Campbell, J. A., and W. W. Lamar. 2004. The Venomous Reptiles of the Western Hemisphere (2 Vol.). Cornell University Press, Ithaca, New York <link>

Ditmars, R. L. 1910. Reptiles of the World : Tortoises and Turtles, Crocodilians, Lizards, and Snakes of the Eastern and Western Hemispheres. Macmillan Co., New York <link>

Gutiérrez, J., C. Avila, Z. Camacho, and B. Lomonte. 1990. Ontogenetic changes in the venom of the snake Lachesis muta stenophrys (bushmaster) from Costa Rica. Toxicon 28:419-426 <link>

Eatherley, D. 2015. Bushmaster: Raymond Ditmars and the Hunt for the World's Largest Viper. Arcade Publishing, New York, New York <link>

Foster, C. D. 2015. Bushmaster: Raymond Ditmars and the Hunt for the World’s Largest Viper [book review]. Copeia 103:1107-1109 <link>

Novotny, R. J. 2015. Bushmaster: Raymond Ditmars and the Hunt for the World's Largest Viper [book review]. Herpetological Review 46:657-659 <link>

Wood, L. N. 1944. Raymond L. Ditmars: His Exciting Career With Reptiles, Animals and Insects. The Junior Literary Guild and Julian Messner, Inc., New York <link>

Zamudio, K. R., and H. W. Greene. 1997. Phylogeography of the bushmaster (Lachesis muta: Viperidae): implications for neotropical biogeography, systematics, and conservation. Biological Journal of the Linnean Society 62:421-442 <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.

Life is Short but Snakes are Long 2015 Milestones

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Dear reader,

Instead of debuting my planned new content for this month, I wanted to take a moment to thank you for your readership, to review the several milestones reached by Life is Short but Snakes are Long in 2015, and to outline where it's headed in the future.

The back cover of the paperback edition of Harry Greene's opus Snakes:
The Evolution of Mystery in Nature, bearing the review by eminent
nature writer David Quammen from which this blog takes its name

Life is Short but Snakes are Long reached half a million unique views this year (by over 320,000 unique readers from nearly every country) on September 28th, 2015. When I began writing it on April 4, 2012, I would never have imagined that so many people would want to read about snakes. Since that time, the pace and intensity of my dissertation research has increased steadily, and my goal for this year was to publish one article a month, which I am proud to say I have achieved (unless you think that this one is cheating, which I kind of do). Even though I wrote fewer articles this year, many of them were more ambitious than my past articles, in that they synthesized large bodies of literature that I personally knew little about before I started writing.

Countries and regions from which readers have accessed Life is Short
From what I can see on this tiny map, we're missing only Svalbard,
Western Sahara, Turkmenistan, and North Korea

My other goals for this blog include: 1) to provide referenced, reputable information that is not available elsewhere, 2) to synthesize & translate information from the peer-reviewed literature, and 3) to indulge my own broad interests. I know I've been successful with #3, which was important to me because I was afraid of becoming too specialized in the process of getting my PhD. Whether or not I've succeeded at numbers 1 & 2 you'll have to tell me. Apparently at least a few people think so, because articles from Life is Short but Snakes are Long have been syndicated by HerpNation Media and linked to, covered, or republished (with permission) by:

• National Geographic (twice!)
• Scientific American
• BBC Earth
• Discover Magazine
• The Conversation/Huffington Post
• Biodiversity Heritage Library
• Small Pond Science
• Access Utah on Utah Public Radio
• Logan Herald-Journal
• Salt Lake City Tribune
• Utah State Today
• The Sierra Club
• The Other Herpcast
• Center for Snake Conservation
• Partners in Amphibian and Reptile Conservation
• North Carolina Herpetological Society
• HerpDigest

I also found out that one of my posts was nominated for a ‘Best Science Writing Online 2013’ contest (although it did not win). Because of the blog, I've also been asked to provide review services on snake biology to Bones on Fox TV, The Blacklist on NBC, and the children's book publisher Cherry Lake Publishing. Finally, I was invited to travel to San Antonio, Texas, in May for the International Herpetological Symposium to speak at their Science Café and also in their general program about Life is Short but Snakes are Long, which I really enjoyed. I want to thank the many editors, writers, scientists, publicists, and reporters who thought my writing was good enough to republish or pay attention to in some form.

My Sonoran Coralsnake (Micruroides euryxanthus)

I also reached a personal herping milestone this year: 100 snake species seen alive and in the wild, on July 30th, 2015, with a Sonoran Coralsnake (Micruroides euryxanthus) that I found on Portal Road in Cochise County, Arizona. This was an especially exciting snake for me because it was my first wild elapid and because I was there with the American Museum of Natural History Southwest Research Station's  Field Herpetology of the Southwest class, where the enthusiasm was nothing short of infectious. I also published several peer-reviewed journal articles and short notes this year, including one that I came across as a direct result of writing Life is Short but Snakes are Long. Because I'll be writing and (hopefully) completing my dissertation in 2016, I'll likely be relying more heavily on updating and re-posting existing material, since I'll have less time to research and write new material. But, I have some new articles planned that I've already begun working on, so there should be a mix of old and new in 2016.

Life is Short but Snakes are Long would not be possible without support from volunteer translators Alvaro Pemartin & Estefania Carrillo, from Utah State University, particularly my advisor Susannah French and the Ecology Center, and from my loving girlfriend and editor Kendal Morris.

Thank you, and happy 2016!

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