If you need to identify a snake, try the Snake Identification Facebook group.
For professional, respectful, and non-lethal snake removal and consultation services in your town, try Wildlife Removal USA.

Tuesday, January 26, 2016

Bushmaster


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.



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




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.



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."



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>

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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, December 29, 2015

Life is Short but Snakes are Long 2015 Milestones


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:
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!

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.

Monday, November 30, 2015

Snakes that are Good Parents

Almost all mammals and birds care for their young to some extent, but most amphibians and reptiles do not. We tend to think of snakes as particularly asocial, and in many cases this is probably true. But, a growing body of evidence contradicts the generalization, made as recently as 1978, that "all reptiles produce precocial offspring without postnatal parental care", and shows that some snakes, in particular, are more caring parents than we typically think.

Vipers

A female Timber Rattlesnake (Crotalus horridus)
with her newly-born young
Probably the group of snakes most well-known for parental care are now the vipers, which is somewhat ironic considering the fierce but undeserved reputation of these venomous snakes. Although it was documented as early as 1850, parental care by vipers was not widely known or accepted by the scientific community until the 1990s; like crocodilians, it was assumed that these animals were too vicious to exhibit such caring behavior. When Laurence Klauber, at the time the world's foremost authority on rattlesnakes, wrote in 1956 that "Their propinquity [to aggregate]...does not result from any maternal solicitude; rather it is only because the refuge sought by the mother is also used as a hiding place by the young.", he was uncharacteristically incorrect; in hindsight, his words now seem almost willfully ignorant. In the 1990s, credible reports of parental care in wild pitvipers began to accumulate, corroborating the many older stories listed by Klauber, and in 2002, a seminal review paper based around two studies using radio-telemetry and DNA proved once and for all that mother rattlesnakes do stay with and care for their young. Today, you can read a whole blog about parental care in rattlesnakes, and we think that parental care is widespread (but not ubiquitous) among the ~230 species of pitvipers (aka crotalines or New World vipers). This is particularly remarkable because many of them give birth to live young, which they guard until the young's first shed, even though they may not have eaten for 9-10 months beforehand. It appears that the completion of the first shed cycle is the cue for them to separate, an event which is mediated by the same hormone in snakes as it is in birds and mammals. Because snakes swallow their food whole, the mother can't really feed her offspring, and they forage for themselves after they disperse. Pitvipers are the only snakes known to care for their living young; other snakes with parental care limit themselves to care of their eggs.

Pythons

A mother African Rock Python (Python sebae)
brooding her eggs
The next most well-known example of parental care in snakes is egg-brooding behavior in pythons, first documented in 1835. All 40 species of pythons lay eggs, and most of them coil tightly around them throughout incubation, forsaking food. As with vipers, early reports of this behavior were dismissed, but by the 1930s observations of pythons in zoos showed that they did indeed brood their eggs. Some species that live in cold climates, such as Indian Pythons (Python molurus) and Carpet Pythons (Morelia spilota), also generate heat using muscle contractions ("shivering"). Measurements taken of brooding Indian Pythons have shown that they can increase the temperature of their clutch by 7-10°F. Even though mother pythons may brood for up to 2 months, studies have found that, at normal temperatures, they rarely shiver and lose only about 6% of their body mass, suggesting that the costs of brooding are relatively small compared to the benefits, which also include reduced water loss by the eggs and hatchlings that develop faster and are larger and more active. The brooding instinct in mother pythons is very strong—lab experiments have shown that they will brood the eggs of other pythons just as readily as they will brood their own, and they will even brood rocks that are the same size as their eggs (a behavior reminiscent of the well-known fixed-action pattern of egg-retrieval behavior in graylag geese). Today, pythons are frequently used as models to study female reproductive behavior and life-history trade-offs.

King Cobras

Top: A female King Cobra guarding her nest
Bottom left: A diagram of a typical King Cobra nest
Bottom right: King Cobra eggs in an excavated nest chamber
From Hrima et al. 2014
That female King Cobras (Ophiophagus hannah) use their coils to build a nest of sticks and bamboo leaves and guard their eggs for two to three months has been known at least since 1892. Detailed observation of nest-building and attendance were made in captivity at the Bronx Zoo from 1953-1956, and wild King Cobra nests were surveyed and detailed observations made in 19691. King Cobra nests are the largest and most complex of any snake's, measuring up to four feet in diameter and rising to a similar height, with an internal chamber for the 20-50 eggs and sometimes a second one above for the snake, which abandons the nest just before the eggs hatch. The female must select her nesting material and bring it to the nest site, because the species of bamboo that are most commonly used in building the nest are not the most abundant species in the surrounding area. There are also some anecdotal reports that male King Cobras will guard the nest and/or the female. Some sources suggest that female King Cobras are more aggressive towards humans when they are guarding their nests, but most suggest that their behavior is no different than at any other time.

Other snakes

A female Mudsnake (Farancia abacura)
coils around her eggs in a subterranean nest
Maternal attendance or guarding of clutches of eggs is widespread in snakes, but observations in the wild are still fairly uncommon, mostly due to the difficulty of locating nesting sites. There are several excellent reviews of this topic, including those written by Rick Shine (1988), Carl Gans (1996), Louis Somma (2003), and Zach Stahlschmidt and Dale DeNardo (2011).

Other snakes that have been observed guarding their eggs in the wild include:
It's worth noting that, unlike the case with pythons, survival or physiological benefits to the eggs have not been documented in any of these cases. In addition, there are numerous anecdotal reports of egg attendance in other snakes, many of which are based on hearsay and are not backed up by data, photographs, or even descriptions. So, expect this list to grow, but keep in mind that parental care in snakes is still, and will probably always be, the exception rather than the rule.

Costs and benefits

Except for pythons and pitvipers, the costs and benefits of parental care in snakes have not been examined, and I've mentioned some of the evidence for both in pythons already. Why do rattlesnakes and other pitvipers care for their eggs or young? There are several non-mutually-exclusive theories, including:

A mother Pigmy Rattlesnake (Sistrurus miliarius) with
her brood. Because rattlesnake rattles are made of segments
that form each time the snake sheds its skin, newborn snakes
have only one segment and cannot yet make sound.
1. To protect them from predators. This might involve any or all of the following:

  • Physical concealment, especially of the eggs, which are less well-camouflaged than the adults.
  • Deterrence of predators, which may recognize an adult viper as a threat but not an egg or a juvenile.
  • Active defense from predators, using venom or the threat thereof. This may be especially important prior to the first shed of the young, since they would probably suffer their heaviest mortality during this stage because of their small size, inexperience, hampered eyesight and pit organ sensitivity, and, in rattlesnakes, their inability to use their rattle.
  • Socially-facilitated retreat from predators, in which the parent helps the young escape an attack by physically moving them, showing them what to do, or distracting the predator. These may seem like surprisingly sophisticated behaviors for snakes, but several observations of mother snakes and their young support this idea, and we are learning that many snakes have subtle but complex social lives and communication abilities that have long been underappreciated.

Antipredator benefits of parental care in snakes may vary geographically or in other ways, because some species of pitvipers do not seem to change their defensive behavior when they are guarding their young, but others are more defensive, and still others are less defensive but more distracting.
Young Tiger Snakes (Notechis scutatus) snuggling
and data showing that the more litter-mates
they snuggle with, the more slowly they cool off
From Aubret & Shine 2009
2. Litters or clutches of several species of young snakes, including some rattlesnakes, aggregate together, without their mothers, in order to conserve water or heat—which, if they were mammals, we would call snuggling. Experiments have shown that they prefer to snuggle—sorry, I mean aggregate—inside shelters that contain their own scent cues, and that snuggling kept them warm, which helped them slither to shelter faster. No one has tested whether young pitvipers that snuggle with their mothers have higher body temperatures or lower rates of evaporative water loss than those snuggling with one another, but physics suggests that they would, since larger animals have a lower surface-area-to-volume ratio and thus lose heat and water more slowly. The presence of the mother may also offset the increased visibility or olfactory conspicuousness to predators of a bunch of aggregated young snakes. If this is the primary benefit, it is easy to see how maternal attendance of eggs could evolve into maternal attendance of the young, because we think that live birth has evolved many times in snakes, and parental care may have evolved and been lost as many as six and ten times, respectively, in vipers. It's probable that we will continue to fill in the gaps in our knowledge. For example, perhaps we're overlooking the behavior in some poorly-studied vipers, as we did in North American pitvipers for over a century.

Viper family tree showing the evolution of parental care.
A few details have changed but the basic shape of the tree
is the same. Abbreviations: O=oviparous, V=viviparous;
Tr=tropical, Te=temperate. From Greene et al. 2002
3. The week or so of parental care may represent an imprinting period for the young snakes to learn the scent of their mother and of one another, similar to the time a young sea turtle spends imprinting on its natal beach or a young salmon on its natal stream. This would be especially important for snakes in cold climates because they use each others' scent trails to locate hibernation sites. Although there is no direct evidence for the third hypothesis, it is suggestive that, at least in the Americas, temperate pitvipers stay with their young, but live-bearing tropical pitvipers, which do not need to hibernate, do not2. Other explanations include that memories of their siblings' scents help young snakes avoid inbreeding later in life, or that they promote other social behaviors, such as communal basking. Some new data suggest that the adult behavior of pitvipers differs when they are deprived of a maternal attendance period. Tall tales about snakes abound, and initially social behavior ranked among them (there are still false tales about parental behavior in snakes, such as the idea that they swallow their young). Parental care in vipers may just be the tip of their social iceberg. Research over the last decade has shown that vipers make use of chemical information left behind by other vipers when they choose their foraging sites, like a dog sniffing a fire hydrant. This kind of cryptic sociality in snakes can lead to things like inheritance of birthing rookeriesnesting sites, and hibernation sites over many generations. Some research even suggests that pair-bonding might happen between male and female copperheads. Some lizards build multi-generational homes; might we one day discover snakes doing the same? If we do, my money is on vipers.



1 The Kenyan herpetologist J.H.E. Leakey collected eggs from these nests and acknowledged in his paper the support of "the management of the International Hotel, who never once raised any objections to our housing live King Cobras in our rooms."



2 Intriguingly, the only two Neotropical pitvipers known to have parental care are also the only two that lay eggs. One is the Colombian toad-headed pitviper (Bothrops colombianus), about which very little is known. The other, the Bushmaster (Lachesis muta), well-known by comparison, is nevertheless a secretive denizen of primary rain forests. In 1910, Inaugural Bronx Zoo herp curator Raymond Ditmars and his Trinidad correspondent, R. R. Mole, were the first to publish a photograph of a female Bushmaster guarding her eggs. They wrote of Bushmasters guarding their eggs in the wild, and numerous subsequent captive snakes have borne these observations out. Although Eyelash Pitvipers (Bothriechis schlegelii) have not been observed to guard their young, they may do so because their young shed several days after birth, like those of temperate pitvipers, rather than within 24 hours of birth, like most tropical live-bearing pitvipers. The pattern of parental care in Old World vipers, about which we have far less information, appears to be more complicated still.
ACKNOWLEDGMENTS

Thanks to my parents, for indulging my interest in snakes and encouraging me to pursue a career studying them, and to Jim Williams, Peter May, J. Lanki, and Matt Nordgren for the use of their photos.

REFERENCES

Aubret, F., X. Bonnet, R. Shine, and S. Maumelat. 2005. Energy expenditure for parental care may be trivial for brooding pythons, Python regius. Animal Behaviour 69:1043-1053 <link>

Aubret, F., X. Bonnet, R. Shine, and S. Maumelat. 2005. Why do female ball pythons (Python regius) coil so tightly around their eggs? Evolutionary Ecology Research 7:743-758 <link>

Aubret, F., and R. Shine. 2009. Causes and consequences of aggregation by neonatal tiger snakes (Notechis scutatus, Elapidae). Austral Ecology 34:210-217 <link>

Bates, M. F. 1985. Notes on egg clutches in Lamprophis inornatus and Psammophylax rhombeatus rhombeatus. The Journal of the Herpetological Association of Africa 31:21-22.

Benedict, F. G., E. L. Fox, and V. Coropatchinsky. 1932. The incubating python: a temperature study. Proceedings of the National Academy of Sciences 18:209-212 <link>

Brashears, J., and D. F. DeNardo. 2012. Do brooding pythons recognize their clutches? Investigating external cues for offspring recognition in the Children's Python, Antaresia childreni. Ethology 118:793-798 <link>

Brown, G. P., and R. Shine. 2007. Like mother, like daughter: inheritance of nest-site location in snakes. Biology Letters 3:131-133 <link>

Brown, W. S., and F. M. MacLean. 1983. Conspecific scent-trailing by newborn timber rattlesnakes, Crotalus horridus. Herpetologica 39:430-436 <link>

Butler, J.A., T.W. Hull, and R. Franz. 1995. Neonate aggregations and maternal attendance of young in the Eastern Diamondback Rattlesnake, Crotalus adamanteus. Copeia 1995:196–198 <link>

Campbell, J. A., and W. W. Lamar. 1992. The taxonomic status of miscellaneous Neotropical viperids, with the description of a new genus. Occasional Papers of the Museum, Texas Tech University 153:1-31 <link>

Case, T. J. 1978. Endothermy and parental care in the terrestrial vertebrates. American Naturalist 112:861-874 <link>

Clark, R. W. 2007. Public information for solitary foragers: timber rattlesnakes use conspecific chemical cues to select ambush sites. Behavioral Ecology 18:487-490 <link>

Clark, R. W., W. S. Brown, R. Stechert, and H. W. Greene. 2012. Cryptic sociality in rattlesnakes (Crotalus horridus) detected by kinship analysis. Biology Letters 8:523-525 <link>

Cunningham, G. R., S. M. Hickey, and C. M. Gowen. 1996. Crotalus viridis viridis (Prairie Rattlesnake). Behavior. Herpetological Review 27:24 <link>

DeNardo, D. F., O. Lourdais, and Z. R. Stahlschmidt. 2012. Are females maternal manipulators, selfish mothers, or both? Insight from pythons. Herpetologica 68:299-307 <link>

Gans, C. 1996. An overview of parental care among the Reptilia. Pages 145-157 in J. S. Rosenblatt and C. T. Snowdon, editors. Parental Care: Evolution, Mechanisms, and Adaptive Significance. Academic Press, San Diego, California, USA <link>

Graves, B. M. 1989. Defensive behavior of female prairie rattlesnakes (Crotalus viridis) changes after parturition. Copeia 1989:791-794 <link>

Greene, H.W., P.G. May, D.L. Hardy, J.M. Sciturro, and T.M. Farrell. 2002. Parental behavior by vipers. Pp. 179-206 In Biology of the Vipers. Schuett, G.W., M. Höggren, M.E. Douglas, and H.W. Greene (Eds.).  Eagle Mountain Publishers, Eagle Mountain, UT <link>

Hibbard, C. W. 1964. A brooding colony of the blind snake, Leptotyphlops dulcis dissecta. Copeia 1964:222 <link>

Hoss, S.K. and R.W. Clark. 2014. Mother Cottonmouths (Agkistrodon piscivorus) alter their antipredator behavior in the presence of neonates. Ethology 120:933-941 <link>

Hoss, S. K., D. H. Deutschman, W. Booth, and R. W. Clark. 2015. Post-birth separation affects the affiliative behaviour of kin in a pitviper with maternal attendance. Biological Journal of the Linnean Society 116:637-648 <link>

Hoss, S.K., M.J. Garcia, R.L. Earley, and R.W. Clark. 2014. Fine-scale hormonal patterns associated with birth and maternal care in the cottonmouth (Agkistrodon piscivorus), a North American pitviper snake. General and Comparative Endocrinology 208:85-93 <link>

Leakey, J. 1969. Observations made on king cobras in Thailand during May 1966. Journal of the National Research Council of Thailand 5:1-10.

Mori, A., and T. M. Randriamboavonjy. 2010. Field observation of maternal attendance of eggs in a Madagascan snake, Leioheterodon madagascariensis. Current Herpetology 29:91-95 <link>

Oliver, J. A. 1956. Reproduction in the king cobra, Ophiophagus hannah Cantor. Zoologica 41:145-152.

Reiserer, R., G. Schuett, and R. Earley. 2008. Dynamic aggregations of newborn sibling rattlesnakes exhibit stable thermoregulatory properties. Journal of Zoology 274:277-283 <link>

Savary, W. 1999. Crotalus molossus molossus (northern blacktail rattlesnake). Brood defense. Herpetological Review 30:45 <link>

Schuett, G., R. Repp, M. Amarello, and C. Smith. 2013. Unlike most vipers, female rattlesnakes (Crotalus atrox) continue to hunt and feed throughout pregnancy. Journal of Zoology 289:101-110 <link>

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Somma, L. A. 2003b. Reptilian parental behaviour. The Linnean 19:42-44 <link>

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Wasey, G. K. 1892. A nest of King Cobra's eggs. Journal of the Bombay Natural History Society 7:257 <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.

Friday, October 30, 2015

Are there any countries without snakes?


Global distribution of all snake species combined
Public domain from Wikipedia
Terrestrial data from Ernst & Ernst (2011) and Cogger et al. (1998)
Sea snake data based on Campbell & Lamar (2004), Phillips (2002),
Ernst & Ernst (2011), and Spawls & Branch (1995)
Snakes are found in almost every country in the world, but there are a few places without wild1 snakes. Snake-free land generally falls into two categories: remote islands, mostly formed by volcanism or as atolls, that have never been part of a continental land mass and/or have been isolated from continents for a long time, and continental areas that are or were covered by ice within the last 26,000 years and haven't been recolonized since (for example, there are snake fossils from northern Canada, where no snakes live now, from a time when it was much warmer). There are also snake-free parts of the oceans, and probably there are some urban areas that are so disturbed that no snakes live there any more (e.g., downtown Manhattan), although they once did.

Iceland

Iceland is a volcanic archipelago just outside the Arctic Circle. Despite its high latitude, Iceland is warmed by the Gulf Stream and has a temperate climate, so snakes might actually do fairly well there, especially if they could take advantage of its plentiful geothermal features, as the high-altitude hot-spring snakes of Tibet (genus Thermophis) have done. However, Iceland has never been connected to any continent—instead, it was formed about 20 million years ago by a series of volcanic eruptions in the Mid-Atlantic Ridge, which separates the Eurasian and North American plates. It's been at about its current latitude the entire time, and, as far as anyone knows, has never been colonized by snakes. Today, the closest snakes are adders (Vipera berus) in both Scotland (470 mi away) and Norway (600 mi away), both of which are separated by a great deal of very cold ocean.

Ireland

Unlike Iceland, Ireland was once connected to other land masses. Parts of it are at least 1.7 billion years old. At the end of the Precambrian, two pieces of rock that would become Ireland could be found beneath the sea, one piece connected to the continent of Laurentia and the other piece to the smaller continent of Avalonia, both around 80° South. Over the next 50 million years, these two parts drifted northward, eventually uniting and breaking sea level near the equator about 440 million years ago, in the Silurian Period. Throughout the late Paleozoic Era, Ireland sank back under the sea and gained 65% of its modern mass as limestone deposits from huge coral reefs. At the beginning of the Mesozoic, Ireland was at the latitude of present-day Egypt and had a desert climate, and by the time snakes evolved (150 million years ago, in the late Jurassic-early Cretaceous) Ireland had separated from any other land mass, and has been connected on and off to this day. There is some debate over how recently a land bridge connected Ireland with Great Britain and, by extension, mainland Europe, with the consensus resting on the idea that Ireland was isolated by ocean by 16,000 years ago, at which time the climate was still quite cold and there was a lot more ice in Ireland than there is now. Although it's not insane to think that snakes might have colonized Ireland from Europe sometime during the 90 million years that preceded the Pleistocene Ice Ages, as they have since re-colonized Great Britain, so far no one has found any snake fossils in Ireland. But, viviparous lizards, natterjack toads, and common frogs have managed to make it to Ireland, and the slowworm has been introduced there, so it could happen one day. Likely successful colonists include adders (Vipera berus), grass snakes (Natrix natrix), or smooth snakes (Coronella austriaca) from Great Britain, France, or Scandinavia. The Irish climate is highly moderated by the gulf stream, with much milder winters than expected for such a northerly area, so snakes could do quite well there.

Cape Verde

Cape Verde is an island country consisting of 10 volcanic islands in the central Atlantic Ocean, 350 miles off the coast of the western African countries of Mauritania and Senegal. The Cape Verde Islands were all formed by the same volcanic hot spot, the oldest 26 million years ago and the youngest just 100,000 years ago. They have never been colonized by snakes from mainland Africa. There is a single reference to the Striped Sand Snake (Psammophis sibilans) on the island of Sal in a 1951 paper that, according to the authors, was an accidental introduction from Guinea-Bissau. Neither this snake nor any other has ever been recorded again from Cape Verde, although the archipelago is home to 31 endemic lizard species, more than any other island chain in the Macaronesian region.

New Zealand

New Zealand was part of Gondwana (aka Gondwanaland), the more southerly of the two supercontinents formed by the breakup of Pangaea 200-180 million years ago. Gondwana comprised the present-day continents of South America, Africa, Australia, India, and Antarctica as well as New Zealand. Today, New Zealand is the highest part of a mostly-submerged continent called Zealandia that broke away from Gondwana between 100 and 80 million years ago. Since that time, New Zealand has developed a unique flora and fauna that does not include any terrestrial snakes, which makes sense since it has been isolated since around the dawn of their evolution (and has been mostly submerged several times since). However, a steady trickle of reports of sea snakes, borne by oceanic currents beyond their normal range to New Zealand waters and beaches, was summarized in 1997, at which time an amazing 69 records of 2 species were known, dating back to 1837 (more records and a third species have been added since). About 90% are of pelagic sea snakes (Hydrophis platurus; formerly Pelamis platurus, also known as yellow-bellied sea snakes), a very widespread species that is infamous for vagrancy and recently made headlines when one washed ashore in Ventura County, California. The remaining 10% of records are of banded sea snakes (Laticauda colubrina), a species that normally sticks more closely to shores, and judging by their morphology most of these have likely come to New Zealand from Fiji or Tonga. In 1995, one specimen in the British Museum collected in New Zealand in 1925 and formerly classified as L. colubrina was re-identified as a new species from New Caledonia, L. saintgironsi, by herpetologists revising the widespread Laticauda colubrina complex.

Map of pelagic sea snake records from New Zealand
(1837-1997)
From Gill 1997
High sea surface temperatures in 1969-1975 and again in 1988-1990 coincided with major influxes of tropical and subtropical fishes, sea turtles, and sea snakes (up to 16 a year) carried to New Zealand waters by the East Australian Current. Most records are of single animals, but in March 1985 four H. platurus were found on Tokerau Beach in Northland. About three-quarters of sea snake records are from Austral autumn (March-May), and many are from the north coast of the north island, but H. platurus has been found all around the North Island, including in the Cook Strait, and once even on the north coast of the South Island (at Pakawau, Golden Bay, in March 1974)! All L. colubrina records are from the north-east coast of the North Island, except for one at Castlepoint, Wairarapa, in August 1977. All records are of adult snakes, and most (79%) were alive when found, usually washed ashore, but occasionally swimming freely. One even swam up a stream near the sea! Even more amazingly, several sea snakes have been found alive inland from the coast, including a May 1938 record of H. platurus "some distance" from the sea at Table Cape on the Mahia Peninsula, a January 1990 record of L. colubrina "well above" the high-tide line at Whangaruru Harbour, an April 1938 record of H. platurus 200 feet from the sea on a lawn at New Plymouth, and, most incredible, a September 1945 record of L. colubrina alive at Te Aroha, near Hamilton, which is over 12 miles from an estuary over a range of hills or over 27 miles from the ocean along the Waihou River. Unlike H. platurus, which is almost incapable of moving on land, L. colubrina is reasonably good at terrestrial locomotion, which could explain the inland presence of these snakes. Alternatively, the author of the review paper suggested that the snakes could have been carried inland by birds.2

New Zealand also owns the Chatham Islands 560 miles to the east, the Kermadec Islands 620 miles to the north, and Tokelau 2000 miles to the northeast3, but no sea snakes have been reported from these islands, probably because so few people live there. Like vagrant birds, even the records from mainland New Zealand surely represent just a small percentage of the total number of marine reptiles that have reached New Zealand over the years. However, New Zealand is still widely considered to have no native snakes, since H. platurus  stop feeding at sea temperatures below 18°C and die at temperatures between 14.5 and 17°C (the average sea temperature in the coldest month in northern New Zealand is 16°C).

Kiribati

Kiribati is a Pacific Island nation that straddles the region of the central Pacific Ocean where the Equator and the International Date Line cross, making it the only country that is in all four hemispheres. It consists of four island groups totaling 32 atolls and one coral island. Of these, approximately the eastern half (the Phoenix and Line Islands) are apparently devoid of snakes; at least, they are listed as having no snakes in the most up-to-date and authoritative guide to the reptiles of the Pacific Islands. This guide takes a conservative approach in listing only species that are confirmed by a museum specimen or literature record, so it's possible that at least pelagic sea snakes are found in the waters of eastern Kiribati. What is certain is that the western half of Kiribati (Banaba and the Gilbert Islands) is home to breeding populations of banded sea snakes (Laticauda colubrina), and possibly pelagic sea snakes as well. Additionally, there is a single record of an ornate reef seasnake (Hydrophis ornatus), a species that is normally found much farther west, from the Gilbert Islands. This might represent a vagrant, but more likely it is a misidentified or mislabeled specimen. So, Kiribati has no terrestrial snakes, unless you count banded sea snakes, which mate, lay eggs, and sometimes digest food on land, but hunt, catch prey, and spend much of their time in the ocean.

Tuvalu

Tuvalu is a Pacific Island nation south of Kiribati comprising three reef islands and six atolls and totaling 10 square miles, making it the fourth smallest country in the world. Like Kiribati, Tuvalu has no terrestrial snakes unless you count L. colubrina, but unlike Kiribati it has literature records of pelagic sea snakes off its shores. Happily, Tuvalu has decided to honor this species by putting it on one of its coins! It's a commemorative coin rather than a coin that's actually part of normal circulation, but still, it's pretty cool to have a snake on your money. Tuvalu is also home to at least 9 species of lizards and the introduced cane toad, so it's possible that snakes could show up there one day. In fact, it's even possible that a native, endemic blindsnake could have escaped detection on Tuvalu (or any other Pacific island) to this day. The only reason the Federated States of Micronesia aren't on this list is because of two unexpected species of endemic blindsnakes, Ramphotyphlops adocetus and R. hatmaliyeb, described in 2012 from two small islands, one in the eastern part of FSM and the other in the western part.

Nauru

Nauru is a relatively isolated Pacific Island nation and is one of the only countries smaller than Tuvalu (at 8.1 square miles, only Monaco and Vatican City, both in Europe, are smaller). Unlike many Pacific Island nations, Nauru is a single island. Nauru has no native terrestrial snakes, but it does have H. platurus off its shores, and it also has what is likely an introduced species, the ubiquitous Indotyphlops braminus or Brahminy Blindsnake, the only unisexual species of snake. It's actually amazing to me that we're on the seventh entry and haven't encountered this species yet, considering how widespread it is globally. The original native range of I. braminus is unknown, but it probably evolved in continental Asia. Because a single individual constitutes a reproductively-competent population, it has since spread all over the world, and it's unclear how long it has been established on Nauru or elsewhere in the Pacific. Many similarly-widespread species in the Pacific owe their distribution to human-assisted transport, the precise timeline of which is difficult to determine. Given the harm done to Nauru's environment by phosphate mining during the 20th century, it's unlikely that any native terrestrial snake would have survived.

Marshall Islands

The Marshall Islands (see above map) have close political ties with the USA, but they are self-governing. They are located north of Kiribati, west of the FSM, and south of Wake Island. The authoritative guide to the reptiles of the Pacific Islands lists only I. braminus from the Marshall Islands, but other sources suggest that at least a few brown treesnakes (Boiga irregularis), infamously introduced to Guam, have been found there as well, and it's possible that H. platurus and possibly other sea snakes are found off its shores. Both the Gilbert Islands in Kiribati to the south and Pohnpei and Kosrae in FSM to the west have L. colubrina, although an official page states that the Marshall Islands have no sea snakes. So, as far as we know the Marshall Islands have no snakes that are native and terrestrial (unless you count I. braminus as native, considering that we don't know how long it's been there).

Vatican City

The Vatican is a walled enclave within the city of Rome, Italy, with an area of 110 acres and a population of 842, making it the smallest internationally-recognized independent state in the world, both by area and population. I couldn't find any references confirming or denying the presence of wild snakes in the Vatican, but other wildlife seem to be pretty minimal, which makes sense considering that Rome has been a large city for thousands of years. But, snakes and other wildlife can hang on in some amazingly urbanized places, so I wouldn't completely rule out the presence of a few of the eight species of snakes that can surely be found in the surrounding Italian countryside. Monaco, another European microstate with a very dense population and a high degree of urbanization, is another possibility for a snake-less nation, although, given Monaco's reputation as a playground for the rich and famous (30% percent of its population are millionaires), there are certainly some who meet an alternate definition of the word "snake" within its walls.

Cover of a joke book that's blank inside
So there you have it: a maximum of ten countries out of 196 "without snakes", depending on where you want to draw the line. If we start expanding into territories or disjunct sections of larger countries, the list grows considerably, including places like Greenland, the Falkland Islands, Bermuda, Hawaii4, Wake Island, Johnston Atoll, Howland & Baker Islands, the Marquesas Islands, the Pitcairn Islands, Sala y Gomez, Isla Malpelo, St. Helena, the Faroe Islands, the Isle of Man, many Arctic and Antarctic islands, and Antarctica itself, which is owned by no country. And of course, as you can see from the map at the top, there are also large mainland areas of northern Europe, Asia, and North America, as well as the southern tip of Patagonia, that are too cold for snakes (although Vipera berus gets above the Arctic Circle in Scandinavia), not to mention the Atlantic, Arctic, and Antarctic Oceans5.

In the course of the research I did for this post, I found many travel articles promoting the snakelessness of some of these places as overwhelmingly positive, as I'm sure it is for many ophidiophobic travelers. But, the risk that snakes pose is way, way smaller than the fear we have of them, and in my mind the real danger is that many people see eradication of snakes as a positive thing, despite the fact that many of them are in real danger of extinction. Mauritius barely made it off this list, with one of two native species extinct and the other hanging on thanks only to captive breeding and reintroduction efforts. St. Kitts & Nevis could lose its only native snake, the Saba or orange-bellied Racer (Alsophis rufiventris), and native snakes have gone extinct or become critically endangered on many other islands throughout the Pacific and Caribbean due to centuries of forest clearance, overgrazing, development, and the introduction of invasive species, not to mention the many continental snake species threatened by sprawling development and habitat fragmentation. So, please, let's keep this list from growing.



1 Given the growing popularity of herpetoculture, I'd be willing to bet that there are captive snakes in every country, although a few countries have stringent laws banning any captive snakes, including as pets as well as in zoos and research facilities.



2 Studies have shown that, although many Pacific birds avoid pelagic sea snakes, naive Atlantic birds will try eat them (only to throw them up, since they are apparently poisonous as well as venomous). New Zealand's birds might be sufficiently naive to try to eat one.



3 Zug's Reptiles and Amphibians of the Pacific Islands lists Tokelau as having no snakes, not even sea snakes, but does not cover the Chatham or Kermadec Islands.



4 Hawaii has introduced Brahminy Blindsnakes and, unlike many Pacific Islands, it is known that these colonized the island chain more recently, in 1930, when they were imported from the Philippines in potted palm trees. Hawaii also has pelagic sea snakes and there are a few records of introduced brown treesnakes and boa constrictors, but neither species has established a breeding population (yet).



5 A study evaluating the probability that pelagic sea snakes could enter the Caribbean and Atlantic through the Panama canal, as lionfish have, concluded that there were no real barriers to their colonization of the eastern side of the Americas, but so far this has not happened.


ACKNOWLEDGMENTS

Thanks to Kerry Nelson for doing some of the background research for this post as part of a discussion in the Wild Snakes: Education & Discussion Facebook group.

REFERENCES

Edwards, R. J., and A. J. Brooks. 2008. The Island of Ireland: Drowning the Myth of an Irish Land-bridge? Pages 19-34 in J. J. Davenport, D. P. Sleeman, and P. C. Woodman, editors. Mind the Gap: Postglacial Colonisation of Ireland. Special Supplement to The Irish Naturalists’ Journal <link>

Gill, B. J. 1997. Records of turtles and sea snakes in New Zealand, 1837-1996. New Zealand Journal of Marine and Freshwater Research 31:477-486 <link>

Heatwole, H., S. Busack, and H. Cogger. 2005. Geographic variation in sea kraits of the Laticauda colubrina complex (Serpentes: Elapidae: Hydrophiinae: Laticaudini). Herpetological Monographs 19:1-136 <link>

Hecht, M. K., C. Kropach, and B. M. Hecht. 1974. Distribution of the yellow-bellied sea snake, Pelamis platurus, and its significance in relation to the fossil record. Herpetologica 30:387-396 <link>

McKeown, S. 1996. A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing.

Vasconcelos, R., J. C. Brito, S. Carranza, and D. J. Harris. 2013. Review of the distribution and conservation status of the terrestrial reptiles of the Cape Verde Islands. Oryx 47:77-87 <link>

Wynn, A. H., R. P. Reynolds, D. W. Buden, M. Falanruw, and B. Lynch. 2012. The unexpected discovery of blind snakes (Serpentes: Typhlopidae) in Micronesia: two new species of Ramphotyphlops from the Caroline Islands. Zootaxa 3172:39–54 <link>

Zug, G. R. 2013. Reptiles and Amphibians of the Pacific Islands: A Comprehensive Guide. University of California Press, Berkeley, California, USA <link>

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.