Rattlesnake Roundups Dissertation

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?

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).

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.

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.

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. biserialisP. 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.

I’m from the Netherlands where we don’t have rattlesnakes. I had recently ‘moved’ to California and had not seen, let alone heard a rattlesnake before, but when I opened the trailer door that summer night to let one of the dogs out, I knew immediately, possibly instinctively, that the loud, hard to describe sound that greeted me outside belonged to a rattlesnake. It resembled the rattling of the wooden children’s toy, but amplified and sped up, accompanied by an eerie harsh whisper-like sssshhhhhhhhhhh.

I must have spooked the animal with the sudden light beam erupting from the door swinging open. Grateful for the warning, I grabbed my eager-to-exit dog – she is blind and deaf, so had not gotten the message – by the collar, shoved her back inside and closed the door without even having seen the snake.

Curious, of course, I grabbed a flashlight and observed the beautiful 4-feet western rattlesnake from a safe distance. This was my first encounter with this species, but definitely not the last. I have seen many since as I live here in rattlesnake country, just a half hour drive from Hollywood’s Sunset Strip that, at some point not too long ago, was of course rattlesnake country too.

When you choose to live here, it is your duty to learn about these legless neighbors and how to co-exist with them.

For uncaring people, finding a rattlesnake in their yard or anywhere else does not present much of a dilemma. They apply the ‘shovel method’, a disrespectful way to say they kill him or her with a gardening tool.

Killing rattlesnakes, or any other snake for that matter, is not only barbaric and cruel, but also ignorant, as snakes play an important role in the ecological system.

The natural diet of rattlesnakes consists of rats and mice, squirrels, young rabbits, gophers, small birds, frogs and large insects. They keep the populations of rodents in check. That’s how a healthy ecosystem works!

The above means that rattlesnakes do not deliberately stalk human beings. They do not see you as a food source.

It also means that if you don’t want snakes around your house, you should remove outside food sources, such as food waste, pet food and birdseed that attract rattlesnake prey. If there is no prey there will be no snakes.

Snakes do not built their own dens. They will utilize pre-existing shelters such as rodent nests and rabbit holes, woodpiles, rock crevices, garbage heaps, long grass, brush & undergrowth, piles of building materials or the crawlspace under your home. If you don’t want snakes in your yard, remove or make inaccessible potential shelters!

A short lawn or pavement offers no hiding places for snakes and makes it easy for you to spot a rattlesnake.

You could build a rattlesnake proof fence around your entire backyard or, much better, a selected area where your children play, your pets frolic and you sit down to sunbathe, drink a beer, barbeque or read. Use mesh that is not wider than a quarter of an inch in diameter or use solid un-textured material, as snakes cannot climb smooth surfaces; they need grip. Construct a fence of a minimum height of three feet and make sure to remove the vegetation bordering the fence or anything else leaning against the fence that a rattlesnake might use to crawl over.

Know your snakes! The presence of some snake species can actually deter rattlesnakes. Gopher snakes defend their territories against encroaching snakes and kingsnakes, black racers and indigo snakes are ophiophages: they kill and eat other snakes, including rattlesnakes.

There are several types of snake repellents on the market, naphthalene flakes or mothballs (paradichlorobenzene or 1,4-dichlorobenzene) that you should ignore, as there is no proof that they are effective and, depending on use, these products might be bad for your health as well.

There are snake traps available, usually referred to as ‘snake guard’ or ‘snake trap’, open-ended flat boxes with a sticky bottom that work like ‘roach motels’. These contraptions are designed to get a snake looking for shelter stuck with his or her head inside. The victim usually dies from starvation, exposure or from being eaten by a predator or scavenger.

There are also snake fences for sale, which consist of synthetic netting on small posts about a foot high that you stake to the ground. They work in the same vein as the drift nets that are emptying the oceans of life: a snake that tries to crawl through the net will get caught and suffer the same fate as if he or she was caught in a trap.

Cruelty in any form to get rid of snakes should be unacceptable.

Killing a snake does not deter other snakes from coming to your backyard. If you don’t want a snake near your house, prevention is the only effective way and certainly the only ethical way.

Approximately 300,000 dogs and cats are bitten by venomous snakes each year in the United States, according to the Red Rock Biologics website, a vaccine manufacturer.

Some dog owners pay for ‘avoidance training’ to get their dogs to steer clear of rattlesnakes. Electrical shock collars are used as ‘negative stimulation’ on the dogs and live, rendered-harmless rattlesnakes are exploited for the dogs to encounter before being shocked. This is inherently cruel to both species. It is also questionable if the training is effective. A running or playing dog might never even notice the snake that ends up biting him or her.

A vaccine, licensed by the United States Department of Agriculture, Crotalus Atrox Toxoid was developed to provide protection for dogs against Western Diamondback Rattlesnake venom. Because of the similarities in the venom, “this vaccine may also provide protection against the venoms of the Western Rattlesnake (including the Prairie, Great Basin, Northern and Southern Pacific varieties), Sidewinder, Timber Rattlesnake, Massasauga and the Copperhead. Partial protection may be obtained against Eastern Diamondback Rattlesnake venom, but does not provide protection against venom from the Water Moccasin (Cottonmouth), Mojave Rattlesnake or Coral Snake”, according to the manufacturer.

The treatment in no way provides immunity! Vaccinated dogs are said to experience less pain, less swelling, less tissue damage, experience a faster recovery and have a reduced risk of permanent injury from rattlesnake bites than unvaccinated dogs, but there seems to be little scientific data to back up these claims.

UC Davis School of Veterinary Medicine states on the subject:

“…Although there may be circumstances where a rattlesnake vaccine may be potentially useful for dogs that frequently encounter rattlesnakes, there remains little fact-based data to support the efficacy of the vaccine to date.”

Vaccination might buy you a few extra minutes to reach a vet, but, again, prevention is the way to go: Keep your dog on a short leash, walk them in the early morning when snakes are less active, stay on clear trails and avoid rocky and overgrown areas.

Snakes don’t have ears; they sense movement from vibrations rather than sound! They’ll probably be aware of your presence long before you are aware of theirs.

A rattlesnake’s first line of defense is to remain motionless or retreat. Rattlesnakes use their color and pattern to blend into their surroundings to hide from both prey and predators. They often hunt by sitting still, waiting for a prey animal to pass within striking distance. They do not rattle, because that would give away their location.

If you surprise or threaten a rattlesnake they offer an audible warning, but they will still do everything they can to avoid confrontation and to avoid striking, biting and using up their valuable supply of venom. Venom is intended to kill and digest prey, so they’re reluctant to bite, and 25 to 50% of all bites are dry – no venom is injected, according to Herpetologist Leslie Anthony.

A snake is a very vulnerable creature: no legs, no ears, bound to the ground, no body armor to speak of, no formidable size, not particularly fast, but tasty to many carnivorous and omnivorous predators. Poisonous venom is their last line of defense.

A rattlesnake fang has an opening near the end, connected by a duct to a poison gland behind the eye. Normally, the fang lies against the roof of the mouth, but when needed, the fang is pushed forward and the poison injected into the deepest part of the wound.

They will not strike without a reason, but they will aggressively defend themselves. A snake’s instinct is to protect itself! With his or her body partly coiled and the tail rattling loudly, the head up ready to strike, a rattlesnake will normally give you a last, very clear warning to not come any closer or (s)he will attack!

Remember, however, that there might not be an audio warning. Young rattlesnakes are born with fangs and venom but will not produce a rattle for the first couple of weeks. Rattles on older snakes may be broken off, malformed or silent. Wet snakes are said not to rattle. Do not rely on the rattler as the only form of identification!

There has been a lot of discussion lately about rattlesnakes that are said to have evolved to remain silent instead of using their rattle as a warning. Some claim that rattlesnakes that do not rattle to remain undetected are less likely to be discovered and killed by humans, and that this trait is passed on to succeeding generations.

At the Wildlife Waystation, where all accompanying photos were taken, the rattlesnakes rarely rattle and are not aggressive. The (wild) snakes are truly protected here; no one will kill or harass them and they might have learned that.

If ‘hot’, meaning aggressive, snakes are encountered on the property, they usually look very skinny which is abnormal as there is plenty of food around on the sanctuary and ‘our’ rattlesnakes are normally well fed and happy. The suspicion is that these are snakes removed from urban yards and dumped in the canyon by ‘exterminators’. Sometimes new snakes, displaced by brushfires elsewhere, move in from the outside.

In the end the duty really rests with you to avoid being bitten: behave responsible, with common sense, be alert if you live in rattlesnake habitat. Be wary, be certain and keep safe. Leave the snakes alone!

Snakes are ectothermic, which means that their body temperature adjusts to that of the environment. If the air temperature is low, they will seek warmer spots, position themselves on surfaces that absorb heat from the sun. In the heat of summer they will protect themselves from overheating by taking cover in the shade of rocks and vegetation during the day and become more nocturnal, coming out in the cool of the evening or the night. The ideal air temperature for rattlesnakes lies between 70° and 90°F or 21° to 32°C.

If you really have to move a rattlesnake, spraying cold water from a distance might just work, as they do not want to cool down too much.

Never pin – holding the animal down with force at their necks – a rattlesnake. It is harmful to them and traumatic, as predators will normally attack their necks and heads in an attempt to avoid the fangs.

If you absolutely need to handle them use snake hooks or snake tongs.

According to the Centers for Disease Control and Prevention (CDC) “[i]t has been estimated that 7,000–8,000 people per year receive venomous bites in the United States, and about 5 of those people die.”

More than half of all rattlesnake bites are provoked by the person bitten!

A 1988 USC Medical Center (Los Angeles) study found that 44% of snakebites were accidental, more than half resulted from the victim handling a snake, 28% of the victims were intoxicated and 90% of the victims were male, most of whom were in their 20s. In other words, stupidity is the main reason for people to get bitten by a snake.
Most snakebites are avoidable by leaving the snake alone. Don’t try to catch, kill, handle or provoke and harass a rattlesnake into acting in self-defense.

Watch where you walk and where you put your hands. A rattlesnake’s striking distance can be up to one third to one half of its overall length. Rattlesnakes can swim and can climb trees!

Juvenile rattlesnakes can be very small and just as dangerous as adults.

The summertime nocturnal habits of rattlesnakes mean they come out when human eyesight starts to fail. Use a flashlight when walking about and wear good footwear.

As the majority of bites occur on the hands, arms, feet, lower legs and ankles, clothing is an important defense against snakebites.

If you go hiking off the beaten path, make sure your cell phone is charged (only useful when there is cell phone coverage and then you are not that far off-the-beaten-path after all) or even better, take a buddy.

Keep alert as you hike, walk, climb. Stick to well-used trails and do not wander off into rocky areas, tall grass, underbrush and weeds. Step on and not over logs and rocks. Do not stick your hands in places where you cannot see them. You could carry a stick to thump the ground. Don’t sit down on tree stumps, logs or rocks without first checking the surroundings.

Check a campsite before setting up. Arrive in daylight and set up in daylight. Shut the tent flap at night and check before going to bed that no snakes are inside.

When you encounter a snake that you think might be poisonous, keep calm. Send children, pets and scared adults indoors or a safe distance away.

Don’t do anything to provoke the snake, move away slowly and leave it alone.

Again, most rattlesnakes will only strike if acting in self-defense. If you remain out of the way, there will be no harm done.

Make sure that young children understand the dangers of rattlesnakes, know what to do to avoid a rattlesnake encounter and how to behave if they do encounter a rattlesnake.

Relocating a rattlesnake isn’t necessarily a humane option. Rattlesnakes use familiar dens to survive colder spells and predation. Female rattlesnakes give birth around their dens in fall and the young benefit from that security.

An early 1990s study radio-tracked timber rattlesnakes in Pennsylvania to compare behavioral differences between snakes that had always lived in a particular area versus snakes that had been relocated to that area from 5 to 107 miles (8 to 172 km) away. According to the authors the “results clearly indicate that long-distance geographic translocation (i.e., relocation) results in decreased survival and an alteration of the behavior of C. horridus. Specifically, translocated snakes made frequent and extensive movements. The pattern of movements suggested either the snakes were searching for familiar environmental features, or they were exploring the new territory in order to become familiar with the existing conditions. Translocated snakes suffered from higher rates of overwintering mortality, predation, and disease than did residents. Only four snakes out of 11 (36.7%) are known to have survived through two complete active seasons following translocation.”

If you need to relocate a snake, only take him or her a short distance from your house or work location, no more than a couple of hundred meters. This allows the animal to stay within the area it knows and close enough to its den to find it back.

Even when observing all precautions you can still just have bad luck. Rattlesnake bite symptoms may include:

-Puncture marks at the wound

-Redness and swelling around the wound

-Pain at the site of the wound

-Nausea and vomiting

-Labored breathing

-Blurred vision

-Increased salivation and sweating

-Numbness or tingling around your face and/or limbs.

First aid measures you can and should take in case of a (suspected) rattlesnake bite:

– Get some distance between yourself and the snake.

-Remain calm and immobile! Panic and activity will increase your heart rate and spread the venom through your body faster.

-Seek medical attention as soon as possible. Dial an emergency number or call out for help and/or secure prompt transport to a hospital emergency room.

– Remove jewelry, watches, tight clothing, shoes and other constricting items from the affected area. Bites from venomous snakes can cause rapid and severe swelling.

-Try to remember the color and shape of the snake or take a photo. The identification of the snake can help with the treatment of the bite.

-Lay or sit down with the wound below the level of the heart. Elevation of the bite will increase circulation and spread venom more rapidly.

-Clean the wound with soap and water, but don’t flush.

-After cleaning, cover the wound with a clean, dry dressing.

If you’re out in the wilderness, without a chance of help, stay calm and inactive, get as comfortable as possible and wait for the venom to leave your system. In most cases, snakes don’t inject enough venom for the bite to be fatal.


-pick up the snake or try to catch it in any other way.

-go on a revenge killing spree.

-wait for symptoms to appear; if bitten, seek immediate medical attention.

-apply a tourniquet. It could restrict blood flow to such an extent that the resulting damage is worse than a snakebite.

– make an incision of any kind. It could cause infection and worsen the wound.

-suck out the venom. You could poison yourself and it is important to retain traces of the venom for identification.

-apply ice or immerse the wound in water. Ice could do more damage than good.

-drink alcohol or caffeinated beverages or administer drugs or medications. All of these can increase your heart rate and spread venom faster. Instead, stay hydrated with water.

If the snake that bit you was venomous, you’ll likely get treated with antivenin, a combination of antibodies made to counteract snake toxins, in combination with a broad-spectrum antibiotic to prevent infection. A tetanus shot may also be given.

An exceptionally cruel and ignorant way to ‘deal’ with rattlesnakes is still practiced in some areas of the states of Texas, Oklahoma, Kansas, New Mexico, Pennsylvania, Alabama and Georgia and is referred to as roundups. A roundup is a carnival-freak-show-kind of redneck-hillbilly gathering where each year tens of thousands of rattlesnakes removed from the wild are displayed and slaughtered for entertainment, food and profit.

The claim is that roundups prevent rattlesnake overpopulation, but the mechanisms to keep a natural balance in a healthy ecosystem work in all directions. Snake populations themselves are maintained by prey abundance, levels of predation by their natural enemies and disease. This means humans do not have to cull or otherwise remove snakes (or any other native animal!) to ‘manage’ nature! Nature needs no human managing, it needs to be treated with respect and that means in most cases leaving it alone!

There are no ‘bag’ or ‘take’ limits for roundups and there is no monitoring or reporting. The collectors are rewarded cash prizes for bringing in the highest number and biggest snakes.

An estimated 80% of rattlesnakes at roundups are collected by ‘gassing’: Gasoline or ammonia is dispersed from a pump-up sprayer into suspected rattlesnake dens to intoxicate and irritate the animals, forcing them to emerge so they can be captured.

The ‘gassing’ method is controversial as it pollutes surrounding land and water and may impact up to 350 other wildlife species as collateral damage that share the same burrows with the rattlesnakes; many of these are insect species, but also other snake species.

29 States have already banned the practice of ‘gassing’ rattlesnakes.  A proposal to ban ‘gassing’ in Texas was introduced in late 2014, but was killed by Texas Parks and Wildlife by removing the proposal from their November 2016 agenda. The commission “decided that, at this time, there is insufficient support from legislative oversight or the potentially regulated community for the department to move forward with regulating the use of gasoline to collect rattlesnakes”, John Davis, wildlife diversity program director at the Texas Parks and Wildlife Department, said at the time. Rattlesnake roundups depend on the ‘gassing’ method of take and had lobbied hard to can the bill. Roundups are defended as a cultural tradition and beneficial to the communities because it brings in money.

The practice has likely contributed to the decline in some rattlesnake species. In March 2016, the Sweetwater Rattlesnake Roundup collected and slaughtered more than 21,000 rattlesnakes. In a 2006 paper, the American Society of Ichthyologists and Herpetologists estimated that 125,000 rattlesnakes were being killed annually for roundups at that time. This barbaric practice has to end!

People and rattlesnakes can peacefully co-exist, and if you use common sense, the chances of being bitten are very low. The best protection against rattle- and other venomous snakes is awareness, knowledge and prevention.





L. Walker, J. A. Dorr, R. J. Benjamin, & G. R. Pisani (2009). Successful relocation of a threatened suburban population of timber rattlesnakes (Crotalus horridus): combining snake ecology, politics, and education IRCF Reptiles and Amphibians, 16 (4), 210-221

Nowak, E.M., Hare, T, & McNally, J (2002). Management of ‘‘nuisance’’ vipers: effects of translocation on western dia- mondback rattlesnakes (Crotalus atrox). Biology of the Vipers, 533-560

R. Mohr (2010). Autoecology of the timber rattlesnake (Crotalus horridus) in the South Carolina mountains Dissertation, Clemson University

Reinert, H., & Rupert, R. (1999). Impacts of Translocation on Behavior and Survival of Timber Rattlesnakes, Crotalus horridus Journal of Herpetology, 33 (1) DOI: 10.2307/1565542

Sealy, J. (1997). Short-distance translocations of timber rattlesnakes in a North Carolina state park: a successful conservation and management program. Sonoran Herpetologist, 10, 94-99


















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