Tuesday, June 26, 2012

Readers Write In: Do Snakes Eat Their Prey Alive? It Depends.

This e-mail (and picture) arrived in my inbox a couple weeks ago:

I recently happened to accidentally disturb a Ratsnake that was constricting a baby rabbit. When I touched the snake's tail, he uncoiled but began to start swallowing the rabbit. Because I interrupted the constriction, the baby rabbit was still alive but the snake continued to engulf it anyway. Is it unusual for a snake to consume a meal that is still alive?

Randy Y.
Midlands, South Carolina

  First off, I was glad to see that A) the snake in the picture was correctly identified as a normal component of the local wildlife and B) it wasn't bludgeoned to death.

  To answer this question, we must first consider why snakes constrict and kill their prey at all. To put it simply, snakes kill their prey because eating your dinner alive is a dangerous job when you have no arms or legs but prefer meals with sharp teeth, claws, and/or beaks.

  Squirrels, for example, are common meals for snakes. Squirrels are not generally known for their fearsome nature; but, you should have seen the little ones I helped cared for when I volunteered at a wildlife rehabilitation center many years ago. When I walked by their cages they would rush towards me repeatedly and bare their teeth in vicious displays of ferocity. In my memory, they roared. I'm not sure if I'm remembering that part correctly but I do know I was terrified when it was my turn to feed them.

   In any case, capturing a squirrel, rat, or even a rabbit, can be a dangerous proposition for a snake. So, what some snakes do is: 1) use their mouth to quickly grab their intended prey and, 2) in a flash, wrap their body around their soon-to-be meal and suffocate it. When the snake senses that their dinner's heart is no longer beating, the snake then begins to swallow it. I should add here that different kinds of snakes have different strategies for catching prey. In this post, I am speaking of the snakes, such as Ratsnakes, that are known as constrictors.

   That all makes sense, but as Randy observed, sometimes snakes skip the constricting step (you may remember me writing about how hognose snakes exhibit some similar behaviors). Why do snakes sometimes do skip constricting their prey? Well, when a snake is busy and pre-occupied with wrapping itself around a rat or other animal, the snake runs a high risk of becoming a meal for another predator, like a vigilant hawk. Another reason snakes might not want to constrict their prey before eating it is because it takes a lot of work and energy.

   Despite the risks of constricting their prey, a snake is not likely to skip this step when their meal could hurt them. A few laboratory studies have been conducted on the subject and it is generally thought that the more harmless the meal is, the more likely a snake will just start swallowing it without bothering to constrict it first. What kinds of meals don't represent a considerable danger? Baby rodents, birds, and rabbits, like the one in South Carolina. 

  Does it sound gross and distasteful to imagine swallowing defenseless prey? Well, what did you have for lunch?

Want to Learn More? Check Out These Scientific Articles:

A. Mori (1991). Effects of prey size and type on prey-handling behavior in Elaphe quadrivirgata Journal of Herpetology, 25 (2) DOI: 10.2307/1564643

A. de Queiroz (1984). Effects of prey type on the prey-handling behavior of the bullsnake, Pituophis melanoleucus Journal of Herpetology, 18 (3), 333-336 DOI: 10.2307/1564088

Friday, June 15, 2012

Readers Write In: Hiker Seeks Help for Snake Anxiety

   Given this recent and excellent summary of the roles snakes have played in our cultural history, a summary that delves deeply into some possible root causes of the fear many people feel of these animals, I thought it was an appropriate time to post this recent e-mail I received from a hiker aspiring to traverse the Appalachian Trail:

…I love to hike! I've been section hiking the Appalachian Trail for several years now and have been building up my supplies to do a thru-hike in two years. Lately, though, my section hikes and the thought of thru-hiking have become sources of a huge amount of anxiety and I can barely get through them mentally now. I feel in total discordance with my environment and with the wilderness and it has become thoroughly depressing. The source of my anxiety is snakes (emphasis mine). I have always been terrified of snakes. I have recurring nightmares about them. They seem to represent some inner turmoil or conflict for me. That's the only way I can logically explain this crippling phobia. I know in my mind that snakes are simply active, working participants in their ecosystem and I have immense respect for that, but in my heart, the thought of seeing one fills me with dread. Lately, because I have been reading Appalachian Trail memoirs and informational books, I have become more and more aware of their presence and I cannot seem to take my mind off of them when on the trail. I guess what I'm writing to you for is advice. I need to be able to take my place in nature and walk with it, and that means walking with snakes.

Kelly L.

   First off, I admire Kelly's goal of hiking the Appalachian Trail. This monumental feat is something I fantasize about accomplishing someday. One of the interesting things about the Appalachian Trail is that it criss-crosses several mountain ranges that represent excellent Timber Rattlesnake (Crotalus horridus) habitat. Unfortunately though, I don't think that many hikers fully appreciate their encounters with these magnificent animals and I suspect their populations near trails have been severely diminished.

   I also respect Kelly's appreciation for the natural world and all of its denizens, despite a, "crippling phobia" for snakes. I replied that a fear of snakes was a common one but I just don't get it. They're just animals. They're interested in the same things all animals are, like mating, eating, and not getting eaten themselves. But, snakes are so reviled. It's too bad, I wrote. It makes me cringe when I do educational demonstrations and the kids clamor to get close to the snakes, at least until they see the adults shrieking or otherwise carrying on. It would be funny if that was the end of it; but, I think a culturally encouraged fear of snakes is a huge reason people are so callous (or even enthusiastic) about killing these animals as well as being a huge influence in fostering irrational fears.

   I hope the readership of this blog can offer some advice to Kelly. Are you a hiker of any natural areas, including the Appalachian Trail? Do snakes represent a danger to you? How have you managed to hike alongside these animals? Have any of you (hikers and non-hikers included) overcome a fear of snakes? How?

  In a follow-up e-mail, Kelly was enthusiastic about receiving advice via this blog and wanted to clarify:

...I've read a lot about snakes being killed on the trail and have been instructed to do so more than once as a treatment for my phobia. Let me be clear, I have absolutely no interest in murdering an animal whose environment I choose to inhabit. In fact, the more I talk about the beautiful and practical aspects of snakes, the less intense my anxiety gets. I have concluded that my fear is not necessarily of the actual snake, but the anxiety that I associate with them, which I am sure is culturally based, like you said.

Let's help Kelly out.

Saturday, June 2, 2012

The Serpent's Tale: Snakes in Mythology and the Modern World

   The following article is a guest post by John Worthington-Hill. Although his primary focus is snakes, John has an overarching passion for the natural world and its conservation. He enjoys spending as much time outside as possible, mostly herping (that is to say, finding amphibians and reptiles), bird-watching and photographing wildlife. John recently received his BSc in Wildlife Conservation in the UK and is currently living in India while working on a number of herpetological studies. He aspires to pursue a career in snake research and help to improve our relationship with snakes, perhaps the most misunderstood animals in the world.

    Snakes are exotic. It doesn’t matter whether they’re in zoos, rainforests or back gardens, there is something unfamiliar and perhaps disconcerting about snakes. But their elegance and captivating aura cannot be denied. They sit in silence with infinite patience, and stare with an un-nerving, unblinking eye. They flow over the ground, unchallenged and unhindered, like quicksilver. They disappear in full view, they melt into the undergrowth. They swallow other animals intact and whole, sometimes engulfing prey larger than themselves, as if it were an illusion. They strike with lightning speed, and mercilessly squeeze the life from their victims. Some administer a toxic concoction of lethal proteins and enzymes with needle-like fangs. Many species are capable of causing rapid and spectacular death; you might say it’s not surprising that snakes have earned themselves a reputation!

    Few people are indifferent towards snakes, there is something about them that either sparks fascination or makes the skin crawl. Despite the aforementioned attributes, the fear of snakes is fuelled mostly, in humans at least, by irrational revulsion. Snakes rank higher than rats, spiders or cockroaches as the most disliked animal. However, the vast majority of people that fear snakes will never have seen a wild snake, fewer still will ever have been bitten by one. So what is the root cause of this negativity? Experiments have shown that primate response to snakes ranges from terror to curiosity, mobbing and instant consumption. In general, non-human primates respond adversely to snakes, and, considering survival strategies and adaption by selection, it’s obvious how an aversion towards a potentially deadly hazard is useful for wild animals. Interestingly though, young children are rarely afraid of live snakes, and are perfectly happy to handle snakes as big as they are! 

   A recent series of experiments investigated the reactions of toddlers to convincing fake snakes hidden among toys. Almost invariably, snakes were spotted immediately. The response was to stop moving and look to the parent for guidance, but not raw fear. Maybe this suggests a retained adaptive response to elongate creatures, and may go somewhere in explaining the extreme perceptions of some people towards snakes? But, although fairly common, Ophidiophobia (the fear of snakes) only seems to manifest itself with age (and perhaps parent’s and society’s influence) but not personal experience. So if the distrust and loathing of snakes is a learned emotion, where does it come from?

   It’s fair to say that this group of animals has had a rough ride in literature; they certainly haven’t escaped our mythological exploits, story-telling and scare-mongering. In fact, snakes have found their way into the psyche and customs of almost every culture they encountered, inspiring outlandish legends. In Norse mythology, Jormungand is a giant sea serpent that encircles the world and is so long it can grasp its own tail. As the legend goes, if Jormundand let go of his tail, the world would end. The God Thor is depicted battling with the “World Snake” throughout Norse artwork. And the biblical tale of a talking serpent that led Eve astray has left a long legacy of mistrust with snakes being portrayed as the embodiment of slyness and devilry...

"The Lord God said to the serpent, 'because you have done this, cursed are you above all wild animals; upon  your belly you shall go, and dust you shall eat all the days of your life.'" - Genesis

   The negativity roots even further into history. 4,000 years ago, long before genesis, in the epic of Gilamesh, the snake was portrayed as a sneaky thief, stealing the herb of immortality from the King as he swam. Shakespeare mentions the adders native to the United Kingdom in most of his plays. The adder is wrongfully accused of regicide in Hamlet, and in A Midsummer Night’s Dream, Hermia accused Lysander of having, “a doubler tongue than an adder.” But there is a nicer reference, “And there the snake throws her enamell’d skin, weed wide enough to wrap a fairy in.” Today, the rotten reputation of snakes is evident in the trials of Harry Potter and Indiana Jones. The film ‘Snakes on a Plane’ used CGI to adorn the star cast with menace and scare-factor. Popular sayings like “speaking with a forked tongue” and “snake in the grass” perpetuate negative views of snakes. In some circles, snakes were rotten from the off, the condemned! Negative stereotypes have accumulated and been reinforced through time, transcending generations, and today, snakes are dragging a ball and chain of prejudice that is going to be hard to shake.

   But it’s not all bad press. The earliest evidence of man’s interest in the serpent world is painted on cave walls in Southern Europe, and carved into bone and wood 30,000 years ago. Indeed, snakes feature in some of the earliest known artwork; it’s obvious that they played a key role in ancient cultures and traditions.

   Snakes are prominent in the cosmology of many paleolothic, aboriginal and contemporary cultures, and our spiritual relationship with snakes is incredibly diverse. The mystery and ambivalent nature of snakes has led to conflicting assessments of them, polar opposites in some cases. They can be revered and demonized, worshipped and accursed.

   Serpents represent peace and healing to the early Greeks and Romans, and a pair of entwined snakes still symbolises the medical profession. The drug-induced visions of South American Indians are dominated by talking snakes, spiritual messengers. An American Revolutionary War flag featured the words, “Don’t Tread On Me” and a picture of a Timber Rattlesnake (Crotalus horridus) to symbolise independence and defense of one’s home against a threat. 

   Today, the States (mainly Southeast) host annual rattlesnake round-ups where thousands are butchered and sold for their meat and skin, extirpating local populations and threatening some species with extinction. Despite claims of concerns for public safety, and venom research, round-ups are fuelled mainly by financial gains. The practice used to be called ‘Adder (Vipera berus) bashing’ here in the UK. Elsewhere in the States, fundamental Christian sects worship and freehandle Copperhead vipers (Agkistrodon contortrix) and C. horridus in religious ceremonies. The words, “...they shall take up serpents” (Mark 16:17-18) are taken literally and have inspired followers to handle venomous snakes for centuries.

   Australian Aborigines hailed the serpents as Creators, with snakes featured throughout the history of Aboriginal culture and art. The Papuan blacksnake has become the totem snake of the magic men of Papua New Guinea. And snakes also appear commonly in the belief systems of Eastern religions. Despite the high numbers of snakebite morbidity and mortality throughout Asia, cobras are highly respected in both Buddhist and Hindu cultures. The cobra, Naga, is depicted raising Buddha off the ground while he meditates and spreading its hood to shelter him from the rain. Naga receiving Buddha’s touch in return, symbolised by the thumb and finger print markings on the hood of Spectacled cobras (Naja naja). Many Buddhist communities live alongside cobras, allowing them to remain in the paddi-fields and rice stores, eating rats and sometimes biting people.

   However, the pious pedestal on which snakes are perched in certain cultures may be their downfall. The medicinal capability of animal parts is predominantly an Eastern notion. Snake blood, gall bladders and various other bits are much desired in Chinese medicine. But illegally sourcing these quasi-elixirs is having devastating effects on wild populations. Rice production also suffers as the natural predators of rats are systematically removed from duty. In a sad irony, wild snakes are harvested to make medicines in remedy for conditions bought on by malnutrition. An estimated 45,000-109,000 Southern Indonesian Spitting Cobras (Naja sputatrix) are collected for their skins annually, that’s just one species. Imagine the extent of the problem and the wider ecological impact!  

   Snake meat and snake wine are common place in Asian restaurants, and a massive tourist attraction, particularly with Westerners. And everyone is familiar with the archetypal image of the snake charmer, but perhaps not familiar with the fact that most of the snakes in these displays have had their fangs pulled out or mouths sewn shut. But the mystical capabilities of snakes is not just an Eastern phenomenon. Not too long ago, it was widely held that the fat of V. berus had medicinal properties, including curing snakebite. And the shed skin of an adder stuffed into a hat was thought to cure headaches and hangovers! But in the modern day, our relationship with snakes has taken a perhaps unexpected turn, especially considering the stir over snake-derived medicines in the East. It seems counter-intuitive that snake venom, the toxic concoction capable of such gruesome effects and implicated in so many human fatalities, might actually be useful to modern medicine. But scientists comb venoms and toxins for their biochemical properties, and it’s the specificity and efficacy of venom to hit key metabolic pathways that makes it so useful in treating disorders like high blood pressure, heart disease, stroke, Alzheimer’s disease and cancer.

   Clearly, our relationship with snakes is a complex one. Some beliefs may seem absurd, but the consequences can be devastating. Today, the desire in the East for snake-derived medicines still burns, putting tremendous pressure on wild populations and driving some species to the brink of extinction, and further. Exploitation is unsustainable. Heading the clash between snake and man is a snakebite epidemic of shocking proportions in parts of Asia. An estimated 50,000 people die as a result of snakebite in India every year. Segregation and extermination of snakes are not long-term solutions, community education and practical problem solving to satisfy the needs of people and snakes, are. The power of education and socio-economic conservation strategy is demonstrated in the example of the Irula Tribe of Southern India who used to catch snakes to sell for their skins. Now they use their expert skills to find and catch snakes to be milked for venom research. The snakes are released unharmed and the Irluas maintain a self-sustaining business model.

   Although still prevalent, generally, as our understanding of natural history has advanced, the magic properties, strange powers and superstitions associated with snakes have become less real and relegated to folklore. But, while some might say there is generally a greater awareness now of nature as a whole, there is still an underlying distrust of snakes. The most obvious threat today is the indiscriminate and wanton killing of wild snakes. This type of behavior is driven by fear and ignorance, a kind of misguided knee-jerk reaction. Many people fear snakes and see it as their duty to rid the plant of these nasty and dangerous creatures. 

Why should people care about snakes? Many instrumental justifications can be given to support the conservation and protection of snakes. Some might not seem obvious, but snakes are tremendously valuable to medicine, agriculture, the environment, and even the economy. But does the simple fact that they exist, that they are alive, imply an ethical relationship to them? This is a seminal consideration, and one with far-reaching theoretical and practical implications not just for snakes, but for people too, and ultimately the natural world as a whole. Herpetologist Harry Greene said, "If man can learn to see value in snakes, he will more easily appreciate other creatures."

   The predicament snakes find themselves in today symbolises the choices humans face in the coming decades. Education is key, and everyone is a teacher. In the words of Senegalese conservationist Baba Diou:

"In the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught."


Thanks to Zachary Mastoon for granting permission for his cave artwork photos and to Mark O’Shea for his photo of the reptile farm raid which was sourced from his website, www.markoshea.info