LAWRENCE — Every March 17, lovers of Irish culture around the world commemorate the life and legend of a fifth-century missionary best known for spreading Christianity in Ireland, but also for driving all of the island’s snakes into the sea.
But could the tale of St. Patrick conceivably explain Ireland’s lack of snakes? Is it even possible to herd snakes? Could these long-banished serpents someday make their way back to Ireland?
Between lashings of green beer and plates heaped with corned beef and cabbage, such questions gnaw at every Hibernophile.
The University of Kansas’ Biodiversity Institute has one of the world’s foremost assemblage of herpetologists — and that's not blarney. These researchers, like St. Patrick himself, show a legendary penchant for chasing snakes. In honor of St. Patrick’s Day, a group of scientists in the Division of Herpetology flashed their gift for the gab in pondering both the science and myth behind the Patron Saint of Ireland.
Q: Legend holds that St. Patrick drove all the snakes from Ireland in the fifth century. Would it be possible for one man to drive snakes from an entire island nation? How might one man go about it?
Rich Glor, curator of herpetology: I’m not going to fact-check the legend — after all, the guy was a saint, and who am I to question his accomplishments? Normal humans have had a very difficult time eliminating some island snake populations. The brown tree snake, for example, was accidentally introduced to the island of Guam, which previously had no snakes. Guam’s birds, some of which were found nowhere else in the world, were poorly prepared for this new predator, and many have been driven to extinction or near extinction as a result.
Concentrated efforts to exterminate the tree snakes have included electrified snake containment fences and teams of hunters using trained snake-sniffing dogs, but it seems like the snakes are there to stay. On the other hand, however, humans have done a very good job of driving snakes to the brink of extinction. In the United States, for example, humans have undertaken a more than century-long effort to exterminate rattlesnakes. This effort, which continues to this day in some parts of the country, has resulted in the extinction of rattlesnakes across much of their ancestral range and has led to the classification of many rattlesnake populations as endangered.
Historical records suggest that individual snake hunters were often responsible for wiping out entire populations by capturing and killing all of the individuals as they emerged from communal hibernation dens in the spring. St. Patrick’s task would certainly have been easier if Ireland’s legendary snakes used the same type of communal hibernation strategy as rattlesnakes. Other rattlesnake hunters use even more nefarious strategies: Snake hunters at rattlesnake roundups, for example, often spray gasoline into snake dens and catch the snakes as they exit the den attempting to flee the noxious fumes, but a man of the cloth seems very unlikely to have adopted such a grotesque approach.
Luke Welton, the Herpetology Division’s collections manager: It’s quite interesting that no native snakes are currently known from Ireland, despite a number of species occurring in more southerly parts of the United Kingdom. One consideration is that the climate of Ireland would likely keep any potential populations of ectotherms fairly small, which would make them much more susceptible to extinction or eradication.
Q: Supposedly, St. Patrick drove the snakes into the sea. Can a person drive snakes in a given direction, and would they perish if you drove them into an ocean?
Jeff Weinell, graduate student: During fieldwork, herpetologists often use drift fences (sheet metal or mesh partially buried along one edge) to direct snakes and other small reptiles toward a particular direction (usually into a bucket). However, this method wouldn't work to direct most snakes into the ocean, and, therefore, St. Patrick probably didn't use drift fences. Some snakes do live in the ocean, but these species are only found in the Pacific and Indian oceans. If St. Patrick found a way to put all of the snakes of Ireland directly into the ocean, most probably would have perished. However, many snakes are good swimmers, and some of them may have been able to find their way back to shore.
Glor: For anybody who’s not a saint, herding snakes might be even more difficult than herding cats. Herpetologists sometimes use low fences to corral snakes, but even this is only partly effective. Most snakes would perish if forced into the ocean. Ocean-dwelling snakes, which are not found anywhere near Ireland, have numerous specializations that permit them to live in the ocean that other snakes lack. For example, ocean snakes have special physiological mechanisms to cope with saltwater. They also have flattened oar-like tails and specialized scales that allow them to swim in ocean waters.
Q: If it wasn't St. Patrick’s doing, what are the scientific reasons for the lack of snakes in Ireland? Are there other places without snakes? Why?
Katie Allen, graduate student: The scientific reason there are no snakes in Ireland is actually a result of the last Ice Age. As recently as about 19,000 years ago Ireland was buried in 3,000 meters (9,800 feet) of ice and was essentially an arctic wasteland. After the glaciers melted, the Irish Sea formed and created a 50-mile-wide barrier between the island and the mainland. During the Ice Age, snakes were not able to survive in Ireland, and afterward they were not able to cross the large, cold sea to reach it. There are several other islands that naturally do not have any snakes, including Greenland, Iceland, New Zealand and Hawaii. These islands are snake-free for similar reasons; either climate or distance from the mainland prevents colonization. Iceland, New Zealand and Hawaii have also banned pet snakes in order to keep their islands free of scaly invaders.
Q: Are there any reptiles in Ireland?
Glor: Yes, Ireland has one lizard species, which is called the "common lizard" but is actually unusual among lizards because it gives birth to live young rather than laying eggs.
Allen: Only one species of lizard is native to Ireland, the viviparous lizard (Zootoca vivipara). This species is widely distributed across Europe and Asia and is able to live farther north than any other terrestrial reptile. One of its adaptations to this cold lifestyle is to give birth to live young instead of laying eggs. Aside from this lizard, there are several species of sea turtles that inhabit the coastal areas of Ireland.
Q: What would be the most effective way to drive snakes from your yard, garden or house?
Glor: Why would you want to drive snakes from your yard, garden or house?
Brown: That’s the last thing I would do. The real question is, “How can we attract more snakes to our yards, gardens, and yes, even basements of our houses?” If we had more snakes around, we wouldn’t have to buy traps and poisons to handle household pests like rats and mice.
Q: What are the benefit of snakes to an ecosystem like the one in Ireland? Are snakes a benefit to humans in ways that are underappreciated? What are the drawbacks of snakes?
Glor: Nobody knows what effect snakes could have on an ecosystem like Ireland’s. In some ecosystems, snakes are major predators of small animals like mice. I don’t think snakes are a benefit to humans in ways that are underappreciated. Most snakes have no drawbacks outside of causing irrational fear in some humans. Some snakes are venomous and can be dangerous to humans.
Brown: In all seriousness, and particularly with regard to human health issues, snakes are highly beneficial. For example, scientists have documented that the primary reservoir for the explosive spread of Lyme disease in this part of the country are ticks, which are transported by mammals like deer and rodents. Additionally, most people contract Lyme disease doing regular household things like gardening or raking leaves in their own yard because they come in contact with ticks carried by rodents. I would much rather have a healthy population of harmless black rat snakes in my yard than an infestation of filthy, debilitating disease-carrying rodents. But, you know, that’s just me.
Welton: Snakes are quite beneficial ecologically. They are the controllers of rodent and pest populations and are exactly the kinds of predators that keep vectors of some human diseases at bay. No snakes would likely mean an increase in diseases like hantavirus and plague, which are carried by rodents. Besides just the disease aspect, would you rather have one snake in your garage or basement, or several hundred mice or rats?
Q: Why do people dislike snakes? Why does our culture associate snakes with evil?
Glor: Many people have done research on this topic without firm answers. Some people believe a fear of snakes is hardwired due to our ancestors’ interactions with deadly venomous snakes. One need look no further than the first chapter of the Good Book to get a sense for why our western culture associates snakes with evil; after the snake deceives Eve in the Garden of Eden, God curses snakes over all other animals and tells the snake “on your belly you will go, and dust you will eat all the days of your life” (which makes one wonder how snakes were getting around prior to the curse).
Brown: Sometimes I think people don’t like snakes because of the way they move. People just get creeped out by “slithering” snakes and almost instinctively recoil when they first see a snake. Unfortunately, humans also react violently when they see a snake move — by what scientists term “lateral undulation” (slithering). However, scientists infer from the existence of many well-preserved transitional fossils of intermediate forms that snakes evolved from ancestors that possessed limbs. Not only does the fossil record tell how the ancestors of today’s snakes lost limbs and evolved elongated body plans over evolutionary timescales, but in today’s “primitive” living snakes, the vestiges of those limbs can be seen — in pythons, for example, that still have tiny claws at the base of their tails. So we can actually view snakes as just one group of very specialized, highly successful lizards. Strangely, in this instance, the biblical account and evolutionary biology’s explanation are curiously aligned. And yet no one ever tries to exterminate lizards on their property or dig up lizard dens with the goal of mass-murdering all inhabitants.
Welton: In my opinion, society is largely the reason most people fear snakes. I don't know that there is a single group of animals that has had so much misinformation disseminated about it. One could argue that this fear stems from the Garden of Eden story and that all snakes are inherently bad. While I believe that definitely plays a part, I think the fear is a symptom of a larger problem associated with a lack of education. Too often, completely harmless (nonvenomous) snakes meet their end because of common defensive strategies (striking with mouth agape, rattling their rattle-less tails in debris or leaf-litter) that are intended to fool a would-be predator. This needless slaughter could almost always be prevented if one cared enough to become educated about the wildlife in their own backyard.
Q: Might snakes return to Ireland, due to changing climate or pet snakes being released into the wild? What would be the most likely species to thrive in Ireland?
Glor: Yes, this is definitely a possibility. Snakes found in nearby England are the most likely colonists.
Q: What are the main threats to snake biodiversity today globally?
Glor: Habitat loss is the greatest threat to biodiversity. In cases, specific populations are overexploited by pet trade.
Brown: And overall persecution by humans. Globally, when snake populations come in contact with human populations, the outcome usually is unfortunate and does not bode well for the long-term viability of the snake population. I agree with Luke, though — education is the key ensuring the conservation and long-term survival of the world’s 3,650 species of snakes.
Image by William Murphy, via Flickr.