Sonoma County snakes still out and about — Do you know what to watch for?

This time of year, it is not uncommon for hikers to encounter three of our most common and charismatic local snakes - the garter snake, the gopher snake and, of course, the northern pacific rattlesnake. Like us, these snakes avoid the hottest days of summer and seem to enjoy this magical time when summer slides into fall. Because trails and roads in our open space areas are now rimmed with dry grass and other senescent vegetation, snakes are even easier to spot than during the more verdant days of spring and early summer.

Snakes are among that class of creatures (along with spiders, bats, and sharks) that provoke fear and loathing among a good portion of the human population. From Adam and Eve to Harry Potter, snakes have been dreaded and demonized, portrayed as treacherous and even vindictive. While it is certainly true that some venomous snakes can deliver a nasty and potentially fatal bite, lumping all snakes into the category of killer blinds us to their many mind-blowing talents and the beneficial role they play in our local ecosystem.

Snakes evolved from lizards some 200 million years ago. Although there are some legless lizards today, there are no legged snakes! Some more primitive snakes - like pythons and boas - still have vestigial hind legs. Romantically referred to as “anal spurs,” these tiny clawed limbs are used by some species to hold onto their chosen one during mating. All snakes lack eyelids and therefore never blink. Rather, their eyes are covered by a transparent membrane called a brille. When snakes shed their skin, the brille is shed with it. As any pet snake owner will tell you, the brille becomes cloudy just before molting, giving us a clue about what is about to happen. Unlike lizards, who tend to shed their skin in patches, snakes gracefully leave behind a mostly intact tubular marvel, often at the entrance to their burrow.

Of the 33 native snake species in California, at least a third occur in Sonoma County. Some we rarely see either because they are nocturnal, or very small, or spend most of their time hanging out underground. Garter snakes, gopher snakes and rattlesnakes, however, are encountered relatively frequently, although identifying them can be difficult because of the great variation in their coloring and the fact that they have tendency to mimic one another.

The garter snake

The garter snake (genus: Thamnophis) is the most common snake in North America. Often erroneously dubbed the “garden snake,” this ubiquitous serpent is named for its resemblance to the striped garters once worn by men to hold up their stockings or sleeves. The garter snake is the only type of snake on the continent that lives as far north as Alaska. Relatively well-adapted to cool climates, most garter snakes are excellent swimmers and hibernate in large dens, which makes them susceptible to collection for the pet trade. Garter snakes are not dangerous to humans, as long as you don't mind being smeared with foul-smelling slime. When threatened, garter snakes release a stinky bad-tasting musk and spread it across their skin by writhing. This strategy, designed to make themselves distasteful to predators such fox and coyote, causes curious humans to go running for hand sanitizer. Like the northern pacific rattlesnake, garter snake young are born not in eggs but directly from the mother's body, a type of live birth known as ovoviviparous (the young are nourished in an egg sac retained in the mother's body). In cooler climates, the longer mom keeps those eggs inside her body, the more likely her young are to fully develop.

Perhaps the most mind-blowing adaptation of the garter snake is its unique ability to eat newts … sometimes. The three species of pacific newts found west of the Rocky Mountains (all three of which occur in Sonoma County) defend themselves against predators by harboring a highly toxic chemical in their skin called tetrodotoxin, or TTX, the same deadly poison found in pufferfish and some other aquatic species. Garter snakes and pacific newts have been engaged in an evolutionary “arms race” in which the predator (garter snake) evolves an increasing tolerance for the defenses of its prey (the TTX in the skin of newts). In response, the prey evolves a toxin of ever-increasing potency to keep up with its predator. A jaw-dropping 3 minute video by National Geographic about this arms race can be viewed here: http://video.nationalgeographic.com/video/weirdest-newt. A similar “arms race” is occurring between rattlesnakes and ground squirrels (see below).

The gopher snake

I think of gopher snakes (Pituophis cateniferas) the “gentle giant” of our local serpentine wildlife. Unlike garter snakes and rattlers, gopher snakes kill their prey by constriction. Indeed, they are an important member of the food chain that keeps rodent populations in check. Slightly larger than a rattlesnake when fully grown, a gopher snake is often mistaken for a rattler because of its similar diamond-like pattern. Unlike a rattlesnake, however, a gopher snake's skin tends to be glossy, its head more narrow, its pupils are round, as compared to the vertical cat-like pupil of the rattlesnake, and its tail tapers to a point. Gopher snakes have a curious habit of freezing in the middle of a trail or path as a hiker approaches, hoping to become invisible but nevertheless inviting us to observe them up close. They also have the habit of imitating rattlesnakes when threatened, by coiling as if to strike, flattening their heads, shaking their rattle-less tails and hissing. Because the hissing sounds like a rattle, many a gopher snake has been killed unjustly.

I confess that gopher snakes are irresistible to me and I enjoy picking them up when I am lucky enough to encounter one. No one should ever handle or pick-up a snake unless one hundred percent certain of its identity. If you do pick up a snake (non-venomous only!) in the wild, always use two hands-one behind the head and a second at least half-way down the body. Dangling a snake with one hand behind its head will impede its respiratory system and deprive the snake of oxygen.

Northern pacific rattler

The northern pacific rattlesnake (Crotalus oreganus oreganus) is the only native venomous snake in our area capable of harming humans. Unlike some other species of venomous snakes, our local rattlers are relatively shy and if given the chance would rather shimmy away from you than strike. Although rattlesnakes are singled out as dangerous purveyors of poison, it is interesting to note that all reptiles have toxic saliva, made up of the same basic chemical composition as the venom of cobras. Yet, most are harmless to humans. How is that possible? According to Marin County naturalist and snake-lover David Herlocker, “What makes a snake more or less toxic has to do with the concentration, or potency, of the venom, and the efficiency of its delivery mechanism.” Rattlesnakes have fangs that inject venom very effectively. Garter snakes lack fangs. Instead, they simply hold their prey in their teeth while their relatively mild venom works its way in. Thus subdued, the rodent or other prey item becomes much easier to swallow whole.

Venom is not the only reason rattlesnakes are such effective hunters. As a member of the group of snakes known as pit vipers, a rattlesnake can find its prey in the total darkness using special openings, or pits, on either side of its face. The pits sense heat given off by potential prey. By moving its head side to side, the snake is able to hone in on its prey by sensing and moving towards the spot where the heat is most intense. The California ground squirrel, a favorite meal for a hungry rattler, has figured out how to trick the rattlesnake by increasing the temperature of its tail. This throws the snake off its game; causing it to strike the relatively thin tail while the fat juicy body of the squirrel remains untouched.

Like the coevolution of the garter snake and the newts, rattlesnakes and ground squirrels in an arms race of their own. A recent study found that California rattlesnakes' venom is carefully calibrated to overcome the specific defenses of the squirrels in their neighborhood. Thus the potency of the venom varies measurably from place to place, even within a relatively small area. A Santa Rosa rattler, for example, could have venom that is much more toxic than a similar snake in Sonoma. A Sonoma ground squirrel used to the wimpy venom of the local snakes might succumb quickly if visiting Santa Rosa. From the time they are pups, ground squirrels generate anti-venom proteins in their blood stream, the levels of which are in part determined by the potency of their local snake population.

Infant vs adult rattlers

This is a very common question and it has a complicated answer. About 20 percent of bites from an adult rattlesnake are “dry” bites, meaning the snake attempts to defend itself without using venom. Because producing venom is “expensive” to the snake, it makes sense to not waste it if a dry bite will do the job. It is true that baby rattlesnakes are more “on the prod” than adults, meaning they are more likely to deliver some venom with every bite. This doesn't necessarily mean that baby snakes are more dangerous. Part of the confusion comes from the fact that the chemical makeup of adult rattlesnake venom is different than the babies'. Adult rattlesnakes have a venom that is a primarily a blood toxin (hemotoxin). It works by starting to pre-digest the flesh of the prey item even while the snake is still holding it in its fangs. As the prey animal is still alive and struggling, its own heart pumps the venom throughout its body. The venom of baby rattlesnakes, on the other hand, is more of a neurotoxin that paralyses its prey (mostly lizards) since the snake may be too small to wrestle its wiggling meal down the hatch. Ounce for ounce, the baby snake neurotoxic venom is technically more toxic than the adult snake venom. But even if a baby snake empties its venom glands, you are getting a lot less than if an adult does the same. The other factor, of course, is that baby snakes have tiny little button rattles and can't make that loud hissy lawn-sprinkler sound that so effectively alerts us to the adult snakes. Because the quieter young snakes are more difficult to spot, hikers must avoid reaching into crevices are behind rocks if you can't see what you are doing.

Other common sense strategies to avoid snakebites include:

If you encounter a rattlesnake, stay at least 6 feet back. Chances are it will go on its way very quickly. If rattlesnake feels threatened, it may coil and rattle its tail preparing to strike. Rattlesnakes can strike about one-half the length of their bodies (a three foot snake can strike about 18 inches away). A six foot buffer between you and the snake keeps you well out of reach and reduces stress on the snake as well.

If the snake is blocking a trail, wait for it to go on its way before proceeding. Never attempt to get the snake to move or rattle by yelling, clapping, or poking it with a stick.

If a rattlesnake is blocking a trail and does not move after a short period of time, go back the way you came and take an alternate route.

If you are bitten by a rattlesnake, call 911 or go to the nearest hospital. Do not apply a tourniquet and do not attempt to “suck the venom” from the wound.

Jeanne Wirka is the Director of Stewardship for Audubon Canyon Ranch (ACR).