snakebite – EYNC Rattlesnake Study

Love is in the air

Rattlesnake love, that is!

I’ve been getting lots of questions after last night’s (17 April) KCRA News interview with a local “rattlesnake hunter” who makes his living keeping us all safe from rattlers. If you have been reading my blog, you know there is nothing new to be alarmed about. The last few hot days have not brought out the rattlesnakes. Indeed, general emergence from their winter dens occurred more than a month ago. Male rattlesnakes continue to be busy looking for and trying to mate with as many females as they can while the females hunt for mice, rats, and other prey. As sit-and-wait ambush predators, the females don’t move much and thus are seldom encountered by people. But the males have been and will continue to constantly search for females until late May or June, in the process turning up in yards and on trails and other places where they encounter people.

Once again, most bites can be avoided by watching where you put your unprotected hands and feet and leaving rattlesnakes alone when you encounter them.

We have been encountering numerous pairs of rattlesnakes in the Effie Yeaw Nature Preserve over the last few weeks. Here are brief video clips of a couple of examples: First, our telemetered Male 62 (blue/white paint in rattle), entwined with an unmarked female. These snakes were not moving during my brief visit but the males often accompany the females for many days but cannot keep courting them continuously (click here for video). You can see why in the video of Male 37 actively courting Female 41… it takes a lot of energy! (click here).

On 1 April, several hours after I videoed Male 37 courting Female 41, I returned and just missed a fight between two males over Female 41. As I approached, I briefly saw both males, with heads and necks high off the ground, twisted around one another. But one quickly fled, either from me or he had had enough of Male 37…who is a big healthy male rattlesnake! In any event, Male 37 was all excited and remained raised off the ground for a minute or more, guarding his girl (see photo below).

Male 37 still ready to fight shortly after another male retreated. Female 41 is coiled in the shade just below the male. I had videoed Male 37 courting Female 41 just a few hours before this scene. — Male 37 still ready to fight shortly after another male retreated. Female 41 is coiled in the shade just below the male. I had videoed Male 37 courting Female 41 at this spot just a few hours before this scene.

A video made a few years ago of two males fighting on the concrete in front of the Effie Yeaw Visitor Center doors is on the Nature Center website (or click here to see it).

General emergence appears to be underway (after a couple of false starts)

After a couple of false starts during warm periods in mid and late February, a new series of cool storms kept the Effie Yeaw Nature Center rattlesnakes immobile through the first half of March. On days with a little sunshine, both telemetered and other rattlesnakes were frequently found basking at the entrance to their shelters but they did not venture away from them. Natural selection tends to remove animals from the gene pool that wander too early and get caught in a late-season freeze. As if to demonstrate that it was cool temperature and not the rain that was keeping them inactive, several rattlesnakes were found lying out in the rain on days when the temperature was in the high 60s, despite the clouds.

Male 49 lying in the rain on 4 March 2016. Rattlesnakes are very adept at harvesting rain and dew, being very capable of sucking individual droplets off of vegetation or their own bodies. While that will drink from standing water when available, they don't seem to need such water sources and we have not detected tham traveling to either the ponds near the Nature Center or to the river. — Male 49 lying in the rain on 4 March 2016. Rattlesnakes are very adept at harvesting rain and dew, being able to suck individual droplets off of vegetation and their own bodies. While they will drink from standing water when available, they don’t seem to need such water sources and we have not detected them traveling to either the ponds near the Visitor Center or to the river. The only rattlesnakes discovered over the past two seasons around the Visitor Center (and its water sources) have been males during the breeding season – presumably looking for females, not water.

While the rattlesnakes continued to bask on sunny days, none of the telemetered animals moved between 29 February and 17 March. Then today, I discovered that 7 of the 9 telemetered rattlesnakes had left their shelters and moved significant distances in the past two days.

I haven’t seen courtship yet. Female 41 and Male 49 hung out together for a month (16 February through 15 March) but they were only rarely touching one another and were usually coiled a couple of feet apart with no courtship observed. She is now hunting several dozen yards away and Male 49, without a transmitter, has disappeared.

The important message, however, is that rattlesnakes are on the move and encounters between people and rattlesnakes will increase immediately. Unfortunately, I have already seen photos of a rattlesnake bite from a few days ago in the foothills. Watching carefully where you put your hands and unprotected feet and leaving snakes alone when you encounter them would prevent almost all bites. If you must walk in vegetation or rocks where you cannot be sure what you’re stepping on, wear high-top shoes or boots that cover your feet and ankles. Of course, boots that cover some of your calf are better but most accidental snakebites (where the person is not intentionally interacting with the snake) are to the ankle and below.

Remember, you can’t save all the cute animals, eat all the tasty ones, kill all the ones that scare you, and have a functional ecosystem, too!

Early emergence has begun!

As sunny 70+ degree days have been warming the ground recently, body temperatures of the telemetered rattlesnakes have been creeping up… but only from the 50-60F range into the higher 60s. Then, yesterday, I found Female 41 laying in the grass next to the log where she has spent the past two winters. But just being visible doesn’t constitute emergence.

I returned late this morning and found Female 39 visible for the first time, basking in dappled sun under the end of the log where she has spent the past two winters.

IMG_0091; 16 February 2016 — This was all that was visible of Female 39 this morning but it takes only a small surface area in the sun to act as a radiator and warm the entire snake.

Then, not only did I find that Female 41 had moved about 20 feet from her winter shelter to a smaller nearby log, but I watched as Male 49, a large non-telemetered animal with white/green paint in his rattle, arrived at the same log and joined her. Although they coiled next to each other, I saw no actual courtship behavior during the 45 minutes I watched.

IMG_0117.CR2; 16 Feb 2016 — Male 49, just a few feet from joining Female 41 this morning. Without a transmitter, I have no way of determining his body temperature or knowing where he spent the winter. An encounter with him is purely chance but white/green paint in his rattle makes him easily recognizable.

Body temperatures of Males 37 and 38, both of which spent the winter high on the bluff north of the preserve, were around 90F at midday today. Because their winter locations are almost inaccessible, I don’t know if they have actually left their hibernacula but they were both definitely in the sun today. Remember that ground temperature is much higher in the sun than the air temperature, particularly on south-facing slopes.

As of today, the other five telemetered rattlesnakes remain relatively cool and out of sight and the weather forecast looks like cloudy skies, cooler temps, and more rain over the next few days.

The study animals did not begin to leave their winter shelters until the end of the first week in March last year. Although this is three weeks earlier than last year, it is certainly a limited emergence with many snakes remaining underground and inactive. But the fact remains that some rattlesnakes have left their winter shelters, so “rattlesnake season” is definitely underway.

Remember that being careful where you place your unprotected hands and feet and leaving snakes alone when you find them would prevent almost all rattlesnake bites!

More baby rattlesnakes… and the Biggest Rattlesnake Myth!

Checking on our pregnant female rattlesnakes this morning disclosed another brood of kids in a different location. These appear younger than the ones discovered with Female 55 last night because their eyes are not yet cloudy white. Although only one was observed with the BurrowCam (see 19 second video), it is almost certain that there are more. Eight is the average litter size for Northern Pacific Rattlesnakes. However, these kids are also deep underground and, like those found last night, have only been observed with the BurrowCam.

Clearly, there will be baby rattlesnakes roaming around the American River Parkway within a few days, and some may have already shed and emerged from their mothers’ gestation shelters. Remember, the lack of snow pack and low reservoir levels have not affected the rodents and lizards along the American River, so the rattlesnakes are fat and healthy. Click here for more on how drought affects rattlesnake behavior.

Remember that, while venomous and dangerous, bites from baby rattlesnakes tend to be far less dangerous than bites by medium and large rattlesnakes. Clinical data comparing bites by rattlesnakes of different sizes clearly shows that big rattlers are more dangerous. Click here for a PDF of “Large snake size suggests increased snakebite severity in patients bitten by rattlesnakes in southern California” (2010, Wilderness and Environmental Medicine 21:120–126).

The idea that babies are more dangerous is likely the most common rattlesnake myth. Regardless of how much of their venom babies inject, adult rattlesnakes have a lot more venom, so are capable of much worse bites. Think about it: laboratories that produce venom to sell to pharmaceutical companies and other research institutions do not want baby snakes, they want big snakes because they produce a lot more venom. Data from these labs indicate that the venom yield from three-foot rattlesnakes is 100X the yield from one-foot juveniles. The photos below are actual venom extractions from a nearly three-foot male (left) and a 13-inch newborn (right) Mohave Rattlesnakes. I’d take a bite from the little one rather than the adult any day!

Actual venom extractions from an adult male Mohave Rattlesnake (left) and a 13-inch baby (right). Note that the baby produced one drop that did not even make it to the bottom of the beaker. (50 mL beakers; about the size of a shot glass) — Actual venom extractions from an adult male Mohave Rattlesnake (left) and a 13-inch baby (right). Note that the baby produced one drop that did not make it to the bottom of the beaker. (50 mL beakers; about the size of a shot glass)

So there will be little rattlesnakes, about the size of pencils, around wooded and brushy areas for the next couple of months. To be sure, while their bites are less dangerous than bites by bigger snakes, any rattlesnake bite requires evaluation in a hospital emergency department without delay. By spring, the babies will be much more scarce because the little guys have many more predators than the adults.