courtship – EYNC Rattlesnake Study

Transmitter Removal

It was with a bit of a heavy heart a week ago this morning that I watched my favorite EYNC rattlesnake, Male 37, glide into a hollow log… this time without a transmitter.

Denise and I arrived at Effie Yeaw late on Tuesday, 10 April, and unloaded the boxes of equipment and supplies we would need to remove surgically-implanted transmitters from a dozen rattlesnakes. EYNC’s Executive Director, Torey Byington, had consented to allowing us to take over part of the EYNC kitchen and the wonderful staff graciously shared their lunch room with a make-shift surgical suite for the next few days.

I wanted to allow the telemetered rattlesnakes to hibernate with their transmitters one last winter to complete my 2017 data with verified winter den locations. Plus, because their immune systems and their ability to heal wounds slow down considerably when they’re cold, I routinely avoid surgeries just before hibernation. Thus, I was committed to returning this spring to remove the transmitters.

I was worried about the weather as we prepared for the drive from Arizona. While mid-April is usually warm and the rattlesnakes are very active (females hunting for food and males hunting for females), recent weather had been cloudy with unseasonably cool temperatures and the forecast was for more of the same. Yet, the naturalists at the Nature Center were telling me that visitors had been reporting rattlesnake sightings on the occasional sunny days, so we stuck with the original plan and hoped for the best. We were not disappointed.

Even though it was overcast, cool and breezy, Denise and I headed out into the preserve Wednesday morning to capture as many of the telemetered rattlesnakes as possible. While I usually use only a snake hook and put captured rattlesnakes in a cloth bag, many escape capture with the hook and getting an unhappy rattlesnake safely into a cloth bag is not a quick process. So, for this effort, we used a clamp stick (photo below) and put the snakes in plastic buckets. Grabbing them with the clamp stick is more stressful for some of the snakes but prevents most escapes and putting them in a bucket is quick, easy and safe.

Capturing Male 46 for transmitter removal on 11 April 2018; Denise Garland Photo.

Despite the cool cloudy weather, we were relieved to have nine of the rattle-snakes in buckets by early afternoon!

However, Males 36 and 37 were inaccessible inside hollow logs and, not surprisingly, we had no radio signal from Female 80. Her signal vanished last summer after she ventured into the residential area at the top of the bluff. Her transmitter might have failed prematurely, she could have been carried far away by a hawk or owl, or a homeowner could have destroyed her and her transmitter… we’ll just never know for sure.

Over Thursday and Friday, I completed surgeries on six of the animals. Males 36 and 37 remained inaccessible inside their respective logs on Thursday but Friday dawned clear and sunny and my hopes of capturing them was high. After a couple early surgeries to allow things to warm up outside, I went out again to look for them – and it became apparent why they were hidden and not moving.

Male 46’s transmitter removal surgery on 14 April 2018. Denise Garland Photo

As I approached the log where Male 36 had been sheltered, a smaller chocolate brown unmarked (not previously captured) female rattlesnake was coiled in the sun at the open end of the log. Using a mirror to reflect sunlight into the log, I could see Male 36 coiled in the shadow behind the female. Now things became clear… Male 36 was not moving around because he had already found a female and was hanging out with her! I had an idea: I gently lifted the female away from the log and moved her a hundred feet or so away. Within a few minutes, Male 36 was sniffing around where she had been laying. Ten minutes later, enough of him was protruding from the log for me to capture him. One down and one to go!

The sun was also shining on the log where Male 37 had been. But this time I found Male 37 outside the log, on top of and courting another unmarked female. I captured him and, after a pang of guilt, took his female too.

By the end of a long day Saturday that included the last five surgeries, all the transmitters had been successfully removed, nine rattlesnakes had been released and our equipment was repacked for the drive home. Males 36 and 37 were the last two surgeries Saturday night and needed to recover overnight before release.

So, on our way out of town early the next morning, we released the two males. Male 36 glided back into the same log where I had captured him; I saw no sign of the female I had moved. Finally, I released Male 37 into his hollow log followed by the female he had been courting.

My last act was to leave my EYNC keys behind in an envelope, turn out the lights and lock the door. The field work is done but much data analysis, DNA analysis and writing remains. I will be forever grateful for the support and encouragement of many people and several organizations.

Acknowledgements

Recently retired EYNC Executive Director Paul Tebbel initially invited me to study rattlesnakes at EYNC. Over the past four-plus years, Paul and the entire staff and cadre of volunteers at the Nature Center were encouraging, supportive and genuinely interested in what I was doing. Torey, the new ED, has been wonderful, as well. The ARNHA board of directors consented to my study, trusted me that it could be done safely, and several board members took a personal interest in my work. Mary Maret, Resource Specialist for Sacramento County Regional Parks, facilitated the necessary county permits and was personally very supportive. Laura Patterson at California Department of Fish and Wildlife expertly managed issuance of my Scientific Collecting Permits. Rulon Clark added me to his laboratory group at San Diego State University as an adjunct researcher, allowing my field work to be approved by SDSU’s Institutional Animal Care and Use Committee – an essential detail needed to publish results in reputable scientific journals. Finally, Fred Andreka and Holohil Systems have been providing me with small dependable surgically-implantable radio transmitters for nearly twenty years and Holohil’s John Edwards has provided amazing customer service.

Thank you to everyone, including the countless EYNC visitors who stopped to talk and ask questions on the trails, many of whom seemed to walk away with an altered opinion of rattlesnakes!

Will rattlesnakes be more abundant this year?

I’ve been getting this question a lot lately. And my response is, “It depends on where you are.”

Actually, it depends on the local weather in recent years where the question is being asked.

Many of the female rattlesnakes in the Effie Yeaw Nature Center preserve have been reproducing annually since at least 2014, including the drought years prior to this extraordinarily wet winter and spring. And, as I have written here before, that’s unusual – at least according to similar studies of other species of North American rattlesnakes. This far from the equator, most pitvipers only produce a brood every two or three years because of the time it takes females to replenish sufficient fat stores to support another pregnancy (they lose 30-50% of their body weight with each litter). But along the American River Parkway during 2014, 2015, and 2016, there was enough local rain each winter to get the annual plants growing and everything blooming, providing plenty of food for insects, squirrels, voles, and other small animals. The insects fed the abundant lizards that reproduced like crazy each year, and the rattlesnakes fed on the small mammals and lizards that were plentiful. So rattlesnakes and other mesopredators (mid-level predators in the food chain; i.e. they are eaten by bigger predators) have been thriving locally, despite the historically low reservoir levels and skimpy snowpack in recent years. And because rattlesnakes produce only one brood per year, they can’t do better than they’ve been doing.

On the other hand, when local drought reduces the availability of the rattlesnakes’ prey (i.e., reduced local rainfall significantly suppresses plant growth, which negatively affects everything else up the food chain), that changes the snakes’ behavior. Among other things, movement and courtship slows significantly and reproductive rates are almost certainly reduced.

So, in an area like the American River Parkway, this wet spring is not likely to increase the rattlesnake population because they can’t reproduce much better than before all the rain. However, in areas where reduced rainfall in recent years significantly impaired floral growth , rattlesnakes will be better fed and more active this year and they are more likely to successfully produce young.

But it is important to understand that what people interpret as “abundance” is usually just a change in behavior. I studied this phenomenon in Mohave rattlesnakes in the southern California desert for my MS thesis. In dry conditions, predators get most of their water from the body water of their prey (we’re all about 70% water). So, when rodents are abundant, rattlesnakes are well hydrated, behave normally, and males search constantly for females during spring and fall. But when their prey becomes scarce and other water sources are not available, they reduce water loss by remaining coiled and moving less, thus reducing the amount of skin exposed to the dry air. This is important because cutaneous (through the skin) evaporation accounts for about 75% of the snakes’ daily water loss.

As a result, during local drought, people encounter rattlesnakes less frequently – not because there are fewer rattlesnakes but because they remain hidden and move around a lot less (top photo, below). During non-drought times, people see more rattlesnakes because their behavior is not inhibited and they crawl around a lot more (bottom photo, below), especially the males during their courtship season.

So, if you live in an area like the American River Parkway, where there has been lush growth of grasses and other annual and perennial plants in recent years, this wet year should make little difference in the apparent abundance of rattlesnakes.

But if your neighborhood has been dry with little springtime plant growth in the last few years, you may see an increase in rattlesnakes this year for two reasons: the males may be searching for females much more than before, plus there may be more baby rattlesnakes in September and October this year (and likely next) as a result of females having plenty of rodents to eat this year.

What a confusing spring!

March weather had the rattlesnakes along the American River Parkway confused! As I have mentioned before, the rattlesnakes usually emerge and begin to bask when the average temperature at ground level remains at or above about 50F. They are usually deep enough underground during the winter to escape daily high and low fluctuations, so it is the average that eventually penetrates to them and signals that winter is likely over. But not this year.

Most telemetered rattlesnakes emerged in March but remained at their hibernation sites, basking on sunny days as they usually do before leaving their winter shelters. But rather than getting drier and warmer, the weather throughout April was a constant mixture of rain and cloudy cool days and nights. Of the few rattlesnakes that left their winter hibernacula, two returned while others became inactive at other sites. The rattlesnakes do just fine in the rain. In fact, they drink rain and dew when it’s available. And cloudy weather is not a deterrent to activity if it is accompanied by warm temperatures. But nighttime air temperatures below 50F followed by overcast cool days are not good for activity in animals like reptiles that depend on the environment for their body heat.

So, in late March and throughout April, the few stretches of several sunny days with relatively warm nights in between produced some sporadic rattlesnake activity. But it was not until the end of April that more consistent sun and heat produced vigorous widespread rattlesnake activity.

A courting pair of rattlesnakes on 28 March, next to the log under which they spent the winter. The male is on top of and mostly obscuring the female, which is paying no attention to him.

As expected, when we had activity, we observed lots of courtship. This is, after all, the peak of courtship activity, followed by almost no reproductive activity from June to mid-August before an untick in courtship again in the fall.

But by far the most interesting discovery this spring was by one of my UC California Naturalist students who found a small male rattlesnake with no rattle! (See photos below) Now I hesitate to mention this, for fear of starting a panic about rattleless rattlesnakes. Please remember several things:

Rattlesnakes missing their entire rattle are extraordinarily rare. So rare, in fact, that they usually rate a note in a biological journal. This one will!
No rattlesnake has a long pointed tail like our many harmless snakes.
Rattles can be missing due to either injury or genetic mutation.
This little snake appeared to be recently missing the end of his tail and had other serious but healing injuries. Apparently a close call with a predator!
Identify rattlesnakes by looking at the tail! Yes, rattlesnakes have elliptical pupils and heat-sensitive facial pits but some harmless snakes have elliptical pupils and both these characters are too small to be clearly seen from a safe distance (two-times the length of the snake). Some harmless snakes also have rather triangular heads, especially when they have been frightened and are behaving defensively. But no rattlesnake has a long pointed tail like our harmless snakes and all of California’s dangerous snakes are rattlesnakes.

Check out the following images…

Our rattleless Male 87, on the day of his capture, 09 April 2017. He is only about two feet long. Note that his appearance is “rattlesnake” in every way except for the stump of a tail without a rattle.

Dorsal x-rays of Male 87’s tail (right), compared to a normal rattlesnake’s tail (left). The large opaque “club” in the normal tail is the calcified stylus inside the tail to which the shaker muscles attach (the hollow keratinized rattle on the normal tail is present but invisible to the x-rays). Many thanks to Hazel Ridge Veterinary Clinic for the radiograph.

One of several other healing injuries on Male 87. (The scale is centimeters; 2.54 cm = 1 in)

This is a harmless but badly frightened gopher snake that has just been stepped on by a hiker. Note how it has flattened its head into a triangle. It was also vibrating its tail in the grass, producing a good imitation of a rattlesnake. But a look at its tail reveals that it is not a rattlesnake (see next photo) and, therefore, a harmless California snake.

No rattlesnake has a long pointed tail like this gopher snake.

To be sure, there are dangerous snakes in other parts of the United States that have long tails without rattles (cottonmouths, copperheads and coral snakes, in southern and eastern states). But in California and other northwestern states, the only dangerous snakes are rattlesnakes.

Look at the tail to identify rattlesnakes!

And, yes, Male 87 was processed and released, just like all the others. While he has no paint in his rattle, he won’t be hard to recognize!

More baby news

First, I have added a link on the main menu to a new video (UC Santa Cruz Video). Bethany Augliere and Brendan Bane from the UC Santa Cruz Science Communication Program visited the EYNC Rattlesnake Study last May and recently posted the resulting video, which satisfies one of the requirements for their graduate degree program. I hope you enjoy it!

Back to baby rattlesnakes

As of 22 September, all three telemetered reproductive females (39, 53 and 75) had left their birthing shelters. Two are clearly hunting and the third is just a few feet away, being courted by a male.

Female 39 produced a brood in the same hollow log for the third year in a row. Then, immediately following the kids’ neonatal sheds on 14–15 September, she made a long move to the same place in the blackberry thicket on the other side of San Lorenzo Way – also for the third year in a row. As I observed last year, she apparently knows where to find a reliable meal after the kids leave the house!

Female 75 abandoned the ground squirrel burrow she had been in for weeks between 17 and 19 September and moved to a blackberry thicket near the Duck Pond. Although I never observed babies in the burrow with her, the tunnel was deep and she was sometimes out of sight of my three-foot-long Burrow Camera. After she left, however, a single neonatal shed “skin” was visible in the burrow and I recovered it yesterday. Hopefully, DNA from it will confirm that Female 75 produced a litter and reveal who the father was. Since multiple paternity is common in rattlesnake broods, the DNA from this skin will not identify the paternity of any other siblings.

Recovered neonatal exuvium from ground squirrel burrow occupied for weeks by Female 75; 23 September 2016 Original DROID IMG_20160923_125147783.jpg — Recovered neonatal exuvium (shed corneal skin layer) from the ground squirrel burrow occupied for weeks by Female 75. Tying a tool designed to retrieve dropped screws to the Burrow Camera allowed the “skin” to be fished out of the burrow.

Female 53 left her shelter in the stream bed between 19 and 22 September, moving only about 4 meters to another shelter where she is accompanied by a non-telemetered male, CROR 72 (green/yellow paint in his rattle). Note the postpartum skin fold in the frame shot (below) and then watch the brief video of the two rattlesnakes together. (click here)

Postpartum Female 53. Note the long lateral fold of empty skin along her abdomen, typical after loosing 30-50% of her body mass during birth. — Postpartum Female 53. The long lateral fold of empty skin (yellow arrows) along her abdomen is typical after loosing 30-50% of her body mass during birth.

The underground void that Female 53 just left remains occupied by an unmarked female with babies. You can see fresh neonate skins on top of and stuck to this female and it is difficult to tell if the kids in the video have shed yet. I suspect the recently shed skins belong to Female 53’s litter which has already departed and the remaining babies belong to the unmarked female. If I am right, these babies will remain with mom for a few days more. However, if the fresh sheds belong to them, they and their mother will be gone the next time I visit. It is important to remember that maternal accompaniment of neonate rattlesnakes has only been known since radiotelemetry has been used to study these animals. Watch the video here.

So it appears that the 2016 birthing season is nearly complete. People around the American River Parkway and other places where rattlesnakes live will be encountering baby rattlesnakes with some frequency between now and the onset of cold weather. But, at the size of pencils, the little guys have many predators and few of them survive until spring.

First baby rattlesnakes of the season at EYNC

We have kids!

Just a quick post to let you know that as of last Saturday, 3 September, Females 39, 53 and 75 were all still visibly pregnant.

Females 39 (red/blue) and 53 (blue/yellow) laying together in their gestation shelter on Saturday, 3 September, illuminated by sunluight reflected from a mirror. Both were still pregnant. They are laying on top of a recently shed skin from another large rattlesnake. — Females 39 (red/blue) and 53 (blue/yellow) laying together in their gestation shelter on Saturday, 3 September, illuminated by sunlight reflected from a mirror. Both were still pregnant. They are laying on top of a recently shed skin from another large rattlesnake.

But yesterday afternoon, 6 September, a newborn baby was coiled in the hollow log where 39 and 53 had been on Saturday. I could not see the adults well enough to tell which one had given birth. There were undoubtedly other kids that were not visible. Since the neonates start a shed (ecdysis) cycle almost immediately after birth, which turns their eyes bluish-white, this one’s clear eyes indicate he is not very old.

A newborn northern Pacific rattlesnake in the hollow log with females 39 and 53 on 6 September. His eyes are still clear, indicating he is no more than a day or two old.

As of Saturday, I could not see neonates in the burrow with Female 75.

Since my last post, I also came across the first Fall courtship. Early on 29 August, I came across an unmarked male courting Female 66, who is not pregnant this year and has been hunting all summer. A couple hours later, the apparently happy pair were copulating! Remember, these rattlesnakes have a bimodal courtship season: they court in the Spring, lay low during the hot months, and resume courtship in late Summer/Fall.

Female 66 is almost hidden by an unmarked male courting her on 29 August 2016 — Female 66 is almost hidden by an unmarked male on top of her on 29 August 2016. Note his tail wrapped around and under hers.

Female 66 copulating with an unmarked male on 29 August 2016 — The same pair copulating two hours after the photo above was made. The marked and telemetered female has white paint in the top half of her rattle; the male’s rattle is not marked with paint.

Pregnancy, growth and drought

We currently have transmitters implanted in six female rattlesnakes. We have been tracking Female 39 since 2014 and Females 41 and 53 since 2015 and all are currently pregnant and in their gestation shelters where they will likely thermoregulate for six weeks or more. Furthermore, they have all produced a brood during each season we have been following them, so this will be the third year in a row for Female 39 and the second in a row for 41 and 53. And we don’t know how many consecutive years they might have reproduced before that! Each has returned to the same gestation refuge each year, although 41 uses a different location than 39 and 53, who gestate together. We have also found pregnant unmarked females in both places in past seasons with these girls.

That’s not all. We have three new females this season, numbers 66, 75 and 80. These snakes do not appear to have settled into gestation shelters yet (and I don’t know where they were in previous years) but I just implanted a transmitter in Female 80 a few weeks ago and could feel six fetuses in her belly…it felt like she had swallowed six soft ping pong balls! I’m not sure about the reproductive status of 66 and 75, since their surgeries were earlier in the year and both had so much material in their intestines that it made identifying small embryos with confidence difficult.

Another opportunity to assess the health and growth of the rattlesnakes at Effie Yeaw Nature Center occurred day-before-yesterday (13 July) when Kelly came across an adult rattlesnake at the end of the Visitor Center building early in the morning. Per protocol, she expertly maneuvered it into the capture bag and deposited it in the holding barrel for me. It turned out to be Male 52, a rattlesnake previously captured, processed, and released without a transmitter early in May 2015. At that time, he was 30.7 inches in total length and weighed 11.6 ounces. He now measures 33.5 inches and weighs 18.9 ounces. While increasing 9% in length and 63% in mass in 14 months, he has shed three times (see photo below).

For those of you new to the blog, I inject acrylic paint into the first hollow segment of the rattle, next to the black live segment at the end of the tail. With a different color combination for each snake, it allows me to visually identify them. As the snake grows and sheds the corneal layer of its skin periodically, it produces a new rattle segment with each shed. The segment with the paint is thus moved away from the tail until it eventually breaks off. When this seems imminent, as in Male 52 above, I inject paint into another segment to preserve the marking.

The constant growth of all the rattlesnakes being sampled and the annual reproduction of many of the females attests to the health of not just the rattlesnake population but the overall small animal community in the riparian habitat at Effie Yeaw Nature Center. While the region is undeniably in a severe long-term drought, enough local rainfall has occurred to keep the annual plants, shrubs, some trees, and the food web they support healthy.

Finally, I want to share with you a little bit about a presentation I made at the annual Joint Meeting of Ichthyologists and Herpetologists last week in New Orleans. I have reproduced the published abstract (summary) of my talk below. Please excuse the Latin names. Crotalus scutulatus is the scientific term for the Mohave rattlesnake and Crotalus oreganus is our own northern Pacific rattlesnake. While recent drought has not yet affected the rattlesnakes or their prey in the areas of northern California I have sampled, 2002 was a rainless year in the Mohave Desert, with no plant growth and a dramatic reduction in the availability of kangaroo rats and other small mammals that make up the great majority of the rattlesnakes’ diet there. During 2002, Mohave rattlesnakes changed their behavior very significantly, staying tightly coiled and avoiding wind and sun while moving very little and not courting or mating.

The take-home message I delivered in New Orleans was that (1) these animals are used to hot dry summers and get most of their water from their prey; (2) regional drought does not necessarily equal local drought; (3) rattlesnake behavior is probably not affected by drought until prey availability is affected; (4) water-stressed rattlesnakes minimize exposed skin by remaining coiled most of the time; (5) when water-stressed, they don’t move more, they move a lot less than usual; and (6) there is no evidence that they leave their normal home range during a drought.

In other words, there is zero evidence to support the frequent news media claims that drought drives rattlesnakes into yards.

Emphasis now on hunting and shedding

Before I launch into what’s been going on with the Effie Yeaw rattlesnakes over the past few weeks, I want to pass on a link to a recent interview with Dr. Bree Putman. Bree was a grad student with Matt Holding (lead author of the journal article I linked to in my last post) in Emily Taylor’s lab at Cal Poly San Luis Obispo before she moved on to Rulon Clark’s lab at San Diego State to finish her Ph.D. In Bree’s interview (click here), she talks about ground squirrels and northern Pacific rattlesnakes and she describes some of the very intriguing behavioral questions many of us would love to answer.

Back to EYNC rattlesnakes –

This female California ground squirrel was clearly nursing pups on 26 April at Effie Yeaw Nature Center. — This female California ground squirrel was clearly nursing pups on 26 April in the Effie Yeaw Nature Center preserve.

I have not seen a courting pair of rattlesnakes since 28 April, when three rattlesnake pairs were found together in different locations. Male 37 was found with unmarked adults that were likely females on 11 and 14 May but no courtship was observed. But as the spring courtship season wound down, California ground squirrels began producing pups and the emphasis of both rattlesnake sexes turned to hunting.

After not finding a telemetered rattlesnake in or very near a ground squirrel burrow during the first 400+ observations this year, Male 46 was found in an ambush coil facing an active burrow a foot away on 9 May. In the five weeks since, several rattlesnakes have been found close to or inside squirrel burrows on several occasions.

At the same time, the snakes have also been hunting heavily in vole (aka: meadow mouse; Microtus californicus) tunnels in the grass.

Male 46 visible in a vole tunnel on the morning of 3 June 2016. Original RAW IMG_2192.CR2 — Male 46 uncovered (arrow) in a vole tunnel in the grass on the morning of 3 June. Although you cannot see it here, voles construct a maze of above-ground tunnels in thick dry grass that protects them from most predators… but not rattlesnakes. I hope you can appreciate just how impossible it would be to learn about the habits of these snakes without radiotelemetry!

And since about the end of May, the rattlesnakes – especially males – have been shedding.

Pre-shed Male 38 on 14 June 2016 Original RAW IMG_2320.CR2 — The rattle of pre-shed Male 38 under a log yesterday, 14 June. The new rattle segment forming in the base of the tail is whitish and covered by the last couple rows of scales. He is easily identified visually by red/green paint in his rattle.

Periodically shedding the corneal layer of the skin (called ecdysis; for more info, click here) takes snakes out of commission for a week or more and males seem to put it off during the spring mating season. It’s a bit like race car drivers waiting for a yellow caution flag to make a pit stop!

Even more interesting is that the rattlesnakes have favorite places where they go during this process and it is not uncommon to find several pre-shed individuals of both sexes together this time of year. Like hibernation, there seem to be many logs and burrows where they could shelter while waiting to shed but they congregate in just a few of them. Those of us who study rattlesnake behavior would love to know why. What is so special about certain locations? Or is it something else… like family ties or some other social interaction?

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).

Courtship has begun

Despite persistent cool mornings and alternating sunny and cloudy days, nine of eleven telemetered rattlesnakes have left their winter shelters and the remaining two have been basking regularly and will undoubtedly be on the move soon. We have also been finding plenty of new rattlesnakes basking and now have 27 animals processed and marked with colored paint in the rattles, in addition to the eleven with radios.

As I have already described, Female 41 was one of the first to leave her hibernation site and was soon joined by Male 49, a snake marked last season but not telemetered. Male 49 and Female 41 remained in close proximity at the same location from 16 February until 20 March and, although they were occasionally coiled in contact with one another, I never saw the male courting her. Male 49 followed when Female 41 moved more than 50 meters between 20 and 24 March but there has still been no witnessed courtship. However, the grass is very thick at their new location, making her hard to see and him impossible to spot if he’s not with her (and I don’t want to step on him… they’re very fragile!).

On 22 March, I came across Female 55, another animal processed last year and released without a transmitter, basking alone at the edge of a large log. But when I returned on 24 March, she had company: an unmarked (no paint in the rattle) male on top of her, jerking, chin-rubbing, and tongue-flicking – typical courtship behavior (you can view a 2015 clip of Female 41 with another male here).

Female 55 basking alone in the afternoon sun on 22 March 2016. Note her rattle with red over yellow paint, visible through the grass on the left side of the photo. Without a radio, she had not been seen since June of last year.

type here — Then two days later, on 24 March, Female 55 is almost completely hidden by a new male on top of her; you can see his unmarked rattle in the middle foreground of the photo. Although the male is distracted by me in this picture, he had been vigorously courting the female just moments before. Unfortunately, the video camera auto-focused on the grass, making the resulting image unusable. Courtship continued at this location for at least three days but they were gone on 29 March, replaced by Male 35, who was enjoying the sun by himself yesterday afternoon. Although he would retreat under the log when I approached closely, he would re-emerge within minutes as soon as I backed away.

We can expect the females to hunt for the next two-to-three months, after which pregnant females will retreat to their favorite gestation shelters to thermoregulate until their kids are born around the first of September. Non-pregnant females will continue to hunt through the summer. Males will spend most of their time looking for receptive females until late May/early June, after which they, too, will hunt full-time for voles and ground squirrel pups until courtship resumes in late summer.

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!