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.


Baby season update

Just a quick update on our reproductive females:

On Monday, 7 September, I found Female 53 missing from the hollow log where she had been gestating with Female 39, who was still present. This is the hollow log where I photographed a new baby on 6 September (see my last post) and I could glimpse youngsters deep inside the log again on the 7th. After considerable searching, I detected 53’s radio signal and followed it to a sycamore tree near the edge of the American River, 368 meters (402 yards) from where she had been. Since that day, she has moved a hundred meters or so back toward the oak woodland but has settled into a small cavity in the rocky riverbed.

This morning, 15 September, I found multiple shed “skins” from babies back at the hollow log and Female 39 was gone. I had checked the log yesterday and found no neonatal sheds.

Fresh neonatal shed "skin" (actually, the shed outer or "corneal" layer of the skin) in the log where Female 39 has been gestating since 14 June.
One of the neonatal shed “skins” (actually, just the outer or “corneal” layer of the skin) found this morning in the log where Female 39 has been gestating since 14 June.


Female 39’s radio signal led me to her 195 meters away, where she was coiled in dappled sun with lots of loose skin hanging on her. The babies shedding over the past 20 hours and the departure of Female 39 confirms that the kids were hers and were only a day or two old when discovered on 6 September (about 11 days between birth and the postpartum shed). Inspection of the inside of the log today with the BurrowCam revealed no rattlesnakes.

Then, when I checked Female 53 in her rocky riverbed hole this morning, she no longer appeared pregnant. In the BurrowCam video (link after the still photos below), look closely beyond her, just right of the center of the frame (next to the snail), beginning about 41 seconds into the clip. For the next 8 seconds, you can see a shiny wet baby moving behind her! I have circled the place to look in this still frame:

Female CROR 53 in streambed burrow Frame grab at 47 seconds into original BurrowCam video; 15 September 2016
The place to look for the shiny moving baby in the video is circled in this still frame grab.

Also, compare the appearance of her abdomen in today’s video to her 3 September photo (in my last post).

Female CROR 53 in streambed burrow Frame grab at 57 seconds into original BurrowCam video; 15 September 2016
Female CROR 53 in her streambed burrow at 52 seconds into the video clip. The violet sutures remaining from her May transmitter surgery are circled, indicating that we are looking at her posterior abdomen, which is no longer swollen.

Today’s 60-second BurrowCam video can be viewed on YouTube (click here).

Meanwhile, Female 75 remains in her burrow, still without kids, while Female 80 is still high on the bluff and inaccessible.

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.
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.

Just when you think you know what to expect…

Well, we are entering that time of the season when we can expect to find baby rattlesnakes any day now. Of course, the youngsters will not be roaming around where they might encounter people for about 10-14 days after birth…so we usually don’t encounter them on trails and in yards until early September.

But our six telemetered females are displaying a variety of behaviors indicating that all may not be about to produce babies. Six weeks ago I reported that Females 39, 41, and 53 were all pregnant and in the gestation shelters they have used repeatedly to thermoregulate before giving birth in previous years. Furthermore, I could feel six fetuses in Female 80’s belly when I implanted her transmitter in June.

Since that mid-July report, Females 39 and 53 have behaved predictably for expecting moms, remaining in their gestation shelter, and both appear to be about to produce kids. In the photos below, note the abdominal girth of these females, with scales pulled widely apart.

Female 39 in her gestation shelter on 20 August 2016 - the same shelter she has used to incubate her kids for three years in a row. Her body temperature at the time of the photo was 32C (90F).
Female 39 in her gestation shelter on 20 August 2016 – the same shelter she has used to incubate her kids for three years in a row. Her body temperature at the time of the photo was 32C (90F).
Female 53 in a different part of the same hollow log as Female 39 on 20 August. Femape 53's body temp was 30C (86F).
Female 53 in a different part of the same hollow log as Female 39 on 20 August. Female 53’s body temp was 30C (86F).

This will be the third consecutive year that Female 39 has produced offspring and the second for Female 53, so far as we know. We were not monitoring them previously. Between the first of July and yesterday, 23 August, the average body temps for Females 39 and 53 have been 28C (82F) and 29C (84F), respectively.

Six weeks ago, Female 41 had just returned to the gestation shelter she used the previous two years, which led me to believe she was likely pregnant again. However, after staying only three weeks, she left and has been spending her days mostly out of sight in various ground squirrel burrows during August. I have not been able to get a good look at her in recent weeks but her behavior and average body temperature of 26C (79F) suggest that she may not reproduce this year. Although Female 41 produced kids in both 2014 and 2015, I want to remind readers that skipping a year or two between broods is far more common than annual reproduction for temperate-latitude pitvipers.

Our remaining three telemetered females are new to the study this year, so I have no data from previous years. Female 66 has behaved quite normally for a non-reproductive year: hunting continuously throughout the spring and summer. Her July-August average body temp has been 22C (72F).

Female 66 in a typical ambush coil in late May. She continues to move around and hunt during July and August.
Female 66 in a typical ambush coil in late May. She continues to move around and hunt during July and August.

Female 75, however, appears ready to produce babies, although she has been moving back and forth frequently between two ground squirrel burrows 17 meters (56 feet) apart. Her average body temperature during July and August has been 27C (81F).

Female 75 on 23 August, illuminated by sunlight reflected from a mirrow, a few inches inside one of the two ground squirrel burrows she has been occupying in recent weeks. Again, note her distended abdomen. Body temp was 27C (81F) at the time of the photo.
Female 75 on 23 August, illuminated by sunlight reflected from a mirror. She is a few inches inside one of the two ground squirrel burrows she has been occupying in recent weeks. Again, note the distended abdomen with scales pulled apart. Body temp was 27C (81F) at the time of the photo.

Finally, there is Female 80. When I captured her and implanted her transmitter in June, I could clearly feel six fetuses lined up in her abdomen. Shortly after I released her at her capture site near the base of the bluff, she climbed up the hillside and has remained near the top ever since. On three occasions, I have climbed that steep, loose, and treacherous slope but have failed to locate her. Her radio signal seems to emanate from thick ornamental ivy growing down from a residential backyard under fig and valley oak trees. She is also just above an underground wasp nest. Just to be clear, I am far more comfortable with rattlesnakes than a nest of wasps – especially where I cannot easily run away! Since I have no previous data from her, she could be in her usual gestation shelter. However, her July-August body temperatures are not consistent with a gestating female, with an average of 23C (73F). I’m not sure how this is going to play out…

Just for comparison, the seven telemetered males have been moving around a lot, hunting and occasionally hanging out with the pregnant girls for a day or two at a time. Their average July-August body temps range from 17C (63F) to 26C (79F), with the average between the boys of 23C (73F). Note how closely these data match non-reproductive Female 66’s average body temp of 22C (72F) during the same period.

A big impressive rattlesnake at over 38 inches and about 1.5 pounds (last October), Male 37 ignored us yesterday as he crossed the trail in front of me and an EYNC visitor with whom I was chatting. The visitor was quite impressed and I never tire of watching these amazing and interesting animals with such an undeserved reputation for aggressiveness!
A big impressive rattlesnake at over 38 inches and about 1.5 pounds (last October), Male 37 ignored us yesterday as he crossed the trail in front of me and an EYNC visitor with whom I was chatting. The visitor was quite impressed and I never tire of watching these amazing and interesting animals with such an undeserved reputation for aggressiveness!

That’s it for now. Next post will almost certainly be (cute!?!?) baby pics!

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
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.

Cardwell abstract

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?


New research on ground squirrels’ resistance to rattlesnake venom

I have mentioned before that much research has been done on the interactions, both behavioral and biochemical, between Northern Pacific Rattlesnakes (Crotalus oreganus) and California Ground Squirrels (Otospermophilus beecheyi). And that research continues.

It started, so far as I know, with studies by UC Davis psychology professors Donald Owings and Richard Coss in the 1970’s, when they became interested in how California Ground Squirrels behaved when confronted by Northern Pacific Rattlesnakes. Several researchers have since spun off various aspects of the relationship between these two species, including Dr. Rulon Clark and his students at San Diego State University, who study the phenomenon from the rattlesnakes’ perspective. A common thread among these studies is that the adult squirrels are largely resistant to the rattlesnakes’ venom, often surviving with nothing but a nasty wound that eventually heals (although adult squirrels occasionally succumb, vividly illustrated by the photo accompanying the Washington Post article linked below).

But while adult ground squirrels seldom die from rattlesnake bites, their pups are much more vulnerable and the rattlesnakes hunt them intensely, starting about this time of year. I have linked a 60-second video made by Denise and I in July 2014 of our Male 36 (yes, the same one just recaptured after 20 months) preying on a ground squirrel pup while the pup’s mother tries to defend her offspring (Read original account here).

Tail-flagging and pushing grass at the snake are common behaviors by adult California Ground Squirrels when confronted by rattlesnakes. In this one-minute clip, the snake had already bitten a pup, which is laying in the grass and out of the frame at the start. The adult squirrel soon retreats to the stricken pup, which appears as a dark area in the grass. The adult squirrel’s attempts to deter the rattlesnake appear to work momentarily a couple of times as the snake turns away but almost immediately comes back toward the bitten pup. Near the end of the clip, the snake reaches the pup and bites it again. Although the pup runs out of the frame, it only makes it a few feet. The rattlesnake follows and swallows it a few minutes later. Excuse the background helicopter noise, as the fire department was conducting an operation in the river nearby. View the video here.

I bring this up now because my friend, videographer George Nyberg (who produced the very nice 2015 video of my rattlesnake study), has alerted me to a new Washington Post article on the biochemical “arms race” between Northern Pacific Rattlesnakes and California Ground Squirrels (view article). Thanks, George!

Matt Holding, whose research is the focus of the WP piece, is a former graduate student of another friend, Dr. Emily Taylor at Cal Poly San Luis Obispo. Jim Biardi, second author on the new study, is a former member of the UC Davis group that originally studied ground squirrels and rattlesnakes.

The Washington Post does a nice job of describing how natural selection works: in short, there is always variation among individuals and some are better adapted than others to feed themselves (or avoid being eaten!) and those individuals tend to survive longer and produce more offspring, which carry the genes for those successful traits. Less successful traits are passed on less frequently (i.e., fewer offspring are produced). The peer-reviewed paper upon which the WP article is based was published in the journal Proceedings of the Royal Society B (volume 283, issue 1829, April 2016). However, since this is not an open source journal, access to the complete manuscript is not easily available to the general public right away.

Male 36 finally recaptured!

If you have been following my rattlesnake study from the beginning, you know that we struggled through some faulty transmitters early in the project (search “failed transmitters” for previous info). The first six transmitters I implanted failed early. Several failed during hibernation (2014/15) and, because I knew where the snakes spent the winter, I was able to capture them when they began basking in the spring. Two, however, proved to be a bigger problem.

Male 36’s transmitter was first to fail in September 2014, with two months of activity remaining that season. Male 37’s transmitter lasted into the winter but he hibernated high on the bluff under a thick mat of vegetation, making his exact location very difficult to visit and impossible to pinpoint. Thus, both emerged in the spring of 2015 without functioning transmitters.

Both eluded recapture until October 2015, when I found Male 37 (details here) under the log I call “The Community Center” because everybody visits it from time to time. Males visit looking for girls, pregnant females hang out there to thermoregulate and give birth, and both sexes use it for shelter while waiting to shed (but nobody spends the winter there). I replaced Male 37’s transmitter then, leaving only Male 36 unaccounted for – until last week.

After twenty months, I had just about given up on finding Male 36 again. But when I checked around The Community Center one day last week, I was thrilled to spot his rattle with red/red paint! Like Male 37 last fall, Male 36 was also pre-shed and using The Community Center for shelter while he waited to complete the process.

Pre-shed Male 36, with failed transmitter, at Refuge 01, Effie Yeaw Nature Center, on 11 May 2016, moments before his recapture. Original RAW IMG_1531.CR2
Pre-shed Male 36, with failed transmitter, at The Community Center on 11 May 2016, moments before his recapture. If you look closely (partly obscured by grass), you can make out the new light-colored rattle segment forming under the skin at the rattle base.


Just like Male 37, I captured Male 36 and kept him several days until he shed. His transmitter was replaced and he was released yesterday.

Male 36 disappearing into
Male 36 disappearing into The Community Center yesterday with a new transmitter and re-marked rattle (his rattle is quite long and likely to break soon, potentially taking his original paint with it). Note how clean and crisp his pattern appears after shedding, compared to the photo above.


The return of Male 36 fills my permit quota of seven telemetered males. We currently have five females telemetered and I am holding out, hoping to get a couple of females radio-tagged farther out in the northeastern portion of the preserve where few of our current snakes venture. Interestingly, Male 38 was hanging around with two females out there last week, including last Saturday when I was hosting a video crew from UC Santa Cruz. While I would have loved to get a transmitter into one of them, they were too wary and repeatedly escaped when approached.

I wish more people could see just how hard these fascinating creatures try to avoid confrontations with people!



Interesting rattlesnake news

How well do rattlesnakes tolerate surgically-implanted transmitters?

As I have discussed before, there is a long (20+ years) history of telemetry studies of rattlesnakes in which individual animals tolerate the transmitters for years, enduring periodic surgeries to replace the radios. The animals thrive, repeatedly producing offspring and growing at the same rate as rattlesnakes without transmitters.

I bring this up because of a phone call last weekend from the landowner where I conducted my El Dorado County field study. He had just encountered the first Northern Pacific Rattlesnake I ever marked and telemetered, still identifiable by the yellow-over-yellow paint remaining in his rattle. He is now an exceptionally large male with twelve rattle segments – but in 2009, he was a young animal with a tapered unbroken rattle. He eventually endured four annual surgeries to implant and replace transmitters, followed by a fifth surgery in 2013 to remove his last radio.

Here is a PowerPoint slide of Male 01
Here is a PowerPoint slide I use to illustrate how marking the rattles helps to judge growth and shedding frequency. The photos are of my Male #1. It also demonstrates how the rattle breaks over time. According to my friend, the 2011 paint is now just two segments from being lost but the snake is big,  healthy, and thriving. You can see that, once the early tapered segments are gone, the rattle offers little insight into the age of the snake.

Male 01 being sighted alive and healthy is just more evidence that the surgical protocol and other study methods used by me and many of my rattlesnake-researcher colleagues is well tolerated by the animals we seek to learn more about.

Rattlesnake intelligence?

Despite my frequent admonition that we often tend to give rattlesnakes and similar animals too much credit for cognitive thought, friends at San Diego State University recently published some compelling evidence that rattlesnakes may learn from experience and apply those lessons to anticipate and mitigate problems during future similar circumstances. Bree Putman and Rulon Clark have spent years studying rattlesnake predation tactics by setting up video cameras on hunting rattlesnakes and recording their predatory encounters with small mammals. (This works because rattlesnakes are ambush hunters that sit still for long periods of time, waiting for prey to wander by.)

While reviewing 2000 hours of video, Bree and Rulon discovered two examples of rattlesnakes using their heads and necks to move foliage out of the way that might otherwise interfere with a strike when prey wanders close (click here for video). The animals involved were Northern Pacific Rattlesnakes – the same species as we have in the Sacramento area. Similar behavior has been reported a couple of times in the past, once involving a Prairie Rattlesnake (Crotalus viridis) and once involving an Arizona Blacktail Rattlesnake (Crotalus molossus); both these incidents were witnessed by observers but not recorded.

Thus, evidence continues to accumulate that rattlesnakes are likely more social and maybe more intelligent than previously thought – although many habits are undoubtedly genetically programmed by natural selection. The new report by Putman and Clark is contained in the current issue of The Southwestern Naturalist (volume 60, number 4; December 2015).

For more interesting videos of natural predatory behavior by rattlesnakes, go to Rulon’s YouTube page.

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).