16 March: General emergence has occurred!

The day after I saw Male 37 in the flat woodland (7 March), down from his winter shelter on the hillside, Male 38 was found about 10 meters (33 ft) from his hibernaculum, where he remained coiled in the grass for several days while basking when possible. Although other telemetered rattlesnakes remained at their winter shelters for most of last week, they were often found basking in the sun, as were several unmarked rattlesnakes.

I caught and marked several of those new basking rattlers and, as it appeared that another cold snap was unlikely, I implanted transmitters in CROR46, captured on 6 March, and in a new female, CROR47, captured a few days later. I could not palpate any fetuses in Female 47 and I don’t think she is pregnant but it’s possible, as it is very early in the year.

As of today, Female 41, who produced kids last season and apparently hibernated by herself, was coiled in deep green grass about 30 yards from where she spent the winter (below), apparently hunting. CROR 41 16Mar2015AMale 35 was coiled in deep grass under a live oak tree he frequented last year. He’s the one who spent so much time in the vegetation near the bike rack, silently welcoming guests much of last summer. We’ll see where he goes next.

You may remember that Male 40’s transmitter was the most recent to fail prematurely. Well, I was able to recapture him today. I also recaptured Male 38, who’s transmitter is still working but is part of the batch that have been failing early. Both will be released with new transmitters in the next day or two. Males 36 and 37 remain on the loose with failed transmitters.

Finally, Male 46 and Female 47 have found each other and were laying in the sun together this afternoon (below). There was no active courtship when I saw them (they were very still) but I’m not buying that this is a platonic relationship this time of year!CROR46 & 47_16Mar15

As you can see from the photos, these rattlesnakes are almost impossible to see in the thick carpet of green grass that covers the park now. And when approached too closely, they disappear silently into the grass – as Female 47 did as soon as I tried to get closer after the photo above. Of course, the green grass makes it very easy to step on a rattlesnake!

As of today, Female 39 is the only telemetered animal that has not left her winter shelter, although her body temp has been warm (indicating she has been basking, although I haven’t seen her) and, several days ago, she moved to the other end of the log where the location of her radio signal was identical to that of Male 35 for a couple of days before he left. Hmmm…!

I also heard two different California ground squirrels incessantly chirping their alarm call this afternoon. When they are signaling a hawk or coyote, they usually chirp once or twice and dive for cover. When they continue to chirp over and over, it is often a snake (unlike a hawk or coyote, once they discover a snake, they can avoid it without going underground). Unfortunately, I didn’t have time to investigate today.

7 March 2015

There’s lots to report during the past 1.5 weeks…

On February 26, I came across another unidentified young adult rattlesnake at the refuge where so many others appear to have spent the winter. He or she was basking in the sun but escaped into the refuge, showing me in the process an unbroken rattle of about 7 segments with no paint. No time for photos, either. No other snakes were found basking that day.

I found Male 38 and Female 41 basking in the late afternoon on both 1 March and 3 March. Their body temperatures were 70F & 86F, respectively, on 3/1 and 84F & 90F on 3/3.

On the afternoon of 6 March, Female 41’s body temperature of 86F indicated she had been basking earlier but she was out of sight when I looked for her. By comparison, body temps for animals that have not basked recently have been around 10-14C (50-57F). While I did not find any of the marked snakes visible on 6 March, I did find a new male basking and captured him – CROR46. He has an unbroken rattle of 8 segments, making him relatively young but, at 264 g (9.3 oz), he is a good candidate for a transmitter. I will have to research the extended weather forecast for our area and if another cold snap looks unlikely, he will get a transmitter. I will also photograph his face and compare him to the unmarked snake photographed at this refuge on 14 February.

Just after 10 AM today (7 March) I found Female 41’s radio signal (her transmitter is not from the problem batch) rapidly increasing in pulse frequency, indicating she was cool but warming rapidly in the sun. Unlike some of the other basking rattlesnakes in the area, I have never found her basking in the open, out from under cover; she only exposes a small part of her surface area to direct sun while remaining sheltered. Take a look at the photo below and note how little of her was in the sun, yet her body temperature increased from 48F to 59F as I monitored it over just 20 minutes!

CROR41 basking Original IMG_5509.CR2

Finally, I spent some time around midday today checking some the favorite places for Males 36 and 37 – both are carrying dead transmitters. Surprisingly, I came across an adult rattlesnake at the base of the hill where both hung out last year. The snake was only partly exposed, with head and anterior body already in a hole and its tail hidden in the grass. Just as quickly as I saw it, it continued down the hole but not before I could clearly make out Male 37’s yellow/red rattle markings. Although I couldn’t capture him (without tearing up the environment, which I won’t do), he was 32 m (105 ft) from his winter refuge high on the hillside… so spring emergence is definitely underway! I have been told by several other people of recent rattlesnake sightings but this is the first of our study animals to be found away from his hibernaculum this year.

24 February 2015

Little has changed over the past ten days; fence lizards basking midday when it’s sunny but no rattlesnakes out when I have checked. The only interesting development was on 19 February, when I found that Female 41 had moved again, this time about 7 m (23 ft) to another smaller log where she was out of sight.

Today, I started collecting data on my Droid smartphone, rather than taking paper notes. Using a program called iFormBuilder, I have been able to create a menu that allows me to record twenty-nine observations of things like where a snake is, what it’s doing, temperatures, other environmental data, nearby flora, etc., mostly by making choices on drop-down menus. When I’m done, it automatically up-links to my computer at home where the data is waiting to be saved in an Excel spreadsheet. This not only helps standardize the data I collect but it saves an unbelievable amount of time by eliminating the need to manually enter data from paper notes. I used a similar system during my 40-month field study of Mohave rattlesnakes (2001-2004) and recorded something like 150,000 data points during more than 3700 encounters with the snakes; if that had been done on paper, I would still be working on data entry!

At 12:17 PM, I found a small unmarked male rattlesnake laying in the sun at the same refuge shared by CRORs 35, 38, 39, 40 and several others. He was captured (CROR45) and processed. At 242 grams (9 oz), he is large enough for a transmitter (the rule is the transmitter should not exceed 5% of the snake’s body mass, so my 9 g transmitters require a snake of 180 g (6 oz) or larger), however, releasing him with a fresh surgery when the weather is likely to be cold for weeks to come is not good. Physiological processes in ectotherms (animals that rely on the environment for body heat rather than making their own) slow way down when they get cool, which includes their immune systems and their ability to heal wounds. So Male #45 will be processed (measured, marked, etc.) and released where he was captured without a transmitter.

Before releasing him, however, I wanted to see if he was the same snake I saw on 14 February, since his body size and rattle looked very similar. But after comparing a photo of his face with my photo of the unidentified snake from 14 Feb, I found that they are not the same animal. In the photos below, note the difference in shape of the margin of the postnasal scale at (1), the speckling pattern of the preocular scale at (2), and the shape just under the eye of the margin of the dark postocular stripe at (3). Of course, there are many other dissimilarities in the photos… bottom line, it’s not the same animal.Compare 45 with UNID

The last development to report from 24 February is that I could not get a radio signal from Male #40. Thinking that he might have left the refuge with all the warm sunny days, I walked around for awhile without detecting his signal, so I returned to the refuge and used the burrow camera to look forCROR40 24Feb15 him. Sure enough, there he was (yellow/blue paint in his rattle). This is the third transmitter to fail prematurely and all are from the same batch of refurbished units (they last a year and, after removal from the snake, are returned to the manufacturer to be rebuilt with new batteries). As I have mentioned previously, the manufacturer very rarely gets a bad lot of batteries which then affects an entire series of their transmitters. The good news is that I have no more of that batch of transmitters. The bad news: CRORs 35, 38, and 39 all have those transmitters in them. Transmitters have already failed in 36, 37, and now 40. Hopefully, I can catch Male #40 basking and catch him before he leaves the refuge – which could be any time, given the unseasonably warm days. I am reminded that one of those transmitters functioned for over a year in the last telemetered rattlesnake at my El Dorado Hills study site, so maybe all of them don’t contain bad batteries. Nonetheless, I will replace the transmitters in 35, 38, and 39 as soon as they leave their winter refuge, rather than waiting for their normal 12-month replacement.

14 February 2015

Since 2 February, fence lizards continue to bask on sunny days but the rattlesnakes have been out of sight and their low body temperatures suggest that they have not been basking.

However, another new unmarked rattlesnake was spotted today at 1:02PM, laying partly in the sun at the refuge used by most of the other telemetered animals. This one had a complete unbroken rattle of 7 segments plus the birth button and was a different rattlesnake than the one I saw on 2 February. It was in a place where I could not have captured him before he escaped so I didn’t disturb him/her. This is, indeed, a popular refuge. I can barely wait to see if all these rattlesnakes return next winter!UNID CROR 14Feb15B

2 February 2015

Beginning with my first visit to the study site on 3 January, I began measuring ground temperatures with an infrared thermometer, rather than the mercury-filled glass thermometer I have used for a long time. The infrared thermometer is much faster (just point and pull the trigger) and actually gets the surface temperature, rather than the air just above the surface, since conduction with the ground has the biggest influence on the snakes’ body temperature unless they’re in direct sun.

3 January was also the coldest day I have experienced at this study site so far, with the shade surface temp at 4C (39F) at 10 AM. The body temps of males # 35, 38, and 40 (all in the same refuge together) were 45F, 50F, and 48F, respectively. Female #39, in the same refuge as the boys but several feet away, was 52F. Female #41, spending the winter by herself (as far as I know) in ground squirrel tunnels under a large live oak, was 41F.

On 2 February at 2:13 PM, I came across another small unmarked rattlesnake basking in diffuse sun (high thin overcast) at the refuge with CRORs 35, 38, 39, and 40. This snake fled into the refuge when I approached and was not captured.

Also on 2 Feb, female #41 had moved about 20 feet from among the live oak roots to under an old log she had used briefly last summer but she was out of sight either in or under it.

InteresOriginal IMG_5318.CR2; 11 February 2015tingly, on every sunny day recently, fence lizards (Sceloporus occidentalis) have been active, basking on logs, despite the season.

23 December 2014

2:03 PM  Clear, sunny, slight breeze, 12C (54F) in the shade

Male #40 was coiled loosely in the grass and partially exposed to the sun next to the log he is sharing with several other rattlesnakes this winter. His core body temperature was 16C (61F) and he immediately uncoiled and disappeared under the log as I approached. (The body temperature is calculated from his transmitter pulse interval.)

All others were cool and out of sight.

9 December 2014

12:58 PM; 100% thick low overcast, 15C (59F), everything is wet in between two significant rain events.

I heard the sound of a wet rattle rattling at the log where four of our telemetered snakes are located and found a small unmarked male in the new green grass – CROR44 (I’ll explain “CROR” below).  This snake is small at 638 mm (25 inches) and 141 g (5 ounces) but has a broken rattle with only two segments.Coo44 rattle 100dpi_4x6 Upon closer examination, this little guy was found to have some fresh and significant trauma to his posterior abdomen and tail area, including a deep penetrating wound at his cloaca (derived from the Latin word for sewer, the cloaca is the single vent that empties the digestive, urinary, and reproductive tracts in lower vertebrates). Since this rattlesnake was about the same size as the unmarked snake I saw but didn’t capture at this log on 15 November (see photo of tail in 2014 Update #13), I compared scale markings on the tail with the photograph and concluded that this is the same rattlesnake. Sometime in the past three weeks, something got a hold of this snake before he could get all the way under the log and injured him severely, as well as pulling off most of his rattle (the rattles are hollow, brittle and easily damaged). Since my study intends to observe and document natural occurrences (and my permits do not authorize interference in the natural processes), I measured and marked this injured snake (no transmitter surgery) and released him under the log. I am doubtful, however, that he will survive, as his abdominal wound looks deep and they do not heal well when they are cold (e.g., over the winter).

After checking on all of the other telemetered rattlesnakes (none had moved recently), I checked on male #37 on the hillside and found only static at his radio frequency. Given the time of year, the cool weather, and the fact that all other snakes seem to be down for the winter, it is hard to imagine that anything has happened to him. His transmitter has simply failed prematurely, just as the radio in male #36 did a few weeks ago. This is not a common occurance but tends to affect multiple transmitters when it does occur because they were often refurbished from the same batch of batteries. Like male #36, we can only hope to find him in the spring, either around the buildings or courting a telemetered female. I think there’s a good chance of that, though.

An explanation of CROR: Taxonomists and other biologists, at least in the herpetology field, seem to be moving away from the subspecies concept. In giving study animals identifying monikers, we have long used the initials of the genus, species, and subspecies names, plus a number. Thus “Coo36” would be Crotalus (the genus) oreganus (the species) oreganus (the subspecies) number 36 (if he were a southern Pacific rattlesnake, he would be Coh36 for Crotalus oreganus helleri). As taxonomists continue to either lump subspecies together or elevate them to full species status, the numbering convention had to change. So now we are using the first two letters of the genus and the first two letters of the species, so Crotalus oreganus #36 becomes CROR36!

Welcome to the Effie Yeaw Nature Center rattlesnake study blog!

I started implanting radio transmitters in Northern Pacific Rattlesnakes (Crotalus oreganus) at Effie Yeaw Nature Center a few days after the issuance of our final permit in May 2014. Soon thereafter, I started emailing “Rattlesnake Updates” to EYNC staff and docents — with no inkling of how popular the Updates  would become.  By the end of the 2014 season, the email list had grown substantially!

As a result, I have switched to a blog for 2015 and beyond. In this way, you can elect to be notified automatically of new entries [Subscribe], go back and check out what you’ve missed, and the web address can be easily shared with others. One of the links on the menu at left (EYNC Rattlesnakes in 2014) will take you to an explanation of how the study and Updates began and PDF files of the thirteen emailed Updates from 2014. Other menu links will take you to information about Effie Yeaw Nature Center and to a brief introduction to me.

The EYNC rattlesnake study would not be possible without the consent and support of the board of directors of EYNC’s parent organization, the American River Natural History Association and the staff of Effie Yeaw Nature Center, particularly Executive Director Paul Tebbel. Necessary permits have also been granted by the County of Sacramento Department of Regional Parks and the State of California Department of Fish and Wildlife.

I hope you enjoy learning about the private lives of these amazing and timid creatures!

Mike Cardwell