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