And then we continued south, our geographical goal the southern tip of Baja.
Red Diamondback Rattlesnake, Crotalus ruber. (But see Murphy et al., 1995, who synonymized C. ruber with C. exsul, the Cedros Island Rattlesnake).
We collected most mornings, processed specimens most afternoons, and, after inadequate supper, either drove blacktop roads looking for live or freshly dead herps, or lantern-walked the exhausting moonscape of that place.
It was during the latter that this snake was discovered. It was in a boulder-strewn arroyo, not far from the oasis town of San Ignacio, which is a bit south of the peninsula’s geometric centre. Red diamondback rattlesnakes can get quite big (4-5 feet), but are reputed to be relatively docile. Thus it was odd that this one started rattling when we were still very far away.
I heard it first. Its tail was vibrating so rapidly that to me it sounded more pressurized-gas-leak than rattlesnake. It took a long time to find the snake in that rugged place of rocks and crevices, where sound bounces around. Plus, this was long after sunset. Lanterns illuminate, but also cast deep shadows.
Dr. Bob, leader of the expedition, caught the snake. It was in a small, low-ceilinged cave in one wall of the arroyo, coiled on a ledge at face level—a bit unnerving.
After the snake was extracted, I looked into the cave. There was enough room for two or three people to sit. In the floor there was a perfectly symmetrical bowl-shaped depression, perhaps 7 inches wide. Was this a place where corn or some other grain was once milled? How long ago would that have been? I ran my fingertips through the bowl.
The snake may have been hyper-sensitive because it wasn’t feeling well. The obvious mass inside it turned out to be two things: a wood rat (Neotoma), and a wood rat-sized length of Cholla cactus (Cylindropuntia). It was difficult to understand how it could have swallowed such a thing. The spines had penetrated the wall of its gut. It probably would have died a lingering death had we not found it. Instead, it succumbed to an injection of barbiturate. Unfortunate snake, in any case.
Its tissues may have been used in the study cited.
Murphy, R.W., V. Kovac, O. Haddrath, G.S. Allen, A. Fishbein and N.E. Mandrak. 1995. mtDNA gene sequence, allozyme, and morphological variability among red diamond rattlesnakes, Crotalus ruber and Crotalus exsul. Can J. Zool. 73: 270-281