Monday, December 12, 2011

Red Racer Snakes Spectacular Animal


Red Racer on 24 July 1974 between 0700 and 1030 h I observed three unusual instances of opportunistic carrion feeding by two or three Masticophis flagellum  piceus  at a field collectors’ campsite in Whitewater Canyon, Riverside County, California (33º57.422'N, 116º38.650'W, 536 m elev.). During the previous evening (23 July 1974) researchers at the camp prepared about a dozen museum study skins of local rodent specimens including field mice (Peromyscus) and pocket mice (Perognathus and Chaetodipus), all < 35g live mass. We skinned the animals, removed the heads, opened the abdominal cavities to evaluate reproductive condition, and discarded the carcasses randomly in sparse desert vegetation along a nearby road embankment. During the night the skinless carcasses desiccated rapidly in the high temperatures and extremely low humidity. They were also contaminated with desert gravel and the hardwood sawdust used during preparation.

The next morning (24 July 1974) at 0700 h, a Red Racer (ca.1200 mm TL) was outstretched in open view in full sunlight along the above embankment, rapidly engulfing one of the desiccated mouse carcasses. An attempt to catch the Red Racer snake failed and it escaped rapidly, still grasping the mouse carcass. Air temperature at 0700 h was 28°C, and ground temperature in direct sun was ca. 40°C. Three hours later we noticed a second Red Racer (1175mm TL) engulfing a very dry mouse carcass at the same spot on the embankment where the first snake had been. The ground temperature (determined later) at the site was 44°C, and the shaded bulb air temperature was 42°C.

About 20 minutes later we saw a third Red Racer (1180 mm TL) outstretched and engulfing a mouse carcass < 2 m from the spot where the first snakes were seen. I collected the second and third specimens with dust shot and deposited them in the UC Davis Museum of Zoology. The stomachs of both specimens were empty, but I cannot be certain that either collected snake was not the specimen seen at 0700 h. in foraging even in snakes thought to rely primarily on prey movement and other visual cues.

Summarized 35 literature reports of natural Red Racer snake scavenging (spanning at least 24 snake species and assorted carrion) to show that snakes utilize carrion more often than commonly believed. Not unexpectedly, these reports reveal that snakes generally use olfaction to locate carrion, and they suggest that some snake species forage specifically for carrion.


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