Microhabitat and Prey Odor Selection in Hypsiglena chlorophaea
We studied the effects of various shelter and prey odor combinations on selection of microhabitat characters by the Desert Nightsnake, Hypsiglena chlorophaea, a dipsadine snake. We also examined the activity patterns of these snakes over a 23-h period. Three prey odors were tested, based on field work documenting natural prey in its diet: lizard, snake, mouse (plus water as control). In the first experiment, each odor was tested separately in various shelter and odor combinations. We found that snakes preferred shelter to no shelter quadrants, and most often selected a quadrant if it also had prey odor in the form of lizard or snake scent. However, snakes avoided all quadrants containing mouse (adult) odor. In the second experiment, all three odors plus water were presented simultaneously. We found that snakes showed a preference for lizard odor over the others, but again showed an aversion to mouse odor, even compared to water. The circadian rhythms in both experiments showed generally the same pattern, namely an initial peak in activity, falling off as they entered shelters, but then again increasing even more prominently from lights off until about midnight. Thereafter, activity tapered off so that several hours before lights on in the morning, snakes had generally taken up residence in a shelter. Prey preference correlates with field studies of dietary frequency of lizards, while activity exhibits strong endogenous nocturnal movement patterns.Abstract
Test Arena. (A) Experiment one. For each of the four quadrants A–D, a choice was provided—A: no shelter, prey odor; B: shelter, prey odor; C: no shelter, no prey odor; D: shelter, no prey. (B) Experiment two. An odor was provided in each of the four quadrants A–D—A: Mouse (M), B: Snake (S), C: Lizard (L), D: water, plus a shelter in each quadrant. The four odor/shelter combinations were changed and positioned at random during each of the trials. Circles, petri dishes with prey odor (closed circles) or water (open circles); rectangles, shelters.
Total amount of time (minutes) spent in quadrants for all snakes during each 23-h trial for Experiment one (shelter and odor choices). Standard deviations are at the top of each bar.
Total amount of time (minutes) spent in quadrants for all snakes during each 23-h trial for Experiment two (prey odor preferences). Standard deviations are at the top of each bar.
Activity patterns. Average number of movements for all snakes per hour during the 23-h period. (A–C) Activity patterns for Experiment one for each of the three prey odors—lizard, snake, mouse. (D) Activity patterns for Experiment two, where all three prey odors and water were presented simultaneously.
Contributor Notes
Associate Editor: G. Haenel.