Life History and Ecology of the Five-Lined Skink, Eumeces fasciatus. Henry S. Fitch

The skink is quick to make adjustment whenever its temperature appreciably exceeds this optimum level, and is in extreme discomfort at only a few degrees higher temperature. At slightly lower temperatures, however, the skink experiences no discomfort, and only slightly decreased efficiency in its various functions, and its thermoregulatory behavior in making readjustment toward the optimum is likely to be leisurely and interrupted unless its temperature drops below 28°C.

      Catching the skinks in the experimental terrarium at frequent intervals to take their temperatures involved some disturbance to them, interrupting their thermoregulatory behavior. The experimenter’s first attempt to grasp a skink sometimes failed, and it then dashed about the terrarium for several seconds, probably altering its temperature somewhat. Nevertheless most of the lizards’ movements were motivated by thermoregulation. This was especially evident when they were left undisturbed, and is illustrated by the following notes on behavior of an adult female and half-grown young of fasciatus and a young E. obsoletus on the afternoon of July 21, 1952.

2:58	All resting over cooled metal.
3:01	Female runs to line of sunshine and shadow, coming to rest with approximately half her body in sunshine, the other half in shadow over the cooled metal.
3:03	Female reverses position so that hindquarters previously in shadow are now in sunshine, and forequarters are in shadow.
3:031⁄2	Young runs to middle coming to rest in sunshine on screen.
3:04	Female moves back to the cool end.
3:05	Young moves to edge of cooled metal but not over it, in a narrow m
3:051⁄2	E. obsoletus moves from cool end to middle, partly in sunshine.
3:07	E. obsoletus adjusts its position in narrow middle strip of shadow just off the cold end.
3:08	Boards used for shading adjusted back slightly so that E. obsoletus is in sunshine.
3:081⁄2	E. obsoletus moves back to cold end.
3:10	Young still at middle, but resting mainly over cooled metal with tail partly in sunshine.
3:101⁄2	Young moves out into sunshine at middle.
3:11	Female moves out into sunshine at middle. E. obsoletus moves over cooled metal to its edge, coming to rest partly in sunshine.
3:12	Female moves back over cooled metal.
3:131⁄2	Air temperature 33.3°C. E. obsoletus shifts a short distance so that it is resting entirely over the cooled metal, with only part of its tail receiving sunshine.
3:17	Young moves about in sunshine, then comes to rest in shadow with half its body over cooled metal.
3:19	Young shifts so that more than half its body is in sunlight in middle section.
3:20	Young shifts away from sunlight, coming to rest with most of its body over the cooled metal.
3:211⁄2	Female moves from cooled metal to sunshine in middle strip.
3:23	Female moves out of sunshine, partly over edge of cooled metal.
3:30	Young moves off cooled metal, coming to rest over edge of warmed metal in narrow middle strip that is in shadow.
3:301⁄2	Young moves back away from warmed metal, pauses briefly, and then moves over cooled metal coming to rest there.
3:31	Female shifts so that about half her body is in sunshine in the middle.
3:32	Female shifts back into shadow, partly over cooled metal.
3:33	Boards providing shade readjusted so that female is in sunshine.
3:331⁄2	Female moves back into shadow over cooled metal.
3:38	Female moves to edge of cooled metal, resting partly in sunshine; sky is becoming slightly overcast.
3:40	Temperature of female 33.4°C.
3:41	Temperature of young 32.8°C.
3:43	Temperature of E. obsoletus 32.4°C.
3:45	Young moves to shaded edge of warmed metal. Finds a dead spider dropped there and eats it.
3:47	Temperature of female 32.3°C.
3:48	Temperature of young 36.4°C.
3:50	Temperature of E. obsoletus 33.8°C.
3:52	Sky partly overcast with thin layer of clouds; observations concluded.

      Having once emerged from its hiding place a skink becomes more or less independent of the temperature of the air and substrate, as it is capable of thermoregulation through insolation. However, after a period of cooling and inactivity in dormancy, or merely resting for the night in temporary shelter, the skink is dependent on warmth from the air or substrate or both to become sufficiently activated so that it can emerge and take advantage of direct sunlight. About 10:00 a. m. on April 13, 1951, when the air temperature was a little less than 10°C., a large adult male rustling among dry leaves attracted my attention. Obviously recently emerged from hibernation, he was caked with dried mud and his eyelids were nearly sealed shut. He had been sunning, however, and was active enough to elude my attempts to catch him, as he scurried into a deep crevice under the ledge. On the morning of March 24, 1951, while the temperature was still between 10° and 15°C., a subadult skink, the first one of the season, was seen sunning itself at the entrance of a deep crevice under the ledge. This skink was still not fully active, and its movements were stiff, yet it was alert and wary, and it quickly retreated back into the crevice. During the first week of May, 1952, skinks were active in abundance and numbers were caught daily in funnel traps and pitfalls. On May 9, however, the maximum air temperature was 16.5°C. with cloudy sky and occasional showers. Under these conditions skinks stayed under cover; none was seen in the open nor caught in a trap, and several found under rocks were slow and sluggish. On May 10 a terrarium with several adults was placed in dilute sunshine beside a window in an unheated room. After a period of basking the skinks