Life History and Ecology of the Five-lined Skink, Eumeces fasciatus Part 6

No. 2. At hilltop ledge, under flat rock 13 10 1 inches, with one edge sunken in soil; exposed to suns.h.i.+ne for most of day.

June 24, 1951. Female, snout-vent length 70 mm., tail 27-51, weight 5 gms.

Nine eggs, one of which measured 14 8 mm.

July 18, 1951. Nine eggs still in their original nest cavity, attended by the female; she escaped into crevice behind the rock. The eggs were in slightly damp soil, and in contact with the undersurface of the rock on their upper sides; one egg was 17 10 mm.

July 26, 1951. Eggs caked with dried mud; still attended by female.

July 30, 1951. Dry and empty eggsh.e.l.ls in nest cavity, evidently all the eggs had hatched; no other trace of female nor of young; July 28th seems most probable hatching date--if, on the 27th, some of eggs almost certainly would have shown signs of hatching on the 26th when they were examined, and if on the 29th some stragglers almost surely would have remained at the nest on July 30.

No. 3. In small gully, on lower slope in hickory woods, beneath rock 9 9 1 inches, shaded by trees on south side for much of the day, especially during latter part of morning.

June 24, 1951. The gravid female was deep in nest burrow.

June 29, 1951. When rock was lifted no trace of nest was visible except for slightly disturbed loose soil at the point where it had been. When some of this loose soil was cleared away, nest was revealed, with 11 eggs, mud-stained, approximately 12.5 8 mm. The female was cold and sluggish, and did not attempt to escape, but cowered in the back of the nest burrow, with jaws gaping; she was caught and marked.

July 20, 1951. Eight eggs remaining in the nest--two were accidentally destroyed in moving them. These two were fertile and contained live embryos, one of which measured 29 mm. in over-all length. One of the remaining eggs was 16.5 10 mm. Female was present with the eggs.

July 25, 1951. Eggs still present in the nest cavity; female not in evidence, but might have been concealed in corner of nest chamber as it was not disturbed.

July 28, 1951. Female was again found with the eggs. One or more of the seven remaining eggs were punctured in moving them during their examination. Eggs about 16 10 mm.

August 3, 1951. Female was in nest with the eggs some of which are slightly indented from drying.

August 6, 1951. When rock was turned, female darted out and ran to cover about ten feet away. The eggs had hatched but two young remained in the nest cavity, still rather slow and feeble in their movements and not yet fully active. When routed from cover a second time, the female ran back to the nest rock and took shelter beneath it.

No. 4. On upper slope above ledge, under a rock 18 9 inches, in site shaded most of day; burrow nearly concealed beneath rock.

June 24, 1951. Nest occupied by a gravid female, apparently ready to lay.

June 30, 1951. Rock covering this nest has been undermined by a mole tunnel, and many nearby rocks are undermined also. The eggs were almost certainly destroyed by the mole's tunneling and may have been eaten by it, since no remains are in evidence.

No. 5. At hilltop ledge beside old abandoned road, beneath flat rock nine inches in diameter and about 1-1/2 inches thick, shaded for first half of morning and most of afternoon, but exposed to mid-day suns.h.i.+ne.

June 29, 1951. Standing water in bottom of nest chamber 1-1/2 inches below underside of the rock. Some of the eggs are more than half submerged. One egg is 14 8 mm.

July 21, 1951. Entrance of abandoned nest burrow has been enlarged by running water channelled through in run-off during and after heavy rains; shrivelled remains of eggs present at the bottom of the burrow.

No. 6. On gra.s.sy hilltop a few yards from ledge under flat rock, 9 6 2 inches.

July 23, 1951. Large female (snout-vent length 75 mm.) with three eggs, 16 22 mm.

July 27, 1951. Female escaped from nest cavity as rock was raised. Three eggs were still in the nest, and a young skink was partly emerged from one. A second egg not yet hatching was somewhat flaccid, 16 mm. long, heavily coated with dried mud. The third egg much shrivelled, was opened and found to have a dead fetus, perhaps a week short of hatching.

July 28, 1951. The flat rock which formerly covered the nest cavity was found to have been raised and displaced, and no trace of the female, eggs or young remained. Of possible predators that might have moved the rock and destroyed the nest, skunk and opossum seemed the most likely, but there was no definite clue as to the predator's ident.i.ty.

No. 7. Two feet northeast of pond rock pile, under rock about one foot square on upper surface with maximum thickness of about eight inches, lying with upper side at 45-degree angle. The nest was under one edge, with approximately three inches of rock over it. The rock was exposed to suns.h.i.+ne throughout the day, except for gra.s.s shading its edges.

July 23, 1951. When rock was turned, the female darted out of the nest cavity, but in her dash to escape she dropped into a nearby pitfall.

When handled, she voided feces which contained the nearly intact sh.e.l.l of a skink egg. Six eggs present in the nest; one selected as typical was 11-1/2 8 mm. The eggs were slightly misshapen and might have been damaged from drying.

July 26, 1951. When rock was raised, female darted out and escaped. The six eggs still remained in the nest.

August 2, 1951. When rock was raised the female was not in evidence, and only three eggs could be found; they had fallen from the nest cavity to the bottom of the depression where the rock was imbedded and were somewhat dried and indented.

No. 8. North slope, beneath rock approximately 18 15 4 inches, at edge of small gully, where shaded most of the time including mid-day hours.

July 20, 1951. Female attempted to escape from the nest. Four eggs visible in nest, one 15-1/2 10 mm.

July 25, 1951. When rock was raised the female ran from the nest.

July 27, 1951. When rock was raised the female was in the nest with the eggs; she ran and hid beneath a boulder five feet away. After a few minutes she emerged and ran 15 feet to a hickory sapling and climbed it.

July 28, 1951. Female was not in the nest but the four eggs were still present.

July 30, 1951. Female found dead and partly eaten by ants beside rock one foot from nest; eggs still present in the nest.

July 31, 1951. Eggs still present in the nest.

August 3, 1951. Eggs still present, including some deep in the nest cavity which apparently were overlooked previously.

August 6, 1951. One much indented egg found outside the nest cavity was opened and found to contain a live fetus, seemingly fully developed and normal. The opened egg was placed on damp soil in a shady place near the nest, but two hours later the hatchling had been killed and partly eaten by swarms of ants.

August 9, 1951. The remaining eggs had disappeared, evidently taken by a predator as no empty sh.e.l.ls remained to indicate that the young had hatched.

HATCHLINGS

Cagle (1940:229 and 232) has graphically described and ill.u.s.trated the hatching of the five-lined skink, and numerous observations in the present study have served to corroborate his description. The first indication that the time of hatching is at hand is a twitching or jerking movement within the egg which continues until the sh.e.l.l is slit.

According to n.o.ble and Mason (1933:5) the sh.e.l.l is slit with the elongate premaxillary egg tooth which has its distal third bent forward nearly at right angles to its base. Some young remain for an hour or more with only the snout visible, however, once the head is extruded it is not again withdrawn unless the lizard is badly startled. The eyes are opened and blinked slowly, closed for a few minutes, and opened again.

After the eyes have become adjusted, the fore-body emerges and the front legs are freed. In one clutch, observed by Cagle, hatching time for individual eggs varied from 45 minutes to five and three-fourths hours.

If startled by visual or tactile stimuli, the little skink may lunge forward through the slit sh.e.l.l, with a sudden straightening of its body, and rush away for several inches. Its movements are slow, stiff and clumsy as compared with those of a skink that is a few days old and fully active. Hatching of a clutch ordinarily extends over 24 hours or more. Some of the young may be fully hatched and active before others from the same clutch have slit their eggsh.e.l.ls.

Eggs ready to hatch ordinarily weigh somewhat more than one gram, up to at least as much as 1.7 grams, but much of this weight is made up of water absorbed during incubation. The hatchlings usually weigh from .2 to .45 grams. For each of two eggsh.e.l.ls recently vacated, that were washed and squeezed dry, weights were approximately .125 grams.

Hatchlings of the same brood differ perceptibly in size with several per cent variation in total length, and weight. Some seem to be less fully developed than others. On July 8, 1952, hatching of the last young in a clutch was observed. Upon emergence, it differed in appearance from the others of the brood hatched a few hours earlier. The top of its head bulged slightly as in fetuses. The umbilicus was not yet closed, and the protruding yolk ma.s.s hindered the hatchling's movements and made crawling difficult. In order to progress it had to stand high off the ground to prevent its ventral surface from dragging. Protrusion of the yolk ma.s.s has been described in newly emerged hatchlings for the closely related _E. anthracinus_ (Clausen, 1938:3-7) as well as in _fasciatus_.

Cagle (_loc. cit._) states that the ma.s.s of yolk is at first about 3 mm.

in diameter, but is completely used at the end of the third day. A group of young retained by him, without food, died the sixth day after hatching, seemingly from starvation. Three of five recently hatched young were found by Cagle to have eaten ant pupae placed in a box with them on the preceding day, even though the skinks still retained the yolk ma.s.ses. One hatchling of this group ate its own tail that had been broken off in handling. Cagle described a color change taking place during the first few hours after hatching; the ground color, dull greenish at first, darkens to an iridescent black, the pale stripes are altered from an original tan color to bronze, with a tinge of reddish on the head, and the ventral surface which is partially transparent showing the outlines of the internal organs at first, soon becomes opaque white.

Contrary to the statement by n.o.ble and Mason (1933:5) that in captivity the hatchlings seldom stayed together more than a few hours, litters of young fully active, a day or two after hatching were found in the nests with the females still looped around them on several occasions. On one such occasion, although the brood scattered immediately into surrounding vegetation where they hid, I succeeded in catching the female and six of the young, and put them all together in a nylon bag to carry them back to the laboratory. Several hours after the bag had been placed on a table it was noticed that the family had again gathered into a compact cl.u.s.ter in the bag with the female's body looped around the young in the characteristic brooding position seen in those with young or eggs in their nest cavities. When hatching is complete, the female may leave before the young have dispersed. On August 5, 1950, a nest under observation was found to have all of the young or most of them still cl.u.s.tered in the cavity, but the female was not in evidence. The young were active, and immediately took alarm as the rock was raised exposing them. Almost instantly, they scattered and vanished. Subsequent search revealed five of the young, each poorly concealed in tufts of gra.s.s or under dry leaves or other ground litter at the edges of the depression where the rock had lain. Once hidden, these young were reluctant to run again and depended on concealment.

Having once left the nest, the young probably do not return to it, as many nests examined within a few days after hatching were never found occupied either by females or young after their original dispersal. As soon as the dispersal occurs family ties are permanently severed. On July 19, 1950, a group of active hatchlings was observed moving about over a log, on what was probably the first day of activity away from the nest. The log was in the bottom of a steep-walled gully, where it had come to rest the night before. It had been an erect but dead and partly undermined snag on the edge of the gully, and was blown down that night in a violent thunderstorm. Most of the log was held clear of the rus.h.i.+ng water in the bottom of the gully by projecting limbs. The little skinks were darting in and out of holes and crevices in the log, pausing frequently to bask. As many as four were in sight simultaneously, but probably the total included several more, as it was difficult to keep track of individuals. An adult female, presumably the mother of the litter was also present, but she took no interest in the young, and they showed no evidence of dependence on her. On the contrary, several times when one or another of the young happened to come near the female in the course of its wandering, and noticed her, it was seen to shy away in sudden alarm.

[Ill.u.s.tration: FIG. 11. Sizes on specific dates of young hatched in 1950 and 1952. Approximate size ranges at different times of year, and differences in trend between the two years are brought out.]