Relatively few temperature readings on gravid or brooding females under natural conditions were obtained as they were easily disturbed and tended to desert their nests at slight provocation. To avoid desertions handling was kept to a minimum. Occasionally gravid females were caught in the open, but most of them were in nest burrows under flat rocks. These females found in nests were mostly cold to the touch, and the temperature readings taken on some of them usually approximated the air temperature, being either higher or lower (depending on whether the air was cooling or warming and whether the lizards were warmed by contact with rock or soil receiving sunshine). On May 23, 1952, 22 skinks were seen, four adult males, seven adult gravid females, and 11 young. Of these the adult females all were in nest burrows, and were cold and slow; consequently all of them were caught without difficulty. The males and young, however, were either fully warmed or warm enough to escape rapidly, so that only three of the young and no adult males were caught. Temperatures of the females tested were 25.6°, 23.6°, 23.5°, 22.3°, and 19.4°, and for the three young, 32.8°, 28.4°, and 28.4°. Air temperature varied from 20.5° to 24.8°. For the total of 30 females in nest burrows whose temperatures were taken in 1952, the average was 26.3°C, ranging from 16° to 34°. Gravid females, and those with nests and eggs were rarely seen in the open.
The five-lined skink is confined to a region where summer rains are frequent. It is evident that a regular supply of drinking water is one of the most critical ecological requirements. Bogert and Cowles (1947:19) found that an E. inexpectatus experimentally kept at high temperature lost moisture at a more rapid rate than any other reptile tested (including two other kinds of lizards, four kinds of turtles, an alligator, and three kinds of snakes). They remarked that this rapid moisture loss presumably accounts for the inability of skinks to survive in containers when no moisture is readily available, and also accounts for their absence in truly arid habitats. The Natural History Reservation is situated near the western edge of the species’ range in a climate that may be near the limit of its range of tolerance. However, on most summer mornings low woodland vegetation is copiously laden with dew, and this evidently fulfills the need for drinking water. Diminution of surface activity and retirement to underground retreats seem to be closely correlated with cessation of rains in late summer. After rainless periods in August and September, when morning dew is no longer available these skinks, especially the adults, are no longer regularly seen in the open. They have retreated to underground shelters where they spend nearly all their time. The time of disappearance varies from year to year and the correlation with varying weather conditions seems obvious. While no actual experiments were performed to determine the moisture requirements, it is evident that the need for moisture rises sharply with increased temperature. Skinks that are dormant in hibernation survive for periods of months without drinking, with but little loss of weight. In their underground shelters temperature is low and presumably relative humidity is high. At temperatures above their optimum of approximately 34°C. the skinks are especially subject to rapid moisture loss, since evaporation of body moisture is resorted to as a device to keep the temperature below the lethal level. The skinks subjected to extremes of temperature in an experimental terrarium were seen to lap up condensed moisture on the cooled metal plate at intervals of a few minutes. After an hour or more in the experimental terrarium they seemed somewhat debilitated. Skinks brought from the study areas to the laboratory for weighing and other records, were ordinarily returned on the following day. When circumstances prevented adherence to this schedule in hot summer weather, mortality could be expected in the skinks kept in cloth bags or glass containers, unless water was provided. Dramatic weight loss of up to more than 30 per cent was recorded in some individuals, kept at the high temperatures which usually prevailed in the laboratory, over periods of days in the summer. Skinks having access to drinking water often ingest amounts far beyond their immediate requirements, which may be stored in the bladder and drawn upon over periods of days as it is needed, or may be utilized to dampen the soil of the underground shelter and raise the humidity, as incubating females seem to do.
Geographic Range and the Deciduous Forest Habitat
Eumeces fasciatus corresponds in its distribution with the original hardwood forests of eastern North America, as mapped by Braun (1950:cover folder) and the “Oak-Wild Turkey Biome” of Shelford (1945:240). Few species of vertebrate animals have ranges that coincide more closely with this extensive area (exclusive of the northern edge, that part characterized by Braun as the Hemlock-White Pine-Northern Hardwoods). This latter is a mixed forest which actually is transitional between the more typical deciduous forest farther south and the Taiga Biome (or Formation) to the north, which is dominated entirely by conifers. At the northern edge of its range Eumeces fasciatus is much less generally distributed than it is farther south. Although it is well established and even may be locally numerous in South Dakota, Minnesota, Wisconsin, northern Michigan, Ontario, northern New York, and Connecticut, the locality records from these states are few, and seemingly represent isolated and widely separated colonies that are able to persist because of favorable combinations of environmental factors not of general occurrence in the surrounding regions. [Figure 6] shows the extent of the hardwood forests as mapped by Braun (excluding the transitional Hemlock-White Pine-Northern Hardwoods Association) with specific locality records of E. fasciatus included in all outlying portions of the range. The locality records are those published by Taylor (1936:206-212) supplemented by other marginal records, more recently published, by Hamilton (1947:64) for New York, Breckenridge (1944:97) for Minnesota, Hudson (1942:42) for Nebraska, Smith (1950:185) for Kansas, Brown (1950:116) for Texas, Neill (1948:156) for Georgia, and Neill and Allen (1950:156) for Florida. Along the northern edge of its range, the skink invades the Hemlock-White Pine-Northern Hardwoods Association, in Massachusetts, New York, Pennsylvania, Ontario, Michigan, and Wisconsin, but does not penetrate far into it anywhere. Correspondence of its northern limits with those of the Oak-Chestnut, Maple-Basswood, Beech-Maple and Oak-Hickory associations is remarkably close, considering the fact that the boundaries of these climax associations are not sharply defined; rather they merge by gradual stages into the northern coniferous forests, with outlying peninsulas and islands where conditions are favorable.
The outlying northern localities where E. fasciatus occurs within the Hemlock-White Pine-Northern Hardwoods Association are all within the region of Pleistocene glaciation, which 20,000 years ago, or even more recently, were covered with the continental ice mass during Wisconsinan time. Yet the localized northern populations of skinks evidently are relicts from a time when favorable conditions were more widespread in the general region. Braun (op. cit.:464-465) indicates five successive postglacial stages in the trends of climate up to the present, as revealed by bog pollen profiles: (1) Cool and moist; (2) warm and dry; (3) warm and humid; (4) warm and dry; (5) cool and moist. Stages 2 and 4 would have been most favorable for encroachment of the skink into glaciated regions, whereas stages 3 and 5 might have caused retrenchment of its populations. In view of the localized habits of individuals, and the lack of any mechanism for rapid dispersal, the time available seems no more than adequate for the distance of 200 miles or more northward that the skinks must have moved since the final retreat of the ice sheet. This northward movement involved crossing of formidable barriers such as the Great Lakes. Even minor barriers such us small rivers and creeks, might be expected to halt population movements for long periods.
Fig. 6. Geographic distribution of Eumeces fasciatus as indicated by published records (marginal and near-marginal records shown, excluding those of doubtful validity). (1) Distribution of the Deciduous Forest Formation of eastern North America, as mapped by Braun (1950), but excluding the Hemlock-White Pine-Northern Hardwoods Association that is transitional to the more northern coniferous forests. (2) The shaded area in Kansas that is outside the Deciduous Forest Formation comprises the Kaw River District, Cherokee Prairie District, and southern Osage Savannah Biotic District (Cockrum, 1952).
The over-all geographic range is approximately square, roughly a thousand miles across, from north to south and from east to west. On the east and south it is limited by the Atlantic Ocean and the Gulf of Mexico. On the north and west its limits correspond with those of the hardwood forests. On the northwest, it reaches southwestern Minnesota and the southeastern corner of South Dakota, extending far out into peninsular extensions of the Oak-Hickory Association which penetrate westward into the prairies along the main river valleys.
In Kansas it occurs over the eastern one-fourth, west to the Flint Hills, and a little farther west in peninsular extensions of the forest along some of the main river valleys. In Braun’s map the Deciduous Forest Biome is shown to reach only the eastern edge of Kansas along the Kaw River and Missouri River at and near their junction, the Osage (or Marais des Cygnes) River valley near the Missouri border, and the southeastern corner of Kansas. However, for almost 100 miles farther west from the Missouri border, the country has the aspect of a savannah with scattered groves of trees on hillsides and along streams, providing suitable habitat. The distribution of the five-lined skink in eastern Kansas corresponds well with certain “Biotic Districts” as mapped by Cockrum (1952:12), namely the Kaw River, Osage Savannah (southern part), and Cherokee Prairie. Conversely the skink is excluded from the Short Grass Plains and Mixed Grass Plains Biotic Districts which occupy nearly all of the western three-fourths of the state. There are two specimens in the University of Kansas Natural History Museum, labelled Ranson, Ness County. This locality, in the western third of the state, more than 150 miles from any other recorded station, may represent an isolated colony; however Smith (1950:185) states that the record needs verification, and it is not included in the map, [Figure 6].