Southeastern Five-lined Skink
Plestiodon inexpectatus

Common Name:

Southeastern Five-lined Skink

Scientific Name:

Plestiodon inexpectatus

Etymology:

Genus:

Plestiodon is derived from the Greek words pleistos meaning "most" and odontos meaning "teeth". Plestiodon = Toothy Skinks.

Species:

inexpectatus is derived the Latin prefix in meaning "not" and the Latin word expectare meaning "expectation". This refers to the unexpected discovery of this skink in the well-known lizard fauna of North America.

Average Length:

5.5 - 8.5 in. (14 - 21.6 cm)

Virginia Record Length:

7.6 in. (19.4 cm)

Record length:

8.5 in. (21.6 cm)

Systematics: Described originally as Eumeces inexpectatus by Edward H. Taylor in 1932 based on a sample of 36 specimens from southeastern North America (Taylor, 1932a). He designated the type locality as "Citrus Co., Fla." (= Florida). All authors in the Virginia literature have used the current nomenclature. Taxonomy for Plestiodon follows Taylor (1935, Univ. Kansas Sci. Bull. 23: 1–643) and Brandley et al. (2012, Zool. Jo. Linn. Soc. 165: 163–189). No subspecies are recognized.

Description: A moderate-sized skink reaching a maximum snout-vent length (SVL) of 89 mm (3.5 inches) and a total length of 216 mm (8.5 inches) (Conant and Collins, 1991). In Virginia, maximum known SVL is 79 mm (3.1 inches) and maximum total length is 194 mm (7.6 inches). Tail length in the present study averaged 60.8 ± 4.1% (53.2-65.7, n = 91) of total length.

Scutellation: Body scales smooth, overlapping, and glossy; scale rows around midbody 27-32 (ave. = 30.0 ± 1.2, n = 74); scales around tail 10 scales posterior to anal opening 18-22 (ave. = 20.0 ± 1.2, n - 68); midventral subcaudal scales same size as other scales on tail; supralabials usually 7/7 (84.3%, n = 83) or other combinations of 6-8 (15.7%); posterior labial scale and temporal scale usually separated by 1-2 postlabials anterior to ear opening; labial scales between rostral and first supralabial entering eye (= preorbital supralabials) usually 4/4 (85.4%, n = 137) or other combinations of 3-5 (14.6%); postnasals present; mental single; postmentals 2.

Coloration and Pattern: Five narrow, orangish, white, or cream stripes on a black to brown background; stripes extend along body and onto about half length of tail; middorsal stripe forks behind parietal scales, and rejoins on snout (but see "Juveniles"); stripes on head reddish orange; dorsolateral stripe originates above eye and runs posteriorly along scale rows 4-5 (counting from dorsal midline) onto tail; lateral stripe originates on supralabials below eye, passes through ear opening, and runs along body above insertion of hind limb onto tail; sublateral light stripes may be present in axillary region; lateral body color fades into ventral coloration, with no distinct separation; venter pale bluish, dark gray, or nearly black posteriorly, at least to base of tail; chin and anterior venter cream to white with a tinge of orange; temporal region of subadults chestnut; original tail brownish gray to slightly purplish; venter of tail cream; regenerated tail grayish brown.

Sexual Dimorphism: Adult males have reddish-orange heads in the breeding season; the 5 dorsal stripes fade with age. Stripes may be obscure in the largest males, but females retain them throughout life. Adult males averaged slightly larger (66.5 ± 5.6 mm, 55-79, n = 59) than adult females (ave. = 63.0 ± 5.0 mm, 55-75, n = 51). Sexual dimorphism index was -0.06. Head width of adult males was larger (ave. = 10.5 ±1.3 mm, 8.0-12,6, n = 43) than in adult females (ave. = 8.9 ± 0.6 mm, 7.5-9.8, n = 32). Vitt and Cooper (1986a) determined that the differences in head size remained after the effects of variation in body size were removed.

Tail length relative to total length (males 58.3- 63.7%, ave. = 62.0 ± 1.3, n = 19; females 53.2- 65.7%, ave. = 58.8 ± 8.2, n = 19), number of scale rows around midbody (males 27-32, ave. = 30.1 ± 1.3, " = 29; females 27-32, ave. = 29.9 ± 1.1, n = 31), and number of scale rows around tail 10 scales posterior to anal plate (males 18-22, ave. = 20.1 ± 1.3, n = 28; females 18-22, ave. = 20.0 ± 1.3, n = 28) were not sexually dimorphic.

Juveniles: Juveniles possess 5 distinctly narrow light stripes on a black background. Head stripes are bright orange or reddish orange, changing to yellowish on the body and to bluish on the tail. The dorsolateral stripes may occur as a series of small spots. The middorsal stripe is not connected to the head stripes, that is, the junction of the arms of the fork is incomplete. The blue color on the tail extends onto the body to about the insertion of the thighs. The chin and throat are pale with an orange tinge; this color is replaced by black to dark gray on the venter, undersurfaces of the hind limbs, and tail base. Sublateral light lines, or suggestions of them, may be present, especially in the axillary region; they fade with age. At hatching, Virginia juveniles were 24-29 mm SVL (ave. = 26.0 ± 1.2, n = 46) and 57-68 mm total length (ave. = 62.9 ± 3.1, n = 16). Bodymassat hatching is unknown.

Confusing Species: Plestiodon inexpectatus is often confused with the other two skinks in this group, P. fasciatus and P. laticeps. Both of these species possess the dorsolateral stripe on scale rows 3-4 (counting from the middorsal line) and the enlarged (wider than long) midventral subcaudal scales.

Geographic Variation: In Virginia, scutellation, color and pattern, and body size do not exhibit geographic variation. Regional geographic variation has been examined by Davis (1968).

Biology: Plestiodon inexpectatus is found in drier habitats than P. fasciatus. Habitats include dry pine forests, mixed pine-hardwood forests, early successional stages of lowland pine communities, edges of fields and woods, urban woodlots, and around artificial structures, such as sawdust piles and buildings. This species is often found under debris and logs on the ground, and in logs and under bark. The individual from Alleghany County was found under a rotting board in a cultivated field surrounded by pine forest (Hoffman, 1945a). Plestiodon inexpectatus is less arboreal than P. fasciatus and P. laticeps. Juveniles emerge from hibernation and enter it later than adults. The earliest observation of an active lizard is 3 April and the latest is 12 December, both juveniles. Overwintering sites are in decaying logs and deep in cracks of some artificial structures.

Plestiodon inexpectatus is carnivorous, preying mostly on invertebrates. The following prey types have been found in Virginia specimens: ground beetles, unidentified beetles, grasshoppers, wood roaches, caterpillars, wolf spiders, unidentified spiders, and a centipede. One 55-mm female contained a female wolf spider (Lycosidae) with her full compliment of eggs. The diet of this skink has not been systematically studied in Virginia, nor have predators been recorded. Mount (1981) discussed the decline of P. inexpectatus in Alabama due to predation, especially on eggs and juveniles, by the introduced fire ant (Solenopsis invicta). Fire ants have been introduced into Virginia (W. H. Mitchell, pers. comm.) and may pose a real threat to this species in the Coastal Plain. Plestiodon inexpedatus is especially vulnerable because it inhabits relatively xeric habitats and does not often climb or nest high in vegetation (Mount, 1981).

Surprisingly little is known of the reproductive biology of Plestiodon inexpedatus. Females are oviparous and lay one clutch of eggs annually, in June and early July, in decaying logs and stumps and under decomposing logs on the ground. I have no evidence for multiple clutches. Males and females reached maturity at about 55 mm SVL. Skinks in South Carolina reached sexual maturity in about 21 months at about 54 mm SVL (Vitt and Cooper, 1986a). Mating dates are unknown for Virginia, but based on the occurrence of the orange coloration on the heads of males, it is probably in April and early May. Oviductal eggs have been found in Virginia females between 10 June and 12 July. Clutch size averaged 8.3 ± 1.5(7-11, n = 6). A female attending her nest was found on 14 July. Full-term eggs in nests averaged 14.2 ± 0.8 x 11.0 ± 0.7mm (length 13.5-16.0, width 10.5-12.0; n = 7). Egg mass at oviposition in South Carolina was 0.446 g (Vitt and Cooper, 1986a). Length of incubation is unknown. Known hatching dates are between 15 July and 2 August.

Nothing is known of the population ecology of this skink, in spite of its abundance in some areas of its range.

Plestiodon inexpedatus uses the same escape behaviors as P. fasciatus. Cooper and Vitt (1987b) experimentally determined that adult males in the breeding season are able to identify conspecific males from male P. fasciatus and male P. laticeps by chemosensory investigation (tongue-flicking). This avoids costly interspecific aggressive interactions. Males do not defend a home range or a large portion of it, but may defend specific sites or engage in aggressive behavior without regard to location (Cooper and Vitt, 1987a). In experiments on South Carolina lizards, male P. inexpedatus were found to court females of P. fasciatus and P. laticeps, as well as of their own species, and forced copulation with female P. fasciatus was observed on two occasions (Cooper and Vitt, 1987c). The function of the blue tail in juveniles, described in the P. fasciatus account, also pertains to this species.

Remarks: Other common names used for this skink in Virginia are Taylor's scorpion lizard (Dunn, 1936) and Florida Five-lined Skink (Smith, 1946; Reed, 1956, 1957b).

The geographic distribution of P. inexpedatus in Virginia is puzzling. Why should there be seemingly isolated populations in the Ridge and Valley physiographic region? No specimens have been found in Alleghany County since the adult female was found in 1945 (Hoffman, 1986). Similarly, no specimens have been found in Page County since the collection of a juvenile in 1937. Clearly, additional survey work is needed.

Conservation and Management: This skink is not currently a species of special concern in Virginia because of its widespread distribution, its abundance in pine-associated habitats, and its occurrence in some human-altered environments. The persistence of pine flatwoods and other xeric habitats, especially in southeastern Virginia, is expected. However, skink populations in those areas undergoing extensive urbanization are likely to decline and some populations will be extirpated. The possibility of local population extinctions of P. inexpedatus caused by the introduced fire ant is real. All observations on mortality by these ants need to be reported. Eradication of all outbreaks of this introduced pest is paramount.

References for Life History

Photos:

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