Japanese Grass Lizards and Five-Lined Skinks: Two Often-Confused Japanese Reptiles
Small lizards commonly seen in Japanese parks, grasslands, and gardens include the Japanese Grass Lizard (Takydromus tachydromoides) and the Japanese Five-Lined Skink (Plestiodon japonicus). Although these two species are often confused with one another, they actually belong to completely different families. Understanding the differences and similarities between them enables proper care in captivity.
Classification and Physical Differences
| Feature | Japanese Grass Lizard | Japanese Five-Lined Skink |
|---|
| Family | Lacertidae | Scincidae |
| Scientific Name | Takydromus tachydromoides | Plestiodon japonicus |
| Total Length | 16–27 cm (including tail) | 15–25 cm (including tail) |
| Body Surface | Rough, bumpy scales | Smooth, glossy scales |
| Body Color | Brown to grayish-brown with vertical stripes | Adults tan to brown; juveniles black with yellow stripes + blue tail |
| Eyes | Large and round (endearing appearance) | Slender (sharp appearance) |
| Tail Characteristics | Extremely long (60–70% of total body length) | Thick and relatively short |
| Movement | Swift, escapes through grass | Fast, low movement along ground |
Juvenile five-lined skinks are particularly notable for their distinctive "blue tail" (which disappears in adults). This blue coloration is thought to be an adaptive feature that directs predators' (especially birds') attention toward the tail, facilitating escape through tail autotomy.
Ecological Differences
Habitat and Preferred Environment
Japanese Grass Lizard
- Prefers open areas with grass and low shrubs
- Active on and among plants and vegetation
- Skilled at vertical movement (climbing grass stems)
Japanese Five-Lined Skink
- Prefers areas under stones, leaf litter, and concrete crevices
- Moves swiftly along the ground, quickly burrowing into holes
- Enjoys basking on stones
Diet
Japanese Grass Lizard
- Small insects, spiders, small arthropods
- Eats crickets (Gryllus and Acheta), mealworms, dubia nymphs, two-spotted crickets
Japanese Five-Lined Skink
- Small insects, spiders, earthworms (similar to grass lizards)
- Also feeds on relatively larger prey
Reproductive Differences
| Reproductive Trait | Japanese Grass Lizard | Japanese Five-Lined Skink |
|---|
| Reproduction | Oviparous (2–4 eggs laid May–July) | Oviparous (4–16 eggs laid May–July) |
| Parental Care | No parental involvement after laying | Female guards eggs until hatching (egg attendance behavior) |
| Incubation Period | 40–50 days | 40–50 days |
The maternal behavior of female five-lined skinks guarding their eggs is a rare form of parental care among reptiles. After laying eggs, the female remains with the clutch, protecting it from predators and licking the eggs to maintain cleanliness.
Captive Care Comparison
Enclosure and Space
| Item | Japanese Grass Lizard | Japanese Five-Lined Skink |
|---|
| Minimum Enclosure Size | 45 cm W × 30 cm D | 45 cm W × 30 cm D |
| Ideal Enclosure | 60 × 45 × 45 cm | 60 × 45 × 30 cm |
| Height | 45 cm or taller (for climbing behavior) | 30 cm or taller (for burrowing behavior) |
| Substrate | Coconut husk, red soil, leaf mold | Red soil, sand, leaf mold (deep: 5–10 cm) |
Grass lizards require height (vertical layout with plants and branches), while five-lined skinks need deep, burrowable substrate.
Temperature and Humidity
| Item | Japanese Grass Lizard | Japanese Five-Lined Skink |
|---|
| Daytime Temperature | 25–30°C (basking spot 35°C) | 25–30°C (basking spot 35°C) |
| Nighttime Temperature | 18–22°C (tolerates lower temps) | 18–22°C |
| Humidity | 50–70% | 60–80% (prefers damp areas) |
| Hibernation | Nov.–Mar. (wild individuals) | Nov.–Mar. |
Ultraviolet (UVB) Requirement
Both species synthesize vitamin D3 from ultraviolet radiation (sunlight) in the wild. In captive care, UVB lamps (5.0–10.0 UVB) are essential. UVB deficiency leads to metabolic bone disease, causing limb deformities and fractures.
Feeding
- Primary Food: Crickets (two-spotted and house crickets), mealworms, dubia nymphs
- Supplementary Foods: Waxworms, black soldier fly larvae (calcium-rich)
- Supplements: Dust feeder insects with calcium powder (containing vitamin D3) before feeding
- Frequency: Once daily (adults) or every other day
Hibernation Management
As native Japanese species, hibernation is a natural part of their life cycle.
- Hibernation Method (Outdoor-style Natural Management): Reduce feeding in autumn, allowing the lizard to naturally enter dormancy as temperatures decline
- Non-Hibernation Method (Complete Indoor Management): Use heaters and UVB lamps year-round, maintaining 23–25°C to keep the lizard active throughout winter
- Both methods support healthy captive care, but complete indoor management requires continued feeding and water provision
Collection and Legal Considerations
Japanese grass lizards and five-lined skinks are currently not subject to collection restrictions (with the exception of certain municipalities and protected areas), and capturing them for captive care is legal.
However, wild-caught individuals carry risks of pesticide exposure and parasitic infection. After collection, isolate the animal for a health check and have a fecal examination performed by a veterinarian to screen for parasites.
Summary
Although Japanese grass lizards and five-lined skinks appear similar, they differ in family, behavior, and preferred environments. Grass lizards are characterized by active, vertical movement in vegetation, while five-lined skinks are characterized by ground-dwelling, burrowing behavior. Both are hardy reptiles well-adapted to Japan's natural environment, and with the three basic elements of proper UVB exposure, temperature control, and appropriate diet in place, they are relatively easy to maintain in captivity. Understanding the differences between these two species and creating environments suited to their individual needs is key to successful long-term care.
