Thick-Tailed Barking Gecko

Thick-tailed barking gecko（圖片來源：Matt from Melbourne, Australia，採用 CC BY 2.0 授權）

The thick-tailed barking gecko (Nephrurus milii, formerly Underwoodisaurus milii) is a terrestrial, nocturnal gecko known for its distinctive defensive behavior. When threatened, it arches its body, emits a sharp barking sound, and waves its tail in a display meant to deter predators. Its tail is thick and heart-shaped, serving both as an energy reserve and as a prominent visual signal during defensive displays. Adults typically measure 12–16 cm in total length and weigh between 15 and 30 grams, with females generally slightly larger than males. Their coloration ranges from reddish-brown and orange-red to dark brown, marked with white or yellow spots and banding. These scattered bright markings across the back and limbs resemble a starry sky, giving rise to the Chinese common name.

This species is distributed across southern Australia, including southwestern Western Australia, the Nullarbor Plain, and extending into parts of New South Wales and Victoria. Its natural habitat consists of semi-arid shrublands, rocky outcrops, and open woodlands. During the day, individuals shelter in rock crevices or self-dug burrows to avoid high temperatures, emerging at night to forage. Compared with many other Australian geckos, this species shows relatively high tolerance to cooler conditions, capable of enduring temperatures around 10°C in winter, making it one of the few geckos adaptable to temperate environments.

The thick-tailed barking gecko is an insectivorous predator, feeding primarily on crickets, beetles, moth larvae, and occasionally small vertebrates of suitable size. It relies on keen vision and rapid striking behavior, typically accelerating suddenly at close range to seize prey. In the wild, its lifespan averages around 10 years, while individuals in captivity can live over 15 years with proper care. Although most geckos are solitary, this species may share shelters during the day in small aggregations, which is thought to enhance heat retention.

Thick-tailed barking gecko（圖片來源：不明，CC0 1.0 公共領域）

Housing Requirements in Captivity

To maintain thick-tailed barking geckos in captivity, their semi-arid natural environment should be closely replicated. As a ground-dwelling species, they require sufficient floor space; for a single adult, an enclosure measuring at least 60 × 45 × 45 cm is recommended. For a small group consisting of one male and multiple females, a larger enclosure is necessary. Although they cannot climb smooth glass surfaces, providing rocks or branches still requires a secure lid to prevent accidental escape.

The enclosure should include multiple hiding places, such as rock shelters, bark pieces, artificial tunnels, or ceramic tiles, reflecting their natural behavior of retreating into crevices or burrows during the day. Hides should be snug enough to allow the animal to press its body against the surface, enhancing its sense of security. Both dry and humid hides should be provided to facilitate moisture regulation and proper shedding. Suitable substrates include sand mixed with clay, mineral sand, or commercially available reptile sand substrates, which also allow limited digging behavior. Calcium sand or materials that may cause impaction if ingested should be avoided.

Daytime ambient temperatures should be maintained between 25–28°C, with a localized warm spot reaching around 30°C provided by a heat mat or lamp, allowing the gecko to thermoregulate. Nighttime temperatures can drop to 18–20°C. For breeding purposes, a simulated winter cooling period may be introduced, lowering nighttime temperatures to 10–14°C for approximately two months. Humidity should be maintained at 40–60%. Light misting is recommended, but prolonged dampness should be avoided to prevent fungal growth or skin issues. Water intake primarily occurs through licking droplets formed after misting, though a shallow water dish can be provided as an additional source. As a nocturnal species, UVB lighting is not strictly required, but low-level UVB or daylight simulation lighting may help maintain circadian rhythms.

Feeding Conditions

In captivity, the diet should consist primarily of insects such as crickets, Dubia roaches, cherry roaches, black soldier fly larvae, and mealworms. To ensure balanced nutrition, feeder insects should be gut-loaded with nutritious foods such as carrots and dark leafy greens prior to feeding. In addition, insects should be dusted with calcium powder and vitamin D3 supplements, particularly for breeding females, which have higher calcium demands.

Juveniles and subadults should be fed daily or every other day, while adults can be fed every 2–3 days. A typical feeding session consists of approximately 3–6 appropriately sized crickets. Feeding is best conducted at night or under dim lighting, when the geckos are most active. Live prey is preferred, as it stimulates natural hunting behavior. Although some keepers attempt feeding pinkie mice, this is generally unnecessary and may lead to obesity and health risks over time, so it is not recommended.

All feeder insects must come from clean sources to avoid pesticide contamination or parasites. Any uneaten insects should be removed promptly, as crickets or roaches may bite the gecko, and dead insects can decay and promote bacterial growth. A clean water source should always be available, even though most hydration is obtained from droplets and misting.

Breeding Conditions

Successful breeding typically requires a period of brumation. After approximately two months of exposure to lower temperatures, gradually returning to normal conditions stimulates reproductive activity. The breeding season generally occurs from spring to summer. Males pursue females and grasp the base of the tail or neck with their jaws during copulation.

Females lay eggs approximately 4–8 weeks after mating, typically producing two eggs per clutch, with 3–6 clutches per breeding season. A moist laying box should be provided, using substrates such as coconut fiber or vermiculite. Eggs should be carefully transferred to an incubator, with recommended incubation temperatures of 26–28°C. Incubation lasts approximately 45–70 days. Temperature can influence sex ratios, with higher temperatures tending to produce more males and lower temperatures more females.

Hatchlings measure around 4–5 cm in length and should be housed individually in small containers with paper towel substrates for ease of cleaning. They should be fed small crickets or micro roaches. Frequent calcium supplementation is necessary, along with access to a humid hide to assist with shedding. Breeding is generally recommended only after individuals reach at least 18 months of age to ensure the health of the female.

Preventing Invasive Spread

The thick-tailed barking gecko is native only to southern Australia and does not naturally occur elsewhere. However, due to its presence in the global pet trade, released individuals in non-native environments may pose ecological risks. Despite its relatively small size, its nocturnal insectivorous behavior could impact local insect and arthropod communities if populations become established, potentially disrupting food webs.

Keepers must act responsibly and never release captive individuals into the wild. If unable to continue care, animals should be rehomed to suitable keepers or transferred to authorized animal rescue organizations.

Author: Shui-Ye You