Underwoodisaurus milii

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For the African genus called "barking geckos", see Ptenopus

Underwoodisaurus milii
Underwoodisaurus milii.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Carphodactylidae
Genus: Underwoodisaurus
U. milii
Binomial name
Underwoodisaurus milii
  • Phyllurus milii
    Bory de Saint-Vincent, 1823
  • Cyrtodactylus Nilii [sic]
    Gray, 1831 (ex errore)
  • Gymnodactylus milii
    Loveridge, 1934
  • Underwoodisaurus milii
    Bustard, 1970
  • Nephrurus milii
    Bauer, 1990
  • Underwoodisaurus milii
    Cogger, 2014

Underwoodisaurus milii is a species of gecko in the family Carphodactylidae. The species is commonly known as the thick-tailed or barking gecko, referring to its distinctive plump tail and sharp, barking defensive call. The genus is also often called thick-tailed geckos as a group, along with the species Uvidicolus sphyrurus.


The specific name, milii, is in honor of French sailor and naturalist Pierre Bernard Milius.[2]


Thick-tailed geckos are reddish-brown with bands of white and yellow spots, and a paler underbelly. They usually grow to 120–140 mm in length.[3] Their original tail is black with several pale bands, however regenerated tails have little pattern. When threatened, they will arch their backs and "bark". Thick-tailed geckos are found in rocky outcrops across southern Australia, and are slightly more cold-tolerant than many other Australian gecko species. They are nocturnal, and shelter underneath rocks or in burrows during the day. They feed on insects and small vertebrates.

Unusually for reptiles, this species forms aggregations in their retreat sites during the day. The reasons for this are unknown. However, it has been shown that this behavior results in a higher aggregate thermal inertia (they stay warmer) than would be found in solitary geckos of this and related kinds in similar circumstances.[4] In the same source, it was suggested that aggregating for physiological benefits may precede the development of other kinds of social behavior.


When threatened, they will arch their backs and bark. They also do this in breeding season. This species, and some other species of gecko have the unusual habit of licking their eyes after eating, presumably to keep the eyeshield clean.[3]


They are found in southern regions of Australia.

Their distribution in Western Australia is throughout the southwest, the goldfields, wheatbelt, and nullarbor regions to the east, and to Shark Bay in the north. They are also found at the Houtman Abrolhos and the Archipelago of the Recherche.[5]

Conservation status[edit]

The species has not been assessed for the IUCN Red List, nor the Australian EPBC Act, and may be kept as a pet with the appropriate license in at least some states of Australia.


  1. ^ "Underwoodisaurus milii ". The Reptile Database. www.reptile-database.org.
  2. ^ Beolens B, Watkins M, Grayson M. 2011. The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN 978-1-4214-0135-5. (Underwoodisaurus milii, p. 178).
  3. ^ a b Griffiths, Ken (1987). Reptiles of the Sydney Region. Three Sisters Publications Pty Ltd. p. 63. ISBN 0-9590203-3-0.
  4. ^ Lancaster J, Wilson P, Espinoza RE. 2006. Physiological benefits as precursors of sociality: Why banded geckos band. Animal Behavior 72: 199-207.
  5. ^ Browne-Cooper, Robert; Brian Bush; Brad Maryan; David Robinson (2007). Reptiles and Frogs in the Bush: Southwestern Australia. University of Western Australia Press. p. 128. ISBN 978-1-920694-74-6.

Further reading[edit]

  • Bory de Saint-Vincent JB. 1823. Dictionnaire Classique d'Histoire Naturelle, Volume 7. Paris: Rey & Gravier. 640 pp. (Phyllurus milii, new species, p. 185). (in French).
  • Cogger HG. 2014. Reptiles & Amphibians of Australia, Seventh Edition. Collingwood, Victoria, Australia: CSIRO Publishing. xxx + 1,033 pp. ISBN 978-0643100350. (Underwoodisaurus milii, p. 283).