How to Identify the Habu (Identification Guide)
A venomous pit viper native to the Ryukyu Islands of Japan, identified by its triangular head, heat-sensing pits, and greenish-brown body marked with irregular dark blotches.
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Key identifying features
The Habu (Protobothrops flavoviridis) is a venomous pit viper native to the Ryukyu Islands of southern Japan, including Okinawa. It is identified by its broad, triangular head that is distinctly wider than its neck, heat-sensing pits located between the eyes and nostrils, and a stout, muscular body covered in keeled scales.
Coloration & pattern
The dorsal color ranges from olive-green to yellowish-brown or tan, overlaid with a series of irregular, dark brown or blackish blotches or a zigzag-like pattern running down the back. The blotches often have lighter borders, creating a mottled, camouflaged appearance well suited to the forested and vegetated habitats it occupies. The belly is typically pale yellow or cream, sometimes flecked with darker markings.
Head, eyes & scales
The head is large, broad, and triangular, clearly distinct from the narrower neck — a hallmark trait of pit vipers. Between each eye and nostril lies a heat-sensing pit organ used to detect warm-bodied prey. The eyes have vertically elliptical pupils, typical of nocturnal pit vipers. Scales are keeled (ridged) rather than smooth, giving the body a rough, textured appearance.
Size & body shape
The Habu is a relatively large pit viper, with adults commonly reaching 1.2 to 1.8 meters (4 to 6 feet), and some individuals growing longer. The body is thick and muscular, tapering to a moderately short tail, consistent with an ambush-predator lifestyle.
Range & habitat where you'll see it
This species is found throughout the Ryukyu Islands of Japan, including Okinawa, Amami Oshima, and surrounding islands. It inhabits forests, agricultural fields, rocky areas, and often areas near human habitation, particularly at night when it is most active. It is frequently encountered in and around dense vegetation, stone walls, and forest edges.
How to tell it apart from look-alikes
The Habu's large triangular head, heat-sensing pits, vertical pupils, and keeled scales distinguish it from Japan's non-venomous colubrid snakes, which typically have narrower heads, round pupils, and smooth scales. Within the Ryukyu Islands, it can be confused with other pit vipers such as the Tokara Habu or Sakishima Habu, so precise island locality and subtle differences in blotch pattern and size help refine identification. Its larger size and mottled olive-brown blotched pattern also distinguish it from smaller, more slender Japanese snake species.
Frequently asked questions
What are the key features that identify a Habu?
A broad triangular head with heat-sensing pits, vertical pupils, keeled scales, and an olive-brown to yellowish body with dark irregular blotches.
Is the Habu venomous?
Yes, the Habu is a venomous pit viper native to the Ryukyu Islands of Japan.
How large does the Habu get?
Adults commonly reach 1.2 to 1.8 meters (4 to 6 feet), with some individuals growing even longer.
Where in Japan is the Habu found?
Throughout the Ryukyu Islands, including Okinawa and Amami Oshima, in forests, fields, and areas near human settlements.
How can it be told apart from non-venomous Japanese snakes?
By its triangular head, heat-sensing facial pits, vertically elliptical pupils, and rough keeled scales, all of which non-venomous colubrids lack.