The adult male of this species tends to have the most developed rostral horn, but both males and females do show this characteristic trait. The function of this horn is unknown.
  • Size

    27.6 inches (70 cm)
  • Diet

    Coarse and leafy brown algae
  • Range

  • Habitat

    Channels, moats, lagoons and seaward reefs

Physical Characteristics

  • Body usually greenish-gray in color with a bony horn or rostrum protruding from the front of its head in front of the eyes.
  • Dorsal and anal fins are yellowish with thin blue lines.
  • Two blue plates with sharp, forward-pointing spines on either side of the caudal peduncle.
  • Thick leathery skin with tiny non-overlapping scales and small teeth with finely serrated edges.
  • Lobes of the caudal fin are extended into slender thread-like filaments; more apparent in the male.
  • Can reach approximately 27.6 inches (70 cm) in length.

Animal Fact

This unicornfish develops long, trailing tail filaments as it grows.

Diet / Feeding

  • Diet consists of coarse and leafy brown algae.

Range / Habitat

  • Occurs in the Indo-Pacific from the Red Sea and East Africa to the Marquesas and across the tropical Pacific to southern Japan, throughout Micronesia and east to Hawaii.
  • Juvenile lives on clear coastal reefs with algae growth.
  • Adult prefers shallow reef slopes adjacent to deep water.
  • Found in channels, moats, lagoons and seaward reefs, particularly in areas with strong surges, preferring depths usually no greater than about 33 feet (10 m).

Reproduction & Growth

  • Has been observed practicing pair spawning, particularly at the outermost area of a foraging group.
  • In some areas, it has been observed migrating in schools around the outer reef edges and spawning during both the full and new moons.

Conservation Status

  • “Not Evaluated” on the IUCN Red List.

Additional Information

  • Does not recover quickly from environmental or other stresses since its population doubles between 4.5 and 14 years.
  • With age, the male tends to have a better-developed horn, peduncular spines (spines in plates just before the tail), and caudal (tail) filaments than its female counterpart.
  • Usually swims within a small group.
  • Function of the rostral horn on the forehead is unknown.


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