Fast Facts

  • Classification
    Species
    lewini
    Genus
    Sphyrna
    Family
    Sphyrnidae
    Class
    Chondrichthyes
    Subphylum
    Vertebrata
    Phylum
    Chordata
    Kingdom
    Animalia
  • Size Range
    The Scalloped Hammerhead grows to 4.2 m in length.

Introduction

The Scalloped Hammerhead sometimes forms large migratory schools, dispersing at night to feed in deeper waters. The adult females are believed to live in deep water and only move onto the continental shelf to mate and when giving birth. After a period of 9-10 months they give birth to an average litter of 25.

Identification

The Scalloped Hammerhead has an undulating margin to the front of the head with an indentation medially. It has a low second dorsal fin and a relatively straight posterior pelvic fin margin.

The species is brownish-grey to olive or bronze above and pale below. Adults have dusky pectoral fin tips, but no other markings. Juveniles have dark pectoral, lower caudal and second dorsal fin tips.

Habitat

The species occurs in coastal and offshore waters. It is not an oceanic species.

Distribution

Scalloped Hammerheads occur in most tropical and warm temperate waters worldwide.

In Australia it is known from north-western Western Australia, around the tropical north and south to the central coast of New South Wales.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information.  Source: Atlas of Living Australia.

Sphyrna lewini

Ozcam map of Scalloped Hammerhead specimens in the Australian Museums. http://ozcam.ala.org.au/occurrences/search?q=Sphyrna%20lewini&zoom=off#mapView

Feeding and diet

Their diet consistes mostly of teleost fishes and cephalopods.

Other behaviours and adaptations

The Scalloped Hammerhead sometimes forms large migratory schools, dispersing at night to feed in deeper waters.

Sharks can detect weak electrical fields using electrical sense organs called the ampullae of Lorenzini. These are connected to the exterior via pores in the shark's snout. This ability allows some species to detect the electrical cues that emanate from prey animals and even the weak electrical currents flowing through the earth's magnetic fields. Some species can detect voltages as low one millionth of a volt.

Breeding behaviours

The adult females are believed to live in deep water and only move onto the continental shelf to mate and when giving birth. After a period of 9-10 months they give birth to an average litter of 25.

Danger to humans

It is considered a potentially dangerous species that has occasionally displayed its threat posture to scuba divers who have approached too closely (Thomson et al, 1979).

References

  1. Allen, G.R. 1997. Marine Fishes of Tropical Australia and South-east Asia. Western Australian Museum. Pp. 292.
  2. Allen, G.R. & R. Swainston. 1988. The Marine Fishes of North-Western Australia. A Field Guide for Anglers and Divers. Western Australian Museum. Pp. 201.
  3. Compagno, L.J.V. 1984. FAO species catalogue. Vol. 4, Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Part 2 - Carcharhiniformes. iii-x, 251-655.
  4. Hutchins, B. & R. Swainston. 1986. Sea Fishes of Southern Australia. Complete Field Guide for Anglers and Divers. Swainston Publishing. Pp. 180.
  5. Klimley, A.P. 1993. Highly directional swimming by scalloped hammerhead sharks, Sphyrna lewini,and subsurface irradiance, temperature, bathymetry and geomagnetic field. Marine Biology. 117: 1-22.
  6. Last, P.R. & J.D. Stevens. 1994 Sharks and Rays of Australia. CSIRO. Pp. 513.
  7. Randall, J.E., Allen, G.R. & R.C. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Crawford House Press. Pp. 557.
  8. Stevens, J.D. 1987. Sharks. Golden Press. Pp.240.
  9. Thompson, D.A., Findley, L.T. & A.N. Kerstitch. 1979. Reef Fishes of the Sea of Cortez. John Wiley & Sons. Pp. 302.