ANIMAL SPECIES:Scalloped Hammerhead, Sphyrna lewini (Griffin & Smith, 1834)
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.
Alternative Name/s
Kidney-headed Shark.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.
Size range
The Scalloped Hammerhead grows to 4.2 m in length.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.
Distribution by collection data
Biomaps map of Scalloped Hammerhead specimens in the Australian Museum collection.
Habitat
The species occurs in coastal and offshore waters. It is not an oceanic species.
Behaviour and adaptations
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.
Mating and reproduction
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.
Living with us
Danger to humans and first aid
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).
Classification
- Species:
- lewini
- Genus:
- Sphyrna
- Family:
- Sphyrnidae
- Class:
- Chondrichthyes
- Subphylum:
- Vertebrata
- Phylum:
- Chordata
- Kingdom:
- Animalia
References
- Allen, G.R. 1997. Marine Fishes of Tropical Australia and South-east Asia. Western Australian Museum. Pp. 292.
- 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.
- 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.
- Hutchins, B. & R. Swainston. 1986. Sea Fishes of Southern Australia. Complete Field Guide for Anglers and Divers. Swainston Publishing. Pp. 180.
- 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.
- Last, P.R. & J.D. Stevens. 1994 Sharks and Rays of Australia. CSIRO. Pp. 513.
- Randall, J.E., Allen, G.R. & R.C. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Crawford House Press. Pp. 557.
- Stevens, J.D. 1987. Sharks. Golden Press. Pp.240.
- Thompson, D.A., Findley, L.T. & A.N. Kerstitch. 1979. Reef Fishes of the Sea of Cortez. John Wiley & Sons. Pp. 302.
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Female and male Scalloped Hammerhead pups View full size
Kerryn Parkinson
© Kerryn Parkinson
The anterior region of a male Scalloped Hammerhead pup View full size
Kerryn Parkinson
© Australian Museum
Lower surface of the head of a Scalloped Hammerhead pup View full size
Kerryn Parkinson
© Kerryn Parkinson
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