Great Hammerhead, Sphyrna mokarran Click to enlarge image
Great Hammerhead, Sphyrna mokarran (Rüppell, 1837) Image: Albert Kok
© CC BY-SA

Fast Facts

  • Classification
    Species
    mokarran
    Genus
    Sphyrna
    Family
    Sphyrnidae
    Order
    Carcharhinidae
    Class
    Chondrichthyes
    Subphylum
    Vertebrata
    Phylum
    Chordata
    Kingdom
    Animalia
  • Size Range
    The species grows to 6 m in length but rarely exceeds 4.5 m.

Introduction

The Great Hammerhead has a very tall first dorsal fin.


What do Great Hammerheads look like?

Identification

This species has an unmistakeable hammer shaped head and a very high first dorsal fin. Its head width is less than 40% of the total length and the pelvic fins have concave posterior margins.


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Where do Great Hammerheads live?

Habitat

Found on or adjacent to continental and insular shelves and seamounts down to 300m

Distribution

It occurs in tropical and warm temperate seas worldwide.

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



What do Great Hammerheads eat and how do they mate?

Feeding and diet

Great Hammerheads feed on fish, crustaceans and cephalopods. It has also been found that they prey on the Australian Cownose Ray, Rhinoptera neglecta

Reproduction

Great Hammerheads are born at approximately 65cm and males mature at ~255cm TL while females mature at ~210-228cm TL. They are viviparious (give birth to live young that develop in the female) and produce between 6-33 pups per litter.



How have Great Hammerheads adapted?

Behaviours and adaptations


  • Brain

    Hammerheads possess the largest and most complex brain of all sharks (Mantas and Devil rays have the largest brain of all Elasmobranchs). Large to process a diverse array of sensory information from the lateral line and electrical and magnetic fields.

  • Eye and optic nerve

    Hammerhead Sharks have eyes on the ends of the hammer shaped head which give the shark excellent binocular vision. A hammerhead can improve its stereoscopic vision even further by rotating its eyes and sweeping its head from side to side allowing for almost 360o vision.

  • Olfactory system

    Smell and taste are extremely important to a shark. The nostrils have highly sensitive membranes which can pick up even the trace of amino acids in the water. Large olfactory organs in the brain process this information and enable the shark to zero in on the source of a scent by swimming up current. They also use their olfactory system to find mates by detecting pheromones and it may even help guide transoceanic migrations and be a navigational aid.

  • Electrosensing

    Electrosensing is a most extraordinary shark sense and can detect tiny electric fields given off by living animals, inanimate objects and even water over the earths magnetic fields. Using the special jelly filled sensory organs known as ampullae of Lorenzini, sharks and Hammerheads especially, can detect prey at close quarters (up to 50cm) even when hidden. Hammerheads, with their large broad wing-like heads, have more ampullae than any other group of sharks. This allows them to quickly and accurately locate, prey buried in the sand. A Hammerheads ability to detect electric fields is also used to orientate sharks within the earths magnetic fields, allowing for cross ocean migrations. Smooth Hammerheads, Sphyrna zygaena, use this sense to follow ‘magnetic highways’ along the ocean floor, linking their day time aggregation sites and night time nocturnal feeding sites.


References

  1. Bray, D.J. 2020, Sphyrna mokarran in Fishes of Australia, accessed 05 Aug 2022, https://fishesofaustralia.net.au/home/species/1969
  2. Ebert, D.A., Fowler, S., Compagno, L., 2016. Sharks of the World, Wild Nature Press, pages 1-528
  3. Hoese, D.F., Bray, D.J., Paxton, J.R. & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia. parts 1-3, pages 1-2178.
  4. Last, P.R. & J.D. Stevens. 2009. Sharks and Rays of Australia. Edition 2. CSIRO. Pp. 644, Pl. 1-91.