10 Fascinating Facts About Broadnose Sevengill Cowsharks

10 Fascinating Facts About Broadnose Sevengill Cowsharks

Broadnose Sevengill Cowsharks should be considered the ambassadors for sharks, with their smiley faces.  We are fortunate to be able to dive with them at Miller’s Point in Simon’s Town. Here are some interesting facts we’ve discovered about these sharks:

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  • There are four species of cow shark, the bluntnose sixgill, the bigeyed sixgill, the broadnose sevengill and the sharpnose sevengill.
  • Their seven gills link them to Triassic period sharks, making them the most primitive species of shark.  All other sharks (except for sixgill cowsharks) have five gills.
  • The white spots you sometimes see on the back of a sevengill cowshark are caused by a fungal infection.
  • They can be found at depths of between 1m and 50m in the temperate coastal waters of  southern Australia, New Zealand, Japan, east and west coasts of South America; west coast of North America to Alaska and Southern Africa.
  • These sharks are ovoviviparous, which means they do not lay eggs but give birth to their young.  Gestation is approximately 12 months, followed by a year of recovery. Females usually give birth to large litters, of between 80 and 100 pups.
  • Broadnose sevengill cowsharks measure between 34 and 45cm at birth.  Males mature at 4 -5 years of age, by which time they measure between 130 and 170cm in length.  Females mature at 11 years of age, at an average length of 200cm.  The maximum recorded length is 290cm.  The lifespan is estimated to be up to 50 years.
  • They prefer low visibility and can co-ordinate their movements according to the tides, enabling them to move in and out of shallow bays – important to their feeding and breeding habits.
  • Sevengill cowsharks are effective predators and scavengers, often hunting in packs.  Appearing slow and cumbersome, they are capable of an amazing burst of speed when attacking their prey.  Juvenile cow sharks eat small sharks, bony fish and smaller rays, whilst adults prey on sharks, rays, sea lions, dolphins, seals, bony fish, carrion, octopuses, skates, octopus, molluscs, and crustaceans.  Adults only feed sporadically, sometimes once every 5 – 7 days.  Newborn pups eat about 10 times what the adults eat and feed far more often.
  • In certain locations, broadnose sevengill cowsharks have been observed spy hopping – holding their heads above water and seeming to look around. This behaviour is rare among sharks but has been regularly observed in Great White Sharks. It may be an adaptation to aid in the capture of marine mammals.
  • Broadnose sevengill sharks tend to ignore divers and are sometimes quite inquisitive, swimming directly towards divers and turning away at the last minute, or swimming over their heads.  When visibility is poor, they are a lot more confident and tend to approach far more closely than they would otherwise.  They will, however, turn and swim away when intercepted.
  • Unlike Great White Sharks, sevengill cowsharks are not protected in South Africa.  Their main predators are great white sharks and larger sevengill cowsharks.

Here are some of our favourite videos made whilst diving with the Broadnose Sevengill Cowsharks at Miller’s Point in Simon’s Town:

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