In June 2012 a 3.8 m adult male white shark weighing 507 kilograms washed up on the rocky shore of Dyer Island, Gansbaai, South Africa. The dead shark was retrieved by the Dyer Island Conservation Trust (DICT) and transferred to the Department of Environmental Affairs to await a necropsy (animal autopsy).
Scientists from DEA, Bayworld, Shark Spotters and DICT assisted with the necropsy of the large male white shark. Photo by Adrian Hewitt
The shark appeared to be in prime condition and should have been at the top of his game as a predator. There were no external signs of injury and his robust physique, perfect set of sharp dentures and a bulging stomach were all signs of good health.
To call this shark a top predator is an understatement. A necropsy performed in August to determine cause of death revealed SIX young cape fur seals in the shark’s stomach – a surprise even to the senior scientists involved! This seal smorgasbord weighed in the region of 100 kilograms!
The sheer size of the shark’s liver was another surprise! At approx. 70 kg it equates to roughly 14% of its sharks total body mass. (An average human liver makes up just 2% of the total body mass). In white sharks, the liver serves a number of important functions including buoyancy and nutrition. The liver consists of fats and oils which are buoyant in water and allows the shark to maintain its position in the water column with minimum energy expenditure. The particularly large fins of the white shark aid with balance and provide lift, just like wings on an airplane.
Newly weaned seal pups (around 6 months old) have a blubber rich layer consisting of tightly packed fats/lipids to keep them warm in cold Western Cape seas. This comes at a high price for some seals as their energy rich blubber is highly sought after by large white sharks.
The seal islands off the South African coast are popular great white hunting grounds in winter when an abundance of the young and inexperienced seals first take to the sea. This sharks stomach contents illustrate perfectly how white sharks will “stock up” on the seasonal abundance of seal prey. It is thought that the energy rich blubber from the pups is stored in the shark’s huge liver to be utilized when food is not as bountiful.
Despite the loss of such a magnificent creature, its body will be put to good use, assisting scientists in learning more about these elusive creatures. Scientists will investigate various aspects (e.g. age and maturity, diet, genetics, reproductive status (hormones), parasites, bacteriology and toxicology) of the biology, behavior and life-history to provide a better understanding of these sharks.
This is an edited version of Adrian Hewitt’s detailed scientific account of the necropsy on the Shark Spotters website. For the full account and photos go to: http://sharkspotters.org.za/csi_shark
Definition of necropsy:
“In vet school, we were taught that the term necropsy refers to postmortem examinations on animals, versus an autopsy, which is an examination of “self”. Since you can’t do an examination (or anything!) postmortem, a human examining a human cadaver was said to be doing an autopsy. A human doing a examination on an animal cadaver was said to be doing a necropsy.” http://vetmedicine.about.com/od/terminology/g/G_necropsy.htm