On Wednesday 26 November a large whale carcass washed to shore at Muizenberg. The carcass was evidence that some out-of-the-ordinary feeding activities had been taking place at sea. Shark bites were evident all over the dead whale and five shark sightings were recorded by Shark Spotters that day. On inspection of the bites it showed many of them to be from white sharks.
White sharks have a diverse diet incorporating fish, sharks, rays, seals, squid, crabs and even dead whales. There is no record of white sharks attacking live large whales as whales can be aggressive and may pose a threat to the sharks. Calves may be vulnerable and from personal observation a mother Southern Right Whale will position herself in between her calf and a white shark when it gets too close for comfort.
However, every year whales die along our coast from old age, exhaustion, entanglement in fishing gear or being knocked by boats. Given the golden opportunity sharks wouldn’t hesitate to scavenge on a dead whale. Whales have a thick blubber layer for insulation against the cold water and this is what is targeted by the sharks. Blubber is rich in energy (almost double that of muscle) and for large active sharks can sustain them for weeks. Scientists have theorized that some large white sharks follow whale migrations to feed on stillborn or weak calves, placentas from birthing or even opportunistic deaths of adults. Whale carcasses may even provide an arena for sharks looking for mates in the open ocean.
Rare observations of the white sharks social nature has been recorded at whale carcasses. While sharks of the same size may feed side by side showing little aggression toward each other, fierce competition or a hierarchical etiquette may inhibit smaller sharks from entering in the feast. Direct observations have shown that smaller sharks patrol the fringes of the carcass while the large animals feed. Large sharks gorge themselves on the blubber showing distinct extended bellies after just a few mouthfuls. They sometimes regurgitate large pieces which drift away, and are quickly picked up by juveniles waiting for their taste of a blubbery meal.
Sharks play an important role in marine ecosystems by weeding out the weak and infirm and scavenging on dead animals that may ‘pollute’ an area. They also continue the natural cycle of life through the transfer of energy from the dead whale to the sharks. There is no right or wrong here, just survival.
BEACH CLOSURE
A stranded whale carcass oozes blood and oils which saturate the adjacent area and can attract sharks from kilometers away. Thus as a precautionary approach the beaches between Muizenberg and Strandfontein were closed for the day. Law enforcement and Shark Spotters were on duty providing the public with up to date information and explaining the situation. The whale carcass caused quite a stir and some locals were not happy that they missed their regular swim or surf, but there are times when we simply need to remember that the ocean and its inhabitants have a rhythm and we are mere guests in their domain. The carcass was removed by the City where it was taken to a dumpsite to be buried. Muizenberg Beach was opened the next day at lunchtime.
Photos courtesy Ian Klopper