SEDGEFIELD NEWS - When a male sperm whale washed up on Swartvlei Beach west of Sedgefield on Friday 31 August it was a rare opportunity for marine scientists to study the species.
The largest of the toothed whale family, sperm whales are also the largest modern predator species on the planet. Preying on squid, they hunt in deep water between 300m and 2 000m, so are not a common sight close inshore along the South African coastline.
What was remarkable was that it washed up within 200m of the female humpback whale that stranded on 29 June, a function of tides, inshore currents and wind patterns at play.
Making the most of the opportunity to contribute to our scant knowledge of this species, marine biologists Danielle Conry and Frikkie van der Vyver from the Plett Stranding Network; Sasha Dines for Oceans Research; Wayne Meyer from Cape Nature; and volunteers from Smart arrived on Saturday morning 1 September to collect samples.
Two priorities
The two priorities were to collect the teeth and to sample the stomach contents. As the whale had washed up over the neap tide, it was still in shallow water which added to the challenge of collecting samples. The lower jaw was removed using a chainsaw and some dragging by a Sanpark 4x4 vehicle.
The whale measured 16.37m, which would have it weighing between 40 and 45 tons. There were 36 teeth in the lower jaw with signs of slight wear. Together with the length and the teeth it can be assumed that it was a mature adult male. With comprehensive measurements and tissue samples collected, the team had to retreat ahead of the incoming tide and leave the stomach sampling for Sunday.
Conditions on Sunday were not ideal as the team prepped up to the threat of rain and wind. Dr Stephanie Plon from the Nelson Mandela University had arrived to assist with stomach sampling. The plan was to make some incisions to create a flap of abdominal blubber which could be pulled away using the Sanparks vehicle.
The carcass had also bloated substantially requiring extra care not to get caught in a gaseous explosion while making the cuts. And erupt it did. Frikkie van der Vyver had just finished making a deep cut when the stomach exploded through the abdominal wall and he was fortunate to be out of the way as it sprayed out.
Dr Stephanie Plon with some of the first squid beaks collected from the stomach.
What did the stomach reveal?
The contents of the stomach included approximately 7.5 litres of squid beaks, internal parasites and several metres of longline rope. There was also a growth on the stomach lining and tissue samples were collected to determine if it was an ulcer or a tumour.
Sperm whales consume up to 900kg of squid a day and it is thought that after digestion of the squid, the beaks do not immediately pass through the digestive tract but are possibly retained in the stomach as a means of protecting the intestine from the sharp edges.
Researcher Frikkie van der Vyver makes the first transverse incision. Photos: Mark Dixon
One theory for their elimination from the stomach is regurgitation. A second theory is that the ambergris, which forms in either the intestine or rectum (no conclusive studies have been possible), is produced to safely eliminate the beaks through the digestive tract.
In terms of the death of this specimen, it is too early to conclude that one particular aspect was the cause of death. While there was rope present in the stomach, it hadn't prevented the whale from eating and digesting it's prey.
The next bit of hard works starts: squid and parasite species need to be identified and a range of samples need to be examined to glean as much information as possible. So, while we contemplate the death of this incredible apex predator, it has provided the chance to learn more of the species.
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