Marvelling at our Marine Mammals |
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by Lucille Byrnes
We on the west coast are privileged to see a number of different species of cetaceans (dolphins and whales) in our nutrient-rich waters, fed by the Benguela Current, among them southern right whales, humpback whales, Bryde’s whales, common dolphins, killer whales, Heaviside’s dolphins and dusky dolphins. There have been reported sightings of Arnoux’s beaked whales, but occasions are rare. You may well be one of the fortunate visitors to the West Coast who can watch whales doing what whales are supposed to do (other than giving Homo sapiens have a nice warm feeling!).
The following descriptions are taken from articles published by courtesy of Dolphin Action and Protection Group’s (DAPG) Dolphin Whale Watch and edited by Meredith Thornton of the University of Pretoria’s Mammal Research Institute (“MRI”). They include information on strandings garnered from Whales and Dolphins of the Southern African Subregion by Dr Peter Best, Extraordinary Professor at the MRI, a book that anyone interested in these creatures should not be without. Copies can be ordered from Cambridge University Press, Cape Town ISBN 13- 978-0-521-89710-5.
Bryde’s Whale was named after a Norwegian businessman, Johan Bryde (pronounced “brew-der”), who was one of the financiers of the SA Whaling Company land station at Durban in 1908 and later expanded the company’s operations to Donkergat, Saldanha, in 1909. It was in 1912 that he financed the first scientific investigation of whales in Southern African waters which showed that a local whale species, previously described from a skeleton found in Burma in 1878 and named B. edeni (in honour of Sir Ashley Eden, Chief Commissioner of Burma at that time), was in fact a new species. Previously, Bryde’s whales had been confused with sei whales, whose external features they closely resemble.
Distribution of this species is worldwide in temperate and sub-tropical warm waters between 40°N and 40°S. Off South Africa, as in other areas, there appear to be two populations: one resident inshore over the continental shelf and another, which is migratory, found off the shelf edge. Whales from these two populations differ in size, scarring, baleen (horny plates growing from the palate - in their case numbering about 280 on either side of the top jaw) shape and reproductive behaviour.
They grow to an average length of 12 m and their weight averages about 12 000 kg, with a maximum of 20 000 kg. Their coastal distribution is recorded mainly between East London and Cape Point, although sightings have been made beyond but taper off after Cape Columbine in the west and Port St John’s in the east and more likely to be encountered at sea than close to shore.
Once thought to be a cold-hearted killer, the orca - as in Free Willy - or killer whale (Orcinus orca), to give it its correct name - and just to clear up any misunderstanding, it is a dolphin, not a whale! - is one of the only cetaceans that live on warm-blooded animals. Today we know that its much maligned reputation is fable not fact, thanks to the many studies and films made about their biology and to see these beautifully marked creatures in the wild is an experience that will remain with one forever.
Says Meredith, “There are three different types of killer whales: transients that are mostly mammal eaters, residents that are fish eaters and the offshore type that probably do both! We suspect that the ones occurring off our coast are the mammal eating type.” The group (pod) is cohesive and consists of the same individuals (males, females and juveniles) that travel together throughout the year and over a period of at least seven years. They are co-operative hunters and a typical pod ranges in size from single animal to about 50 animals. Found worldwide, they are more abundant in Arctic and Antarctic waters where the food source is guaranteed: fish, cephalopods and other cetaceans, seals and seabirds.
They are the super-chargers of the sea and are capable of swimming at speeds of 50 kph and can dive to depths of 250 m. Their ‘spyhopping’ (lifting the head vertically above the surface of he water) gives them a clear view of what’s around them and their ‘breaching’ (leap out of the water) and ‘lobtailing’ (slapping of their flukes on the water’s surface - a sound which carries for a considerable distance) are behaviours which may be used to communicate, navigate and herd their prey.
Songsters of the SeaNamed Megaptera novaeangliae (“big winged New Englander”) by the Yankee whalers of yore because of their enormous flippers, the male humpback whales (Megaptera novaeangliae) are renowned for their song renditions that they deliver during the mating season.
Slow swimmers, humpbacks are well known for their spectacular breaching performances, leaping clear of the water, usually in an arching back flip and falling into the water with a resounding slap. Their distinctive fluke patterns and serrations have enabled scientists to recognise individual whales and follow their movements.
Apart from feeding on krill in Antarctic waters, humpbacks also feed on zooplankton in our coastal waters. In the Northern Hemisphere their diet stretches to copepods and other crustacean zooplankton, a variety of fish species and pteropod and cephalopod molluscs. They feed below or at the surface and employ a number of techniques to ensnare their prey: horizontal lunging (the most common feeding behaviour in South African waters), circular swimming and thrashing “flick feeding” in which the fluke is used to stun or concentrate prey. But perhaps it is their “bubblenet feeding” that’s the most intriguing of all, an action that releases a single large bubble or clouds of bubbles in spiral patterns which corral schools of zooplankton or small fish. There has, however, only been one possible report of bubblenet feeding in South African waters.
Righting the Wrong
Once considered the ‘right’ whale to catch (because of its high oil yield and its tendency to float in the water when killed), the numbers of the southern right whale (Eubalaena australis) are steadily increasing by 7% every year, although its status remains vulnerable. “The 1997 estimate for South Africa was 3100 animals, which,” says Meredith, “means that we should theoretically have more than 7000 in the SA population now!” Easily identified by its V-shaped ‘blow’ (the humpback’s is ‘pear-shaped’) and the pale brownish callosities on the head, the right whale lack a dorsal fin. Its low frequency call - somewhat of a moan - is akin to a spiritual experience.
The southern right is indeed the most prolific of the visiting whales and whose practice it is to move to our waters mid-year to mate and calve, the females having stocked up on krill before embarking on this migration. Once the young are sufficiently strong enough, the journey reverses itself and they head back to colder waters in December. A significant number do stay longer and some (most likely juveniles) may remain all year round. They move up along the west coast in spring to feed in area between St Helena Bay and Saldanha, remaining there while food is still plentiful, before heading off down south to fatten up again (usually from January onwards).
Mass strandingsDolphins and whales that beach singly are, in most cases, either ill, old or injured, but mass strandings are a phenomenon still to be fully understood, although scientists agree it is due to misfortune. As Dr Best writes, “It is very likely that no single cause is responsible for each and every event, and elements of some of the... hypotheses may have to act in combination to produce the circumstances necessary for a mass stranding to occur.” He adds that, “In the case of beaked whales it now seems that human intervention, in the form of mid-range sonar, may have to be added to the list of probable causes.. ” Corrective measures can save a threatened pod, but only Marine and Coastal Management (MCM) officials and helpers who have been specifically trained to do so should attempt to undertake this.
The West Coast has had its fair share of mass strandings, the first report being on Kommetjie beach on Christmas Eve in 1928. The Berg River mouth was the platform for 58 false killer whales beaching themselves in 1936 where all died. Then 26 Risso’s dolphins mass stranded in the St Helena Bay area in May 1989 of which 17 were saved and nine died. Four Arnoux’s beaked whales grounded on a sandbank in St Helena Bay harbour on 7 January 1998, but were saved.
A more recent threatened mass stranding - of a large group numbering about 200 made up of false killer whales, Risso’s dolphins and Atlantic bottlenosed dolphins - took place in October 2003 at an area in St Helena Bay called Doctor Reef, a shallow corner of the bay, making it a veritable whale trap, 81 false killer whales having mass stranded here in 1981. It took MCM officials 36 hours to herd the pod out to sea to safety, thus averting another disaster.
In February 2007 two Risso’s dolphins were rescued in Stompneusbaai and returned safely to the open ocean by MCM inspectors.
Do’s and don’ts
Report any strandings to the nearest Oceans & Coasts (MCM) officials who will take control of the situation in consultation with experts, failing which one of the following:
Nan Rice - 021-7825845 a/h 021-7825845
Michael Meyer - 021-4023911 a/h 021-790267
Meredith Thornton - 021-4813854 / 082 746 5579
If you come across a single stranded animal, do not attempt to push it back into the sea. If you can, roll it into an upright position (they are usually on their sides), taking care to avoid damaging the flippers. Clean around the eyes and blowhole and keep the animal cool by covering it with wet towels or pouring water over it, especially over the flukes and flippers, as this is where the blood vessels are closest to the surface of the skin and help to cool the animal. Be sure to keep the blowhole free of any water or debris. Digging a ditch under the animal’s chest will also help to prevent its body weight from crushing the lungs and suffocating the animal. Talk calmly to the animal, touching it as little as possible and keep onlookers at bay. A dolphin thus attended to can remain out of water for long periods. Remember, carcasses remain the property of MCM and are of great value to science.
And, remember: anyone out at sea that is approached by a whale to within 300m should move away slowly and quietly.
Of the dolphins that inhabit these waters, Heaviside’s dolphin (Cephalorhynchus heavisidii) is the smallest. This species was actually misnamed after Dr Heaviside and was supposed to be name after the captain of an East Indiaman, Cpt Haviside, who was the first person to bring a skull to England in the early 19th century. Found only off the west coast of southern Africa, this species can be easily identified by its blunt (rather than prominent) beak and the triangular dorsal fin. They socialise inshore in small groups in the mornings, while in the afternoons and at night they travel offshore to feed on juvenile hake. They are also very athletic and take readily to the breakers along the surf zone.
The dusky dolphin (Lagenorhynchus obscurus) also frequents the cold Benguela current waters, but not exclusively, also being found south of the Tropic of Capricorn. Its maximum length is 1,9m (by comparison to Heaviside’s 1,75m) and its dorsal fin is sickle-shaped. They are often seen riding the bow waves of boats and cooperating in large groups to corral fish in a bait ball by leaping and slapping the water’s surface with their bodies and tails. Unlike whales that visit our waters for mating and calving, dolphins are food-driven.
When and where to watch
It is difficult to say when is the best time to see these animals, as one can never predict the behaviour of creatures of the wild. Southern right whales are regular visitors to the west coast from the middle winter months, peaking in December; dolphins are a little more difficult because their presence hinges on the availability of food. Having said that, there is the virtual guarantee that visitors will see Heaviside’s dolphins when the northwester pumps into Britannia
Bay, bringing with it shoals of fish - food!
Specific good viewing points are off Sandy Point Harbour in St Helena Bay, Shelley Point, Paternoster and the coastline west of Rocher Pan Nature Reserve north of Dwarskersbos - and of course don’t forget your binoculars!
We are frequently taxed with the question as to why we don’t market the cetaceans more. The answer is simple: rather like spring flowers, we have no control over their movements and there can be nothing more frustrating than marketing something and then not coming up with the goods. However, visitors can be assured that St Helena Bay remains one of the prime spots to observe these creatures of the sea and there is no doubt that watching whales or dolphins at work - or play - is an experience of a lifetime. In the case of boat-based whale-watching it is true to say that bureaucracy killed the cat as there are now no licensed operators on the west coast so the onus falls on us landlubbers to try and satisfy the needs of the whale (and dolphin) -watcher.
Why not make the West Coast your next port of call?
You’re sure to have a whale of a time!
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