Posted on Tuesday, 30 May 2017
Over the years Monique and I have spent a significant amount of time exploring the offshore waters off Cape Point and the Cape of Good Hope, the South Western tip of Africa.
It is here where mixing waters caused by upwelling, different tongues of warm and cold water from both Agulhas and Benguela currents interlacing at different times of the year and a seasonal influx of bait fish and nutrients attract an assortment of mega fauna to the area.
In 1999 when we ran the first pelagic blue and mako shark expeditions off the South African coastline we were completely unaware of the fantastic assortment of open ocean whales and dolphins, collectively known as cetaceans that were on offer.
After doing extensive research on species preferred habitats, looking at old whaling records and discussing sightings with our late friend Barrie Rose, as well as other skilled naturalists and fishermen we built up a picture of where the best areas were to start looking for these amazing creatures. The more we explored the offshore world the more diversity and assortment of shapes and sizes of species we encountered. The diversity was incredible and would surely cover the wish lists of even the most chintzy of species collectors.
What we also learnt was that at certain times of the year in certain depth profiles we would see the same species, obviously attracted to seasonal food sources.
One of these species was the ubiquitous sperm whale, star of Moby Dick, and a marine record holder second to none.
It is the animal with the largest brain, the second deepest diver after the Cuvier’s beaked whale, the world’s largest predatory species and let us not forget vanquisher of “Architeuthis” the gladiatorial sounding name for the giant squid. Can you imagine the scene of these two behemoths having a cross phylum battle for survival in the dark canyons of the ocean where angler fish provide stage lighting for these super heavy weight bouts of the marine world?
We began to see species not seen that frequently alive off our coast, such as southern bottlenose whales, false killer whales, fin whales and more. We fairly regularly saw huge open ocean bottlenose dolphins, almost twice the size of their inshore namesake sometimes making prodigious leaps higher than any other dolphin species we have ever seen. We watched false killer whales catch kill and consume 200lb yellowfin tuna, one after another. How did they do this, as we all know how fast these incredible fish are?
In years gone by Risso’s dolphins, an open ocean species whose ghost like coloring makes them unmistakable used to be a common sighting now is a rarity, what changed?
Answers to these questions are both difficult to come by and vexing to acquire by yourself. By keeping data on all of our sightings over the years and really paying attention to everything we saw we have slowly built up an idea of relationships that are the glue that holds the fabric of the eco system together.
One of the relationships I love the most is that between creatures of different elements, in this case between birds of the air, whales relaying on air but spending most of their time underwater, and tuna who live completely subsurface.
Over time we realized that everything has a tell tale give away and to the passionate observer finding that clue is as exciting as unlocking a natural history Pandora’s box.
Anyone who has been to sea with me knows I am obsessed with birds in terms of what each species behavior symbolizes and I regularly get teased over my “what are the birds doing” comments.
I must point out however that whilst I love birds I do not lay claim to being a great birder, rather a keen bird watcher, as the behavior and antics of these masters of air often betray the secret life of the animals they follow and depend upon for a meal.
We learnt that for seeing certain secretive cetaceans offshore white chinned petrels were our best means of finding these animals, who with their short bushy blow, did not do to much to help the wanton observer find them.
One of the species that the white chins commonly associate with are the curious looking pilot whales, colloquially known with a few other similar colored and sized whales as “blackfish”.
In our water we most commonly see long finned pilot whales and often in groups of upwards of 100 animals comprised of all ages and sizes. Apart from killer whales, adult male pilot whales must have the most ornate and spectacular dorsal fins, often reminiscent of a breaking wave. They are highly sociable animals and very vocal and when you dive with them you can clearly hear their excited chatter underwater, maybe wondering what the hell such an ungainly creature is doing in their world so frequently dominated by creatures of hydro dynamic refinement.
For years when we saw the pilots we would see the birds and knew that there had to be a relationship, but what was it and how exactly did it work?
Did the whales drive fish or squid up to the surface that the birds then fed on in the same way dolphins may ball a shoal of sardines for gannets to plunge dive into?
Did the adult pilots regurgitate food for the young, as often they need to dive to prodigious depths to find squid that the very young would struggle to do?
We had seen the birds eating scraps of squid on the surface before and therefore know that clearly they were benefitting from the whales in some way or another. It was however only on this past week’s adventure that I saw first hand exactly what is happening.
Upon diving down and waiting for the advancing school of pilots to pass me by I observed how first an adult regurgitated and then defecated a large piece and then several slivers of digested squid. Not ten seconds later and the white chins were at the dinner table, diving gracefully and then flying underwater to scoop up their processed meals courtesy of the whales. What was fascinating was that there were also yellowfin tuna following the whales who clearly also benefit from the same food source. I had heard from Doug Perrine and the late Jim Watt how oceanic white tip sharks would follow pilot whales off Hawaii, almost certainly for the same reason. What I found notable was how chunky the poop of the whale was in terms of how poorly the squid was digested. There were many long stringy pieces that the birds gobbled up with great gusto.
Here was an amazing example how various species inter relate and highlights how interconnected everything is. You take the squid out the equation and the whole story never exists…once again nature in perfect harmony!