The Important Whale Research Being Conducted at Cape Vidal

If you’re out on the water near St Lucia between June and November, there’s a good chance the humpback whale you’re watching has already been counted. Quite literally: tallied, timed, and logged by scientists standing on a platform on the dunes at Cape Vidal, in exactly the spot you might be looking back toward from the boat.

The survey in question has been running, on and off, since 1988, which is worth pausing on given what this coastline looked like a generation earlier. The Durban whaling station, once the largest land-based whaling operation in the world, closed in 1975. By the time it shut down, the humpback whales still migrating past that stretch of coast each year had been reduced to an estimated 340 individuals. When the whaling stopped, a global moratorium followed in 1986, and the population that Ken Findlay and Peter Best, leading South African marine scientists, started counting from Cape Vidal a couple of years later was, in effect, the very beginning of the recovery.

Findlay and Best set up the survey to track that recovery along South Africa’s east coast in close to real time. The method is simple: observers stationed about 60 metres from the water’s edge record every whale group crossing a fixed offshore line, using theodolites (instruments that measure horizontal and vertical angles) to pinpoint their position and track them moving north. It’s not glamorous work. But it’s one of the longest continuous whale monitoring efforts on the continent. 

The most recently published round of surveys, done over the 2018 and 2019 seasons, put the number of whales migrating past Cape Vidal at around 10,500 in 2018 and 11,000 in 2019, with sightings peaking in the last days of July into early August both years (wonderful time to come and visit us). Needless to say, that’s a lot of whales moving past a single fixed coastal point in a relatively short space of time. The reason that Cape Vidal is just an opportune location for spotting these fantastic mammals is because as the humpbacks swim north, they tend to funnel closer to the shoreline here. It allows a person standing (or sitting) on a dune to get a great view as they splash about in the ocean. 

The survey actually picked up on a very interesting shift, and it’s something which the researchers are now paying really close attention to. Between 1988 and 2002, the numbers passing Cape Vidal were increasing by roughly 9% a year, a strong recovery curve consistent with a population rebuilding after near-annihilation. The more recent survey data suggests that growth rate has slowed. Alarm bells aren’t quite ringing yet, the data points are still limited, but it’s certainly something to be aware of and monitoring as the years progress. It’s also a phenomenon that researchers don’t fully understand yet. 

There’s a second piece of research that connects directly to what happens after these whales pass Cape Vidal. Photo-identification work, using the shape and markings on the underside of a whale’s tail fluke, has confirmed that individual whales are showing up in South African waters across multiple years and in more than one part of the coast, and that this migration corridor links directly to breeding grounds in southern and central Mozambique (Photo-identification study, African Journal of Marine Science). In practice, that means a whale photographed off KwaZulu-Natal one winter can turn up again, sometimes years apart, off the Mozambican coast, matched by its own fluke pattern in a shared photo database. The whale you see from a boat near St Lucia in July might be recognisable again off Mozambique in September, or off this same stretch of coast two winters later.

Put those two pieces of research together and it’s easy to see why Cape Vidal is a whole lot more than just an opportune picturesque spot to do a little whale watching. It’s the bedrock of very important research. Cape Vidal starts to look less like a scenic whale-watching stop and more like a fixed observation post on a much longer story that’s still being written. The counting platform tells you how many whales are moving through and roughly how that number is changing over time (Cape Vidal population survey, 2018–2019, African Journal of Marine Science). The photo-ID work tells you where individual whales go once they’ve passed, and how often they come back. Time, and time again, the lives and trajectories of these impressive animals are being mapped out, with 40-years of data to back it up. 

We thought it might be interesting for you to read a bit about the research that is carried out in our idyllic part of the world. Because when we take our guests to Cape Vidal and they feel the Indian Ocean for themselves, and get to witness these majestic whales, up-close and personal, it’s good to know that not only is this a location for ‘once in a lifetime’ experiences, made accessible by our crew, but it’s also the spot where real, tangible work is being done. 

Feel like joining us and doing a bit of whale watching yourself after an incredible day on safari? Get in touch and let’s make it happen!