Although most of the baleen whales (filter feeders) have shown good signs of recovery from commercial whaling, particularly the southern right and humpback whales, others such as the Antarctic blue, fin and sei whales are still listed as Endangered or Critically Endangered on the South African Red list.
Adapted article by Els Vermeulen, Research Manager of the Mammal Research Institute’s Whale Unit at the University of Pretoria
Since the late 1960s, the South African population of southern right whales has been researched through annual aerial helicopter surveys, during which we photograph, and subsequently identify, each female that calves along our shore.
These animals are true gentle giants which are easily approachable as they are generally docile, slow swimmers and remain close to shore. This gentle nature resulted in the old whalers naming them the “right whales” to hunt. As a result, during the whaling era, the global population of about 100 000 animals was reduced to only 60 females in the world by 1920.
Because they were close to extinction, the right whale was one of the first whales to receive international protection from commercial whaling and their numbers have bounced back to roughly 20 000 individuals today. This is a remarkable recovery, but still far short of where numbers should be. Over the last decade, this story has taken a more ominous twist. Since 2009, very few whales have been seen along our coastline and their numbers have been fluctuating strongly. In addition, the females are taking longer to produce a viable calf.
It is clear these whales are being affected by something that they haven’t had to deal with before.
Using drones, we were able to tell that our southern right whale females have gotten substantially skinnier over the past two decades. Even on a global scale, our females are the skinniest. Losing weight is not good if you are a large mammal that needs energy to produce a healthy baby.
Our research at Pretoria University quickly started to point towards a feeding-related issue. Knowing these whales only feed in the Southern Ocean, and not along our coastline, it is clear that these whales are telling us a story about some drastic changes occurring in the Southern Ocean. It’s a story we cannot and must not ignore!
We started digging a little more into the foraging ecology of the species, and found that our right whales have also drastically changed where they eat over the past decade, likely due to decreased food availability in areas where they used to find it.
What climatic and oceanographic variability lies at the heart of this, we do not know yet, but we intend to find out. The southern right whales are clearly acting as a sentinel, bringing to coastal South Africa an important message about large-scale environmental changes in the vast Southern Ocean, which is undoubtedly affecting many other marine species.
