The effects of Climate Change on South Africa’s Southern Right

When I first visited Cape Town, I was told that I “would” have the amazing opportunity to see whales. Being an animal lover, I was thrilled! In December of 2012, I visited Cape Town and a friend offered to be my tour guide. She introduced me to the beautiful town of Hermanus and explained how every year, for a few months at a time, the town gets full of people who come from far and wide for the annual whale festival, eager to catch a glimpse of the abundant whales. What a great opportunity to appreciate nature and learn about whale conservation.

Hermanus, Western Cape, South Africa

I later found out that the annual whale festival focuses on southern right whales. These whales migrate from the cold Southern Ocean where they feed in summer, to the calmer waters of South Africa’s coast, to calve and nurse their young in winter.

By doing a quick google search on the southern right whale, you’ll learn a few facts: They are ‘baleen whales’, which means they have no teeth, but rather bristly baleen plates which act as giant sieves to collect plankton from the sea.

Southern right whales got their name from the early whalers, as they were seen as the ‘right whale’ to hunt, mainly because they are slow, they float when dead, and they are rich in blubber reserves, making them very valuable.

Another two interesting facts are that the species is philopatric, which means that when they migrate, they tend to go back to the same calving ground on our coast, and to the same feeding grounds in the Southern Ocean. And secondly, southern right whales are ‘capital breeders’, meaning that their reproduction and their migration habits are dependent on their foraging success. In short, if they eat well, they will migrate successfully and have more calves.

A southern right whale and her calf

Researchers at the University of Pretoria’s Mammal Research Institute Whale Unit, have been monitoring the South African population of southern right whales for decades.

Aerial surveys conducted by the Whale Unit since the 1970s have shown a steady increase in the South African population subsequent to their international protection from whaling. However, in 2009 there was a very noticeable change, as suddenly only half of the so-called “unaccompanied adults” (which includes males and females which do not give birth that year) appeared on our shores, and since then, this part of the population has virtually stopped migrating to South Africa’s coastline. In addition, recent aerial surveys have also revealed a reduction in the rate at which females give birth to new calves in the last decade.

An aerial view of part of South Africa’s southern coastline

Understanding the research:

The Whale Unit’s latest published research, titled “Decadal shift in foraging strategy of a migratory Southern Ocean predator”, published in the peer-reviewed journal Global Change Biology was led by Gideon van den Berg and Dr Els Vermeulen from the Whale Unit, and Dr Emma Carroll from the University of Auckland, New Zealand.

This work helps to understand why we have had fewer sightings of these whales in the past decade, and what may lie at the heart of the observed decreased calving rate. Here is a quick summary:

  • The team used “stable isotope analyses” from skin samples to study the feeding strategies of southern right whales. Comparing samples from the 1990s to those from the late 2010s, allowed them to catch a glimpse of the population’s foraging strategies when calving rates were normal (in the 1990s) and low (in the last decade).
  • Ultimately, they found that compared to the 1990s, South Africa’s southern right whales have radically changed where, and on what, they are feeding.
  • The researchers emphasized that on the one hand, this is a good sign, as it indicates that the whales may have some ability to adapt to changing environmental conditions in their feeding grounds.
  • … and this is an important bit, considering the recent decreased rate at which females are calving, and the decreased presence along our shores, the researchers also indicate that the observed change doesn’t appear to be good enough to ensure good feeding conditions.
  • Many studies have shown that the changing climate is having a massive impact on the ecosystem functioning of the world’s oceans, including on krill populations.
  • The Whale Unit’s findings tell us that the South African population is attempting to adapt to changing ocean conditions, which is altering the availability of their primary food source (krill), but the whales are struggling to keep pace with the changes.

It is always sad to know that the world around us is changing so drastically because of climate change, and every so often we hear of a new species that has become extinct or is endangered. I am sure many of you have grown to love the sightings of southern right whales and are possibly saddened by these latest findings, as we might even feel helpless in the eye of such large-scale environmental problems. But it is important to know what is happening to our whales and our oceans, and maybe when we see one, we will treasure that moment even more so, because we will never know when we will see them again.

A breaching southern right whale

If you would like to help with the ongoing research on the South African southern right whale population, then symbolically adopt a whale from this very population here. Every cent helps to find out more about what is happening in our oceans and to our whales!