Whales need our help

The World Wide Fund for Nature (WWF) South Africa and the University of Pretoria’s (UP) Mammal Research Institute (MRI) Whale Unit is supporting research on the southern right whale. Up until about a decade ago, these marine mammals had made a remarkable recovery from commercial whaling. Now, they face a new threat, with the heavy impact of a warming climate on their food supply. As a result, the number of southern rights visiting South African shores is reportedly declining.

UP’s MRI Whale Unit has been monitoring southern right whale populations since 1969. Their research, using photo-identification images and annual surveys, forms one of the longest continuous datasets for any marine mammal in the world, making it extremely valuable by national and international standards.

Research Manager at the MRI Whale Unit, Dr Els Vermeulen, explains: “Since commercial whaling stopped, the recovery of the southern right whale population was a great conservation success story. But now, the science is telling us that these marine mammals are coming under renewed pressure from a more modern problem likely linked to climate change. Over the past decade, we have been finding that the whales are getting thinner, are calving less often and leaving their breeding grounds earlier.”

In October last year, a three-day aerial survey extending from Nature’s Valley (near Plettenberg Bay) to Muizenberg counted some 414 whales, among them 191 mother-and-calf pairs, mainly between De Hoop Nature Reserve and Walker Bay, Hermanus. This number is higher than that recorded in 2019 and 2020, but remains well below what’s regarded as normal. In addition, since 2009 the number of unaccompanied adults (males, resting females and receptive females) has been noticeably lower, indicating that non-calving right whales are still not migrating to the SA coast as readily as they used to in years gone by.

A worrying trend is that whale mothers also appear to be leaving local breeding areas earlier than normal, which could be having a negative effect on the chances of calf survival.

Southern right whales rely heavily on their foraging success and stored energy supplies to support their reproduction and migration. Their body condition, or ‘fatness’, is extremely important to ensure successful pregnancy and calf rearing. Recent research shows that southern right whale mothers have decreased in body condition by 24% since the late 1980s– clearly their feeding is less successful.