Innovative methods employed by UP’s Mammal Research Institute Whale Unit has led researchers to make new discoveries about the migratory, reproductive and foraging behaviour of southern right whales.

World Whale Day was recently observed to raise awareness of the important role that whales play in our marine ecosystem and the multiple threats they face due to human activities. It is also an opportune time to highlight the cutting-edge work that the Mammal Research Institute Whale Unit (MRIWU) at the University of Pretoria (UP) has been carrying out.

Multiple baleen species of whale can be found along the South African coastline, each contributing to the country’s rich, diverse marine life. Whales can be split into two groups: toothed whales, which have teeth, and baleen whales, which have baleen plates. Baleen plates are long, flexible strips of keratin that extend from the gum in the upper jaw downwards and form part of the whales’ filter feeding apparatus. While some baleen whales, such as southern right and humpback whales, are strongly migratory and undergo annual migrations from high-latitude feeding grounds to more temperate calving grounds, others, such as Bryde’s whales, can be found year-round in South Africa’s coastal waters.

UP’s MRIWU conducts research on these species using a variety of techniques that allow for opportunities to gather vital information on these marine mammals. The unit has been monitoring the South African southern right whales population since 1969, and because of their proximity to the coast during their calving season, researchers have been able to untangle certain aspects related to southern right whales reproduction and population growth rates through observational data. This ongoing monitoring has revealed drastic changes in the past 10 years, including reduced calving rates, altered migration patterns and a decline in body condition.

However, because observational data comes with a fair amount of uncertainty, new and innovative methods have been developed. For example, baleen plates have been sampled and analysed for chemical markers, such as hormones and stable isotopes. The results have revealed interesting facts about southern right whale reproduction: it was found that they experience a gestation period of 15 to 18 months (instead of 12 months as previously believed) and that conception occurs at higher-latitude foraging grounds rather than on coastal calving grounds.

Owing to logistical difficulties associated with offshore research, the migratory and foraging behaviour of southern right whales are poorly understood. As such, satellite transmitters are being deployed just before the whales embark on their annual migration. Through better knowledge of where their preferred foraging habitat is situated, the unit can assess whether the recent reductions in calving rates and body condition can be attributed to reduced prey (krill) availability due to environmental alterations in their offshore feeding grounds.

As humpback whales follow a similar life history, with annual migrations between the coastal waters of southern Africa and high-latitude foraging grounds, a new project has been initiated by the MRIWU to assess the effects of climate variability on calving rates and the health of humpback whales. Find more information at whalesandclimate.org.

In addition, the MRIWU is expanding on research into the inshore Bryde’s whale population of South Africa. These baleen whales range across the coastline of the country, feeding predominantly on sardine and anchovy, which largely dictate the movements of individuals between areas. Although one of the most elusive species to study, genetic research methods are being employed to fill in some of the most critical knowledge gaps for South Africa’s largest resident marine predator. Results of recent research has suggested an overall viability despite their small population size and isolated distribution. Since this population feeds on some of the country's most economically important fish species and holds a national listing as “vulnerable”, this research is imperative in improving on conservation and fisheries management protocols. 

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