The west coast of South Africa is part of the migratory corridor for humpback whales (Megaptera novaeangliae) sub-stock B1, and also a migratory and feeding area for sub-stock B2. So-called super-groups of the species (defined as 20+ individuals feeding close to each other) have been sighted yearly in the area since 2011. During the breeding season of the species, the Mammal Research Institute – Whale Unit, University of Pretoria, performed research activities in the area. For an overview of the occurrence of humpback whale super-groups, our team performed an aerial survey on 7 November 2023, covering the main area used by the super-groups in previous years, from Cape Columbine and Cape Point.
15 groups of humpback whales were sighted, of which one was a super-group, with an estimated group size of 26 individuals. Following that, from 16 November to 05 December 2023, the team was dedicated to boat-based activities. In total, nine boat days were performed during this period, summing 52 h 55 min of activities at sea. In total, 20 groups of humpback whales were logged. From these, three were super-groups, with group sizes ranging from 35 to 70 individuals. We obtained 47 biopsy samples of humpback whales, fluke pictures of a minimum of 70 different individuals, seven faecal samples, 34 zooplankton samples, and four seawater samples. During the fieldwork in the area, other cetacean species were sighted including southern right whale (Eubalaena australis) (n=2), orca (Orcinus orca) (n = 1), dusky dolphin (Lagenorhynchus obscurus) (n=8), and Heaviside’s dolphin (Cephalorhynchus heavisidii) (n=12). The data and samples obtained will help with a better understanding of aspects such as stock structure, diet, and sex of the humpback whale individuals forming the super-groups.
