Report of the Southern Right Whale Aerial Surveys 2025

The southern right whale (Eubalaena australis) population that calves off the coast of South Africa has been the focus of intensive scientific monitoring since 1969. Initiated following the cessation of commercial whaling, this long-term research program employs annual aerial surveys to assess demographic trends. In 1979, the methodology was enhanced through the integration of photoidentification techniques, and other technologies as time progressed, described in Best (1981; 1990; 2011), Best et al. (2001) and Vermeulen et al. (2025). This advancement enabled researchers to distinguish individual whales based on their unique callosity patterns and skin pigmentation features, including brindle coloration, grey blazes, and white patches (Payne et al., 1983). The surveys prioritise the identification of nursing females with calves (cow-calf pairs) and individuals exhibiting distinctive physical traits.

Spanning over 46 years, this comprehensive dataset has become a critical resource for modelling and estimating key demographic parameters of the southern right whale population (Best et al., 2001; 2005; Brandao et al., 2023). Over the past decade, survey results have indicated a decline in reproductive performance, evidenced by lengthening calving intervals and decreasing calving rates (Vermeulen et al., 2025). This trend has been particularly pronounced since 2010, coinciding with a marked reduction in the number of unaccompanied adults observed during annual aerial counts (Vermeulen et al., 2025).

Collectively, these findings underscore the irreplaceable value of long-term studies that track identifiable individuals, as such datasets are essential for quantifying the relationship between reproductive performance and ecological variables over meaningful temporal scales (Vermeulen et al., 2025). The continued monitoring effort is not only critical to provide insights into the current status of the population, but also serves as a foundational tool for understanding broader ecological dynamics affecting population recovery, and guiding conservation strategies.

This report provides the results of the 2025 southern right whale aerial surveys.