Visual health assessment of parous female southern right whales (Eubalaena australis) off the southern Cape coast, South Africa
Sandra HÃ¶rbst, Els Vermeulen and Coleen L. Moloney
Long-term monitoring of the South African southern right whale (Eubalaena australis) population has revealed a decrease in sightings along the coast and an increase of calving intervals within the last few years. As reproductive success is often linked to body condition, the purpose of this study was to conduct a visual health assessment of parous females (based on overhead photographs from the annual aerial southern right whale surveys) to detect potential links between their visual health condition and increased calving intervals as well as environmental indices of the Southern Ocean. The method used was adapted from a visual health assessment method developed for northern right whales (Eubalaena glacialis) by Pettis et al. (2004), adjusted in collaboration with southern right whale researchers from South Africa and Australia.
The main findings were:
â€¢ Health variables derived from overhead photographs were sufficient to detect visual health changes over time. Within the study period, two years (2008 and 2014) had a significant decreased visual health.
â€¢ No direct link between the visual health condition and calving intervals could be found, possibly due to the lack of data on calving intervals post-2014 as well as the fact that only calving females could be assessed with the given data.
â€¢ Significant relationships were found between visual health and Southern Ocean climate indices...