Although shy and somewhat elusive, the Indian Ocean humpback dolphin (Sousa plumbea) is commonly sighted in Plettenberg Bay’s nearshore waters. These dolphins can often be seen swimming along the Keurbooms and Robberg beaches, alone or in small groups of between 2 and 15 individuals. Humpback dolphins can be readily distinguished from other dolphins by the characteristic fleshy hump beneath their dorsal fin, as well as their unique surfacing behaviour of breaking the surface of the water with their snouts, or rostrums, first as they surface to breathe. These dolphins occur along South Africa’s southern and eastern coasts and are found in shallow waters of less than 25 m in depth. Unfortunately, their preference for these inshore waters makes them more vulnerable to anthropogenic threats and the species has recently been listed as Endangered in South African waters, with a likely population size of only 500 individuals.
Humpback dolphins are susceptible to threats such as coastal development, pollution, entanglement and disturbance from boats. Coastal development results in the loss of habitats that serve as important feeding areas for the species, while pollutants, such as heavy metals and organochlorines, accumulate in the blubber of marine mammals through the consumption of their prey and reduce their ability to reproduce successfully. Entanglement in the shark nets set off KwaZulu-Natal to protect bathers from sharks are also a significant threat to humpback dolphins, as a number of dolphins drown every year once becoming entangled in these nets. Humpback dolphins are also very sensitive to boat traffic and have been shown to avoid important feeding areas as boat traffic increases.
The low population numbers and vulnerability of this species to anthropogenic impacts has resulted in growing concerns over the species’ conservation in South African waters. This has led to the establishment of various research projects aiming to better understand their population size, habitat-use and movement patterns off South Africa. Such knowledge is essential for the formulation of effective conservation measures and management recommendations that will help to protect humpback dolphins.
We at ORCA Foundation/ Ocean Blue Adventures aim to contribute to the conservation of this endangered species by developing a dedicated humpback dolphin research project in Plettenberg Bay. The project, once established, will focus on collecting humpback dolphin sighting and photo-identification data, as well as environmental data, which will be used to get a better understanding of the abundance, spatial distribution and movement patterns of humpback dolphins in Plettenberg Bay. The project will be designed and led by a recent addition to the Ocean Blue team; a masters graduate in zoology who spent the last 3 years studying these animals along the Garden Route. Ocean Blue Adventures/ ORCA Foundation also intends to form strong collaborations with other research institutions and organisations currently involved in humpback dolphin conservation.
The project urgently requires financial assistance in order to buy the camera equipment essential for conducting photo-identification research. Any donations towards the project would be greatly appreciated and can be done so by contacting [email protected].
Written by: Danielle Conry
For further reading:
- ATKINS, S. A., PLÖN, S., CONRY, D., PISTORIUS, P., COCKCROFT, V. & ELWEN, S. 2016. A conservation assessment of Sousa plumbea. In: The national Red List of mammals of South Africa, Swaziland and Lesotho, (eds) M. F. Child, E. Do Linh San, D. Raimondo & H. Davies-Mostert. South African National Biodiversity Institute.
- BEST, P. B. 2007. Whales and dolphins of the southern African subregion. Cambridge University Press, Cape Town, South Africa.