Our local ocean sustains a pretty remarkable array of marine wildlife. As our visiting gentle giants slowly leave our shores to return to their southern feeding grounds off Antarctica, we can still count on regular sightings of our other favourite marine mammals – dolphins! Throughout the year we enjoy wild encounters with three different dolphin species, namely, bottlenose dolphin, the common dolphin and the Indian Ocean humpback dolphin.
By far the most prolific of the dolphin species occurring in our area is the inshore bottlenose dolphin, a delightful species that often treats us to above-the -surface acrobatics. Sometimes, usually during the summer months, we are witness to epic spectacles of enormous pods of common dolphins moving through the area, usually when there is an abundance of bait fish present.
The dolphin species we see most often is the Indian Ocean humpback dolphin, but this is not because there is an abundance of the species, on the contrary, these dolphins are in fact very rare, with local populations numbering only about 500 individuals. Their overall numbers throughout their range are in serious decline and they are now listed as Endangered on IUCN Red List.
The reason we see them so frequently is because one of their favourite feeding spots is the shallow and sheltered waters of Buffalo Bay, a spot along our coastline that we visit on a daily basis. The fact that they seem to thrive in this particular area may be due, in part, to the fact that around the corner from Buffalo Bay is the Goukamma Nature Reserve and Marine Protected Area where commercial fishing is prohibited.
The Indian Ocean humpback dolphin (Sousa plumbea) is a member of the Delphinidae family which, until very recently, was thought to belong to the Indo-Pacific humpback dolphin (Sousa chinensis) species. Humpback dolphins occurring in the Indian Ocean from South Africa to India are now recognized as taxonomically distinct from those that occur further east, based on genetics, skeletal morphology, external morphology and colour.
Indian Ocean humpback dolphins are medium sized dolphins, measuring up to 2.5m long, and are easily identified by the prominent hump and elongated dorsal fin on their backs. This shy, shallow water species is usually found congregating in small groups (usually no more than 10), mostly around rocky reefs or sand gullies, usually within less than 400 meters of the shore in waters rarely more than 30 metres in depth. Sadly, this propensity for shallow coastal waters makes them extremely vulnerable as a species.
Their specific habitat preferences (shallow waters close to shore) and restricted distribution range, severely reduces their resilience as a species. They are adversely affected by any environmental changes and anthropogenic threats (degradation resulting from human activity).The leading cause for their decline is incidental mortality from entanglement in fishing gill nets (cetacean bycatch), but the loss, degradation and pollution of our coastal habitats is also a major factor. The milk from lactating mothers has been found to contain high levels of toxicity from human pollution.
Unfortunately, nothing is really being done to mitigate the threats encountered by this species and evidence suggests therefore that declines will likely continue into the future. It is predicted that 50% of the total population will be lost over the next three generations. It is facts like these that should make us all wake up to the sobering reality of our negative impacts on life on earth.
Our only hope is that our coastal waters will continue to sustain healthy populations of this rare and precious cetacean. Next time you see a small pod of humpback dolphins swimming in the surf at Buffalo Bay, give a thought to the vulnerability of the species and remember, everything is connected. Tread lightly on our earth.