On Friday, 31. March, a mass stranding of 38 common dolphins (28 adults, 10 juveniles, 12 males, 26 females) was reported to have occurred along a remote stretch of coast under the protection of Addo Elephant National Park, between Woody Cape and Sundays River mouth, Algoa Bay, Eastern Cape. The local authority dealing with all whale, dolphin and seal strandings, the Port Elizabeth Museum at Bayworld, was alerted. A site visit on Friday by the South African National Parks (SANParks) and the Department of Agriculture, Forestry and Fisheries (DAFF) ascertained that the animals most likely had been stranded 4-5 days previously and were all dead.
A team of 7 people, comprising members from Bayworld, and the Cetacean Research Unit at Nelson Mandela University (NMU) set out from Port Elizabeth early on Saturday to respond to this unusual stranding event. Staff and volunteers from SANParks provided valuable support.
The animals were spread out over a 2km stretch of coastline, comprising both mature males and females, as well as a number of juvenile animals and one calf. The response team was split up into three teams, each comprising an experienced marine mammal researcher and a number of interns and volunteers. Over two days, the teams collected basic information, such as sex, length and maturity status, from each individual dolphin. In addition, carcasses were dissected to obtain vital information on the cause of death of these dolphins.
Dr. Stephanie Plön, a member of the African Earth Observation Network (AEON) at NMU, has been researching dolphin and whale health in Eastern Cape and KwaZulu-Natal waters for the past nine years and indicated that, while the animals were partially decayed, all appeared healthy and in good condition. However, multiple samples were collected from all individuals for further analyses.
Dr. Greg Hofmeyr, curator of the marine mammal research collection at Bayworld, secured tissue samples as well as skeletal material for the extensive marine mammal research collection at the museum. This data will add important information on the taxonomy of this species in South African waters.
Dolphins are at the top of the marine food chain and as such are important indicators of the health of our oceans. No obvious cause for this unusual stranding event could be determined, but no evidence of foul play was found. Future analyses may provide additional information. However, in order for the researchers to pinpoint the cause of individual stranding events it is imperative, that strandings are reported as soon as possible to the local authorities so that better information can be gathered. Investigations into the health status of both incidentally bycaught and stranded dolphins and seals has been supported by the International Fund for Animal welfare (IFAW) to Dr. Plön for the past four years.
This section of the coastline appears to be a unique spot on the southern and eastern coasts of South Africa for mass strandings with four other such events recorded by Bayworld since 1977. However, this stranding event comprises the largest one yet. Dr. Plön and Dr. Hofmeyr regularly attend to marine mammal stranding events along the Eastern Cape coastline, each one providing a challenge in on its own. While such events are tragic for the animals concerned, they are very valuable for research on these animals. Members of the public are encouraged to report any marine mammal strandings (whales, dolphins, seals), dead or alive, to the Bayworld stranding hotline: 071-7242122.