Tuesday, February 2. 2010
Do you remember how in the last (and first) species blog, I explained how some genera of cetacean were in the process of speciation? Another really great example of this is within the genus Sousa where there is currently substantial debate by scientists around the world as to the number of species in this genus.
Initially it was thought that there was only one species, the Indo-Pacific humpback dolphin or Sousa chinensis, that could be found in coastal areas, primarily near a freshwater outflow, from West Africa all the way east to the South China Sea. Many however, consider there to be at least two species; (1) Sousa chinensis – found from the east coast of India, through the Indo-Malay archipelago and east to Australia; and (2) Sousa plumbea – found from South Africa to India. Studies, both morphological and genetic, are currently being carried out to determine the various “splits”.
One “split” that has now been accepted, from both morphological and genetic evidence, is that the animals found in the waters of West Africa are a distinct species, known as the Atlantic humpback dolphin or Sousa teuszii
Compared to the Indo-Pacific humpback dolphin (whether it is one species or two) very little is known on the Atlantic humpback dolphin and dedicated research to date has been very thin on the ground. WDCS has been helping to change this and for the past few years has been funding researcher Caroline Weir to investigate the distribution and behaviour of these dolphins off the coast of Angola.
Both intentional and non-intentional takes are serious threats to the Atlantic humpback dolphin and are thought to be unsustainable. As it is coastal in nature, the Atlantic humpack dolphin faces additional human-induced threats such as habitat destruction and pollution. The consensus is that this species exists as distinct populations throughout its range and for this reason the magnitude of the threats it faces in certain areas are of great concern for the long-term conservation of the species. Caroline’s work therefore has been critical in gathering (and publishing) information on the occurrence of this vulnerable species, possibly one of the most endangered of all delphinids as high levels of direct exploitation and bycatch continue to threaten the small, geographically distinct populations - or at least those that we know about!
Currently listed as Vulnerable by the IUCN and prioritised for research by the IUCN Cetacean Specialist Group (CSG), the Atlantic humpback dolphin is also listed on CITES (Convention on International Trade in Endangered Species) Appendix I – meaning no international trade is allowed, and on CMS (Convention on Migratory Species) Appendix I and II, meaning international co-operation is needed for the conservation and protection of the species in question.
There have been few dedicated studies into the 30 plus species in the West African region and more is known about some populations in the remote Antarctic than off the coast of Africa. Entanglement in fishing nets, coastal development, pollution and destruction of habitats have caused the populations of dolphins and small whales in the area to decline rapidly.
Range countries however have taken some initial steps to work together to protect their small cetaceans. At the end of 2008, under the auspices of CMS during the 2nd inter-governmental meeting of WATCH (West African Talks on Cetaceans and Habitats) 15 country representatives (Angola, Benin, Cape Verde, Chad, Congo Brazzaville, Cote d'Ivoire, Equatorial Guinea, Gabon, Ghana, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Togo) and three non-governmental organisations (WDCS included) signed a ground-breaking agreement for the protection of small whales, dolphins and manatees, which could save the lives of thousands of animals and lead to a safer future for many species.? ?The agreement is the first whale and dolphin conservation agreement in Africa covering a vast area stretching from Morocco to South Africa, and encompassing the Atlantic islands of Macaronesia. As partner to CMS, WDCS was instrumental in helping to make this agreement, which is the fourth of its kind, a reality. Other agreements focus on the conservation of whales and dolphins in the Black and Mediterranean Seas (ACCOBAMS), Baltic and North Seas and surrounding area (ASCOBANS) and the Pacific Islands Region.
So … if all this talk of West Africa has got you asking for more then how about yet another publication by Caroline where she reviews all the existing literature on cetacean occurrence in the region. If anyone is interested in copies of the following papers then you can contact either me (leave a comment via the blog) or Caroline directly (www.ketosecology.co.uk).
Weir, C.R. (2009). Distribution, behaviour and photo-identification of Atlantic humpback dolphins (Sousa teuszii) off Flamingos, Angola. African Journal of Marine Science, 31(3): 319–331.
Weir, C.R. First description of Atlantic humpback dolphin (Sousa teuszii) whistles, recorded off Angola. In Press, Bioacoustics.
Weir, C.R. Cetaceans observed in the coastal waters of Namibe Province, Angola, during summer and winter 2008. In Press, Marine Biodiversity Records.
Weir, C.R. (2010). A review of cetacean occurrence in West African waters from the Gulf of Guinea to Angola. Mammal Review, 40(1): 2-39.
And so I believe that’s enough for everyone to be getting with for the moment – I’ll be back with more species news soon!!