Marine Mammals

Gabon’s coast is home to a remarkable diversity of marine mammals. Some are resident, occupying a variety of marine habitats, while others are migratory species, spending only a part of the year in Gabonese waters. Of particular interest is the humpback whale (Megaptera novaeangliae), which feeds in the cold and food rich waters of the southern ocean but migrates to tropical waters during the southern Hemisphere’s winter to breed. They occur in Gabonese waters between the months of June and November, peaking in August. During the breeding season they can put on a spectacular show as they have a variety of prominent behaviours at the water’s surface, including breaches (leaps into the air) as well ‘fluking up’ or lifting their tails when they dive, revealing the patterned under-surfaces of their tails. The patterns on their tails are unique to each whale and provide researchers with a chance to identify individual whales, and therefore to calculate their population size, and study various behaviours.

Another remarkable species is the Atlantic humpback dolphin (Sousa teuszii) which is rare and endemic to the tropical and sub-tropical waters of the Atlantic coast of Africa (from southern Morocco to Angola). They are found in only a few small and isolated populations, and are at grave risk of extinction mostly from habitat degradation and being caught in fishing nets. The total population size has never been effectively estimated but it is thought that there are less than a two or three thousand individuals remaining. It is also one of the least known dolphin species. Gabon has wild and largely intact coastal and estuarine ecosystems, and therefore provides a safe haven for this species. The transboundary protected area of Mayumba-Conkouati, of southern Gabon and the northern Republic of Congo is one of the most important areas of all for the Atlantic humpback dolphin.

Other species commonly found in Gabon include a variety of oceanic dolphins including the common dolphin (Delphinus capensis), the Atlantic spotted dolphin (Stenella frontalis), the pantropical spotted dolphin (Stenella attenuata) and the common bottlenose dolphin (Tursiops truncatus). Other larger species include the killer whale (Orcinus orca), false killer whale (Pseudorca crassidens), at least one species of beaked whale (Ziphius cavirostris), the sperm whale (Physeter macrocephalus) and the Bryde’s whale (Balaenoptera edeni). We know of several others as well, and to date at least 25 species are known to occur, either frequently or occasionally, in Gabonese waters, while we anticipate finding others as our work continues.

Marine mammals in general are facing ever increasing and more complex threats, which include the effects of industrial activities, chemical pollution, increasing numbers of fishing boats which pose both a direct ‘bycatch threat’ as well as competition for food, and ever increasing amounts of vessel traffic. Many of these activities also emit enormous amounts of noise into the world’s oceans, posing a major source of disturbance for a group of animals that rely more on sound rather than sight. Atlantic humpback dolphins face even more direct threats as they are hunted in parts of West Africa and populations have become fragmented as a result.  For most marine mammal species we still lack a basic understanding of their population status and their basic biology, making it hard to both assess the impacts of anthropogenic threats and mitigate their effects.

In Gabon and the wider Gulf of Guinea region a variety of threats are known and include entanglement in fishing nets, ship strikes, and habitat loss (for instance in the area of Libreville). In order to improve the protection of these vulnerable species it will be necessary to know more on key aspects of their ecology, including our understanding of their distribution, their breeding cycles, their population sizes and their vulnerability to the various threats. Without this information it becomes very difficult to implement effective management strategies. We work closely with government and industry to mitigate any impact on the important marine mammal populations in Gabon’s waters. We also work more widely in the region, with active projects in Angola and Congo, both of which are also visited by the same humpback whales that breed in Gabon. Congo in particular has been found to share important populations of cetaceans with Gabon, (particularly) the Atlantic humpback dolphin. We also support measures to ensure the growing whale-watching tourism industry has a low impact on breeding whales.

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