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Based on both stranding and sighting records, recent data on the status and distribution of whales and dolphins in the Cape Verde Islands are presented, including records of four taxa new to the archipelago, viz. Common minke whale Balaenoptera acutorostrata, Dwarf sperm whale Kogia sima, beaked whale Mesoplodon cf. europaeus and False killer whale Pseudorca crassidens. Distribution elsewhere in the tropical eastern Atlantic and some taxonomic issues are discussed.
The abundance of humpback whales occurring around Boa Vista, Cape Verde Islands, was estimated by markrecapture modelling. Photographs of markings on tail flukes of individual whales were collected during the breeding season. Sighting histories were constructed for each individual and an abundance of 171 animals was estimated using a Jolly-Seber mark-recapture model. Correcting for known biases arising due to sex-specific behaviour and temporary emigration insofar as possible, an estimate of 260 whales was obtained. This is significantly higher than the previous estimate of 99 humpback whales from this region. Due to limited survey effort it is not known how representative the study area is of the entire Cape Verde archipelago and this estimate may be considered to be biased low and serves as a minimum estimate. The high recapture probability (0.37) coupled with the low abundance is consistent with a small local population. The low survival rate (0.86) suggests possible emigration and further studies are needed to assess connectivity between humpback whales breeding in Cape Verde and other breeding locations. The amount of exchange between groups of whales breeding in Cape Verde and adjacent areas remains unknown. It is unclear whether the abundance estimate herein applies to part of an isolated population or part of a larger and continuous one.
During August-September 2014 and 2015, yachtbased surveys were conducted in the Cape Verde archipelago with the main objective of trying to locate humpback whales Megaptera novaeangliae during the late boreal summer (Berrow et al. 2014). Spring breeding humpbacks in Cape Verde waters are known to have their feeding grounds in the high Arctic (e.g. Wenzel et al. 2009). While these animals have generally left the breeding grounds by mid-May, a number of sightings during the summer months (June- August) have raised the possibility that animals from southern stocks may occasionally reach as far north as Cape Verde (Hazevoet et al. 2011).
Gervais’ beaked whale Mesoplodon europaeus (Gervais, 1855) is restricted to the Atlantic Ocean. Although most records are from the North Atlantic, it is probably continuously distributed in deep warm waters around the equator (Mead 1989, Norman & Mead 2001). Its occurrence in West Africa is poorly known, as records are rare. It is classified as Data Deficient (Taylor et al. 2008).