Humpback Whales (Megaptera novaeangliae) in the Cape Verde Islands: Migratory Patterns, Resightings, and Abundance

Abstract

Effective conservation of the endangered North Atlantic humpback whale (Megaptera novaeangliae) which breeds in the eastern North Atlantic around the Cape Verde Islands off West Africa requires information about their spatio-temporal distribution, population size, and migratory patterns. Understanding temporal distribution is particularly important as annually only a portion of this population migrates between high-latitude summer feeding grounds and their breeding grounds. During the winter/spring months between 1990 and 2018, we conducted cetacean surveys targeting humpback whales. Survey periods varied from 30 to 90 days in duration. Collectively, we obtained fluke photographs from 267 individually recognizable humpback whales from this region. These fluke photographs have been compared and included in the North Atlantic Humpback Whale Catalogue which has nearly 11,000 individual flukes photographed from throughout the North Atlantic. Photo-identified individuals from the Cape Verde Islands population have been previously photographed/recaptured on high-latitude feeding grounds in northern Norway (including the Barents Sea and Svalbard archipelago), Iceland, Azores, Tenerife, Canary Islands, and Guadeloupe (southeast Caribbean). Those whales resighted off Azores and the Canary Islands were most often observed in May/June and were presumably en route to their northern feeding grounds. The largest number of recaptures from high-latitude feeding grounds were 44 individual humpbacks (44/267 = 16.4%) identified in both Cape Verdean and Norwegian waters. Twelve humpbacks (12/267 = 4.5%) were identified in the Cape Verde Islands and Iceland. Based on photo-identification of humpbacks in the Cape Verde Islands, we report a high inter-annual resighting rate with 131 whales observed in more than one year (131/267 = 49.1%). While this is partly due to high probability of detection in a small population, these results nonetheless also suggest strong site fidelity to this breeding ground. The estimated total number of individual whales occurring in this eastern North Atlantic breeding area between 2010 and 2018 was 272 (SE 10).