| Summary: | S. Tomé and Príncipe archipelago has been reported as a possible breeding ground for humpback whales (Megaptera novaeangliae) since the whaling period. More recently, the sightings of humpbacks whales have become more frequent off the S. Tomé Island which may indicate a recovery of the populations or the whales returning to a former concentration area of the Southern Hemisphere population. Our objective was to study the occurrence of humpback whales group types and surface activities in this area. Between July 2002 and January 2003, a total of 110 boat-based surveys were conducted around the S. Tomé Island and Rolas Island. When we sighted the animals, recordings of GPS positions, group size, group composition and activity were made. Single whales and groups of mother and calf were the more common group types, but we could also observe pairs, competitive groups and mother and calf with principal escort. Singles were more frequent in August and September, and pairs and mother and calf groups were more frequent in October and November. The observed surface behaviors were normal respiration, breachings, flippers and tail behaviors and resting. The occurrence of humpback whales in this region, between August and November, probably corresponds to a breeding period of a South Hemisphere population feeding in the Antarctica waters. The presence of calves and the occurrence of behaviors typical of breeding periods support this hypothesis, as well as the existence of shallow waters and protected zones. There are plans to study these whales genetically and acoustically to determine stock affiliation.
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