| Summary: | Occurrence and encounter rates of marine mammals in the waters around the MalpeloIsland and to the continent. This work compiles a decade (2001-2010) of marine mammal sightingsin the Malpelo Fauna and Flora Sanctuary (FFS) and the area between the island and mainland coast.Four separate sources of data were consulted, which used visual searching during cruising efforts whileMalpelos surrounding waters were surveyed from a vantage point. Seven species were identified in theFFS: October and November were the months with higher species richness. Tursiops truncatus had thehighest encounter rates (17.78 groups/100 h), followed by Megaptera novaeangliae (1.62) and Stenellaattenuata (0.88). These species were usually within 6 km from the island. Other species seen around theisland include Stenella coeruleoalba, Delphinus delphis, Stenella longirostris and Zalophus wollebaeki.On the other hand, thirteen species were identified during cruises, and March and April were the monthswith the highest species richness. Megaptera novaeangliae had the highest encounter rate (5.94),followed by T. truncatus (3.30), S. attenuata (3.08), D. delphis (3.08) and S. coeruleoalba, Globicephalamacrorhynchus and Orcinus orca, each one with 0.66. Other species seen during the cruises include Stenobredanensis, Pseudorca crassidens, Grampus griseus, Peponocephala electra, Physeter macrocephalusand Ziphius cavirostris. Megaptera novaeangliae were associated to the continental shelf, T. trunctausand D. delphis to oceanic waters, and S. attenuata to both the continental shelf and oceanic waters.Delphinus delphis was more abundant in intermediate waters, during the first trimester (January-March),while T. truncatus was the most abundant species around the Sanctuary during all seasons, suggestingthat is the same population. The latter was also the only species found all year round in both zones(around the island and in oceanic waters), and encounter rates did not change across years. Megapteranovaeangliae had a seasonal presence (mostly June to November) with a higher abundance during thethird trimester (July-September), both around Malpelo and the transect. The presence of humpbackwhales calves suggests that Malpelo is used for reproductive purposes. This new information about themarine mammals found in Malpelo FFS and the area between the island and the continent contributes tothe understanding of these species in Colombian waters.
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