Spatial Ecology of Humpback Whales (Megaptera novaeangliae, Cetacea-Balaenopteridae) from the Mexican Central Pacific1

Abstract: The Northeast Pacific subpopulation of the humpback whale migrates every winter-spring to Mexican waters to breed; however, their use of habitat in the Mexican Pacific remains unknown. We investigated the spatial ecology of the humpback whale in the Mexican Central Pacific (MCP) and connections with other Mexican areas. Surveys to search for humpback whales were conducted in winter-spring 2010–2019. The number of individuals, type of group, and activities were recorded, and flukes were photographed to differentiate individuals observed at Mexican areas. A total of 15,384.4 km were travelled in MCP waters and 462 groups of humpback whales were sighted. The dominant group were single and pairs, observed mainly off Colima coast. The principal activity was traveling, and the least frequent activity was likely-feeding. A total of 420 individuals were photo-identified, and through their sighting history, it was possible to calculate that only 2.14% (1.67–12.5%) of them showed site fidelity; this indicates that the MCP is a transit zone to other reproductive areas. A photographic catalog of 798 individuals from Socorro Island was also analyzed to compare with the MCP catalog, but there were no photo-recaptures between two areas. The comparison with catalogs of 302 individuals from the Guerrero coast and 1,459 individuals from Banderas Bay resulted in interchange indices of 1.02E–06 and 2.93E–07, respectively. The MCP is part of the breeding ground of humpback whales, but it seems to be a transit area that does not offer optimum conditions for permanence and sustained habitat use, possibly due to regional anthropogenic activities.