Abstract
For over two centuries there were no records of Blue Whales Balaenoptera musculus in the Philippines. Whalers recorded Blue Whales in the Philippines in the 19th century, and the next confirmed sighting in the country was of a mother and calf in 2004. Since then 33 subsequent Blue Whale sightings of potentially one individual were recorded between 2004 and 2019, all within the central region of the Philippines around the Bohol Sea. This individual, recognized through photo-identification, was sighted on at least 13 occasions during eight different years: 2010, 2011, 2012, 2015, 2016, 2017, 2018, and 2019. The geographic location and timing of the sightings (January to July) suggest that Blue Whales in the Philippines may extend the outer range edge of the Indo-Australian population that migrate between western Australia, Indonesia, and East Timor. Blue Whale sightings in the Bohol Sea coincide with times of high ocean productivity, although further investigation is needed to determine if they are actually feeding in this region. Acoustic studies and photo-identification matching with other Blue Whale catalogues will clarify the stock identity of Blue Whales in the Philippines and their relation to the rest of the Blue Whale population, with implications for the conservation of this endangered species across multiple jurisdictions.
Highlights
Blue Whales Balaenoptera musculus Linnaeus, 1758 are currently classified as Endangered by the International Union for the Conservation of Nature (IUCN) (Cooke 2018), and sightings in the Philippines are rare
Left side of the dorsal fin of the blue whale encountered in A—2015 © Jom Acebes | B—2016 © Angelico Tiongson | C—2017 © Maita Verdote | D—2012 © Josh Silberg | E—2010 © Jom Acebes | F—2019 © Angelico Tiongson, showing identical semi-circular indentation
November, covering a total area of approximately 2,092km2 of the northern Bohol Sea (Table 1 and Fig. 2), there was a paucity of Blue Whale encounters
Summary
Blue Whales Balaenoptera musculus Linnaeus, 1758 are currently classified as Endangered by the International Union for the Conservation of Nature (IUCN) (Cooke 2018), and sightings in the Philippines are rare. Historical data suggests Blue Whales occurred in Philippine waters (Acebes 2014), their presence was not reported between the end of the 19th century (1870) and 2004. The first confirmed documentation of a Blue Whale in the Philippines occurred when a mother and calf were filmed off Pamilacan Island in the Bohol Sea in February 2004 (Dolar & Sabater 2012; Acebes 2014). Photographs of a baleen whale seen in the same area in May 2004 were confirmed to be a Blue Whale (Sabater 2005). These sightings were brief and no detailed information on the animal and its behavior were recorded
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