Scientists Confirm Sightings of Endangered Pygmy Blue Whale in Southern Philippine Waters

For years, a group of researchers have been tracking a mysterious whale that they initially thought belonged to another blue whale subspecies.

A solitary whale frequently spotted in the Bohol Sea in the southern Philippines has long had a nickname: Bughaw, or “blue.” Now, thanks to recently published research, the whale also has a confirmed species and subspecies, knowledge that could shift understanding about the distribution of whale populations throughout the southern Pacific.

Bughaw, a pygmy blue whale, known to frequent the Bohol Sea. Until recently experts thought this species did not venture into Philippine waters. Image courtesy of Jo Marie Acebes / BALYENA.ORG.

True to his name, Bughaw is a blue whale (Balaenoptera musculus), a species that until recently experts thought did not venture into Philippine waters. Given the whale’s location and relatively small size, estimated at 19-22 meters (62-72 feet), he has been identified as a pygmy blue whale (B. m. brevicauda), a different subspecies from the true blue whale (B. m. musculus), which can grow up to 30 m (98 ft).

No blue whale sightings were reported in the Philippines between 1870 and 2004. The first time was when a mother and calf were spotted by a TV crew in the Bohol Sea. The pair were initially identified as Bryde’s whales (B. edeni), a species known to visit the area. Since then, there have been 33 documented blue whale sightings in the Philippines, all in the Bohol Sea.

The Bohol Sea, north of the Philippines’ southernmost island of Mindanao, is considered one of the country’s important marine mammal areas (IMMAs). It’s also a key marine biodiversity area. Jo Marie Acebes, co-author of the study recently published in the Journal of Threatened Taxa, says the proper identification of Bughaw highlights the need to properly manage this region, which is threatened by unsustainable fishing practices. She says managing “commercial fisheries is just one part of it but is a really significant one, not just for the whales but for the coastal communities who depend on marine resources.”

Bughaw has a semicircular indentation on the left side of his dorsal fin, which in blue whales is relatively small and positioned far back on the body. His tail has notches both on the left and right tips; the left side of his body has identical blotches. Blue whales, in general, have a large, broad, U-shaped head; a prominent fishy ridge; and project a tall, dense, broad blow.

There are four recognized bluewhale subspecies: B. m. musculus, which inhabits the North Atlantic and North Pacific; B. m. intermedia in Antarctic waters; B. m. brevicauda (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean; and B. m. indica in the northern Indian Ocean. These subspecies are acoustically separated into 10 distinct populations.

The Philippines lies near the areas where B. m. brevicauda, B. m. indica, and B. m. musculus are known to range, the study notes. The timing of the blue whale sightings in the Philippines, from January to June, narrows down the identification further, suggesting Bughaw is a pygmy blue whale. The Indo-Australian population of B. m. brevicauda is known to migrate west during this period, passing Australia, Timor-Leste and Indonesia, where it ends its migration by June. Finding Bughaw within the Bohol Sea, north of Indonesia, means the Philippines, and particularly the Bohol Sea, may be an extension of the northern migration path of the Indo-Australian population, the study says.

The Bohol Sea could be a feeding ground for blue whales, according to the study. The sea’s distinctive underwater topography, as well as its connections with deep basins (the Pacific Ocean to the east and the Sulu Sea in the west), contribute to productivity of marine life in the area. Its relatively short continental shelf — the shallow, sun-kissed seabed that runs from the shoreline until it drops off into deeper waters — makes it more of a pelagic, or open ocean, zone than a coastal one.

These conditions, coupled with water movements, cause upwelling, a process in which cold water rises from the deep, bringing to the surface nutrients that makes the area an ideal fishing ground, Acebes says. The time when the blue whales arrive in the area coincides with “months of high productivity,” the study notes.

While Bughaw has been spotted in various spots around the region, researchers say there’s a need to conduct more studies to confirm whether the Bohol Sea is also a breeding ground for the species.

Researchers say their combined survey efforts are insufficient to identify blue whale movements and habitat use in the Philippines, since those surveys are done in different months. So far, they have covered 2,092 square kilometers (808 square miles) of the northern Bohol Sea, with another 29,000 km2 (11,200 mi2) left to survey.

“It is very important to keep searching and, the more people looking out at sea, the better,” Acebes says. Her group has been collaborating with three others for more than a decade. “By pooling together our survey effort and data, we were able to get a better idea of the extent of where the blue whale was found and more importantly, we were able to do a photo ID of Bughaw.”

Acebes says five of their encounters with the blue whale happened because local contacts informed them of sightings, which prompted them to look for the whale.

“After years of wondering if that encounter in 2010 during their vessel-based survey was just a fluke (pun intended), it is good to finally confirm that the species is found in our country’s waters,” Acebes says, adding that the next step will be to find a way to confirm the discovery through genetic sampling and analysis.

Ultimately, the researchers say, further acoustic studies matched with photo-identification techniques can help catalog the blue whales of the Philippines, which, in turn, will have implications for both the conservation of this endangered species and its migration routes.

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