Omura, the elusive whale detected over a casual dinner in Malaysia

By Louisa Ponnampalam, Ph.D.

It was a regular night, like any other night for the MareCet team in March 2021. Our team was in the field in Mersing, Johor, and had met up with some colleagues based in the area for dinner. As we chatted over soup and satay, our friend Nazirul casually mentioned seeing a pile of whale bones on Pulau Dayang, Johor a few days prior while he was there for work. My immediate instinct was to ask him if he had taken any photographs. To my relief, he replied “of course”, and proceeded to show me the photographs he took of that pile of bones. Nazirul informed me that a local villager on neighbouring Pulau Aur had found the whale’s remains washed ashore at Teluk Jong, on the western side of the island, probably in 2017 (the villager could not recall the exact date or year). Later on, the bones were transferred to Pulau Dayang, where it remains today.

Just a pile of bones on Pulau Dayang, or, was it? Photo credit: Nazirul Amin

The secret clues contained in bones

It is amazing what bones can tell us sometimes. All around the world, scientists have made discoveries of new species or species occurrences simply from examining bones. It goes without saying that examination of bones and skeletal remains need some expertise or training, nonetheless, the point to be made here is that there is more than meets the eye sometimes, in a pile of bones.

As I looked at a photograph of the whale’s skull, my eyes automatically zoomed in to its right side, to a vertical area that is a part of the brain case known in science as the parietal, where I noticed a hole (scientifically known as the foramina parieto-squamosa). A-hah! It was immediately evident to me that this was an Omura’s whale (Balaenoptera omurai). The foramina parieto-squamosa is one of the most obvious key defining skull morphological features in an Omura’s whale that differentiates it from the skull of a Bryde’s whale (Balaenoptera edeni) (the latter being a species that has overlapping distribution with the Omura’s). That said, I still had a tiny ounce of doubt as to whether I was 100% accurate. I thought to myself, “what if the hole I see on the parietal is merely a crack in the bone, resultant from the degraded condition of the skull?” Nazirul had no other photos of the left parietal to show me, for me to confirm if the foramina parieto-squamosa was present there too.

Back at my desk, I opened up some references that showed the differences between a Bryde’s whale skull and an Omura’s whale skull. I then compared the shape of the posterior end of the maxilla as well as the nasals in the references I had with that of the skull in the photograph. I became further convinced that these skull and bones were that of an Omura’s whale. Though being a scientist, I had to be absolutely sure, so I decided to reach out to Dr. Tadasu Yamada, a world renowned whale taxonomist and former curator at the Museum of Nature and Science in Tokyo, Japan, to obtain confirmation on the species identification of that specimen shown to me in that photograph. Yamada sensei, as I often refer to him, was one of the three scientists who had scientifically described the Omura’s whale and published their findings in 2003.

A rather significant specimen

In less than an hour, I received an e-mail reply from Yamada sensei saying:

“I would say this is B. omurai. As you mentioned we can see foramina parieto-squamosa. In addition, morphology of the parietal, posterior end of the maxilla are additional data telling us this is omurai.”

I was so excited to receive his confirmation, and proud too that I had managed to determine the species correctly!

So what is the big deal about this particular Omura’s whale specimen that washed ashore on Pulau Aur? Or what does its identification mean for marine mammals in Malaysia? To date, there remains very little information about the occurrence and distribution of this elusive baleen whale species in Malaysia’s maritime waters. This identification of the skeletal remains from the photographs taken in Pulau Dayang thus constitutes only the second confirmed record of this species in Malaysia. The first confirmed record of Omura’s whale in Malaysia came from a partial carcass that washed ashore in Cherating, Pahang, in 2008. Similarly, based on photographs I had of the carcass, showing its single rostral ridge clearly, and then later via examination of its skull, I had identified the specimen as an Omura’s whale in 2010, with the identification also confirmed by Yamada sensei. The skull of that whale is now kept at the South China Sea Repository and Reference Centre of Universiti Malaysia Terengganu. That first record of the Omura’s whale in Malaysia was subsequently included in an updated checklist of marine mammals in Malaysia, published in 2012 in the peer-reviewed scientific journal, The Raffles Bulletin of Zoology. Both records of the species in Malaysia are of dead animals from the east coast of Peninsular Malaysia, and there are yet any records of the species from the west coast of Peninsular Malaysia, or from Sabah and Sarawak.

While cetologists (scientists who study cetaceans, i.e., whales, dolphins and porpoises) with enough experience encountering Omura’s whales and Bryde’s whales at sea are able to tell both species apart easily, to the untrained eye, both species look rather alike. I cannot help but to wonder if Omura’s whales are seen by industry personnel working offshore in the Malaysian South China Sea more often than is realized. The MareCet team has sighted Bryde’s whales on several occasions during field surveys around the Langkawi Archipelago, which led to the establishment of The WHALE Project in 2019 to collect scientific information on the species in the area. However, the quest to sight a live Omura’s whale still eludes our team, and our mission to find them continues.

What is an Omura’s whale?

By this point, I have mentioned the name Omura’s whale quite extensively, and one might already wonder what else is there to know about this elusive species? As stated earlier, the Omura’s whale was first described in 2003, by Dr. Tadasu Yamada and his colleagues Dr. Shiro Wada and Dr. Masayuki Oishi, making it one of the newest whale species in town, as it were. Their investigations were based on eight unidentified Balaenoptera whale specimens caught by Japanese whaling vessels in the late 1970s in the Solomon Sea and near Cocos Islands, and a female whale that stranded on Tsunoshima Island, Japan, in 1998. The species was named in honour of the late Dr. Hideo Omura, a prominent Japanese cetologist who had begun studying the detailed biology of balaenopterid whales (baleen whales from the Genus Balaenoptera) since the 1930s and contributed a wealth of knowledge on these animals that spend all their lives at sea. A few years after the species was formally described, another group of researchers found that the Omura’s whale is descended from an ancient lineage of whales, sharing a common ancestor with blue whales at one point in time, before diverging on to its own evolutionary path about 17 million years ago. Due to its relatively small size, the species was often categorized as a “small-form Bryde’s whale” prior to its taxonomic classification as B. omurai. However researchers have since discovered that the Omura’s whale’s traits differ completely from Bryde’s whales and should never be likened to being called a type of Bryde’s whale.

Some of the key defining external features of an Omura’s whale are:

1) a single rostral (on top of the head) ridge (as opposed to three rostral ridges found in Bryde’s whales);

2) asymmetry in lower jaw colouration, with the left lower jaw being dark in colour while the right jaw is white or pale in colour;

3) a blaze on the right side of the body and an asymmetrical chevron (V-shaped mark) on both sides of the body; and

4) a falcate dorsal fin.

Where baleen whales are concerned, this species is one of the smallest, measuring up to 12 m in body length. Data from the 1970s whaled specimens suggest that the species has a lifespan of at least 38 years, although more data is needed on its life history.

The video of an Omura’s whale in Madagascar captured by Dr Salvatore Cerchio of the Omura’s Whale Project, posted onto the SciNews Youtube channel

A review of all available information on Omura’s whales has revealed a global species distribution in at least 95 locations across 21 range states, from mostly tropical waters in the western south Atlantic Ocean all the way across to Oceania. However, it appears that detailed field studies have only been conducted in Madagascar to date, with most of what is known about the species’ ecology derived from the studies there. The International Union for the Conservation of Nature (IUCN) lists the Omura’s whale as Data Deficient (DD) on its Red List of Threatened Species. The species remains one of the least known and least studied of baleen whales, owing to a lack of live sightings and perhaps its distribution in areas that are further offshore which are not easily accessible to most researchers.

Everyone can be a citizen marine mammal scientist

With only two records of Omura’s whales in Malaysia, both derived from dead specimens, our team will be on the lookout for more records and live sightings of the species. We would like to build up the local ecological knowledge of this species and to contribute to the global database and information gaps. To achieve that, everyone can assist us in this mission, by becoming citizen marine mammal scientists — be our eyes on the coast or at sea whenever you are out there, and help us collect new information by reporting any whale sightings (or even dolphins, porpoises and dugongs for that matter) to us. You can very easily report your sighting, along with any photographs or videos of the animal(s) to us via our online sighting reporting form at https://cutt.ly/reportasightingtomarecet or give us a call at +6011 1577 6802.

MareCet is an NGO dedicated to the research and conservation of marine mammals and their habitats in Malaysia.

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