Mini Report: Rare Omura’s whale documented at the Raja Ampat project!
Written by Serena Stean & Mette Rosenberg Carlsen
On the 30th April, 2023 our Raja Ampat Project staff and interns were treated to a once in a lifetime sighting of the elusive Omura’s whale (Balaenoptera omurai). Spotting a number of whales feeding on the surface, the interns quickly geared up and entered the water and were delighted when one of the whales came in for closer inspection whilst sub-surface feeding. This is believed to perhaps be the first underwater footage shot of this species in Indonesia, with previous sightings recorded from above with a drone in the Misool region (see end of article), and stranded whales in other parts of the archipelago.
After some initial head scratching by the science nerds at IOP and some serious emailing to pinpoint the species – identification was confirmed by a number of experts in the field including Dr. Simon Pierce (Marine Megafauna Foundation – https://marinemegafauna.org) who has previously documented the species underwater in Madagascar on citizen science platform iNaturalist (image below) and Dr. Heike Vester who previously studied cetaceans in Raja Ampat (Ocean Sounds – https://www.ocean-sounds.org) – both scientists were genuinely delighted to see our footage and confirm our initial in-house identification.
Photograph: Omura’s Whale (Balaenoptera omurai) iNaturalist submission by Dr. Simon Pierce, taken in Nosy B, Madagascar. (https://www.inaturalist.org/observations/131637346)
The Omura’s whale was described just 20 years ago (Wada, Oishi & Yamada 2003), with the first comprehensive study on ecology, behavior and conservation needs on in Madagascar published in 2015 (Cerchio et al. 2015), and more recently the first study on the global distribution of the species (Cerchio, Yamada & Brownell.2019). You can distinguish Omura’s whale from the closely related Byde’s whale complex as they have just one central ridge, in comparison to three.
As a species it is listed as Data Deficient on the International Union of the Conservation of Nature’s Red List (IUCN 2023), and is protected under Appendix I of the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES 2023).
Although diet, habitat, and ecology of Omura’s Whales has not been well studied, stomach contents taken previously have found euphasids, crustaceans and fish remains (Kawamura 1977; Cericho and Yamada 2018), with lunge-feeding observed in Madagascar (Cerchio et al. 2015). Acoustic calls have been identified and recorded (Cerchio 2017) which will hopefully help uncover the boundaries of distribution and whether the populations prefer coastal, oceanic habitats, or both (IUCN 2023).
Suggested by a number of studies the Dampier Strait has long been thought to be an important cetacean migration corridor (Wilson et al. 2010, Ender et al. 2014, Sahri et al 2021), with known migrations of a number of large whale species (Cawardine 2002).
Since commercial whaling was outlawed by the International Whaling Commission in 1986 it is unlikely the Omura’s whale is targeted except in artisanal fishing, with the biggest threats to its conservation likely to be similar to other rorqual species; bycatch, vessel strikes, noise pollution, entanglement, petroleum exploration and production and coastal industrial development (Cerchio & Yamada 2018; Cerchio, Yamada & Brownell 2019; Ender et al 2014; Thomas et al 2015).
Image: Map showing global distribution of reported Omura’s whales accounts by diagnostic verification method (Cerchio, Yamada & Brownell 2019)
With only 11 previous documented photographic sightings from Indonesia (Cerchio, Yamada & Brownell 2019) we are delighted to have captured such a rare charismatic animal in our data and immediately tried to see how we could contribute to other’s datasets with the sighting. We are now in contact with the Indonesian NGO Cetacean Sirenian Indonesia (CETASI – http://www.cetasindonesia.org) who we will be sharing any recorded visual identifications of cetacean species from all projects moving forwards, adding another arm to our growing citizen science datasets and collaborations. Our Species of Interest list now set to expand once more to account for the insane marine biodiversity that our Raja Ampat project is bringing to our existing species lists.
We hope it’s not too long before this and other whale species decide to reveal themselves, stay tuned for more in the future!
Carwardine M. (2002) Whales, dolphins and porpoises. London: Smithsonian Handbooks and Dorling Kindersley Ltd.
Cerchio, S. and Yamada, T.K. (2018) ‘Omura’s Whale’, Encyclopedia of Marine Mammals, pp. 656–659. doi:10.1016/b978-0-12-804327-1.00186-2.
Cerchio, S. et al. (2015) ‘Omura’s whales (balaenoptera omurai) off northwest Madagascar: Ecology, behaviour and conservation needs’, Royal Society Open Science, 2(10), p. 150301. doi:10.1098/rsos.150301.
Cerchio, S. et al. (2017) ‘A first description of rhythmic song in Omura’s whale (balaenoptera omurai)’, The Journal of the Acoustical Society of America, 141(5), pp. 3544–3544. doi:10.1121/1.4987495.
Cerchio, S., Yamada, T.K. and Brownell, R.L. (2019) ‘Global distribution of Omura’s whales (balaenoptera omurai) and assessment of range-wide threats’, Frontiers in Marine Science, 6. doi:10.3389/fmars.2019.00067.
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Sahri, A. et al. (2020) Using cost-effective surveys from platforms of opportunity to assess cetacean occurrence patterns for marine park management in the heart of the Coral Triangle [Preprint]. doi:10.1101/2020.06.19.160887.
Thomas, P. O., Reeves, R. R., and Brownell, R. L. (2015). Status of the world’s baleen whales. Mar. Mamm. Sci. 32, 682–734. doi: 10.1111/mms.12281
Wada, S., Oishi, M. and Yamada, T. (2003) ‘A newly discovered species of living baleen whale’, Nature, 426(6964), pp. 278–281. doi:10.1038/nature02103.
Wilson, J., Rotinsulu, C., Muljadi A., Wen W., Barmawi, M., Mandagi, S. (2010) Spatial and Temporal Patterns in Marine Resource Use within Raja Ampat Region from Aerial Surveys 2006. A report by the Marine Program of the Asia Pacific Conservation Region, The Nature Conservancy. 3/10.
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