Balaenoptera omurai

Common Name: Omura’s whale

General Description: It is one of the smaller and more streamlined baleen whales with a ‘V’ shaped rostrum and broad flukes having a straight trailing edge. The shape of the dorsal fin is variable but it tends to be high, highly falcate and backswept. There is one prominent rostral ridge (while Bryde’s has three ridges) from the blow-hole till almost the tip of the snout. Accessory ridges may also be present but are not prominent. The body coloration is two-toned, with a darker back and lighter venter. The lower jaw is highly pigmented on the left while the right lower jaw is white, one of the major distinguishing characteristics of the Omura’s. The anterior edges and the inner surfaces of both the flippers are white. Ventrally the flukes are white with black margins. Pale irregular chevrons are present anterior to the dorsal fin on both the sides, the one on the right being more prominent. The right side also has a conspicuous blaze with 2-3 stripes bisecting it that runs over the eye and goes up till the back. There are 80-90 ventral grooves that extend till behind the umbilicus.

omura1Omura's whale sighted for the first time in India, in the Andaman Islands  @ Akshay Malavi

Size: Adults - Females of Omura’s whales grow slightly larger than the males and are known to reach lengths of upto 12m. Calves - 3.5-4m long. Weight - Tentatively upto 20,000kgs.

omura2Omura's whale sighted for the first time in India, in the Andaman Islands  @ Akshay Malavi

Appearance At Sea: A study of the species, off Madagascar, reported sightings of the whale mostly as singletons or in pairs. Loose aggregations although rare, were also documented from the same area. The small size of the species usually makes it possible to view both, blowhole and the dorsal fin when the whale surfaces. This species is not known to lift their flukes during a dive. The Omura’s whale was described as a new species only as recently as 2003, prior to which, the existing specimens were grouped as a ‘pygmy’ form of the Bryde’s whale (Balaenoptera edeni). Hence, much still needs to be learnt about the ecology and life-history of the species.

Found In: This species has been observed to prefer the shallow shelf habitats in the depth range of 4-202m, although it is suggested that they may be inhabiting deeper waters as well.

5 May 2015 Observed in the coastal waters of South Andaman Island off of Port Blair. Malawi Akshay, Game fisher
2014 An individual beached in Car Nicobar Island. Sitaram S., Fisherman.

The species distribution until recently was thought to be restricted to the eastern Indian ocean and western Pacific but presence of a population to the north-west of Madagascar might indicate a more extensive range. Sightings from southern Sri Lanka and Andaman and Nicobar islands in 2017 establish its presence in the northern Indian Ocean. A single stranded animal was reported from Qeshm Island, Iran.

World Distribution: From the limited known records of the species, the Omura’s whale has a distribution in the tropical waters of the eastern Pacific and the Indian ocean.

Could Be Confused With: The Omura’s whale is most likely to be confused with the Brydes whale, Balaenoptera edeni and young Fin whales Balaenoptera physalus, but they can be distinguished as follows:

Omura’s whale 12m One prominent ridge Highly falcate, rising at a steep angle and swept back Asymmetrical coloration on lower jaw with a white right lower jaw.
Chevrons, anterior to the dorsal fin (Right side more prominent).
Blaze present on right side.
Not known to fluke up
Bryde’s whale 16.5m Three ridges on head Variable, steep rise, pointed and often notched. White throat.
Blaze absent.
Rolls over with arched tailstock
Fin whale (not reported from Indian waters) 27m One ridge on head Falcate but rising at a shallow angle.
Ridge present between dorsal fin and flukes.
Asymmetrical coloration on the lower jaw.
Multiple chevrons on back.
Not known to fluke up.

Diagnostic Features: The shape of the fin, single ridge, white right lower jaw and the various colouration patterns as a whole are required for the identification of the species as Omura’s whale.

Stranded specimen: 180-210 short and broad baleen plates are present, which is the lowest number amongst all baleen whales. They are yellowish white at the front, black in the rear, with the middle ones being of an intermediate tone.