Rare Omura whales found off Madagascar

Rare Omura whales found off Madagascar

Scientists have found the largest population of a rare tropical whale species. Omura's whales were feared extinct until October, and now twice as many of them have been discovered off Madagascar.

Omura's whale or the dwarf fin whale (Balaenoptera omurai) is a species of rorqual about which very little is known.Before its formal description, it was referred to as a small, dwarf or pygmy form of Bryde's whale by various sources. The common name and specific epithet commemorates Japanese cetologist Hideo Omura.

Led Dr. Salvatore Cerchio from the New England Aquarium, about 80 Omura s whales of Madagascar were spotted in November off the coast. That doubled the number of sightings in the entire research record of these whales and included five mother/calf pairs and several whales seen before.

In 1999 and 2000, an unidentified species of rorqual was repeatedly seen in the waters of Komodo National Park. On 26 September 2000, an unidentified balaenopterid was sighted off Rarotonga by the group of Nan D. Hauser. It was said to move through the water like a sei whale, the size resembled a minke whale, the head looked like a blue whale, and the chevron resembled a fin whale. Later, it was suggested to possibly be an Omura's whale, but it lacks the asymmetrical coloration and upright, very hooked dorsal fin typical of species. In May 2008, a possible Omura's whale was observed during a birding tour off northern New Zealand. Underwater footages of possible Omura's whales were also taken on Koh Tachai pinnacle, Similan Islands National Park in 2013, and off Nosy Be, Madagascar in 2012.

In October 2015, an international team of scientists, led by Cerchio of the New England Aquarium and Woods Hole Oceanographic Institution, released the first images and field observations of the species from a population off northwest Madagascar. Repeated sightings in that same area suggested that this is a resident group. A month later, Cerchio returned to Madagascar just as extraordinary levels of tiny shrimp known as euphasiids were being found in the water. That hinted that there might be plenty of whales around.

The 80 whales offered researchers plenty of subjects to study, allowing them to gather reams of audio and video data of things like their feeding behavior as well as mother/calf pairs and the species distinct irregular marking and colorings around their head.

The team also collected two weeks of continuous acoustic data from remote recorders including dense choruses of Omura s songs.

It also took two years for a team of conservation biologists, including NMU professor Alec Lindsay, to provide the first-ever scientific documentation of the extremely rare Omura s whale living in the wild off the coast of Madagascar.

At first, we thought they were Bryde s whales, an understandable mistake because of the similar size and habitat, but then with good photographs and underwater video, we noticed they more closely resembled the description of Omura s whales, Cerchio said.

Rare Omura whales found off Madagascar