Please select your home edition
Edition
Selden

New approach to identifying false killer whale populations proves challenging

by NOAA Fisheries 13 Jan 16:06 UTC
False killer whales swim off the coast of Hawaii. © NOAA Fisheries / Adam Ü

Over the past decade, researchers have determined that false killer whales around the Hawaiian Islands have three distinct populations, one of which is endangered.

In a collaborative effort led by Yvonne Barkley, researchers recently used underwater microphones to investigate their whistle vocalizations. They examined these vocalizations to see if they could distinguish between each population. Learning more about the complexity or diversity of their calls would help scientists study their social behavior and support the species' protection.

False killer whales are a large, highly social dolphin species found throughout the Hawaiian archipelago. A combination of photographic, genetic, and satellite tag data determined that the three populations are genetically distinct and sympatric. This means each population is genetically different within the same geographic area:

  • The endangered population associated with the main Hawaiian Islands.
  • A population associated with the Northwestern Hawaiian Islands.
  • A pelagic population dispersed throughout offshore waters.
Scientists do not yet know the exact reasons why these false killer whale species separated.

Each population is managed separately due to differences in their behavior and ecology, as well as the threats that they face. While the main Hawaiian Islands population is endangered, the pelagic population interacts most with fisheries. Still, the differences between the three populations are not fully understood. Like many highly social species, false killer whales rely heavily on vocal communication for foraging, navigation, and social behaviors. This makes them an ideal species to study using passive acoustic methods.

For this study, researchers towed underwater microphones, or hydrophones, behind a ship to collect passive acoustic data during several whale and dolphin research surveys. Barkley and coauthors selected hundreds of false killer whale whistles from the recordings and measured 50 different characteristics from each whistle. They fed these whistle measurements into a machine-learning classification algorithm called "random forest" to see if it could correctly identify each whistle to a population.

The study showed that the whistle characteristics of each population were too similar for the random forest classifier to distinguish them.

However, it correctly classified whistles from the main Hawaiian Islands population more often than the other populations. This suggests that differences in whistle characteristics do exist between the smaller endangered population and the larger populations.

While the classifier did not perform as expected, the researchers gained new insight into patterns within the whistle characteristics. They can use this information to improve future acoustic classification studies for false killer whales.

Related Articles

Why do whales migrate?
Skin molt may drive migration for whales that forage in cold waters Whales undertake some of the longest migrations on earth, often swimming many thousands of miles, over many months, to breed in the tropics. The question is why—is it to find food, or to give birth? Posted on 28 Feb
Unmanned surface vehicles track marine mammals
Scientists successfully tested the feasibility of using Saildrones Scientists successfully tested the feasibility of using Saildrones to follow individual fur seals over long distances while simultaneously assessing their prey and habitat. Posted on 23 Feb
Type D: A new species of killer whale?
Biologists launched an expedition, searching for what could be a new species of killer whale In January 2019, an international team of scientists working off the tip of southern Chile got their first live look at what might be a new species of killer whale. Posted on 15 Feb
International whales of mystery
Where are the 'missing' breeding areas for humpback whales? Every year, humpback whales in the western Pacific Ocean migrate south to winter breeding grounds. Some whales spend their winters in the waters of the Mariana Archipelago, but we know less about humpback whales in the Marianas. Posted on 8 Feb
U.S. & Canada work to reduce whale mortalities
United States and Canada have a shared interest in recovering right whales A message from NOAA Fisheries Assistant Administrator Chris Oliver, who recently participated in a meeting with Canadian officials focused on the conservation and management efforts for the endangered North Atlantic right whale. Posted on 1 Feb
Investigation of gray whale strandings continues
California survey counts migrating whales for a new population assessment Gray whales have begun their annual southbound migration along the West Coast to Mexico. Science teams continue to investigate the cause of more than 200 strandings of dead and often thin gray whales during their northbound migration last spring. Posted on 26 Jan
Little relief in the deep for heat-stressed corals
New research shows coral reefs in deeper water aren't immune to warming seas and coral bleaching A team of NOAA scientists recently examined more than a thousand hot water events on coral reefs across the Pacific Ocean. Posted on 16 Jan
How to help free entangled whales in Hawaii
Course helps to better assist trained responders disentangle large whales Entanglement in ropes, nets, and other marine debris is a major threat to the humpbacks and other large whales of Hawaii. But attempting to free an entangled, multi-ton whale is inherently dangerous. Posted on 16 Jan
Announcing Mission: Iconic Reefs
A large-scale coral reef restoration effort in the Florida Keys I'm excited to let you know that NOAA Fisheries, along with NOAA's Office of National Marine Sanctuaries and other partners, have launched a coral reef restoration effort titled Mission: Iconic Reefs. Posted on 12 Jan
Pacific Islands Must-Reads of 2019
The 10 stories that resonated the most with readers In 2019, we brought you science and conservation stories covering a wide range of topics important to the Pacific Islands region. Posted on 12 Jan
Sailing Holidays 2019 - BOTTOMGrapefruit Graphics 2019 - FooterGJW Direct - Yacht 2019 - Footer