Classifying Indo-Pacific finless porpoise echolocation clicks

Indo-Pacific finless porpoises are aquatic mammals mostly found in the coastal waters of Asia and are one of only two species of porpoise that lack a distinctive dorsal fin. They grow to be around 1.7 meters and often appear to be smiling on their beakless face. Despite their proximity to humans and adorable appearance, no precise estimates for their population exist, although fishing, shipping, and environmental degradation may be causing their numbers to decline.

Zhao et al. measured and analyzed porpoises’ echolocation clicks in the waters surrounding the Chinese province of Hainan. A better understanding of their sounds will allow easier and more cost-effective passive monitoring of their population.

Like bats, dolphins, and toothed whales, Indo-Pacific finless porpoises use echolocation, producing high frequency clicks and listening to the echoes, to perceive their environment.

To record these clicks, the researchers sailed on a small boat to look for the porpoises. Once they made a sighting, they sailed ahead to collect data with a six-arm star-shaped array of 13 hydrophones.

Though click features varied, they found the Indo-Pacific finless porpoises produced higher pitched clicks compared to other porpoise species, perhaps due to their smaller size.

Based on this information, the team is hopeful they can use passive acoustic monitoring to track the porpoise population and inform conservation efforts.

“Marine mammals such as the Indo-Pacific finless porpoise are generally facing more and more challenges from both human activities and climate change,” said author Songhai Li. “However, we know very little about them, including their population dynamic, distribution pattern, and even taxonomic status. We want to encourage more research and conservation effortsregarding these important, lovely, but probably critically endangered porpoises.”

Source: “Echolocation clicks of free-ranging Indo-Pacific finless porpoises (Neophocaena phocaenoides) in Hainan waters,” by Likun Zhao, Giacomo Giorli, Francesco Caruso, Lijun Dong, Zining Gong, Mingli Lin, and Songhai Li, Journal of the Acoustical Society of America (2023). The article can be accessed at https://doi.org/10.1121/10.0017655 .