China Pollution

Seeing in the Dark: How porpoises hear in one of the world’s busiest rivers

(October 21, 2013) Scientists are using medical technology to study the endangered Yangtze finless porpoise and their critical sense of hearing, used for navigation, to understand how these mammals are managing in the very busy and loud waters of China’s high-traffic Yangtze River. “In a noisy environment, they’d have a hard time hearing their prey or their friend. It makes it more difficult for them to conduct basic biological activities such as foraging, communicating, and navigating in the river,” said biologist and lead author of the survey, Aran Mooney.

Published by ScienceBlog on October 21, 2013

The Yangtze finless porpoise, which inhabits the high-traffic waters near the Three Gorges Dam in China, is highly endangered, with only about 1,000 animals alive today. Scientists from Woods Hole Oceanographic Institution (WHOI) and their Chinese colleagues are using medical technology to shed new light on this species’ critical sense of hearing in a waterway punctuated by constant shipping, dredging, and underwater construction.

“We want to understand how they may be impacted by noise,” said Aran Mooney, a biologist at the Woods Hole Oceanographic Institution (WHOI) and a lead author on the study published online this week in the Journal of Experimental Biology.

Marine mammals such as dolphins and porpoises rely on their hearing to navigate, communicate, and find food in the typically deep, dark, and murky waters they inhabit. But what we know about how they hear has been limited to research on just a few species, particularly bottlenose dolphins, because they are relatively common in marine parks and aquaria. This can be a problem when natural resource managers and regulators base aquatic noise pollution policy decisions on data from a limited number of “representative species” when there are over 70 species of toothed whales or odontocetes that live in a variety of aquatic habitats.

This new research shows how variability in the size and shape of toothed whales’ heads across species can result in marked differences in how they receive sound and how sensitive they are to a range of frequencies.

“We’ve learned that there’s more variation than we’ve taken into account on how different species hear,” Mooney said.

He and colleagues at WHOI and the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan, China applied live acoustic sensitivity examinations and computed tomography (CT) scans on Yangtze finless porpoises to begin to identify the auditory variability among toothed whales.

Read the story in full at the publisher’s website here.

Further on this topic

China surveys Yangtze dolphin as extinction looms

Last refuge of rare fish threatened by Yangtze dam plans

China’s beleaguered Yangtze

China activists say dam will kill off rare fish

Pollution harming Chinese sturgeon

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