Featured Research

from universities, journals, and other organizations

Yangtze finless porpoise: Highly endangered mammal trying to cope with constant shipping, dredging and underwater construction

Date:
October 21, 2013
Source:
Woods Hole Oceanographic Institution
Summary:
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 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.

A Yangtze finless porpoise at the Institute of Hydrobiology, Chinese Academy of Sciences in Wuhan, China.
Credit: Photo by Aran Mooney, Woods Hole Oceanographic Institution

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.

Porpoise populations are declining rapidly worldwide. The Yangtze finless porpoise shares the same habitat as the Baiji river dolphin, seemingly the first toothed whale that has become extinct by humans. Like all toothed whales, the Yangtze finless porpoise do not have external ears. It hears when sound reverberates through its head, throat, jaw, and acoustic fat within the mandible.

Scientists conducted hearing examinations on two Yangtze finless porpoises that were originally from the wild, but have resided at the Institute of Hydrobiology in Wuhan for six and 14 years. The hearing exams were similar to hearing tests regularly given to infants.

"Porpoises, like babies, can't tell us if they can hear in their left or right ear, so we measure their hearing physiologically from the surface of the skin," Mooney said.

Broadband clicks and low, mid, and high frequency tones within a normal threshold were transmitted through silicon suction cup sensors on nine parts of the animal's head and body. The scientists non-invasively recorded the porpoises' neuron responses.

The exam results showed that the finless porpoises are sensitive to sound nearly equally around their heads while bottlenose dolphins and beluga whales exhibit a substantial 30-40 decibel difference in sound sensitivity from their jaw to other parts of their head.

The researchers then CT scanned two stranded Yangtze finless porpoise specimens at a hospital associated with Wuhan University to gather information on their skeletal and tissue structure.

"We had the opportunity to scan them in Wuhan and work with the Chinese radiologists, which was very interesting to get a chance to see their facility and how they operate in comparison to WHOI," said Darlene Ketten, a biologist and director of the Computerized Scanning and Imaging (CSI) facility at WHOI. "We've done a lot of these here. But, they had never scanned any porpoises."

The CT images revealed that the acoustic fat pads in Yangtze finless porpoises are thicker and more disc-like in shape compared to the elongated shape of these fat deposits found in other toothed whales.

"Now that we have some hearing data, we are working on modeling how the conformation of these pads and their dimensions and shapes relate to the frequencies and sensitivities," Ketten said.

The morphology of the Yangtze finless porpoise implies that it hears omni-directionally, which means it may have difficulty discerning signals among the clutter of constant noise.

"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," Mooney said.

The differences in hearing sensitivities between the finless porpoise and other species such as bottlenose dolphins and belugas indicate further auditory variations among species. Mooney believes that effective management strategies must consider these variations. He would like to broaden this study to include examinations of other toothed whales, such as the Risso's dolphin, harbor porpoise, and white-sided dolphin, and continue to examine noise impacts on the endangered Yangtze finless porpoise.


Story Source:

The above story is based on materials provided by Woods Hole Oceanographic Institution. Note: Materials may be edited for content and length.


Journal Reference:

  1. T. A. Mooney, S. Li, D. Ketten, K. Wang, D. Wang. Hearing pathways in the Yangtze finless porpoise, Neophocaena asiaeorientalis asiaeorientalis. Journal of Experimental Biology, 2013; DOI: 10.1242/jeb.093773

Cite This Page:

Woods Hole Oceanographic Institution. "Yangtze finless porpoise: Highly endangered mammal trying to cope with constant shipping, dredging and underwater construction." ScienceDaily. ScienceDaily, 21 October 2013. <www.sciencedaily.com/releases/2013/10/131021104246.htm>.
Woods Hole Oceanographic Institution. (2013, October 21). Yangtze finless porpoise: Highly endangered mammal trying to cope with constant shipping, dredging and underwater construction. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2013/10/131021104246.htm
Woods Hole Oceanographic Institution. "Yangtze finless porpoise: Highly endangered mammal trying to cope with constant shipping, dredging and underwater construction." ScienceDaily. www.sciencedaily.com/releases/2013/10/131021104246.htm (accessed July 23, 2014).

Share This




More Plants & Animals News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Stone Fruit Listeria Scare Causes Sweeping Recall

Stone Fruit Listeria Scare Causes Sweeping Recall

Newsy (July 22, 2014) The Wawona Packing Company has issued a voluntary recall on the stone fruit it distributes due to a possible Listeria outbreak. Video provided by Newsy
Powered by NewsLook.com
Michigan Plant's Goal: Flower and Die

Michigan Plant's Goal: Flower and Die

AP (July 22, 2014) An 80-year-old agave plant, which is blooming for the first and only time at a University of Michigan conservatory, will die when it's done (July 22) Video provided by AP
Powered by NewsLook.com
Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Newsy (July 22, 2014) The 83 new genetic markers could open dozens of new avenues for schizophrenia treatment research. Video provided by Newsy
Powered by NewsLook.com
CDC Head Concerned About a Post-Antibiotic Era

CDC Head Concerned About a Post-Antibiotic Era

AP (July 22, 2014) Sounding alarms about the growing threat of antibiotic resistance, CDC Director Tom Frieden warned Tuesday if the global community does not confront the problem soon, the world will be living in a devastating post-antibiotic era. (July 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins