WASHINGTON, Nov. 15 (UPI) -- U.S. researchers say dolphins found weakened or dead near shore often have one thing in common -- they are nearly deaf.
University of South Florida scientists say in a marine world where hearing is as vital as sight dolphins unable to use sound to locate food or find family members often wind up weak and disoriented, The Washington Post reported Monday.
The National Oceanic and Atmospheric Administration says 1,200 to 1,600 whales and dolphins are found stranded off the U.S. coast each year.
Without the ability to hear sounds, researchers say, dolphins can be helpless.
Some scientists think the problem is most likely a combination of old age, birth defects and disease but others point to man-made marine "noise."
Powerboats and huge oceangoing ships fill the water with engine noise. Oil and gas exploration efforts create noise from seismic tests of the seabed. Navy exercises reverberate with the sounds of explosions and sonar.
"These animals that are very finely tuned acoustic machines are now having … to deal with noises, with sounds that their ancestors never knew," says Randall Wells, a senior conservation scientist at the Chicago Zoological Society.