Featured Image Credit: Bahnfrend via WIkimedia
By Emily Persico
Noise pollution is a relatively new disturbance to ocean life. In the long lives of some marine mammals, the circus of noise that we create underwater has increased so much that some creatures have seen the reach of their vocalizations shrink from 1,000 to just 100 miles in their lifetime. We are drowning out the living symphony of sound that once dominated the sea, and replacing it with a cacophony of man-made machinery that causes undue stress, serious injury, and even death to the ocean’s vulnerable creatures.
In a recent study led by Terrie Williams of UC Santa Cruz, scientists have found that different swimming patterns, particularly those induced by sonar, are energetically demanding and hard to stop. For many dolphins and beaked whales, this could mean beach stranding and, eventually, death.
“Not all strokes are the same in terms of energy expenditure for swimming dolphins, and this has enormous implications for the cost of flight from adverse stimuli by wild cetaceans,” explains Williams.
Williams and his research team found that startled animals use 30.5% more energy in their escape compared to relaxed swimming. Even once they escape from the imminent danger caused by noise pollution, dolphins and beaked whales are unable to outswim the stress. Oftentimes, they continue at this energetically costly pace for nearly two hours after the risk has passed.
This research was made possible by six well-trained bottlenose dolphins. These clever cetaceans participated in swimming tests and maneuvered through a maze of hoops while scientists tracked their fin beats, oxygen exhalation, and recovery times, collecting data that is essential in the preservation of our changing ocean.
“In view of the number of cetacean mass strandings across the globe and the increase in human presence in the oceans, such data are critical,” says Williams. “The animals in our care provided that opportunity.”