It appears that right whales increase the amplitude, or the energy in their calls, directly as background noise levels increase without changing the frequency. This suggests that right whales can maintain the signal to noise ratio of their calls in moderate levels of ocean noise.
"To our knowledge, this is the first evidence for noise-dependent amplitude modification of calls produced by a baleen whale," said Parks.
Changing calling patterns can, however, incur costs including increased energy expenditure, alteration of the signal and the information it contains, and increased predatory risks. With increased noise the effective communication range for feeding or mating will shrink and stress levels on individual animals may rise.
"Whether they can maintain their communication range in noisier environments still needs to be tested," said Parks. "Ocean sound levels will probably continue to increase due to human activities and there is a physical limit to the maximum source level that an animal can produce."
Another implication for potential changes in whale calls is that upcalls are the whale calls that conservationists use to monitor right whale populations. They do this using automated acoustic sensors that are looking for specific parameters to tease out the whale calls from other noises.
The research team cautions that "Variability of call parameters also can reduce the effectiveness of detection
|Contact: A'ndrea Elyse Messer|