Could the Whales’ Song Be Silenced? : Noise study: Cetacean lives are guided by hearing; don’t risk causing damage without first knowing all the consequences.
How can we be guardians of the natural world when it is we who threaten it? How can we protect other animals when we don’t know what they are? I ask these questions not despairingly but practically, because every day we have to make decisions in ignorance. How can we assess the importance of what is not known?
I’m thinking about a project called ATOC (Acoustic Thermography of Ocean Climate) and the difficulty of measuring its impact on marine mammals. The project--postponed for hearings--proposes to measure global temperature changes by broadcasting intense sounds into the ocean for 20 minutes every four hours. The project would proceed for two years, with a likely extension to 10. The initial broadcasting sites are Monterey Bay and Hawaii, where several kinds of whales congregate.
Whales are acoustic animals. Their lives are informed not by what they see but by what they hear. When their acoustic environment deteriorates, so do all the basic mechanisms of their sociality--their ability to meet one another; to establish, maintain and adjust the social relationships that support breeding; to locate food; to care for their young and to navigate.
The ocean is a noisy place at best, but it is vastly noisier now than in all of the animals’ previous evolutionary history. Windows of relative quiet in which communication can occur are becoming a scarce and perhaps a limiting resource.
I think that the excellent team that has been assembled to document the impact of the project on local marine mammals has been given an impossible task. They can document short-term reactions to the broadcast sounds, but they cannot document long-term behavior changes because we don’t know what is normal. We lack the knowledge that would enable us to distinguish between changes that are dangerous to marine mammal populations and changes that are sustainable.
The results of a 15-year study of the songs of humpback whales by me, Roger Payne, Peter Tyack and Linda Guinee suggest another dimension of whales’ lives that could be disrupted. For reasons we do not understand, singing is a complex behavior in humpback whales. Their long, complex songs evolve rapidly over time. The songs are learned and the changes passed on by learning. Thus humpback whales, like human beings, are carriers of culture and the culture evolves differently in separate populations. Whale songs include structures and devices we find in human song and poetry--for instance, rhyming.
Singing is always present when humpback whales are courting. Why they sing such elaborate songs, why the songs change and where the changes come from is not known. The lowest, farthest-traveling notes in the songs lie in the same frequency range as the ATOC sounds. These parts of the song may contain information of significance to distant whales. We don’t know howimportant it might be if they lose their function.
We don’t know how humpback whales choose their winter singing grounds, or to what extent they can move if the places they are in become intolerable. We know even less about most other marine mammals. We have no way to assess how much “play” there is in each aspect of their lives, from their basic demography and distribution to their cultural behavior. We only know that acoustic communication is involved at every level.
I’m opposed to a plan that would insert intense sound into the communication channels used by marine mammals. I do, however, support the investigation of global warming by less dangerous methods. There must be ways to study the effects of chemical pollution in the atmosphere without increasing acoustic pollution in the ocean. There must be ways that are more consistent with the lesson we are learning from global warming--that polluting of all sorts is dangerous beyond our powers of prediction.
