Sound is very important for communication. It is especially crucial underwater, where often animals cannot rely on other senses such as vision to communicate. Marine mammals in particular use sound a great deal, whether to communicate within or between groups, detect the presence of predators, locate prey, or even orient themselves in their environment. However, increases in human activity on and in the ocean have also caused the aquatic environment to become much noisier. This article details the concerns researchers have that this increase may interfere with communication and thus have an adverse effect on marine mammal populations.
Several studies have provided examples of groups of marine mammals decreasing activity or even abandoning an area due to a noisy environment. Gray whales in Baja California abandoned a popular breeding lagoon for about a decade due to shipping and dredging in the area. Researchers studying a dolphin population in Shark Bay, Australia, noted that dolphins avoid certain foraging grounds during increased boat traffic.
Sound travels much more quickly through water than through air, which likely compounds the negative effects of noise interference. Marine mammals have developed sophisticated sound systems to communicate with each other and to orient themselves. Toothed whales, such as dolphins, tend to use high frequencies, while baleen whales use lower frequencies. The high frequencies of toothed whales are capable of finding small prey (less than 1 m) tens or hundreds of meters away. The low frequency calls are ideal for long distance communication between the highly migratory baleen whales. One study calculated that shipping noises have caused the "detectable range" of these low frequency signals has decreased from hundreds of kilometers to tens of kilometers. While marine mammals naturally have developed mechanisms to compensate for a noisy environment, the noise caused by human activity is not something they have evolved to deal with, and could have long-lasting effects on both individuals and populations as they struggle to deal with the problems caused by interference in communication. These problems include stress, lost opportunities for feeding or mating, confusion in signals (which may cause strandings in some cases), and extra expended energy as animals attempt to communicate through or over the extraneous noise.
This particular article emphasized the uncertainty factor in examining and addressing this problem. Testing the effects of noise interference on animals than can send signals hundreds of kilometers away presents obvious difficulties. The aquatic environment also makes this research much trickier, and provides fewer opportunities for study of captive or laboratory animals. The increased noise in aquatic environments remains a concern for people interested in conservation and animal welfare.
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I'm wondering about the magnitude of sound interference human activity has in oceans. From the docks, some vessels can get pretty loud. I only assume that it is even louder underwater, and with the abundance of ships in the water, communication must really be compromised in the presence of ships. Really cool article!
ReplyDeleteKevin Tse
I have heard about noise related problems for wildlife in urban environments but never in the ocean. This is a very interesting issue. I would have never considered the noise of boats as being such a big hindrance for aquatic life. Do you know what steps are being taken to deal with this issue?
ReplyDeletePosted by: Sara Weaver
I remember hearing that some whales even beached themselves in areas with a lot of man-made noise too. I think it was naval sonar or something. It's too bad that this is so hard to test and examine. Probably even harder to make rules everyone follows as well. Quieter ships could be helpful in decreasing the noise levels though.
ReplyDeletePosted by Daniel Solomon
I heard about the whales beaching themselves too due to high man-made noise level since the noise stresses and confuse them (or something like that). I don't know any solutions to such problems other than quieter boats (is that even possible in this day and age) or strict rules regulating fishing. In the documentary The Cove the Japanese fishermen take advantage of the dolphins' high sensitivity to sound by banging these metal pipes so that the noise would force the migrating dolphins into the lagoon/cove area. Since the ocean is so vast and food are sparse, I feel that these whales will suffer further from the noisy environment we created. Do the researchers see any solution to help the whales? Are there even "noise-free" places that researchers could use as a control?
ReplyDeletePosted by Leona Chan
As humans we never have to deal with hearing things through a water medium. This article is very interesting as it brings forward important information that most people would not even be aware of. This seems like a particularly difficult thing to avoid and regulate. Patrolling the waters would only exacerbate the situation. What are biologists saying needs to be done to fix this situation?
ReplyDelete-Himanshu
This is just a small example of how human's technological advances have vastly outdone those of nature. In this case (as well as many others im sure), the result is very detrimental for animals. Do you know if this has already led to the extinction of a species?
ReplyDeleteThe article did not discuss possible solutions to this problem, although it did note that in an area where shipping noise appeared to drive a particular group of whales away, they reappeared several years after the shipping had ceased, although it was shut down for economic reasons and not because of the whales.
ReplyDeleteBecause this issue is so difficult to study, it is not clear exactly how much it has affected marine mammal populations. No mention was made of extinction, but it would not be difficult to imagine this problem being a contributing factor to the severe endangerment or even extinction of some of the more threatened species.
Posted by Dana Mirsky