Photo courtesy of www.en.wikipedia.org
It is true that whales and their close mammal cousins don’t have to work in a factory, listen to MP3 players, or ride snowmobiles, but it is also true that they can be exposed to very noisy life under the sea. This has led many groups to examine the ecology and effects of under-water noise on marine life, and this includes the Acoustical Society of America.
The effects of environmental noise on marine mammals and marine life in general are poorly understood- a complete understanding would necessitate good models of water surface tension, underwater sound propagation over large distances, and the susceptibility of various species to this (ship based) noise exposure. Coming to grips with these issues and physical phenomena are a life’s work and indeed many dedicated acousticians and biologists are doing just that.
In a recent study in Biology Letters American and UK scientists examined the feeding and diving behaviors of ten humpbacked whales and found that the whales dove less deeply and had fewer side feeding periods when noisy ships passed overhead. During diving, humpbacked whales roll to the side in order to feed, and the frequency of these rolls was also significantly reduced during shipping traffic.
The scientists used sensors attached to the whales that simultaneously measured elements of movement as well as the sound level of the noise over time.
The authors found that “These results are among the first [to] support that ship noise can impact humpback whales’ foraging, making this source of disturbance a management concern,” and that “Chronic impacts of even small reductions in foraging efficiency could affect individual fitness and translate to population-level effects on humpback whales exposed to ship noise in critical foraging areas.”
The authors noted that these aberrant feeding and diving behaviors were noted at night as well as in daytime even though there is significantly less night time shipping traffic.
