A few minutes later, the truck gets closer, and the sirens become so loud that trying to maintain conversation becomes futile. So, you wait until the sound of the sirens fades into the distance once more. But what if the raucous sirens remained close by all afternoon, and you had to wait for several hours before you could carry on with conversation? What if this happened nearly every day?
It turns out that this is a reality for some whales. A study found that when bowhead whales in the Alaskan Beaufort Sea were exposed to airgun blasts from ships doing seismic surveys used to locate oil and gas reserves, the animals increased their rates of calling to try to be heard over the blasts when they were distant and relatively faint.
But as the seismic vessel got closer to them, the whales sharply decreased their call rates, eventually ceasing to call altogether. To carry out a seismic survey, ships tow along several airgun arrays that typically fire off every 10—20 seconds , over periods of days, weeks, or months, albeit not continuously. If the source level of a sound increases by 10 dB, it means that it gets 10 times more intense. So, the sound of seismic airguns is about a million times more intense than a blue whale call—powerful enough to deafen the largest animal in the world if it happens to be near an active seismic vessel.
Lastly, we should never become complacent about the state of our knowledge Katona An article by R. Reeves quoted some Pilgrims who arrived in North America in They wrote at that time, "Cape Cod was like to be a place of good fishing; for we saw daily great whales, of the best kind for oil and bone, come close aboard our ship, and, in fair weather, swim and play about with us.
What must it have been like to be able to sail among these large mammals as they ambled through the water? Unfortunately most of us will probably never again be able to experience this. Whales are not like California condors, where captive breeding efforts can be employed. Because they are surface feeders, they are especially vulnerable to pollution. An oil refinery in the Bay of Fundy, for example, puts right whales and countless other wildlife species at risk of experiencing the toxic effects of an oil spill.
Northern right whales tend to be docile creatures despite their size of about 17 m, and They do not attack a human unless they feel threatened. They also appear to be playful creatures, breaching out of the water imagine the power needed to get tons airborne , and slapping the surface with their large fins. Some observers even suggest that they stick their tails up out of the water so that their large tail flukes catch a breeze, allowing them to sail.
We can not afford to lose this great creature. Recent work on genetic variation in right whales suggests that Pacific populations of what has been considered Eubalaena glacialis represent a distinct species which is more closely related to southern right whales, Eubalaena australis.
Therefore, northern right whales, Eubalaena glacialis , should not be considered to occur in the Pacific ocean. It is the second largest ocean in the world after the Pacific Ocean. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a now extinct synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
Iteroparous animals must, by definition, survive over multiple seasons or periodic condition changes. Compare to phytoplankton. Chapman, J. Mayo, C. Canadian Journal of Zoology, 68 , pp. Murison, L. Canadian Journal of Zoology, 67 , pp. Payne, R. Natural History, 1 , pp.
Reeves, R. National Parks and Conservation Magazine, 2 , pp. Natural History, 4 , pp. Leatherwood, S. Sierra Club Press, San Francisco. Cummings, W.
Right Whales. New York, N. Ellis, R. The Book of Whales. Knopf, Inc.. Evans, P. The Natural History of Whales and Dolphins. Katona, S. Washington, D. Rosenbaum, H.
Brownell, M. Brown, C. Schaeff, V. Portway, B. White, S. Malik, L. Abstract The focus of this thesis is the use of sound for communication by the North Atlantic right whale Eubalaena glacialis. The surface active group SAG is the predominant social interaction in this species for which use of sound has been documented. Different group compositions in SAGs indicate that both potentially reproductive and non-reproductive groups have been combined under one labeL.
Sound production in SAGs suggests that females form and maintain the groups by producing Scream calls. Males produce Upcalls to advertise their presence as they come into a group or when the female is on a dive. Males may use Gunshot sounds as threat signals to other males in the group or potentially as reproductive advertisement signals to the female.
Some calves produce Warble sounds in SAGs. This may be limited to female calves. Investigate Marine Animals How is sound used to study marine mammal distribution? How is sound used to estimate marine mammal abundance? How is acoustics used to monitor Arctic marine mammals? How is sound used to protect marine mammals?
How is sound used to study the distribution of marine fishes? How is sound used to measure plankton? How is active acoustics used in fisheries research and management? How is sound used to study coral reefs? How is sound used to identify ecological hotspots? Study Weather How is sound used to measure rainfall over the ocean? How is sound used to measure wind over the ocean? National Defense How is sound used to find submarines?
How is sound used to monitor nuclear testing? How is sound used to monitor and defend harbors? Science Tutorial: How do you characterize sounds? Science Tutorial: How does sound in air differ from sound in water? Rossby Dr. Miller Dr. Benoit-Bird Dr. Au Dr. Tutorial: How can we moderate or eliminate the effects of human activities? Description Aerial photograph of North Atlantic right whale and calf. Right Whale Listening Network. Scripps Institution of Oceanography, Voices in the Sea.
References Kenney, R.
0コメント