If dolphins can see, why do they need sonar?
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Sonar has a few advantages.\n\nDolphin eyes and brains are set up in a way that each eye, and each part of the brain sees only in one direction. In other words, a dolphin can see to its left and its right at the same time, with different parts of the brain, but never can it see one image with both its eyes. This means that it can't see ahead very well, and that (and this is just a guess) it cannot see 3 dimensions, only 2. It's a lot like its whole world is like looking at pictures or tv. \nSonar gives the dolphin a good, 3-dimensional picture of what lies ahead in a pretty big cone.\n\nalso, sonar is not as easy to trick as vision. good camouflage can make an octopus or a fish invisible to the eye, but sonar can find them.\n\nsonar can see what is hidden. many dolphins hunt by detecting, with sonar, fish that are under the sand, and then using a concentrated beam to move the sand and get the fish out.\n\nand a no less important one is detail. dolphin sonar can be incredibly detailed. some dolphins can identify a specific shark species at, i believe, a distance of half a mile, and more importantly, tell whether the shark's stomach is full or empty. I can definitely see survival value in that!\n\nfinally, it's versatile. it's a sensory organ, a weapon, a pointing device (dolphins can point things out to each other by directing their echolocation beams), and even a healing device (dolphin sonar is thought to help healing through cavitation - hence dolphin assisted therapy).
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Porpoises (I assume you mean small cetaceans) hunt their food with natural sonar (like bats), and it's sensitive enough for them to distinguish between healthy fish and sick fish (or, presumably, dead fish). So they're not likely to go for a baited hook.\n\nBut the question is, why would you want to catch them?
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Good question!\n\nOne of the coolest adaptations that deep sea organisms have is called bioluminescence.  This allows the organisms to actually produce their own light!  Many of these organisms use the light to attract mates.  Predatorial fish take advatange of this fact, and can lure in unsuspecting prey by simply producing light (in other words, they pretend to be a potential mate).\n\nThe depths of the ocean can be extremely cold, and food can be quite hard to find.  So these organisms have a tendency to gravitate towards sources of food (such as decaying matter) and sources of heat (watervents).  By simply 'coming together' to look for food and heat, they make it much easier to find a potential mate.
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bats are beneficial - they kill mosquitoes and other insects so I would suggest you encourage them rather than discourage them - unless of course they are inside....\nI dont know the answer in that case I think everybody is mostly guessing here - would think something that messes up their sonar would be a problem for them or leaving lights on
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I bet some dolphin told you that, right?\n\nYeah, I though so. So while we're busy attacking them, the dolphins consolidate their grip on the oceans
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Because they are quite vicious predators in the ocean.  They don't just kill everything they see, and they're not known to kill humans, but they are definitely at the top of their food chain.  The Sea World info on them says, "they are the largest predator of warm-blooded animals ever known.  Fishes, squids, seals, sea lions, walruses, birds, sea turtles, otters, penguins, cetaceans (both mysticete and odontocete) [[this means dolphins and other whales]], polar bears, reptiles, and even a moose -- they have all been found in the stomach contents of killer whales."  Have you ever seen a video of an orca killing a seal?  If you have, you'll understand why someone would call them a killer whale.  In one video I've seen, it was almost like a cat playing with its prey.  If not, the link below has a video.
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Dolphin's don't 'sleep' in the sense that we do. They do however have conscious control over their breathing like we do, in which case loosing consciousness in the ocean could be quite deadly. Research into this area suggests dolphins 'sleep' one cerebral hemisphere at a time, meaning they close down one half of their brain for a little while, letting the other half take care of the necessary functions such as breathing.
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One of the transitional forms of the whale, ambulocetus was crocodile-like, build to spring from the water and catch prey on shore.  Killer whales still do this without legs, thrusting themselves up on beaches to snatch seals.\n\nUnfortunately, whale and dolphin beachings are a different evolutionary process.  A number of mechisms have been proposed, and noise polution is high on the list.  It may be that ship engines and industrial noise from the shore cause them to hear the land as open water.  Other mechanisms are proposed, but I don't think we've found one answer (if there is onle one) yet.
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Well. they are still sound and still have to comply with all the laws that apply to sound.\nThe reason we cannot hear them is our ears cannot pick up such high frequency sound.\nBats can hear ultrasound and this is probably why you never see bats in a hospital.. They wouldn't know which way to turn.\nBecause ultrasound has a short enough wavelength it is able to pass through certain things. This is because the wavelenth is of an order of magnitude similar to the molecular spacings in the object is is being "beamed" into.\n\nObviously they are absorbed by objects, like your internal organs otherwise they'd be of absolutely no use whatsoever for us.... When I say absporbtion I also mean reflection and refraction. \n\nThey can travel undeviated if the microwaves are collimated "turned into a focused beam" rather like X rays.
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I was thinking this question only yesterday! How strange! I'd like to know the answer to this one too. I thought Tuna were smaller than Dolphins, so they can't escape through holes in the net.
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Check a aquarium. Also, you can check the Internet and if you live near the coast, there is probably going to be some sort of research center nearby that would have people who know a lot of stuff about dolphins.\nCheck www.dolphins.org\nIt's a dolphin research center, I think.
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Whales communicate through what is known as whale song. These sounds are extremely loud and can be heard for miles. They have been known to generate about 20,000 acoustic watts of sound at 163 decibels. This sound is used by humpback whales and one species of blue whale.\n\nToothed whales such as orcas use high-frequency forms of clicks and whistles. It can act like a form of sonar.\n\nThey also communicate through signals breaching where they thrust themselves out of the water. As this costs the whale 1% of its energy, these signals are not taken lightly.
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.WHALES AND DOLPHINS:\n\nWhales and Dolphins are marine animals. They live in oceans around the world. Whales and Dolphins come from the same family, CETACEA (sey-tay-sha) . They both breath from a blowhole located at the top of their head. Whales and dolpins are mammals. They are mammals because they have lungs not gills,they have hair not scales , and they also have give live birth and don't lay eggs. There are only about 80 kinds of whales and dolphins that we know of right now.\n\nWHALES:\nWhales are very large animals. They can grow up to 100 ft. or more in length. They can weigh up to 200 tons or more. Whales live in families called pods. These pods vary in numbers and consist of family members and family friends. Whales live in these families their whole life. Group living is safer when other whales or sharks attack. It also makes it easier to find food. Whales are always migrating. They travel to find food, breed and have young.\nWhales do not have eyelids. They rely on thick oily tears to protect their eyes. Whales hear from little holes behind their eyes.\n\nWhales talk to each other by making high pitched sounds like whistles, clicks, squeaks, rattles, and groans.\n\nTo help protect the whales from extinction please DO NOT throw nets, fishing lures, or other fishing gear ocean\n\nDOLPHINS:\nDolphins live with the whales in the oceans. But dolphins come much closer to the shore. They will come as close to the shore as you or I can walk without going under water. Dolphins have teeth.\nLooking at a dolphin you would not think it as a nose, but surprise...it does! They have nostrils called blowholes. Over millions of years of evoloution whales and dolphins nostrils moved to the top of their head. This allows them to breath by surfacing instead of them sticking their whole head out of the water.\nThe first thing a newborn dolphin must do is to go to the surface to breathe. But the baby can not swim so its mother and a another dolphin will help push the baby to the surface for its first breath of air. The baby will be able to swim in about 30 min.\nDolphins are fast swimmers. When a speeding boat passes the bottlenose dolphin, it will start to race out in front . They will take off hitting the water and keep going.\nDolphins navigate by following the hills and mountains of the ocean floor, by tracking the sun, by sensing currents, and by tasting the water along the journey.\nA dolphin's sound probably originated in its nasal passages. These nasal passages are located on the top of the head. Dolphins can make sounds to see what lies ahead. This sense is called echolocations. The dolphins' sound waves hit an object and the echo bounces back. Echolocation sounds are called sprays. Sprays are so strong they can stun another whale. Dolphins don't "point" their melons at any other sealife except their enemies.\n\nSHARKS:\nOut of all the species walking, flying, slithering or swimming, there aren't many who have been around as long, survived as well, or come in so many shapes and kinds as the shark. The earliest evidences of sharks are isolated spines, teeth and scales that appeared about 430 million years ago in the Silurian Period, known as the "Age of Fishes". Sharks have a sleek, streamlined design which helps them swim without using up a lot of energy.They certainly need to conserve their energy because they never really sleep and most of them never stop swimming.\n\nSome sharks are fierce predators, and would be happy to eat you if they encountered you. Almost any shark six feet or longer is a potential danger, but three species have been identified repeatedly in attacks: the Great White Shark, the Tiger Shark and the Bull Shark . All three live world wide, reach large sizes and eat large prey such as marine mammals or sea turtles. But most sharks never grow longer than five feet and never even see anyone with legs and arms anyway. People kill thousands more sharks every year than sh
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I've never even found a ship - I've always looked on land.\n\nThe odds against mst be high, but it would be wonderful if we found a whale or shark.  You can see cars so you ought to be able to see them if they were on the surface.  I don't think you'd be able to see just a shark's fin though.\n\nintel_knight has a point, though.  Different places on land do have different degrees of resolution and they won't have put as much emphasis on the sea.  Maybe if you look near the coast in places where you know there are a lot of whales?
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Infrared. Radar. Sonar. does that help?
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Dolphins live in a tribe.There can be up to 150 dolphins in each tribe.The mother is the centre of the family.\n\nWhen hunting they use a method called "Kettle technique".\nThey manage to gather the fish together into a ball shape by letting out piercing cries and by surrounding them with bubbles. In this way it is very easy to catch them.\n\norcas work in co-operation with one another, swimming in unison to create a wave pattern in an attempt to knock the seals off of the ice. This clever hunting technique quickly and efficiently could provide dinner for a pod of orcas.\n\nI once read about a incident where the orcas followed a young blue whale and its mother for 4 days and when it got exhausted they had eaten it.The mother was too big for them and they could possibly not harm it.
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Sleep is one of the last bastions of mystery that Science has yet to conquer. Despite several centuries of study, speculation, and debate, we still really don't know what sleep is or why we need to 'shut down' periodically. We know that all sorts of vertebrate animals – mammals, birds, reptiles, and at least some fishes – periodically enter a period of torpor characterized by a profound change in brain waves.\n\nBut when it comes to whether or not sharks sleep, we just don't know. There have been reports from all over the globe, including Mexico, Japan, and Australia, of sharks resting motionless in caves. These have been called "sleeping sharks", but I can attest that the eyes of these quiescent sharks do follow divers moving about in the caves with them, so they're definitely not asleep.\n\nIn his sweeping epic Paradise Lost, 17th Century English poet, John Milton, asked, "What hath night to do with sleep?" We know from sonic telemetry studies (the underwater equivalent of radio tracking) that at least some shark species -- such as the Reef Whitetip (Triaenodon obesus) and the Tiger Shark (Galeocerdo cuvier) -- are actually more active at night than during the day. Since schooling behavior is partially coordinated by vision, many other sharks are most active at dawn and dusk, when such prey is at a disadvantage. Studies such as these suggest that at least some sharks do not sleep at night.\n\nWe used to think that the Great White Shark (Carcharodon carcharias) was primarily active during the day. But it turns out that this is largely due to observer bias: humans tend to be diurnal rather than nocturnal, and it's very difficult to watch an underwater creature at night. Recent experiments by Peter Klimley using stationary telemetry pods placed along the bottom at the Farallon Islands, we have learned that White Sharks are quite active at night, when they probably feed primarily on bottom fishes. If these bottom fishes are sleeping when attacked, they're certainly in for a 'rude awakening'!\n\nBecause sharks rely on ram-ventilation -- that is, their forward swimming to push oxygen-bearing water through their mouths and over their gills -- this fact begs the question: do sharks sleep at all? Dolphins are conscious breathers, actually having to think about rising to the surface, opening their blowholes, and breathing. From Russian studies carried out in the early 1970's, we know that dolphins catnap in 2 to 3-minute stretches, actually shutting down one hemisphere of their brain at a time. From experiments carried out on a small shark called the Spiny Dogfish (Squalus acanthias), we know that the 'Central Pattern Generator' that co-ordinates swimming movements in sharks is not located in the brain, but in the spinal chord. Thus, it is possible for an unconscious shark to swim.\n\nThere is even a possibility that the sharks' fore, mid-, and hind- brain shut down in sequence, resulting in the shark equivalent of sleep-walking.\n\nI hope this answers your question.