Why do the dorsal fins of captive whales slump over?
401295
I recall hearing about this before... I think it has something to do with the pressure differences between the captive tank and the natural lower depth environment the whale is meant to live in.\n\nGood question!
755167
This is an excerpt from the referenced website:\n"Recovery of diagnostic ankle bones in the skeletons of primitive protocetids during our field work in Pakistan in 2000 confirmed their derivation from Artiodactyla (the mammalian order including cows, deer, hippos, etc.), and showed convincingly that whales did not originate from mesonychid condylarths as Van Valen hypothesized (and we had expected)."\n\nHope this helps.
616811
That's not a tail, it's a dorsal fin and most fish have them.
6533
some whales mate on their sides at the surface and roll over periodically; as far as breathing goes, even if they werent at the surface, they can hold their breaths for pretty long periods of time. certain whales have also been known to mate in groups, but im not personally sure how this works..\n\nanyway, most whale sex is underwater actually and pretty quick, and no they dont get stuck.\n\nif you are really looking for details, here is a good quick site:\nhttp://whale.wheelock.edu/archives/ask00/0221.html
881373
The swim bladder controls the buoyancy of the animal. Normally the amount of gases in the swim bladder keeps the fish neutrally buoyant, and they can regulate these gases to go up or down in the water column.\nThis saves energy because the fish doesn't have to swim actively to stay in one place; even though their tissues are denser than water, they won't sink because the less dense gases compensate for this.
1024818
Carcharodon Megalodon - What a fantastic creature! They had grown to 60 feet long or more and weighted more than 20 tons. Having a voracious appetite, they had to eat at least 2 percent of their body weight daily to maintain their existence. What happened to this fish that lasted 16 million years beginning in the early Mid-Miocene and lasted until the Pliocene/Pleistocene Period? It seems that no one single incident bu several long developing changes occurred that brought about the Megalodon’s extinction. \nEnvironmental changes were as important as any for the demise of this creature. By the late Miocene, about 10 million years ago, a period of major glaciation was under way. This was, it seems, the result of changes going back to the late Oligocene Period that began a slow cooling effect on the world. Changes like Africa colliding with Europe, cutting off the Tethyan Seaway to individual bodies of water represented today by the Mediterranean, Black, Caspian, and Aral seaways. \nAlso, the Indian subcontinent crashed into Asia, which formed the Himalayas. All these movements, over time, seriously altered global patterns of wind and rain which reduced the temperature at mid-latitudes by 27o Fahrenheit. This effect, in turn, brought about major glaciations at the Poles by the late Miocene. This glaciation resulted in the lowering of sea levels by about 650 feet. \nThrough lowered sea level and temperature, Megalodon lost large areas of suitable habitat. This is important because Megalodon lost much of its shallow nursery areas for its pups to grow and develop. Coincidentally, between 3.2 and 2.5 million years ago, the Isthmus of Panama rose from the sea floor, joining South America and North America. This new land bridge caused a great reduction of warm sea flow from the Pacific Ocean, thus helping to cool seas to less temperate waters favored by the Megalodon. \nPredators also seemed to work against the Megalodon. Whales, Orcas in particular, which had been a mainstay in the Megalodon’s diet, had changed. Not only had they grown tremendously, they had become better swimmers with improved musculature and tail structure. Their developments allowed them to move or migrate from local areas to becoming migratory - ranging into Arctic waters, putting them out of reach of the warm water loving Megalodons for large parts of the year. So, it seems, the Orcas became better swimmers while growing to almost the size of the sluggish Megalodon. \nThe mature Megalodon was thus denied a major food source. Also, the Megalodon pups, over time had lost their \nshallow water proteting nurseries and became a snack for the faster Orcas. It would seem, in conclusion, that the adults were too large to get enough to eat and the juveniles were too small not to be eaten by the predators. \n  \nReferences: \nHelm, Bill, Carcharadon Megalodon Extinction, elasmo.com. \nMartin, R. Aidan, Explorations in Shark Evolution, ReefQuest Centers for Shark \nResearch. \nStanley, Seven M., Extinctions, Johns Hopkins University, Scientific American Books, Inc\n\n\n\nThe Megalodon (Carcharodon megalodon, from ancient Greek, megas + don, literally "big tooth") was a giant prehistoric shark that probably lived between about 20 to 1.2 million years ago.\n\nThe Megalodon is known principally from fossil teeth and a few fossilized vertebral centra. Like other modern sharks the skeleton of Megalodon was of cartilage and not bone, resulting in the poor skeletal fossil record. However, Megalodon's large teeth have survived the ages. The teeth are in many ways similar to great white shark teeth and can measure over seven inches long (maximum slant length).\n\nRecent studies cited by Roesch (see external links below) suggest Megalodon was a "close relative" of the Great White. However, a growing number of researchers dispute this close Great White–Megalodon relationship, instead citing convergent evolution as the reason for the dental similarity. Nev
937618
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.
32867
About 75 percent scuttle sideways, the better to keep an eye on approaching predators.\n\nAlso, Because that's the way their legs bend. Muscles work in pairs. A muscle can only retract, or pull; to lengthen again it must relax and be pulled back by another 'antagonistic' muscle.
28681
in addition to what other have said before about becoming disoriented(sickness, storms, earthquakes, sonar equipment), whales can also become beached when they swim too close to shore in search of food and are caught unawares by receding tides.
1005544
The short-fin mako and great white sharks have tail fins that are even lobed, symmetrical, same one top and bottom. This enables them could horizontal motion in the water, or good for going in a straight line from the depths to the surface to take prey. Thresher sharks on the other hand  have asymmetrical tail fins for descending. It's really the shape of the tail fin determines it's movement in the water.
129936
divers will ride the dorsal fins commonly. if you expect they will stay at the surface so you can breath you're dreaming. not to mention the force at the surface of the water ripping you away.
283592
They are part of the food chain for many species, whether it be at the beginning or in the middle. If dolphins disappeared, certain species would become over populated, and others would die off.
628752
Unlike marine mammals such as whales and dolphins with lungs that store oxygen from the surface air, fishes have gills. Gills are a series of membranes located on each side of the fish that function as respiratory organs. As water passes over this system of extremely fine gill membranes, the fishes absorb the oxygen from the water. The gills contain a network of fine blood vessels (capillaries) that take up the oxygen and diffuse it through the membranes. When fishes are taken out of water, they suffocate, because their gills collapse and they are unable to absorb oxygen.In many ways, the interior of the fish resembles that of many other animals. The digestive, circulatory, and nervous systems are very similar to those of other vertebrates. However, what really makes a fish different from other animals is its respiratory system. \n\n\n\nA fish’s respiratory system is determined primarily by the fact that it spends its entire life in water. Unlike the marine mammals such as whales, a fish has evolved in such a way as to not require frequent trips to the surface to breathe air. Fish have developed gills, on which they rely for the oxygen necessary for a fish’s limited metabolism. \n\nMany animals have gills at some stage of their life (even humans have them at an early stage of their development in the womb), but fish retained these gills and they are still a functional part of their anatomy. Fish use their gills to extract oxygen from their watery environment. The process starts with the fish’s mouth, which is how the fish takes in water. When a fish opens and closes its mouth, it is actually pumping water back through the gills and is thus breathing. Most fish have an effective pumping system that involves the mouth and the outer cover of the gills, called the operculum. When the fish’s mouth opens, the operculum closes, drawing water into the fish’s mouth. When the fish closes its mouth, the operculum opens, allowing fresh water to cross the gills. Other fish have a less effective pumping system, requiring them to swim constantly to keep fresh, oxygenated water flowing over the gills. These types of fish, such as tuna, generally swim with their mouths partly open. Incidentally, while many fish have nostrils, the nostrils are used only for a sense of smell, and play no part in respiration. \n\nOnce through the mouth, the water continues past structures called gill rakers. The gill rakers are essentially a filter system for the gills, straining the water to sift out floating food particles or foreign material. After passing through the gill rakers, the water continues through the gill arches and actually passes over the gills, which are suspended between the mouth cavity and the operculum. Each gill is made of two rows of gill filaments, which are extremely thin membranes sticking out into the water flow. Each of the gill filaments is composed of rows upon rows of lamellae, which are thin, disc-like membranes loaded with a capillary network. The water flows across the lamellae, and oxygen and carbon dioxide are exchanged directly across the capillary membrane. The capillaries are situated to take best advantage of the water flow; fish can actually extract up to 85% of available oxygen out of the water. Since water contains only 2-5% of the available oxygen that air at sea level does, such a high efficiency is extremely important. \n\nFrom the gills, the deoxygenated water passes out the operculum, and the oxygenated blood joins the circulatory system. Despite the efficiency, some fish require more oxygen than others. This helps to explain why some fish thrive in specific habitats. For example, trout prefer northern streams because the cool water of the streams tends to retain dissolved oxygen, and the active trout need the extra oxygen. Carp, on the other hand, are sluggish and do not need as much oxygen, which is why carp can thrive in warm, relatively stagnant ponds, such as ornamental ponds. Goldfish, unlike most f
612472
Observations of bottlenose dolphins in aquariums and zoos, and of whales and dolphins in the wild, show two basic methods of sleeping: they either rest quietly in the water, vertically or horizontally, or sleep while swimming slowly next to another animal. Individual dolphins also enter a deeper form of sleep, mostly at night. It is called logging because in this state, a dolphin resembles a log floating at the water's surface.\nWhen marine mammals sleep and swim at once, they are in a state similar to napping\n\nAdult male dolphins, which generally travel in pairs, often swim slowly side by side as they sleep. Females and young travel in larger pods. They may rest in the same general area, or companionable animals may pair for sleeping while swimming.\n\nWhile sleeping, the bottlenose dolphin shuts down only half of its brain, along with the opposite eye. The other half of the brain stays awake at a low level of alertness. This attentive side is used to watch for predators, obstacles and other animals. It also signals when to rise to the surface for a fresh breath of air. After approximately two hours, the animal will reverse this process, resting the active side of the brain and awaking the rested half. This pattern is often called cat-napping.
809981
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.
558077
Many whales live in colder waters and need the layer of fat to keep their body temperature constant.
108792
They are made of wood, which floats because it has a lower density than water.  If you made a ship out of solid gold, it would sink, for example.