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  • Why are whales so big?

    Here's a question that I've never seen any answer to. Whales are bigger than any animal that has ever lived. The largest dinosaurs were maybe 50 tons, whales can fairly easily (if they're allowed) reach 100 tons and the heaviest estimated whale was over 200 tons. No whale ancestor in the dinosaur days was ever any where near the size of modern whales.

    So in our period in history, we have the largest creatures ever - by far. Why do the whales grow so large?

    There are plenty of examples in the fossil record that in a particular animal line - take dinosaurs as the best known example - there is a tendency to gigantism. In other words if all other things remain equal, then through evolutionary time, the largest animals will prevail as they are the most efficient at obtaining food, breeding etc.

    The danger is when change occurs, large animals can't adapt as well or as quickly as smaller animals and tend to be the first to die out. The change as far as the whales was concerned was the advent of man the super-predator. Now some 30 years after most commercial whaling has stopped, the larger species are still no where near recovered, whereas the smaller minke whales for instance have increased enormously in number to the point where pressure for a sustainable fishery is increasing.

    Why are whales so big? Why are they so big now? - more so than any other creatures ever have been when the advantages of large size have always been there and the possibility of growing large always existed.

  • #2
    beats me!
    my best estimation is that when conditions are perferct whales will achieve there full maturity. a time line is unsatisfactory due to global change and conditions. maybe the time and place is just right for whales to prosper or maybe they have more to say about our earth. i think they are a creature that requires a broader study. it seems to me the only thing that has hurt this mammal is human intent such as military testing of sonar or other such radars. it's of interest to me how an aquatic creature such as a whale and a land deweling animal like an elephant are the biggest receptors of sound in water and on land, which i might add are or have been hunted for human prosperity, both of which creatures hear more of the earths activities then no other.
    the farming of cattle is a bit easier then the farming of whales but the practices of being a vegetarian are proven to be the best.

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    • #3
      An interesting question. I haven?t given it any thought before. Here are my thoughts which come to mind now but I don?t claim them to be authoritative.

      Organisms have the potential to grow larger in water than on land because of the support given by the water. There is no need for such bulky strong bones as would be needed on land. By the way, I think many of the large dinosaurs lived in swamps or shallow water where they benefited from buoyant support.

      Large organisms have long gestation periods and few young so population numbers are more susceptible to increased predation. In an environment where there is a moderate level of predation, reproductive rates must be high enough to stand this loss. Potentially, a very large organism would be immune to normal predation simply because of size. In order to select for greater size at the expense of lower birth rates the organism would either have to have a strong defence against predators or there would have to be a temporary removal of predators from their habitat.

      Maybe some environmental conditions gave such a window of opportunity during the development of mammals that didn?t arise during the evolution of fishes.

      An afterthought. Maybe there is an upper limit to the potential size of a cold blooded organism such as fish, that is smaller than the potential upper limit of a warm blooded organism? Warm blooded organisms have arisen relatively recently on a geological timescale so maybe this is the first chance organisms have had to get this big. Maybe there will be more and larger organisms in 50 or 100 million years time.

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      • #4
        They are efficient eaters because they are herbivores and eat nothing!!1

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        • #5
          I apologise for my other post, my sister had a go on the computer. Apologies to everyone. Whales are big because apart form the Japs, no animal can eat them, so they have no predators. THe closest thing to a predator is the Whale Shark, but that is also a herbivore.

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          • #6
            ummmmm ever heard of the US navy's sonar?? probably kills more whales then the Japanese do.

            werd i'm smart!

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            • #7
              http://www.kron4.com/Global/story.as...0&nav=5D7lBwNp

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              • #8
                i reakon it is bcause of them needing fat to survive the winters :!:

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                • #9
                  Re: Why are whales so big?

                  Originally posted by bsimple0
                  i reakon it is bcause of them needing fat to survive the winters :!:
                  yes thats true but that doesnt explain how they got so big

                  Its a beautiful mystery.

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                  • #10
                    Re: Why are whales so big?

                    Well Deep, I guess the answer is "WHY NOT??"

                    psr

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                    • #11
                      Re: Why are whales so big?

                      Actually the reason that whales are so big is related to the medium that they live in. Water provides buoancy so the gravitational pull of a large body isn't the same issue that it would be on land. Also, life in water means that the animal must find a way to reserve body heat (heat is lost about 20 times faster in water than on land). As you increase body size, the surface area to volume ratio decreases, thereby decreasing the amount of area that heat can be lost across. So, a larger body means less heat loss. Whales also have a thick layer of blubber to help minimize heat loss which also contributes to a larger body size. Most large whales migrate and therefore will encounter colder offshore waters at some point. Therefore, thermoregulation is very important.

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                      • #12
                        Re: Why are whales so big?

                        Jeep,

                        Thank you for that insightful and extremely educational reply to this puzzling question. I would like to inform you that I have taken an exceptional shine to you. I like smarty pants'!!!!!!

                        psr

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                        • #13
                          Re: Why are whales so big?

                          Aw shucks psr, that's sweet of you. It just happens to be a subject near and dear to my heart. Now, if the question had been about car repairs or a recipe for a good zucchini bread, well I would've been stumped.

                          Jeep

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                          • #14
                            Re: Why are whales so big?

                            Jeep.....

                            Zucchini bread??? Hmmm......my culinary skills must be sadly lacking.....

                            psr

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                            • #15
                              Re: Why are whales so big?

                              Hi jeeprasr and thanks for your comments. You've answered the how-so-big, but I was inteerested in the "why now?", why not ever in the past?

                              I guess the answer is tied up with the need for so much food requiring such long journey's a high metabolic rate and the need to be a warm blooded mammal to be so active in frigid waters. A question of which came first, the requirement to enter frigid waters to support the food requirement or the being warm blooded and large enough (as a result of enough food) to be able to enter frigid waters.

                              Then again, seals can do it too - while feeding on krill, and they are much smaller.

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