I understand that due to the square-cube law (when something grows 2 times but its volume grows 4 times and it goes on) sauropods were massive but not enough when compared to whales because whales got around the square-cube law by using the buoyant force to balance their bodies in the water. In addition, being mammals allowed them to breathe, oxygen-rich air while fish were limited to oxygen-poor water, this thenceforth allowed whales to grow many times more than the largest fish. So my question is what is the limit to whale size and if there is one what is their true potential?

A question presented by the scientific community and given to the public.

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    $\begingroup$ Food is pretty important. I wonder if the air oxygen argument actually holds since they need to hold their breath whereas fish get a continuous supply. $\endgroup$
    – DKNguyen
    Mar 30 at 2:22
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    $\begingroup$ this would probably be better received on the biology stack since it is not about worldbuilding. $\endgroup$
    – John
    Mar 30 at 2:58
  • $\begingroup$ Probably better on biology. $\endgroup$
    – Mary
    Mar 30 at 3:01
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    $\begingroup$ Re size, note that the whale shark (a fish) at up to 18.8 m in length is as large as some of the whales. Some estimates put the extinct Megalodon shark even larger. $\endgroup$
    – jamesqf
    Mar 30 at 4:52
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    $\begingroup$ Basic error: "when something grows 2 times but its volume grows 4 times and it goes on" should be "when something grows 2 times but its volume grows EIGHT times and it goes on". Linear dimension cubed. $\endgroup$
    – PcMan
    Mar 30 at 5:41

As best we can tell food availability is the relevant limits in whales. its true that the bigger an animal gets the more energy efficient it is, it needs less food proportionally but still needs more total amounts of food. There is a limit to how much food you can find and eat, especially in the lean parts of the year. This is actually why we see dwarfism on islands lower food availability favors smaller size (less overall food needs). Finding food and even feeding itself takes energy and it reaches a point where the energy you expend is equal to or less than the energy you can extract from your food.

There are other limits like blood pressure, internal surface area, digestion time, heat buildup, but whales have not reached any of these.


  • $\begingroup$ So the depending factor here is mainly food like take for example the kiwi is a flightless bird that is in the same family as the ostrich and evolved to be smaller over time due to the lack of potential predators. $\endgroup$ Mar 31 at 1:15
  • $\begingroup$ @ParinChitrada food is the limiting factor that determines maximum size. Food is NOT the only thing that determines size it is however what determines the limit on size. there is a big difference between determining factor and limiting factor. there are plenty of small ratites. there are 40+ species of tinamous for instance. $\endgroup$
    – John
    Mar 31 at 2:26

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