Why are whales so big?

[Paul]

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.