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Usually, when people think about aquatic mammals they picture giant whales or elephant seals and probably think that living underwater requires such a large size. However, this is not the case, according to a study which the journal Proceedings of the National Academy of Sciences recently published. It seems that their growth is in fact more limited than that of animals living on land. It’s interesting that this reveal contradicts some previous ones according to which pressure on body size is not as accentuated underwater.
In fact, it appears that underwater mammals need to preserve heat and struggle to obtain food. This is why their body size is actually more constrained. According to co-author Jonathan Payne, people usually think that mammals underwater are actually enjoying more freedom than those on land. In reality, things are not like that. The water does not allow you to be big, but instead you have to be big to live underwater. It’s just the only way you will survive as a mammal. So, upon analyzing data from both living animals as well as extinct species to see how they evolved, researchers discovered an interesting trend.
A mammal needs to be big underwater, there’s no other option
It seems that when land animals begin living underwater, their body size changes, adapting to the new environment. However, even if you might think that bigger is better when you’re underwater, that is not the case with all mammals. Otters for example are not part of this discussion. This is mainly because large numbers of otter species are still living on land.
According to lead author graduate student Will Gearty, the tree of ancestral relationships is what allowed them to build certain models. This is how they discovered the body size of certain animal ancestors and establish what modern species fit in with their evolutionary trajectory. So, it seems that mammals don’t actually have a choice regarding their size underwater.
Image source: wikimedia
