Why do marine mammals sway their tails vertically, while fish sway them horizontally?
In: Biology
Sea “creatures” use their tails depending upon their design orientation.
Fish with vertical tails wiggle them left to right for locomotion.
Whales, dolphins, manatees and fish with horizontal tails wiggle them up and down to provide locomotion.
It depends on their individual design…
But Fish have vertical tails and some marine mammals, such as whales, have horizontal tailfins, have those due to the way their back moves. It’s all in the spine. Fish move their spine left to right, so their tail needs to be vertical to be the most efficient. This is how their spine is built.
Most fish swim vertically oriented but flat fish, plaice and sole – for example – are horizontally oriented and use their tails and flap them vertically for locomotion.
Marine mammals sway their tails vertically because their tail fins are horizontal. Fish sway their tails horizontally because their tail fins are vertical. They get far more thrust by swaying their tails perpendicular to their tail fins than they would if they swayed them parallel to their tail fins.
No profound answer here:
Mammals need to move between heights in the ocean, i.e. to the surface for oxygen, while, I assume, sharks move larger distances in one height, therefore the different tail
Just an assumption, and by now there are more profound answers.
Id imagine its easier to swim to the surface for air with a horizontal tail than with a vertical one.
They evolved differently than fish. Whereas the ancestors of fish lived in the oceans, you can trace back the ancestry of sea mammals to land mammals that eventually developed tails similar to that of mermaids because their tails evolved from their hind legs.
In fact, in certain pictures of whales like beluga whales, you can actually see their knees.
My guess would be the mammals need to get to the surface of the water for air, so that type of movement was selected by evolution. Fish don’t usually need to go to the surface, so their tail is better for movement forward.
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