A killer whale's (O.orca) dorsal fin is located on top of the animals back and is made up of fibrous, connective tissue, called collagen. A male orca's dorsal can grow up to 6 feet tall, whereas females tend to have smaller ones.
Dorsal collapse happens due to the connective tissue, collagen, that I mentioned earlier. This substance is a lot like cartilage but weaker, giving the fin shape and structure to help the animal balance when swimming. As the dorsal grows this collagen will begin to weaken if there is not enough support from the surrounding water. It grows heavier and heavier until it eventually leans (collapses). Wild orcas are seen to have straighter dorsals than animals in captivity. This is due to water pressure as wild orcas spend the vast majority of their time under water and at greater depths. Their dorsal fins are therefore under the pressure of the ocean surrounding them, giving that massively heavy dorsal support as its weight is significantly reduced when submerged.
However, in captivity the animals spend the majority of their time at the surface and rarely go deep enough for long periods of time for their dorsal to be gaining the same support, therefore, over time the connective tissues give way to the massive pressure and weight that is their dorsal fin. However, this has no detrimental impact on the animal’s health or wellbeing and does not stop them from exhibiting any natural behaviour. It occurs more often at SeaWorld than in the wild as the orcas spend more time at the surface so there is less pressure from the water pushing up against the dorsal. It is not caused by emotions, health issues or lack of exercise.
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