Question: Killer Whale (Orca) Dorsal Fin Collapse
Have you ever wondered why killer whales in captivity have a dorsal fin that is flopped over, or 'collapsed?' Read on to learn the theories.
A male killer whale's dorsal fin can grow to as much as 6 feet tall. Despite the fact that the dorsal fin is very straight, it is not supported by bone, but a fibrous connective tissue called collagen.
A wild orca often travels far, and quickly, in deep water. The water provides pressure to the fin, keeping the tissues inside healthy and straight, and encouraging the dorsal fin to remain straight.
That said, it is not impossible for a wild orca's dorsal fin to collapse or become bent. A study in 1998 of killer whales in New Zealand showed a relatively high rate (23%) of collapsing, collapsed, or even bent or wavy dorsal fins, and noted that this was higher than that observed in populations in British Columbia or Norway. Researchers have theorized that dorsal fin collapse in wild whales may be due to age, stress or altercations with other killer whales.
In captivity, dorsal fin collapse may be related to several factors, including time spent at the water surface, swimming in the same direction in a relatively small pool. The tissue in the dorsal fin gets less of a workout, and less support in the water than it would in a wild whale, and starts to fall over. The same thing can happen to the whale's tail flukes, which often flop over at the ends. Other causes may be dehydration due to warmer water and air temperatures, stress or age.
- Composition of Whale Dorsal Fins (WhaleNet)
- Orca Dorsal Fin Controversy: Experts vs. SeaWorld. (Ocean Advocate Blog)
- Evans, W.A. 1996. 'Flaccid' Fin Syndrome: Natural or Captive Phenomenon. A Capstone Review Paper in Partial Fulfillment of the Requirements for the Degree of Master of Science in Marine Biology. Nova Southeastern University.
- Dorsal Fin Collapse in Killer Whales Explained (Video)
- Visser, I.N. 1998. Prolific body scars and collapsing dorsal fins on killer whales (Orcinus orca) in New Zealand Waters. Aquatic Mammals 24.2,71-81