For orcas, the dorsal fin is actually an indicator of several problems associated with life in captivity. Dorsal fin collapse can be viewed as a symptom; that is, a sign of the existence of something, especially of an undesirable situation.
Captivity has a range of inherent undesirable problems for orcas, including but not limited to aspects that may affect the upright position of the dorsal fin. This “loss of structural integrity” (LSI) can result in partial or total collapse of the dorsal fin. Some of the problems associated with captivity are inadequate depth of the tanks (which thereby results in unnatural exposure to the sun and a lack of natural water pressure) and extreme boredom for the animals, so they spend excessive amounts of time floating or swimming at or near the water’s surface (so there is no support of the fin from the water).
There are also hypotheses that factors such as age, stress, fitness, reduced swimming (due to the relatively small tank size and frequent circling within the tanks), chemicals used in the water, thermoregulation (reduced ability to use the dorsal fin for heat-exchange due to excessive exposure above water (see Figure 1), medications, food, and dehydration play a role in collapse. These are all possible contributors to the fact that LSI typically occurs in captive orca dorsal fins. LSI occurs in all adult male orcas (and many females) in captivity; that is, 100% of captive adult males have totally or partially collapsed dorsal fins. No captive display facilities, including SeaWorld, have conducted relevant research into this phenomenon.
Neither SeaWorld’s response nor Dr. Dold’s video actually address the question of “shape” of a dorsal fin; rather they are attempting to answer an unasked question about LSI in dorsal fins.
However, if they had answered the question “Is the shape of a dorsal fin related to genetics?” and discussed “shape” specifically – then yes, it is believed that the general shape of orca dorsal fins is a function of genetics. For example, resident orcas generally have dorsal fins that are rounded at the tip and are more falcate (curved overall) than transient orcas, who generally have dorsal fins that are pointed at the tip and are more triangular in shape (see Figure 1).
Figure 1. ‘Resident’ and ‘transient’ orcas have dorsal fins that are generally different in their overall shape. It is thought this is one of the physical attributes that is passed on genetically.
SOURCE: Ford and Ellis (1999), p. 55
Additionally, Dr. Lance Barrett-Lennard has documented two adult male orcas (brothers Yuculta (catalogue #B13) and Slingsby (catalogue #B10)), who both exhibit abnormalities in their dorsal fins (“ruffles” and/or “zig-zag” shapes), suggesting that for these individuals there may be a genetic component regarding the structural integrity of their dorsal fins. However, it should be noted that Yuculta’s dorsal fin recently completely collapsed and Dr. Barrett-Lennard has speculated that this total collapse is due to an injury (Barrett-Lennard 2014).
In the SeaWorld video where Dr. Dold discusses the dorsal fins of adult male orcas (‘The Facts Behind Killer Whale Dorsal Fins’), no adult male orcas are shown. Instead, females (and a four-year-old male) are shown, who only have partially collapsing dorsal fins (see Figure 2). However, Figure 3 shows a captive adult male orca (with a typical totally collapsed fin), held at SeaWorld, compared to the straight dorsal fin of a free-ranging adult male orca.
Figure 2. From SeaWorld video (single frame at 0:24 second), ‘The Facts Behind Killer Whale Dorsal Fins’ (taken at SeaWorld Orlando). Bottom left - Kayla, (female, 26 years old); middle left – Katina (female, approximately 39 years old); top right – presumed to be Makaio (male, 4 years old – dorsal fin not visible) and bottom right – presumed to be Nalani (female, 8 years old).
Note partially collapsing dorsal fins, all leaning in the same direction, on all three females in this picture (no adult males are shown, but please see Figure 3).
Figure 3. LEFT: Loss of structural integrity (LSI) of dorsal fins occurs in 100% of adult male orcas held in captivity, worldwide. Such collapse has been clearly associated with ill-health in wild orcas. This is Tilikum, held atSeaWorld Orlando, who has killed three humans. RIGHT: Wild male orcas typically have straight dorsal fins, which can reach 1.8m/6ft in height. This adult male was photographed in New Zealand waters.
SOURCE: both images: Dr. Ingrid N. Visser, Orca Research Trust.
Dorsal fin collapse in orcas in the wild is typically associated with emaciation (the state of being abnormally thin or weak) and/or anthropogenic (human) causes, such as entanglement in fishing gear, bullet wounds or exposure to oil spills (Baird and Gorgone 2005). In the southern resident population of orcas there are three documented cases of drooping or complete dorsal fin collapse in adult males (catalogue numbers: L42, K17, J3) and soon after this LSI was recorded, all three orcas died.
One population of orcas (found in the waters of New Zealand) has an abnormal number of adult males with LSI, as seven out of 30 (23%) show some loss of structural integrity, such as “zig-zag” shapes. Of note is that those fins are still predominantly upright and have remained so for years (see Figure 4). Of those seven, only one adult male (known as Slater, catalogue #NZ100) had a totally collapsed fin. He was only ever observed the one time with the collapsed fin and was not observed again, so is considered to have died. He had an indentation around his thorax indicating entanglement, which may have led to the dorsal fin collapse. Typically, less than 1% of the males from any free-ranging orca population exhibit dorsal fins that are totally collapsed. No free-ranging orca females have been recorded with totally collapsed dorsal fins and partial collapse is extremely rare.
Figure 4. An adult male orca in the New Zealand catalogue who shows loss of structural integrity. Corkscrew (catalogue # NZ15) was first photographed in 1985 with a ‘zig-zag’ shape to his fin, yet the fin remains upright. This photograph, taken 22 years later (in 2007), shows no change in the structural integrity of the dorsal fin. Note the notch in the leading edge of the fin, an indication of fishing line entanglement.
Orca dorsal fins are comprised of fibrous collagen (structural protein) (see Figure 5), not cartilage (flexible connective tissue). Although collagen is found in cartilage, it is not cartilage. The human outer ear is made of cartilage, covered by skin; therefore, Dr. Dold’s comment that the “dorsal fin is a structure like our ear. It’s made of similar material” is incorrect.
Figure 5. Orca dorsal fin cross section, showing the artery (pink) in the center (with veins all around it). These help the orca with thermoregulation, using counter-current heat exchange. The dense fibrous tissue (collagen) is also visible.
SOURCE: Houghton (2012)
However, SeaWorld’s own website page, about orca physical characteristics, does correctly state that the dorsal fin is made of “dense, fibrous connective tissue, without bones or cartilage1.”
References:
Baird, R.W. and Gorgone, A.M. 2005. False killer whale dorsal fin disfigurements as a possible indicator of long-line fishery interactions in Hawaiian waters. Pacific Science 59: 593-601.
Barrett-Lenard, L. 2014. Wild Whales website (http://wildwhales.org/), July 7 whale sightings post.
Durban, J.W., Fearnbach, H., Ellifrit, D. and Balcomb, K.C. 2009. Size and body condition of southern resident killer whales. Contract report to the Northwest Regional Office, National Marine Fisheries Service, Order number AB133F08SE4742, Requisition Number NFFP5000-8-43300.
Ventre, J. and Jett, J. 2015. Killer whales, theme parks and controversy: An exploration of the evidence. pp 128-145. In: K. Markewell (ed.) Animals and Tourism: Understanding Diverse Relationships, Channel View Publications: London. 305 pp.
There is speculation of a genetic component, expressed generally by field biologists to explain the cases of dorsal fin bending and collapse in the wild. But there is no evidence to support or refute a genetic influence.
Please watch this for more information on dorsal fin shape:
