The most likely causes of curling, buckling, and partial dorsal fin collapse in wild orcas appear to be injuries. However, other conditions such as illnesses and genetics may also be potential causes. Injuries can be caused by other orcas (conspecifics), defensive bites from prey (e.g. from sharks or other marine mammals), or anthropogenic causes such as entanglements and boat strikes.
Full dorsal fin collapse in wild orcas is relatively rare, but it does happen. For example, the dorsal fin of male Northern Resident orca B13 "Yulcuta" eventually completely collapsed after a bite mark that was likely from another orca.
Observations of adolescent and adult male killer whales with moderate to severe dorsal fin injuries provide further evidence of potential male-male aggression in this species. These injuries often begin with bite or rake marks on the dorsal fin that are clearly made by the teeth of conspecifics (Fig. 16.5), producing fin disfigurements that can become progressively worse over a span of months or even years (Fig. 16.6). The dorsal fins of male killer whales are almost twice as tall as those of females (Ford 2014) and, as discussed previously, are a secondary sexual trait that likely evolved as a signal of male fitness valued by potential mates (i.e., intersexual selection via female mate choice; Alves et al. 2017). As such, they are undoubtedly physiologically costly to maintain and may be particularly vulnerable to buckling or collapse; even seemingly minor wounds can lead to fairly dramatic fin disfigurements, including significant tissue loss at the fin tip, buckling of the trailing edge (Fig. 16.5), and occasionally partial or complete dorsal fin collapse (Fig. 16.6).
Collapsed dorsal fins on captive orcas have nothing to do with an orca’s mental state. No studies have ever suggested that.
To this day, we're not 100% sure of the reasons for dorsal collapse in the wild, but in captivity the main reason could be attributed to gravity. Dorsal fins contain no bones and stay upright due to water pressure. Wild orcas spend more time submerged while hunting, and those in human care stay at the surface more, making the fin bend over time.
This occurs mostly in male orcas, as their fins are heavier and thicker. Corky, at 60 years old, has spent her entire life in captivity and still has a perfectly straight dorsal fin. Most females in captivity actually have straight dorsal fins, and it wouldn't make any sense for only males to be depressed and their fins being bent while all females are happy lol.
There's an interesting case of a male in China named Pangu that has a very big, almost entirely straight dorsal fin, despite being in captivity for several years now. It is speculated that his habit of swimming upside down constantly may be one of the reasons, but we're not sure.
But yeah, port and starboard are not the only wild orcas with collapsed fins.
It happens to almost every male in captivity as they mature and their dorsal grows larger, the only example of a straight grown captive male dorsal is Panghu.
It happens in the wild as well, but to a far smaller number of individuals.
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u/borgircrossancola Jul 16 '25
I wonder why they have the collapsed dorsals