Chances are, the dolphins we see jumping through hoops in amusement parks everywhere may have undetected injuries, causing them pain as they are forced to entertain us. They are plagued by dental and skeletal injuries in both wild and captive circumstances, but interestingly – although not surprisingly – the dolphins heal significantly better in the wild. Scientists speculate that this can be due to the fact that captive dolphins are forced to do tricks such as pulling trainers through the water or beaching themselves while performing with injured ribs:
...None of the latter specimens has been observed to be the victim of severe crashes between animals, nor had any of them a big accident during performances.
From the state of healing, the fractures must have occurred only a few weeks before death, and they possibly have caused or aggravated the lung diseases they are so often suffering from. It is important to point out that such fractures are generally not recognized general autopsy. Only in one delphinarium specimen, whose skeleton has not been conserved for the study collection, broken ribs were recognized because they protruded into the thoracic cavity.
All these findings give the impression that rib fractures are more common in delphinarium specimens than often is believed; they should receive attention during autopsies.
Another important fact is that in the wild specimens the broken ribs nicely heal. In the delphinarium specimens, however, healing does not seem to follow that easily. One may suppose that the jumps during performances, the swimming in a limited space and occasional beaching during performances or during examination are not favorable for healing.
If, after an accident, rib fractures can be suspected, it seems to be recommendable not to take the animal out of the water for some weeks. Their body-weight, no longer sustained by the surrounding water, could push the rib into the lungs and cause pulmonary lesions.
The old wild specimen with the many broken ribs also shows broken but completely healed lateral apophyses of two lumbar vertebrae. Another wild specimen, caught the river in 1960, had several broken and healed neural spines in the lumbar region. SLIJPER (1931 and 1936) reports several cases of broken apophyses in other species. Although such fractures may be quite common, they heal easily and apparently do not cause much harm to the animal. (Aquatic Mammals Journal).
This study was done in the late 70’s, yet more than three decades later not much seems to have changed in the management of dolphins in captivity. The veterinarians at the amusement parks are either unaware of this information or choose to ignore it – but in either case, dolphins continue to be forced to perform for their supper every day, day in, day out – and no doubt, often in pain, possibly leading to lung problems and death.
According to a 2012 national report on marine mammals, the one park I scrutinized (Sea Life Park, Oahu, Hawaii), has records going back to the 60’s which show that fully a third of the dolphins for which there are records died of causes linked to lung problems – most of those were pneumonia.
Were the lung problems related to rib fractures? It is impossible to know because there is no mention that the veterinarians knew to check the ribcage during postmortem examinations, and amusement parks are no longer required to report the cause of death to the National Marine Fisheries Service. The Marine Mammal Protection Act was significantly reduced in scope in 1999.
As to why dolphins suffer from so many injuries to their spines and ribs, it is likely the result of aggression and accidents and in the confines of captivity they may not be able to find an escape from each other.
Many species of dolphins have been observed to ram or head-butt other dolphins, and in a study of 50 pilot whales who had beached themselves, roughly half showed healed fractures in the jaw, some had been fractured more than once at different points in their lives. Among males the rate was 71%. As with the ribs among wild dolphins, these fractures healed nicely. Taken together then, it would appear that dolphin dynamics can be very aggressive and serious but the cetaceans are well equipped with natural healing ability in the wild .
Dolphins also suffer fractures from net entanglement, so some of the fractures observed in wild dolphins may be related to having survived a run-in with fishing apparatus:
Gross Evidence of Human-Induced Mortality in Small Cetaceans
Many dolphins killed in fishing gear also exhibit ante-mortem broken bones and associated blood clots and macerated soft tissue. Typically these bones include mandibles, flippers, ribs or the vertebral processes.
In any case, the poor rate of healing and high rate of complications illustrate once again the failure of captive conditions to provide adequately for the needs of dolphins and whales.