Marine biologists have documented the first case of a whale shark surviving with a severe spinal deformity.
The 20-foot whale shark was first encountered in 2010 at Ewing Bank, off the Louisiana coast in the Gulf of Mexico.
‘To see such a large animal surviving with a spinal deformity like that is extremely rare,’ Eric Hoffmayer, 50, a research fisheries biologist with the National Marine Fisheries Service, said.
‘Typically, those types of deformities are not compatible with life. Usually, you see more examples of it in embryonic animals.’
The whale shark was first photographed by the research team years ago, but after returning to the same location, they spotted the creature again.
‘We actually put a satellite tag on it and figured, well, let’s learn more about this animal since it’s unique that we’ve encountered it twice now,’ Hoffmayer said.
And despite the obvious physical impairment, the tagged whale shark exhibited surprisingly normal patterns.
‘Watching the animal swim, it obviously impacted its swimming, but because these animals feed on plankton, it still could maintain a certain swimming motion and speed that appears to have limited impacts on its daily habits,’ Hoffmayer added.
Researchers believe the whale shark’s feeding strategy may be key to its survival.
Unlike predatory sharks that must chase fast-moving prey, whale sharks are filter feeders that consume plankton and small fish by swimming slowly with their mouths open.
‘If it were an animal that was feeding on fast prey, it really would have struggled and probably wouldn’t have survived as long,’ Hoffmayer said.
The satellite tag data revealed that the deformed whale shark’s daily swimming speeds, temperature preferences, and depth preferences all fell within normal ranges compared to healthy individuals in the region.
‘What was really interesting was when we put the tags on, we were able to collect data on daily swimming speed, temperature preferences, depth preferences, and everything seemed to fall in line with the other sharks that we tagged in the region that didn’t have the spinal deformity,’ Hoffmayer said.
Researchers believe the condition was likely congenital rather than caused by trauma such as a boat strike.
‘This animal’s got this deformity, but it’s been able to overcome it and still maintain its normal behaviour and feeding habits,’ Hoffmayer said.
‘Looking at the movements and behaviours, this appears to be pretty close to normal.’
He added: ‘It’s been able to overcome this spinal deformity and still do the everyday things that whale sharks do, which is really remarkable.’
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