Traumatized animal radically changes diet and behavior in an unhealthy way: the real story of the “vegetarian shark”

Between my well-documented love for sharks and my famously vegetable-less diet, a recent story about a “vegetarian shark” was destined to be e-mailed to me by friends and family. For those of you unfamiliar with the story, a captive nurse shark at an aquarium in the United Kingdom has been eating lettuce and celery, and refusing to eat normal nurse shark food (crustaceans and fish). As a result of this…no, wait, that’s pretty much the whole story. This animal has been dubbed “the world’s first vegetarian shark”, and my twitter and Facebook feeds have been full of people misinterpreting what this means even worse than the original media coverage did.

This is not a case of an animal “changing the reputation of sharks worldwide, and in the greenest way possible”, as reported on EcoRazzi. This is not a case of “even sharks realizing that vegetarianism is the most environmentally friendly diet”, as some have claimed. The reality is much more troubling. Following an incredibly traumatic experience (a 2009 surgical procedure to remove a rusty hook lodged in the digestive tract), an animal has radically changed its natural behavior in a way that isn’t healthy.

Yes, unhealthy- regardless of your views on the health benefits of a vegetarian diet, I’ve been assured by friends who do eat vegetables that lettuce and celery don’t have a lot of nutritional content. Fortunately, the aquarium staff at the Birmingham Sea Life Centre is aware of this and is working hard to get this animal the nutrition it needs. According to the press release (available online here), aquarium curator Graham Burrows said “we’re having to hide pieces of fish inside celery sticks, hollowed out cucumbers and between the leaves of lettuces to get her to eat them”. One could argue that the fact that the shark is still eating fish (although hidden among veggies) means that it isn’t a vegetarian at all, but that isn’t really the most important point here.

Both TreeHugger and EcoRazzi wrote that “nurse sharks are known for eating algae from time to time”. This is, at best, an incomplete statement. There is no evidence of any shark preferentially eating algae or any kind of plants in the wild. While nurse sharks primarily eat fish and crustaceans, bits of coral with algae growing on them have been found in a few nurse shark stomachs. They most likely ingest this accidentally when they eat fish or crustaceans sitting on the coral. Similarly, bonnethead sharks have been found with seagrass in their stomachs, most likely as a result of capturing crabs sitting in the seagrass. Even I accidentally ingest a small piece of lettuce or tomato every once in a while when I fail to pick all of it off of my sandwich, but to go from this to claiming that I eat lettuce and tomato from time to time is a stretch.

It remains unclear why this shark reacted in this particular way. TreeHugger claimed that being caught by a fisherman  “seems to have left a lasting impression on her — namely, that meaty treats mean trouble,” but this doesn’t really make any sense. If every shark that was caught with a baited hook was repulsed by the smell of fish for the rest of its life, we probably would have seen this behavior before now in one of the countless other captive sharks that were caught by baited hooks.

The stress of captivity alone can be traumatic enough to induce radical and unhealthy changes in the behavior of species like horses, primates, bears, and elephants. Unnatural repetitive behaviors associated with captivity, known as “stereotypies”, include walking or swimming in circles, biting the bars of the enclosure, or intense self-grooming that can even result in injury. It’s extremely unlikely that captivity stress caused the changes to this shark’s preferred diet, as nurse sharks are common aquarium residents and this behavior has never been documented before. The stress associated with a serious injury and associated major surgery may well have been enough to do it. We may never know the reason why this nurse shark is behaving like this. What we do know is that when an animal suffers a traumatic experience and then radically changes its diet and behavior in an unhealthy way, it isn’t something that we should celebrate.