A few months ago the news of a species of shark capable of surviving and putting on weight with an almost exclusively vegetarian diet became viral. It has long been known that the hammerhead shark from the cap (Sphyrna tiburo) ingests large quantities of posidonia, but it was thought that it was mostly an accidental snack, collected near the shore during the hunt for small crustaceans. Instead the aquatic plant not only likes it, but it nourishes it and makes it grow.

The omnivore shark could be in excellent company. Who says there are no other animals that interact with their ecosystem in ways we don't expect? The issue addressed in an article in The Conversation, reminds us that natural environments should be protected not only for the now known reasons, but also for the reasons we do not yet know.

the vices of hippos. We consider, in fact, the definitions of "carnivore" and "erbivoro" used to describe animal feeding habits. They are located at the opposite ends of a staircase, but we seem to have forgotten the intermediate steps. And yet in the ecological sphere there are several hybrid positions.

If the omnivore shark made an impression on you, what would you think of conventionally vegetarian animals, who give themselves to meat? A colossus that is thought to be strictly herbivorous - the hippopotamus - has been observed consuming the carcasses of other animals, including its own kind. We have seen it enough times to fear that this behavior could contribute to the spread of diseases among the populations of this mammal, such as anthrax.

15 things you didn't know about cannibalism Image Adaptability is fine, but not everything is edible: a chea parrot (Nestor notabilis). | Shutterstock

Good mouth. Even rabbits, in some conditions, do not disdain some animal protein. Those in a zoo consumed the chicken and the mice offered to the birds that lived in their own cage. And the list could go on.

In the 1980s, sheep and deer were seen biting the legs and heads of some chicks. A few months ago, the film of a sheep eating a curlew nest caused a sensation in the United Kingdom.

Of similar taste the chea (Nestor notabilis), a New Zealand parrot that loves to shred pieces of meat and blood from farm animals, on the back of which it is perched. A ruthless killer? No. Rather, a skilled opportunist who has expanded his tastes to survive.

No label. These examples suggest that it is not only the characteristics of the digestive system that guide food preferences in the animal world, but also the need and opportunity for supply. Rabbits and sheep do not have anatomical characteristics suitable for catching prey, but this does not exclude that they can obtain energy from animal tissues, if they have the opportunity. It's about getting the most out of the resources offered by the environment. If this means adopting a semi-vegetarian, or carnivorous approach with exceptions, or whatever nuance there is in the middle, so be it.