Penguins may love devouring fish, but it turns out they might not be able to taste them.
While analyzing the genetic data of five penguins, each of a different species, researchers at the University of Michigan discovered that all the birds were missing three of the five basic taste genes. "Based on genetic data, penguins are believed to have sour and salty tastes, but have lost sweet, umami, and bitter tastes,” researcher Jianzhi Zhang told the BBC, adding that the birds likely lost these taste genes when they evolved millions of years ago.
Zhang said that penguins may be unique in this deficiency. He told the HuffPost that “no other bird is known to have lost three tastes. As far as we know, most birds have both umami and bitter taste receptor genes.” Most, however, cannot taste sweetness.
Without this ability to taste umami, or a savory, meaty flavor, it’s possible that penguins -- who are also believed to lack taste buds on their tongues -- are unable to taste the seafood that makes up their diet.
"Penguins eat fish, so you would guess that they need the umami receptor genes, but for some reason they don't have them,” Zhang said in a news release. “These findings are surprising and puzzling, and we do not have a good explanation for them. But we have a few ideas.”
The researchers speculate that the cold environments in which penguins evolved may have played a role in their changing tastes, as the taste receptors for sweet, umami and bitter are said to function poorly in cold temperatures.
Still, though it might strike some as odd that a carnivorous animal can’t taste meat -- or perhaps anything at all, given penguins' reduction in taste function both at an anatomical and sensory level -- researchers say that a lack of taste is likely not such a big deal for the birds: penguins swallow their food without chewing.
"Their behavior of swallowing food whole, and their tongue structure and function, suggest that penguins need no taste perception," said Zhang, "although it is unclear whether these traits are a cause or a consequence of their major taste loss."
The researchers' findings were published this week in Current Biology.