Researchers sequencing the five different taste receptors in penguins were surprised to discover that the animals do not have genes that encode for receptors that are specific for savory meaty flavors (like fish!), sweet or bitter tastes. Instead, the data suggest that penguins are only able to taste the saltiness or sourness of their foods and also suggest that the birds may not be able to taste their fish dinner.
According to a quote from the lead study author Jianzhi George Zhang (University of Michigan, Ann Arbor), “As far as we know, penguins are the only birds that have lost three of the five basic tastes.” He thinks that the protein Trpm5 is at the root of this problem because this protein does not work well at low temperatures. Incidentally, this protein is also important in the detection of the three lost types of tastes. Alternatively, it is possible that the tastes were lost because penguins usually swallow prey whole whereas salty tastes inform the animals of salt intake and sour tastes let them know if a food might be spoiled. “So it’s likely that having sour and salty tastes is still beneficial to penguins,” he says.
According to an article in New Scientist, cats and birds similarly lack receptors that can detect sweet tastes (with the exception of hummingbirds that have re-purposed other receptors to taste nectar). The most extreme loss has been found in dolphins and whales as they can only detect salty tastes.
I do not think that I would enjoy being a penguin. I cannot imagine life without tasting the bitterness of coffee or the sweetness of dessert…