According to genetic studies, during evolution, flightless birds lost three out of five fundamental tastes long ago.

In most animals taste is very critical for their survival, but this may not be the case in penguins, as they swallows fish as a whole, say researchers in China and US.

Many birds cannot taste sweet things, but have receptors to detect bitter and meaty flavors.

Some of the taste genes were found missing when researchers were decoding the genome of penguin.

When looked more closely at the penguins DNA, discovery was made that all species lack the genes for the receptors of sweet, umami, and bitter tastes.

Lead researcher Prof. Jianzhi Zhang, of the University of Michigan, US and Wuhan University, China, told BBC that based on genetic data, penguins have lost sweet, umami, and bitter taste, and are believed to have sour and salty taste only.

Through umami taste, food gets strong and savory flavor that is related to meat.

In carnivores, it is surprising to lack this sense, but it does not matter too much in penguins, which eat food merely by swallowing and do not chew.

According to Prof. Zhang:

The behavior of Swallowing food as whole, and structure and function of tongue propose that no taste perception is not needed by penguins
Although it is not clear if this trait is a cause or effect of their main taste loss

Icy clue

He added:

The findings, published in journal Current Biology, were a puzzle

From the bird’s evolution on ice sheets of Antarctica, one clue comes.

Taste receptors that send signals from sweet, umami, and bitter taste does not work at very low temperatures.

Researchers say, in penguins, this may be the cause of gradual loss in sense of taste.

Interestingly, in almost all birds, the sweet taste is missing. An exception is the humming bird, which feeds on sweet nectar.