A recent study by US and Chinese academics has shown penguins have highly limited taste sensation which prevents them from tasting fish.

According to the Telegraph, the discovery, which revealed penguins only have receptors for salty and sour flavours (not sweet, umami or bitter), was made during an attempt to map the bird's genome.

Professor Jianzhi Zhang, of the University of Michigan, US, and Wuhan University, China spoke about the findings:

"Their behaviour of swallowing food whole, and their tongue structure and function, suggest penguins need no taste perception." 

The research published in Current Biology suggests the polar environment might be the cause, as the brain's ability to detect sweetness and bitterness is affected by low temperatures, causing penguins to lose the ability permanently after many generations.