Birds cannot taste sweetness, at least chickens do not, as it was first discovered in 2004 when the bird’s genome was fully sequenced. After checking other birds as well, researchers discovered that birds lack the T1R2 gene responsible for identifying sweetness.
Researchers from Harvard University and University of Tokyo teamed up to understand what makes the hummingbird special. Hummingbirds adapted taste receptors to sense sugars, as they feed on nectar all day long. They are some of the fastest birds and their helicopter like flying style requires a lot of energy. When the nectar they are feeding on does not contain enough sugar, the birds move to another source of food.
But as their other relatives, hummingbirds cannot taste sweetness, it was thought. Despite lacking the T1R2 gene, hummingbirds managed to find a way of achieving their goal. Usually T1R2 and T1R3 proteins combine to help our tongs identify sugary content. Hummingbirds do it differently.
Because they lack an important gene which produces the sugar identification protein, hummingbirds appealed to another combination. T1R1 and TiR3 combined in the case of these birds to help them identify sugar. The change occurred sometimes between 40 and 72 million years ago, after which hummingbirds branched in around 300 species in the Americas.
Animals never seize to amaze us. Just a couple of days ago, another team of scientists managed to understand how do geckos climb walls.
Hummingbirds adapted taste receptors to sweetness and they get angry when they do not get it
Researchers cloned the taste receptor to from chickens, hummingbirds and swifts. Afterward they tested the receptors’ responses to amino-acids and sugar. Moreover, they mixed chicken and hummingbird taste receptors to understand the receptor’s evolution in time. In the last 40 million years, hummingbirds changed their taste genes 19 times. In their tests, hummingbirds reacted to carbohydrates and sugar, but less so to amino-acids.
“If you look at the structure of the receptor, it involved really dramatic changes over its entire surface to accomplish this complex feat,” Liberies said in the statement. “This dramatic change in the evolution of a new behavior is a really powerful example of how you can explain evolution on a molecular level.”
Further outdoors testing showed that hummingbirds can easily identify sugar. After offering sweet products, water and synthetic sugars and recording their feast on tape, researchers observed some patterns. Even if hummingbirds adapted taste receptors to distinguish sugar, they only ate natural and artificial sugars. They were not keen on synthetic sugars and water.