Callum Jones
Scientists who put GoPros on dolphins in America have been surprised at some of the unexpected facial expressions the sea creatures were making while they were filming.
The US navy dolphins are trained to hunt for underwater mines and defend against enemy swimmers.
Over a six-month period, the dolphins were pictured eating over 200 fish and sea snakes in the San Diego Bay area off the cost of California.
Researchers say they are being studied as they want to learn more about how dolphins communicate with each other when they are hunting. Watch the footage below:
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It seems as though scientists were intrigued a 'side-eye' look the creatures were doing.
We often associate the 'side-eye' with a feeling of contempt or disapproval.
The 'side-eye' is an expression often portrayed by humans, but it is also common for animals to follow suit too.
According to the researchers, the dolphins were not in fact feeling judgy, but rotated their eyes in order to hunt their prey.
They wrote in a study published in Plos One: "It was evident that the visible eye was oriented toward the fish.
"The white posterior sclera was a visible sign that the eye ball rotated forward toward prey.
"At times we see a ring of skin deformation surrounding the eye ball that is probably indicative of eye muscle contractions.
"If the fishes escaped predation and swam past the dolphin, we observed the anterior white sclera as the dolphin rotated the eyeball backward to track the fish as it fled."
The GoPro footage did capture other facial expressions and noises the dolphins made during the six-month period.
Previous research has concluded that the clicks and buzzing sounds dolphins make are used for echolocation so the mammals can sense their surroundings.
Meanwhile the squealing noises they make are thought to express delight, and in the clip they can be heard squealing in celebration when they manage to catch a fish.
The researched continued: "Searching dolphins clicked at intervals of 20 to 50 ms. On approaching prey, click intervals shorten into a terminal buzz and then a squeal.
"Squeals continued as the dolphin seized, manipulated and swallowed the prey.
"If fish escaped, the dolphin continued the chase and sonar clicks were heard less often than the continuous terminal buzz and squeal.
"During captures, the dolphins’ lips flared to reveal nearly all of the teeth. The throat expanded outward.
"Fish continued escape swimming even as they entered the dolphins’ mouth, yet the dolphin appeared to suck the fish right down."