The happiness level of dolphins in captivity has been studied for the first time - and it's produced some rather surprising results.
Scientists studied dolphin behaviour at Parc Astérix, an amusement park in France, and discovered that dolphins born in captivity are actually happier in their tanks than they would be in the open water due to higher levels of interaction with humans.
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The dolphins' happiness was measured using a range of behaviours - most notably a movement known as spy-hopping, which is when dolphins raise their eyes above the surface of the water.
This movement occurred most commonly when a dolphin's trainer or another familiar human was entering its tank, the BBC reports - indicating that's what they enjoyed most of all.
But while some may interpret the research as vindicating marine mammal parks, which have been blasted in recent years for animal cruelty, animal rights advocates say the research doesn't prove anything.
The University of Manchester's Dr Susanne Schultz told the BBC the study could not reveal "if a dolphin in captivity is happier than it would be if it was in the wild", because those born into the wild would not anticipate human interaction.
"I do think it's a valuable finding that dolphins in captivity potentially seek out contact with humans," she added.
"Just because a dolphin interacts with you doesn't mean that it would choose that lifestyle if it was given a choice."
Previous research has shown dolphins in captivity show higher levels of stress, have shorter lives, and are more likely to suffer frustration and depression.