Nature
PUBLISHED
The phrase “crocodile tears” has long been used to shame someone for their insincerity but it seems crocodile tears might be as a real as they come, as a new study has found that the tears of both birds and reptiles are almost identical to our own.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Working with a team of veterinarians from a range of wildlife centers, they captured the tears of macaws, hawks, owls, and a parrot, as well as tortoises, sea turtles, and caimans. I bet that last tear collection was a rollercoaster. They also collected tears from 10 healthy human volunteers, presumably by exposing them to Awakenings and scooping the mess that remained.
All of the tear samples were similar with regards to their electrolyte composition, though bird and reptile tears showed a slightly higher concentration compared to the other species. There was also more urea and protein in the tears of the owl and sea turtles. The study is published in the journal Frontiers in Veterinary Science.
The real variation didn’t begin to show until the researchers looked at how the tears crystallized as they dried, forming completely different patterns that look a bit like a series of squashed snowflakes. The tears of the turtles and caimans were particularly unique, which likely demonstrates that they’ve adapted in some way to function in their aquatic environments.
The researchers acknowledge that their samples are based on captive animals, which could potentially differ from animals in the wild, but the study remains one of the largest comparisons of tear compositions across species.
"Discovering how tears are able to maintain the ocular homeostasis, even in different species and environmental conditions, is crucial for understanding the evolution and adaptation processes, and is essential for the discovery of new molecules for ophthalmic drugs," said lead author Professor Arianne P. Oriá, of the Federal University of Bahia, Brazil. "This knowledge helps in the understanding of the evolution and adaption of these species, as well as in their conservation.”
