What Are Crocodile Tears? Fluid From Reptiles’ Eyes Has Similar Chemical Makeup With Humans

Crocodile tears are often associated with superficial sympathy and insincere displays of emotion. However, in reality, other animals, like crocs, cry, and their tears are just like ours.

What Are Crocodile Tears?

Most of us consider tears a characteristic of humans and a component of the intricate web of human emotion. All vertebrates, including birds and reptiles, have tears, essential for preserving good vision.

According to one study, the tears of non-human animals and our own are dissimilar. The degree of chemical similarity between human eye diseases and the makeup of tears from other species, as well as how these species have adapted to their surroundings, may offer new treatment options.

For the first time, Brazilian vets examined the tears of birds and reptiles, concentrating on seven different species: red-footed tortoises, barn owls, blue-and-yellow macaws, highway hawks, turquoise-fronted Amazon parrots, broad-snouted caimans, and loggerhead sea turtles.

Veterinarian Adrianne Pontes Oriá of Brazil's Federal University of Bahia led the study and was already aware that broad-snouted caimans, a relative of alligators with "beautiful eyes," may remain open without blinking for as long as two hours. In comparison, people blink once every 10 to 12 seconds. Blinking distributes Tears throughout the eye's surface, which maintains moisture and steady vision.

Oriá and her colleagues studied 65 captive animals at a conservation center, an animal care facility, and a commercial breeder in Brazil to analyze the tears of caimans and six other species.

The group carefully extracted tears from the animals' eyes using a syringe or test strips and from ten healthy human volunteers by the laws governing animal welfare. The researchers employed specialized kits to quantify certain substances and mixtures, like proteins and electrolytes (a sodium and chloride mixture).

Remarkably, despite the fact that mammals, birds, and reptiles all have distinct tear-producing organs, all of the species, including human tears, shared comparable chemical composition and electrolyte concentrations, except bird and reptile tears, which had somewhat greater concentrations.

This difference could be attributed to the fact that they breathe air and water, which could disrupt the ocular surface. According to Oriá, their tears need to have higher amounts of electrolytes to prevent inflammation.

Compared to the other species, human tears, caimans' tears, and barn owls' tears all had more protein. These proteins are critical for preserving the ocular surface's stability. Because caimans and owls have large eyes and long blink intervals, their protein contents may be higher. Additionally, caimans live with their eyes submerged in fresh water for extended periods, producing stable tears.

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Why Animals Cry?

According to senior curator Bryan Amaral of the National Zoo at the Smithsonian, animals do cry, but only to moisturize their eyes. Although it's frequently in their best interests to hide them in the wild, animals experience emotions. When a zookeeper finds tears in an animal's eyes, a veterinarian visit is usually necessary to check for corneal scratches or infections.

Three substances combine to make the film that tears are released from analogous glands or tear ducts in humans and certain other mammals - mucus, water, and oil.

The water is a naturally occurring saline solution that contains essential proteins and minerals. The oil keeps the eye from drying out, and the mucus coats the eye's surface and aids in binding the film to the eye.

The phrase "crocodile tears," which describes a person's artificial display of emotion, originates from the odd habit of crocodiles to weep while they feed. However, humans are the only known species to cry due to feelings.

For animals, tears help with eyesight by removing dirt and lubricating the eye. In addition, they guard against infection and nourish the cornea, the transparent, bloodless layer of the eye, said Lionel Sebbag, a veterinary ophthalmologist at Iowa State University in Ames.

Sebbag was not involved in the study.