Four different animals: parrot, caiman, rabbit, and snake

Macaws (top left) don’t like to have an eye exam. They completely refuse to do it after lunch!

You won’t win a staring contest with a caiman (top right). Its tears are so  thick that it only needs to blink once every few hours.

Rabbits’ (bottom left) tears are super stable to help them keep still and hide from predators. A blink at the wrong time could mean the difference between life and death.

Snakes (bottom right) like the bush viper  have a clear skin film called a spectacle that holds tears against their eyes.

Shutterstock.com (All Images)

STANDARDS

CCSS: 6.SP.B.5.B, MP1, MP3, MP5

TEKS: 6.12A

Measuring Tears

What have scientists learned by studying animal tears?

Strips placed on an owl's eyes to measure its tears

Arianne Pontes Oriá

To measure this owl’s tears, Oriá places strips of paper under its eyes. Don’t worry—it doesn’t hurt the owl.

She doesn’t make animals cry for her work, but Arianne Pontes Oriá does study their tears! The Brazilian veterinarian carefully collects an animal’s tears—from owls to crocodiles—and places them on microscope slides. Under magnification, each animal’s tears look like a snowflake, revealing their unique structure. Studying this structure helps Oriá understand these adaptations, including how some animals can go so long without blinking.

Only humans cry to express emotion, but all animals have tears. Tears are essential to keep eyes healthy because they protect the cornea, the clear outermost part of the eye. The watery substance contains proteins, salts, and oxygen that nourish the cornea. Normally blood provides nutrients and oxygen to cells, but there are no blood vessels in the cornea. Blinking helps spread tears across the eye, keeping it clean and moist.

“Different animals have a different stickiness to their tears,” says Sara Thomasy. She’s an animal ophthalmologist who studies and treats animal eyes. If a crocodile’s tears weren’t so thick, for example, they would wash away in the swampy water.

Close-up image of a snake. Text reads: Studying Tears
As tears dry, they leave behind crystal patterns that look like snowflakes under a microscope. Here are few examples from different animals.

Some animals, like snakes, live in dry environments and need extra-moisturizing tears to keep their eyes from drying out. Others, like rabbits, freeze in place to hide from predators. So they need to go for long periods of time without blinking. “Rabbits have a tear film that’s so stable that they only have to blink every half an hour,” says Thomasy.

When researchers collect tears, expert animal handlers restrain the creature. Then the scientists either swab the animal’s eyes or extract the tears using a soft syringe. For some species, it can take more than six months to collect 1 milligram of tears!

“We can use what we learn about animals to help people,” says Thomasy. “It’s very painful when your eye doesn’t produce enough tears. We could find a whole new way to treat dry eye by studying species who have adaptations.”

math-instructional-allaboutgraphsmp4
Watch an instructional video about graphs.
Plotting the Path
Play a fun math game about building line graphs.

Read the research scenarios and determine which type of graph would be best for displaying the data the scientists collect. Record your work and answers on our answer sheet.

Oriá analyzes the different proteins in a caiman’s eye. Each type of protein makes up a different part of the total proteins in its eye. Which graph should she use to display this data?

A researcher records the number of times different animals blink over the course of 5 minutes. Which graph should she use to display this data?

Thomasy collects rabbit tears at the same time every day for one month, and records each day’s tear volume. Which graph should she use to display this data?

A. Oriá wants to create a set of graphs that compare the composition of human tears to barn owl tears. Which type of graph should she use to display this data?

B. Is there another way to represent this data? Explain.

What type of data would a researcher need to collect to make a line graph representing the tear production of a hawk? Explain.

Slideshows (1)
Close-up image of a snake. Text reads: Studying Tears
Studying Tears

As tears dry, they leave behind crystal patterns that look like snowflakes under a microscope. Here are few examples from different animals.

Lesson Plan (1)
Lesson Plan
Lesson: Measuring Tears

View a lesson plan about displaying data with a classroom activity.

Text-to-Speech