Why Do Goats Have Such Weird Eyes?

iStock
iStock

Even with their yelling and fainting competing for your attention, it’s hard not to notice a goat’s eyes. Their horizontal, rectangular pupils seem alien compared to the round pupils of people and dogs and the vertical slits of cats. Why do goats’ eyes look like that? And for that matter, why do cats’ eyes look the way they do? In a new study, vision scientist Martin Banks has found that the shape of an animal’s pupils is a clue to its place in the food chain.

Banks and his team looked at the eyes of 214 different species of land animals, and found a clear relationship between the shape of their pupils and their ecological role. Predatory animals that ambush their prey tend to have vertical slit pupils, while herbivores that are prey for other animals usually have horizontal pupils.

The predator-prey divide in pupil shape suggests that the hunters and the hunted gain some advantage from having a specific type of pupil. To find out what those advantages might be, the researchers analyzed the abilities of the two pupil shapes and how they could serve the different visual requirements of predators and prey.

Goats and other grazing animals (like deer, cattle and moose) that are hunted by predators have a pretty simple strategy for not being eaten: look out for danger and run away if they see it. Their eyes need to be able to do two things to support that strategy. “On the one hand, these animals must see panoramically to detect predators that could approach from various directions,” the researchers write. “On the other hand, they must see sufficiently clearly in the forward direction to guide rapid locomotion over potentially rough terrain.”

Horizontal pupils help here, the team found, because their shape creates a sharp panoramic view that’s wider and shorter than what you’d get with a round or vertical pupil and lets the animal see nearly all around itself. A long horizontal pupil also enhances the image quality of objects ahead of and behind the animal, and helps the eye capture more light along the ground and less dazzling overhead light.

Of course, those benefits don’t apply if the pupil stays oriented the same way and becomes vertically aligned when the animal tilts its head to graze. After watching grazing animals at the zoo, though, the researchers found that their eyes rotate to stay horizontally aligned with the ground whether their heads are upright or face down in the grass.

For a land animal that’s in danger of being eaten by something else and has few options besides being aware of its surroundings and running away, the researchers say that a long horizontal pupil seems to be ideal. In other words, goats have weird eyes because they help keep goats alive.

Meanwhile, the team found that vertical, slit-shaped pupils help small ambush predators like cats and snakes judge the distance of prey and other objects so they know how far they have to pounce.

14 Adorable, Vintage Photos of Rabbits

Chaloner Woods, Getty Images
Chaloner Woods, Getty Images

In honor of International Rabbit Day (held annually on the fourth Saturday of September), we've pulled photographic proof that the furry little mammals have always been appreciated by children and the adults who use a number of rabbit-related phrases and idioms more often than they probably realize.

1. DOWN THE RABBIT HOLE

Nursery school children playing with their pet rabbit Bubbles; 1939.
David Parker, Fox Photos/Hulton Archive/Getty Images

Nursery school children playing with their pet rabbit Bubbles, 1939.

2. DUST BUNNY

 A woman spinning Angora rabbit wool in her garden, 1930.
Fox Photos, Getty Images

A woman spinning Angora rabbit wool in her garden, 1930.

3. MAD AS A MARCH HARE

A young boy holds a pet rabbit, 1955.
Charles Ley, BIPs/Getty Images

A young boy holds a pet rabbit, 1955.

4. BUY THE RABBIT

A golfer makes a practice drive while his pet rabbit minds the balls; 1938.
Reg Speller, Fox Photos/Hulton Archive/Getty Images

A golfer makes a practice drive while his pet rabbit minds the balls, 1938.

5. HONEY BUNNY

School children petting rabbits; 1949.
Chaloner Woods, Getty Images

Schoolchildren petting rabbits, 1949.

6. HAREBRAINED IDEA

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.
Fox Photos, Getty Images

A woman took her Himalayan rabbit, Albrecht Durer, on a walk in Hyde Park, 1939.

7. CUDDLE BUNNY

A little girl petting a large rabbit, 1949.
Chaloner Woods, Getty Images

A little girl petting a large rabbit, 1949.

8. LUCKY RABBIT'S FOOT

Schoolgirls care for pet rabbits, 1932.
Fox Photos, Getty Images

Schoolgirls care for pet rabbits, 1932.

9. PULL A RABBIT OUT OF A HAT

A young magician and his rabbit, 1971.
George W. Hales, Fox Photos/Getty Images

A young magician and his rabbit, 1971.

10. SNOW BUNNY

A woman shows off her two pet angora rabbits, circa 1955.
George Pickow, Three Lions/Getty Images

A woman shows off her two pet angora rabbits, circa 1955. Angoras can be sheared to provide enough wool for two sweaters each year.

11. THE EASTER BUNNY

A little girl holds an Easter bunny on a leash, circa 1955.
George Pickow, Three Lions/Getty Images

A little girl holds an Easter bunny on a leash, circa 1955.

12. A RABBIT TRAIL

Three children hold a rabbit, 1935.
H. Allen, Topical Press Agency/Getty Images)

Three children hold a rabbit, 1935.

13. RABBIT FOOD

A boy feeds his pet rabbit a lettuce leaf, circa 1955.
George Pickow, Three Lions/Getty Images

A boy feeds his pet rabbit a lettuce leaf, circa 1955.

14. RABBITING ON

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.
Central Press, Getty Images

Actresses Fiona Fullerton and Clare Clifford posting some of the many letters sent to the House of Lords and parliamentary candidates to request support for World Day for Laboratory Animals which was instituted that year, 1979.

Fossilized Fat Shows 550-Million-Year-Old Sea Creature May Have Been the World's First Animal

Ilya Bobrovskiy, the Australian National University
Ilya Bobrovskiy, the Australian National University

A bizarre sea creature whose fossils look like a cross between a leaf and a fingerprint may be Earth's oldest known animal, dating back 558 million years.

As New Scientist reports, researchers from the Australian National University (ANU) made a fortunate find in a remote region of Russia: a Dickinsonia fossil with fat molecules still attached. These odd, oval-shaped creatures were soft-bodied, had rib structures running down their sides, and grew about 4.5 feet long. They were as “strange as life on another planet,” researchers wrote in the abstract of a new paper published in the journal Science.

Another variety of fossil
Ilya Bobrovskiy, the Australian National University

Although Dickinsonia fossils were first discovered in South Australia in 1946, researchers lacked the organic matter needed to classify this creature. "Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Edicaran biota were: giant single-celled amoeba, lichen, failed experiments of evolution, or the earliest animals on Earth,” senior author Jochen Brocks, an associate professor at ANU, said in a statement.

With the discovery of cholesterol molecules—which are found in almost all animals, but not in other organisms like bacteria and amoebas—scientists can say that Dickinsonia were animals. The creatures swam the seas during the Ediacaran Period, 635 million to 542 million years ago. More complex organisms like mollusks, worms, and sponges didn’t emerge until 20 million years later.

The fossil with fat molecules was found on cliffs near the White Sea in an area of northwest Russia that was so remote that researchers had to take a helicopter to get there. Collecting the samples was a death-defying feat, too.

“I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone, and repeat this process until I found the fossils I was after,” lead author Ilya Bobrovskiy of ANU said. Considering that this find could change our understanding of Earth’s earliest life forms, it seems the risk was worth it.

[h/t New Scientist]

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