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Why Do Goats Have Such Weird Eyes?

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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.

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.
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There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

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