On a recent trip to the Colorado Rocky Mountains, I saw a large herd of desert bighorns. I was amazed by how they had adapted to their surroundings as they climbed the cliffs.
The horns on bighorn sheep are helpful for protection from predators and are used to get into plants such as cacti. Bighorn sheep have a soft and rigid parts on their hooves to allow them to grip cliff faces, allowing them to climb effortlessly.
I spoke to a few rangers and got great information from them.
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How Do Bighorn Sheep Hooves Grip?
Although not as agile as mountain goats, bighorn sheep are very well adapted for climbing and descending the steep terrain they live in. By climbing up cliffs, they keep most predators away. However, golden eagles will sometimes attack and kill lambs.
The bighorn sheep’s hooves are made of two parts so they can cling firmly to steep and rocky terrain. The hooves are spongy in the center with a hard outer edge. The padded, soft, rubbery soles help them maintain traction and balance as they move up sheer rock faces and through the uneven and slippery ground.
The pad of a bighorn sheep feels like a human heel and digs into the terrain, molding to the surroundings and helping the bighorn grip. The toenail-like outer hoof snags any slight protrusion in the rock face allowing the bighorn to grip on smaller surfaces.
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The hoof prints resemble a deer, with hind patterns slightly smaller than the forehooves. Bighorn prints are less heart-shaped, less pointed, have straighter edges, and are more splayed than deer prints.
If the print has been taken from a bighorn descending on soft ground, their claws may sometimes print two dots behind their hoof print. The bighorn walking stride is approximately 18 inches.
Bighorn sheep are incredible at jumping. They can clear a jump of 15 feet, but this can increase to 30 feet if jumping downhill. This enables the bighorn to escape predators quickly and reach areas out of reach of most animals.
The bighorn’s foot axis is between the third and fourth digits, and they walk on the tips of these with the claws taking the weight. The second and fifth digits are vestigial, and the first has disappeared completely. The two larger digits are the same size forming a cloven hoof.
The vestigial third and the fourth digit are used as brakes when descending steep slopes. The stiffer outer edge of the hoof makes contact with the ground first.
When the hoofs are off the ground, the cloven claws are together, but when on the ground, they spread apart with the body weight transferred to the foot. The sole only bears the weight on soft earth, where the perimeter skin can sink in and the hooves spread apart without much resistance.
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How Do Bighorn Sheep Deal With Predators?
Bighorn sheep have adapted to live in North America’s western mountainous regions, ranging from southern Canada to Mexico.
The bighorn sheep’s predators are wolves, coyotes, cougars, and occasionally the gray fox, bobcat, lynx, black and grizzly bears, jaguar, ocelot, and wolverine. However, the bighorn sheep have adapted to their terrain well.
The bighorn sheep use the steep mountainous habitat to their advantage, using ledges sometimes only two inches (five centimeters) wide to escape.
This terrain is effective against predators such as wolves and coyotes, but predators such as cougars may overcome this.
How Do Bighorn Sheep Deal With Wolves?
The steep, rugged terrain is ideal for getting away from wolves. Wolf predation on other animals, such as caribou and moose, is much higher as they cannot seek the protection they need from the wolves in mountainous territory.
When bighorn sheep move away from terrain such as rocky ridges and into heavily timbered areas, a wolf can cause severe damage to a bighorn herd.
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How Do Bighorn Sheep Deal With Coyotes?
Apart from wolves, coyotes are the most successful predator of bighorn sheep. Coyotes primarily restrict themselves to lambs, with most attacks being incidental.
Coyotes are not thought to be a likely cause of limits in sheep populations. They are not considered effective predators of bighorn sheep as they can escape through the mountainous terrain.
How Do Bighorn Sheep Deal With Cougars?
Cougars appear to be the only predators that can decimate a sheep’s population, even in habitats where bighorns can escape. The prey is usually determined and selected by size.
The less experienced, smaller cougars select smaller lambs, with larger, more experienced adults killing adult sheep. Rams tired from rutting are often preyed upon by cougars.
Cougars kill both rams and ewes and will kill adults or lambs. Cougars are more likely to prey on bighorn sheep when they live alongside mule deer, as this is a great food source for the cougar.
How Do Bighorn Sheep Deal With Golden Eagles?
Golden eagles can be problematic to young lambs, with many being killed because of the bird. However, large sheep are mainly untroubled.
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Do Bighorn Sheep Have Good Eyesight?
Bighorn sheep have horizontal pupils that help them to look for predators. The sheep see panoramically to detect predators that could approach from different directions, and they also need to see forward so that they can run over rough terrain.
The horizontal pupils create a broader and shorter panoramic view than a round or vertical pupil would see, allowing them to see almost every direction. Horizontal pupils give them a higher image quality, allowing them to see better ahead.
The flat shape of the pupil also captures less overhead light while capturing more light from the ground. Bighorn sheep rotate their eyes to stay horizontal to the ground when their heads are up or down.
The horizontal eyes help keep the sheep alive by cutting out extra dazzling lights from the sky, giving them a panoramic view and a better image quality. Bighorn sheep have very wide-spaced eyes, enabling a panoramic view.
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What Do Bighorn Sheep Use Their Horns For?
To get the attention of a ewe, the rams butt heads to compete for their mate. These contests can take up to 24 hours, with the rams running at each other at speeds of 40 km/h and withstanding forces up to 800 pounds.
The impact causes side-to-side vibration at the horn tips. This allows the horns to draw away kinetic energy from the brain cavity and dissipate it. Because of this, the bones have been adapted through evolution to suffer little or no injury or structural damage.
The horn is made from keratin and is filled with a thin cortical bone shell containing a foam-like tubular bone.
Female ewes have longer, straighter horns as they do not use these in the rut. The ewes use their horns to get into spiky cacti to get nutrients and liquid out of the center.
How Have Bighorn Sheep Adapted To Eating And Drinking?
Bighorn sheep have adapted well to desert heat and also snow. Their temperatures can fluctuate several degrees safely, unlike most mammals.
They will rest in the shade of caves and trees in the desert. Desert bighorn can go for several weeks or months without visiting water in the winter, but they usually go to a watering hole every three to five days in the summer.
Bighorn sheep quickly recover from dehydration and can lose up to 30% of their body weight due to dehydration. This allows the desert bighorn to survive in areas away from predators that need water.
Bighorn sheep have a complex stomach to extract all the essential nutrients it needs. The foliage they eat provides the necessary moisture.
The stomach is very complex, with four chambers. Bighorn sheep do not chew their food much before swallowing it. The plants go into the first chamber of their stomach, full of bacteria and other organisms that help break down the plant material.
The sheep spit up the food before chewing it again. This then goes into the second, third, or fourth chamber, where the water and nutrients are taken out of the food.
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References and Further Reading
“Bighorn Sheep: Behavior, Ecology, Conservation” by Arthur M. Bartone
“Bighorn Sheep: A Technical Conservation Assessment” by David R. Thomson, Sharon A. Grossenheider, and Richard H. Yahner
“Bighorn Sheep: Status Survey and Conservation Action Plan” by the International Union for Conservation of Nature and Natural Resources (IUCN)
“The Bighorn Sheep: Ecology and Management” by Joel Berger
“Bighorn Sheep: Ovis canadensis” by David E. McRuer
“Mountain Sheep of North America” by Valerius Geist
“Bighorn Sheep: Kings of the Mountain” by Kevin Hansen