Why Bighorn Sheep Heads Don’t Explode When They Violently Smash Into Each Other

One of Wyoming’s most incredible wildlife experiences is watching bighorn sheep violently bashing their heads together. 

When rams can’t reconcile their differences or are competing for the attention of ewes during the rut, they charge at each other at up to 30 mph and slam their heads together with a crash that can be heard up to a mile away. 

It’s an incredible display that can make people wonder why their heads don’t explode on impact.

Bighorn rams aren’t flippant about head-butting. Their entire bodies are designed to take the brunt of these high-impact duels, and when it comes to full-body impacts, they’re a head above the rest.

“Bighorn sheep are adaptive geniuses,” said Katie Cheesbrough, executive director of the Wyoming Wild Sheep Foundation. “They can sustain a force of over 2,000 pounds energy at impact, and they’ve got a cool range of adaptations that allow them to have these incredible clashes.”

One of Wyoming’s most famous bighorn rams was Bam-Bam, who would not only head-butt his animal rivals, but also cars driving through Sinks Canyon in the late 2000s. He’s been gone for more than a decade, but couldn’t pass up the challenge of a car or truck.

“If he could see his own reflection in the vehicle’s paint, he’d respond to that,” Kent Schmidlin, who was the Wyoming Game and Fish Department’s regional wildlife supervisor at the time, told Cowboy State Daily previously. “He would do what a bighorn ram does and ram into those vehicles, apparently going after his own reflection.”

Horn, Bone And Ossicone

People ram their heads into objects and each other during impulsive moments or as part of various sporting events, but our skulls aren’t designed for high-level impacts. Bighorn rams have better heads on their shoulders — at least for bashing — and many adaptations to ensure their safety when they clash.

“Their horns are covered with a thick layer of keratin, and the curves deflect some of the impact away from their brains,” Cheesbrough said. “Their skulls have two dense layers of bone around their brains, and there’s a honeycombed stress layer between those two layers, which creates a cushion.”

Keratin is the same material that makes up the fingernails of humans. The big horns of bighorn sheep can weigh up to 30 pounds, as much as the rest of its skeleton. 

The National Bighorn Sheep Center in Dubois has an exhibit featuring a bighorn ram skull sliced down the middle to reveal its internal structures. Executive Director Amanda Verheul said that structure allows rams to endure tremendous impacts repeatedly without causing permanent damage to their brains and bodies.

“The skull is thicker at the crown, and that layer of cellular cushioning stretches from that thicker layer all the way into their skull cap,” she said. “The horns cover protrusions on their heads called ossicones, and they’re attached to the skull with a thick layer of gristle.”

Furthermore, Verheul said bighorn rams could literally brace themselves for impact. Before head-butting, the cellular cushioning in the skull and ossicones fills with fluid for even more protection.

“That spongy layer absorbs a lot of the impact to protect the brain,” she said.

That well-protected but mostly hollow structure creates an incredibly resonant sound when the rams collide. The sharp crack of bighorn ram-on-ram action is so loud that it can be heard up to a mile away.

Head And Shoulders

Humans get concussions when their brains bash against the inside of their bony skulls. A layer of fluid separates brain from bone, but that often isn’t enough to absorb a strong, sudden impact.

Bighorn sheep don’t have that problem. 

Cheesbrough said their brains are more tightly packed into their braincases than many other animals.

“Because the bighorn sheep have tightly packed brains, they have less chance for concussions,” she said.

Other aspects of the musculature and skeleton support the specially evolved head. Cheesbrough said the ram’s whole body is designed to absorb this level of impact.

“They have strong, thick neck muscles attached to a strong spine,” she said. “That lets them absorb more impact and protect their spine as well.”

Even with these incredible adaptations, Verheul is consistently impressed with what the rams can endure.

“It’s really intense and incredible that they can live through it,” she said.

Dance For Romance

In late winter and spring, bighorn sheep are placidly grazing and moving through their native ranges throughout Wyoming. Ram will only go head-to-head to compete for females and dominance during their rutting season, usually between the end of October and mid-December.

Bighorn rams coexist peacefully in bachelor herds for most of the year. They only descend to find ewes and confront each other when ready to rut.

Head-butting is the most dramatic and iconic part of the bighorn ram rut, but it’s the climax of a long and complicated mating ritual. Cheesbrough described it as “a dance of dominance” that might end without the climatic finale.

“There's a little tussling that instigates everything,” she said. “If one ram feels like he can take on another, he might kick him in the side or the back. That might instigate some head-butting for final dominance, but there’s a lot of sniffing, kicking, and tussling before that happens.”

Head-butting is the exciting clash that everybody likes to talk about, but there's a lot that happens throughout the rut to establish dominance. Rams often try to escort a harem of ewes away from the other rams without confrontation.

When they resort to head-butting, the rams (usually the younger ones in a similar "weight class') will line themselves up and charge at speeds of 30 mph before colliding. It's an iconic Western showdown, and even though no guns are involved, the sound of horns colliding with horns resonates like a gunshot in the thin mountain air. 

Bighorn rams have what it takes to endure the clash, but Verheul said that’s the dramatic end to a long, complicated ritual. 

“Rams do a lot of dramatic displays before they get to the head-butting,” she said. “There’s a lot of sniffing, kicking, and moving around during the rutting behavior, and dominance is usually established before the head-butting.”

Vulnerabilities

While bighorn sheep are generally healthy during the rutting season, with their bodies at maximum fat content, the rut is stressful for everybody. Verheul said it’s not uncommon to see higher fatalities among rams and ewes at this time, but not because of head-butting.

“The ewes are getting pushed a lot during the rut,” she said. “It puts a lot of pressure on all of them because you might have ewes that aren’t ready to be bred being pushed around by the rams, and that can lead them to places where they’re more suspectable to predators.”

The bighorn sheep rut can allow bears, wolves, and mountain lions to pick off an isolated ewe while the rams are busy pushing everyone around. The sonorous impact of rams slamming their heads together might as well be a dinner bell.

Headbutting can also take its toll. A 2022 study published by the National Library of Medicine determined that bighorn sheep and other headbutting bovids do show evidence of chronic and acute brain trauma.

The brains of bighorn sheep showed less evidence of traumatic brain injuries than other head-butters, like musk oxen, but there was still evidence of long-term impact. Their adaptations, however remarkable, aren’t foolproof.

Give Them A Break

Bighorn sheep are making a comeback. After being decimated by hunting, disease, and habitat encroachment, Wyoming’s bighorn sheep populations are slowly returning to their historic numbers.

“They are not what they once were, but they are better than they have been,” Cheesbrough said. “Bighorn sheep populations were at their highest before European expansion but were decimated across most of the West by the 1960s. Conservation efforts from different wildlife management agencies have worked well, and we've seen an increase in bighorn sheep since those times, but it's still a struggle. They're still not anywhere near where they used to be.”

Bighorn sheep aren’t making it easier on themselves through their rutting behaviors. That’s why Verheul and the National Bighorn Sheep Center are trying to dissuade people from seeking the sheep out when they’re putting on the best show.

“When tourists and eco-tours come to the center, we like to talk about giving the sheep a break during that time of year,” she said. “You can get some great shots and footage of rams rutting, but we ask that they don't push these sheep during this crucial time.”

Verheul said several bighorn sheep were captured around Dubois in 2024 to be tested for Mycoplasma ovipneumoniae, a strain of pneumonia in domestic sheep and goats that can be devastating for their wild relatives. The captures, done via helicopter, disrupted the seasonal movement of the herds near Dubois.

“Encroachment changed up their dynamics this season,” she said. “They didn't come down to their usual area where we see them during rutting season. They stayed up a bit higher this year. That was probably due to several things, like moisture content, warmer temperatures, and habitat, but people can change their patterns.”

Unlike Greater sage grouse, which have specific leks they return to for breeding, bighorn sheep can rut anywhere at any time during the rutting season.  However, the encroachment of trees and people can give them fewer open places for dramatic displays.

“All of these challenges come with a growing population and growing recreation,” Cheesbrough said. “Bighorn sheep are doing okay in Wyoming, but good wildlife management, partnerships, and research are needed to help this iconic species.”

Learning And Watching

There’s a lot of knowledge in the battered heads of bighorn sheep. The bone structure that allows them to repeatedly withstand tremendous forces while headbutting is helping make people safer.

The skulls of bighorn sheep have inspired new designs for safer helmets. Engineers are mimicking the lightweight, spongy design to make human heads safer when extra protection is needed.

Humans shouldn’t butt heads — our skulls aren’t designed for it, even with better helmets. That’s best left to the professionals, and nothing does it better than bighorn sheep.

“If you're in the right spot at the right time, when those males are coming down, and you can catch a glimpse of them headbutting, it’s unbelievable,” Cheesbrough said. “'It's like nothing else in nature.”

Andrew Rossi can be reached at arossi@cowboystatedaily.com.