Battling Animals: Real Head Traumas and Fake Fierceness

Imagine that you’re visiting one of our iconic national parks, such as the mountainous Glacier, the pointy peaked Grand Teton or the rugged Yellowstone. You suddenly hear the unmistakable clack of horns echoing through the clear air, so you quickly bring up your binoculars to scan the rocky ridges, hoping to spot bighorn sheep. There they are: two males rearing up on their hind legs and crashing their huge horns into each other.

Rams (male bighorn sheep) fight to establish dominance in their group. Sometimes they charge at each other as fast as 40 miles per hour. Eventually, one of the rams will end up submitting, and the winner is the new leader. But this process can take hours. It can also take a heavy toll on sheep brains.

Recently, for the first time, scientists say that they can see hallmarks of concussions and other head traumas in the brains of deceased headbutting animals, such as bighorn sheep and musk oxen. This contradicts the commonly held belief that ramming animals do not suffer brain injuries because they have evolved to fight in just that way.

There are other animals, however, who avoid such epic battles by faking their fierceness. Some animal “weapons,” then, are a lot like plastic swords: impressive, but cheap in quality. These creatures pretend to be bigger than they are by building their defenses out of metabolically inexpensive, inert materials, such as chitin (a naturally occurring biopolymer found in the exoskeletons of insects, the cell walls of fungi, and in certain hard structures in fish and invertebrates) and keratin (the protective protein that makes up your hair, nails and skin). These prop weapons are also less costly to maintain.

Headbutting musk oxen

To conduct a scientific study on traumatic brain injuries (TBIs), researchers from the Icahn School of Medicine at the Mount Sinai Hospital in New York City collected and analyzed the brains of three deceased musk oxen from Greenland and four bighorn sheep, which were obtained from parks in Colorado, Utah and The Buffalo Zoo in New York.

One reason for obtaining the brains from these horned animals is that they are known to engage in violent head-to-head collisions, usually in social hierarchy rituals and before mating. For instance, while not quite as fast as male bighorn sheep, male musk oxen may reach speeds of up to 30 miles per hour before impact. Although a few studies have observed symptoms of traumatic brain injury in musk oxen, such as acting dazed, none have directly tested whether the brains of musk oxen and other ramming animals show any damage.

Another reason for procuring brains from these horned animals is that bovids—such as buffalo, cows, gazelles and the animals in this study—have gyrencephalic (folded) brains, like humans. Past studies of TBIs have been difficult to relate to people, since most of the research was performed on smooth, rodent brains. Studying the brains of ramming bovids provides a better model for understanding TBIs in humans.

When the three musk oxen brains from Greenland first arrived at the hospital research center, they looked healthy; and brain scans showed that the overall structure of each animal’s brain was intact. To look for signs of damage, the researchers cut the brains into thin slices and treated them with antibodies made to detect phosphorylated tau proteins, which are found in humans and mice. This form of tau is a sign of damage that is often seen in the brains of Alzheimer’s disease patients or in people who have suffered TBIs, including chronic traumatic encephalopathy (a disease involving alterations of the brain’s structure).

When the researchers looked at the musk oxen brains under a microscope, they saw that one of the antibodies stained them at easily detectable levels. In the bighorn sheep brains, however, a different antibody had lightly detectable levels of staining.

Publishing their results in the science journal Acta Neuropathologica on May 17, 2022, the scientists noted that at first, they were surprised by these findings. A challenge with such studies is knowing whether antibodies used on humans and rodents will work on bovid brains. But the fact that they did detect those antibodies suggests that the brains of these animals, especially the musk oxen, do sustain TBI-like damage.

Curiously, an old, female musk ox brain had about 20 times more staining than the brain of an older male and five times more staining than another female brain. This is the opposite of what the researchers hypothesized, since males are known to ram each other harder and more often than females.

The study does raise some questions that will have to await future research; for example, did the female musk ox brain appear to have more damage than the male one because of differences in skull anatomy? Why did the brains of bighorn sheep have so little damage? And will it be possible to harness the knowledge we gain from these animals to develop better treatments for human TBIs?

Cheating crustaceans

Consider this scenario, ask scientists from North Carolina’s Duke University: Two knights stand face-to-face. One has a plain, average-sized sword. The other has a massive, fear-inducing blade stained with blood. After one quick look at it, the first knight quickly puts his average sword away, backs off to a safe distance and runs for his life.

He’ll never know that the enormous, frightening sword was, in truth, a plastic toy.

From deer antlers to lobster claws, many animals have weapons. They are typically clunky, heavy and large appendages that are metabolically costly for the animals to maintain. Some animals even spend as much as 40 percent of their daily energy budget just sustaining themselves while doing nothing. In a clawed crustacean, such as a crab, lobster or shrimp, weapons can weigh more than a third of their body mass. It’s a lot of extra tissue to feed, even when the animal is perfectly still.

In many of these species, larger individuals have disproportionally larger weapons. For example, if a small animal’s weapon weighs two grams, that of an animal twice as big may weigh five grams—more than double that of the small animal’s weapon. This means that larger animals also have a disproportionately larger energy cost of maintaining their armaments.

Unless they cheat.

Muscles require lots of energy to remain viable, but chitin, the main component of a crab’s shell, is mostly inert. Once produced, it costs virtually nothing to maintain. The same goes for keratin, which comprises bird feathers, rhino horns and your fingernails.

Using one species of fiddler crabs and two species of snapping shrimp, Duke University researchers decided to test if animals could be minimizing the maintenance cost of their weapons by building them out of energywise-inexpensive tissues, such as chitin.

For each species, they looked at the relationship between a weapon’s size and the ratio of soft, expensive tissue to hard, cheap exoskeleton. They found that the larger the weapon, the higher the proportion of exoskeleton it contained. That is, the muscles don’t grow proportionally, leaving larger weapons with more “cheap crunch” and less highly expensive muscle. In fact, large animal weapons are a lot like plastic swords: impressive but ultimately cheap.

Animals that sport exaggerated claws are pretty good at deceiving their opponents, who usually have trouble assessing whether the individual they’re about to engage with is bigger, stronger or simply has a bloated claw.

But that’s not to say that an exaggerated claw is just a prop weapon. Among fiddler crabs who pinch and push each other, a bigger claw may have advantages in direct combat. In snapping shrimp, who fight by throwing extremely high-pressure bubbles at each other, larger claws may bestow an advantage. So, having an oversize appendage can improve performance during fights, but it’s also a way for animals to deceive—and do it in an extremely cheap way.

Many crustacean battles are won by intimidation; and even when they do escalate to full-blown violence, they are rarely lethal. So, having a “plastic sword” often works.

Artful adversaries

We sometimes think of the weapons that animals arm themselves with as honest indicators of how well they can fight, but sometimes those defenses are just physiological tricks that animals use to exaggerate how strong they are or to cheaply deceive a foe.

In battles, the worthiest opponent might be one that physically bests you. But to me, the truly superior nemesis is the one that can outsmart you.

Here’s to finding your true places and natural habitats,

Candy