Tom

Winter in Yosemite

Winter is the quiet time in Yosemite. Days are short, there are fewer visitors and many of the animals spend a lot of their time hidden. Ground squirrels, bears and, of course, cold-blooded animals hunker down in hibernation or torpor for the winter. In very cold places, toads will burrow as deep as three feet to hibernate.

Some animals are active all winter, but nevertheless usually hidden. Meadow voles and mice live out much of their winters in the space that forms between the snowpack and the ground, the subnivean layer. There the warmth from the ground and the insulating layer of the snow keep the temperatures around freezing and the snow protects them from the elements. Unfortunately for the mice and voles, though, long-tailed weasels are well-adapted to hunt in the subnivean layer with their long, skinny bodies and keen sense of smell.

Despite the seeming quiet, there is still a lot going on above the ground. Coyotes and bobcats hunt the meadows when snow cover is thin. Using their acute senses of hearing and smell, they locate animals below the surface and then pounce. The coyote makes a big arcing jump, coming down mouth first, diving into the snow and fairly regularly coming up with a small meal.

The Time Machine

The real pleasure of the winter, though, is the winter time machine – animal tracks. Why are tracks a time machine? Because they allow us to go back in time and see what has happened in the forest since the last snow. One of our winter pleasures is putting on our skis and getting out into the woods shortly after a storm. It’s often surprising how much activity there has been, even in just a few hours after the end of the storm. So while the cold and snow make harder to see animals, it is far easier to see signs showing which animals have recently been out and about and where they were going.

Squirrels

We know, a lot of people are not fans of squirrels, but they are nearly ubiquitous in North America so almost everyone who lives in a place with snow can track them. And squirrels are fascinating animals, fun to watch and to track, especially Theresa’s favorite animal, the chickaree or Douglas squirrel (Tamiasciurus douglasii), a close relative of the more widely-distributed red squirrel (Tamiasciurus hudsonicus). How could you not want to track this guy?

The first thing to notice about squirrels is just how active they are as soon as the storm ends. On a sunny morning after a night of snowfall, the tracks will be everywhere. In the deep cold of winter nights, squirrels often congregate in group nests to stay warm, with males and females gathering in separate nests. But when day breaks, they are out and about. We actually see very few of them compared to summer, but the tracks let you peer into the past to see what they’ve been up to since the end of the storm.

Squirrel tracks also tell the story of how squirrels travel in snow. One thing to note is that the hind feet land in front of the forefeet when squirrels are bounding. Also tracks typically connect tree to tree, rarely passing through any real distance in the open. In soft snow, the squirrels climb a few feet up the tree and then hurl themselves off. We sometimes like to set our skis next to the tracks to estimate just how far they jump. Tom skis a 165cm (roughly 65-inch) ski and the jumps are commonly longer than his skis, so six or more feet.

Why? In soft snow, squirrels are slow waders/paddlers and easy prey. They look like they are swimming, which effectively they are, which makes them slow and vulnerable in light snow. Being such agile climbers and jumpers, it takes less energy and reduces the amount of time they spend out exposed to raptors, bobcats and coyotes if they climb up a few feet and get the next six feet of travel practically for free and almost instantly and then race to the next safe spot.

In very deep snow, they can get even more creative. One time Tom was out alone in one of our favorite spots and in his far peripheral vision he saw what he first thought was a raptor diving from the sky. Instead, it was a squirrel coming in for a landing in what seemed like open ground. The squirrel had walked out along a branch that was maybe 10 feet long and 15 feet up and hurled itself off. In so doing it covered most of the 20 feet between the tree it started on and the sheltering branches of a young sapling buried in snow. As soon as it hit the ground, it started paddling through the snow like it was swimming in a race and soon reached the sapling. The gaps in the snowpack created by the branches of the sapling gave it ready access to the world beneath the snow and down it went, within a few seconds safe from surface hunters.

It’s rare that we get to see these travel jumps, but the tracks tell the tale. It’s easy to ignore such a common animal, but that very ubiquity is one of the things that makes it fun — you don’t have to be a squirrel whisperer to find some tracks to follow.

The great thing about tree squirrels is that they are active all winter and numerous. So it’s rare to go out in freshly-fallen snow and not be able to at least find a squirrel track to follow and study. And there always seems to be something new to learn even from this most common animal.

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Mountain Lion Tracks

In 20 years of living in Yosemite, neither of us has seen a mountain lion (cougar, puma), but fresh tracks in the snow right after a storm sometimes tell us that we have missed a cougar by less than two hours.

One time we saw impressively large cougar tracks come to a set of manzanita bushes. The group of bushes was about fifteen feet in diameter but only a couple feet tall. You would think the easy thing to do would be to a go around, but apparently not. We could see the normal walking track of the lion then, as it approached the bushes, the forefeet and hindfeet bunching together as the cat readied to spring, then nothing. On the other side, we found the bunched tracks of the landing, then back to walking along on its merry way. It looked like the 15-20-foot jump was as trivial as a yawn, not even worth a 20-foot detour to avoid. Sure, we never saw the actual cat, but the tracks gave us a feel for the awesome agility and power of the animal and our minds recreated the scene almost as if we had seen the cat itself.

On another occasion, Tom went for a morning run after a small dusting of snow from the night day and saw not one, not two, but three parallel sets of cougar tracks. That meant there were either three cats in the woods or one cat that has passed by three times in less than twelve hours. Both possibilities were sobering. He spent the rest of the run yelling and making noise (a few months later a park service game camera in the area captured three cats traveling together, probably a mother and two daughters).

While we have seen mountain lion tracks many times in the snow, we only have the one good photo (above). But we have taken some pictures of tracks here in Yosemite West. Note the three-lobed rear pad and the round footprint, clear signs of a cat.

Again, despite countless hours and miles in the forest and despite dozens of sightings of tracks, neither of us has ever seen one of these cats in the wild. But by paying attention to the tracks that let us go back in time and see who was in the woods shortly before us, we have had several “sightings” of mountain lions, disconnected in time.

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Bear Tracks in Winter

Many people think bears hibernate all winter and are never active. We have seen bears down in Yosemite Valley in February feeding on a deer carcass from a mountain lion kill. If there’s food, males and non-pregnant females do not need to hibernate (technically, enter torpor as bears are not true hibernators). Up higher, at our house and above, there is almost never enough winter food, so all bears den up for the winter And yet, every winter, we see bear tracks in the snow.

Bears, as it turns out, do not have watches or iPhones to tell them what day it is, so if they don’t have a den full of cubs, they get up and take a walk and, finding inadequate food, go back into torpor. They might also be out and about if their den was damaged or flooded and need to find a new place to bed down. In any case, we have never seen a high-country bear in winter, but we have seen their tracks in just about every month of the winter.

November

December

January

These are not as clear in the photo, but they are certainly bear tracks, certainly from January (2018) and sort of neat in that if you look you can see the claw marks.

February

We didn’t find any photos of March bear tracks in our library, but there might be some lurking there. In any case, we have seen bears or bear tracks in virtually every month, including not just in Yosemite Valley but up in the higher elevations. The February photos are from elevations of roughly 7000 and 8000 feet, respectively, with a heavy snowpack on the ground.

Also note that you can find bear “tracks” other places than the ground. Sometimes they scratch trees. One theory is that they are trying to show other bears how big they are so they can scare smaller bears off their territory. Not sure if that is just an old myth or has any real research behind it.

Interestingly, in this very snowy winter of 2023 we have been getting out more than usual, and yet we have seen no bear tracks since early December. Apparently very deep snowpacks makes for good sleeping.

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Following a Fox and a Bobcat

One of our best tracking expeditions came after an early-season storm that dropped just a few inches of snow on otherwise bare ground. That meant we didn’t need skis and could follow tracks through thick forest. We soon found a fox track and followed it for a couple of hours which, at the slow pace we were going, was only about a mile and a half. Nevertheless, we learned a bit about foxes that day. In particular, the agility of this fox was incredible. It would jump up on a narrow log covered in snow and walk on it for a while before jumping down and continuing on. No terrain seemed to be an obstacle. At one point, a bobcat crossed the fox track. It tried to jump up on the same log as the fox, but could not match the fox’s agility and we saw the wide mark where it fell and slid down the far side of the log.

Unfortunately, we didn’t take pictures that day so we don’t have fox or bobcat tracks to show, but if you wander the woods enough, you might find your own!

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Martens and Weasels

We have a “go to” area for quick hit ski tours close to the house which we have now been touring for 20 years. Conservatively, we have been there 100 times. Probably closer to 200. A couple years ago we first saw the distinctive 2×2 tracks from a larger member of the weasel family, either marten or fisher. In the 2021-2022 winter, we saw these tracks a couple more times. So, roughly speaking, we saw these tracks three times in 19 years. This year there has been an explosion in the number of these tracks. In a short couple miles of skiing, we typically see at least one set and commonly cross several sets just one day after a storm. Sometimes you can see where the marten drags its body through the snow, probably for the purpose of scent marking rather than just for locomotion and fun as otters (and ravens) do.

Since martens are fiercely territorial and will cover several miles each night criss-crossing their territory to hunt and fend off any interlopers, all these tracks are probably from a small number of animals. The size of an American marten’s range in the Sierra Nevada runs from as little as 0.7km² to just over 7km² (0.7-5.8km² for females, 1.7-7.3km² for males), depending on food availability. Roughly speaking, that means the range would be 1-3km across in general. Given the abundance of one of the marten’s favorite foods (squirrels) in these particular woods, the typical range is probably more in the middle of that range than at the high end, so say about a mile across, maybe less. But this year we have been seeing these tracks across an area that is several miles long. So it seems like our ski touring spots are home to a successful breeding couple. That’s fun if you’re a tracker, but less fun if you’re a squirrel!

Tom has actually seen a Pacific fisher a couple miles from this area and there are other verified sightings not too far away. So it is possible that these are fisher tracks, but martens are far more common, so it’s most likely these are marten tracks.

In most of the conditions we see these, it is impossible to tell them apart. To tell a marten from a fisher reliably, you need a very clear track and precise measurements. The size of their tracks overlaps and so does the distance between them (i.e. the length of their gait). In general, though, fishers have more “loading” on their feet. The feet are slightly bigger, but the animal is much heavier, so they tend to sink deeper. So even though the fisher is bigger, in deep snow, the fisher takes shorter steps and leaves a “ploppier” track. Based on that and the overall prevalence difference, we figure that we’re seeing the somewhat common Pacific marten rather than the rare Pacific fisher.

We also this year came across tracks that at first looked like just more squirrel tracks, which were abundant in the forest we were in. In the soft snow, the individual tracks were not clear, so you couldn’t see the shape of the feet or even the pattern they were landing in, but there were several indicators they did not belong to squirrels.

First, when they passed a tree, they did not take the classic squirrel strategy of climbing a short ways up and jumping off.

Second, they made long forays out into large open areas. Squirrels will venture into the open, but usually only for a short distance or when making a bee-line from tree to tree.

And finally, there were thin imprints of the tail. Squirrels generally leave no tail imprint, but if they do, it would be the bushy tail of the gray squirrel or the less bushy, but not yet thin, tail of the chickaree. With a few other clues, we decided we were most likely looking at the trail of a long-tailed weasel.

The video below was taken by our friend Rachel while hiking with us on Mount Hoffmann in July, 2020. I believe this is the closely-related short-tailed weasel, whose tail is generally one-third of body length or less while the long-tailed weasel tail is usually half as long as the body or more. That said, biologists studying the distribution of the two species in Connecticut found that sometimes they needed to do DNA testing in order to make positive IDs, as they species overlap in size and many other characteristics.

We’re not entirely sure of this ID, but it seems likely to be one of the weasels, either short-tailed or long-tailed, and given that the latter is more common and given the tail-drag marks, we’re guessing that it is a long-tailed weasel. But in snow this soft, there was very little detail in the tracks, so this is just a guess.

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Coyotes

Finally, Tom’s favorite animal to track is the coyote. He has tracked them for several miles, sometimes more than five. They will often stick to a line like they are following a compass heading. And they move fast. We know this because sometimes we see their tracks on the Badger Pass Road soon after the plow has passed or on the Glacier Point Road soon after the cross-country groomer has passed. Since we have a rough idea of when the plow passed and when we passed, we can ascertain that the coyote is on a mission, trotting along no slower than 6mph and probably faster. Tom’s theory is that the coyote is moving fast on a line through relatively open areas in hopes that one of the smaller critters with shorter legs will be struggling through the snow and the coyote can surprise it, overtake it, and get a meal.

We recently (Feb 2023) saw some confounding tracks. From a distance, it looked like the 2×2 lope of a marten, but the size was too big. Upon closer inspection, we saw it was a coyote. Commonly in the snow, coyotes “direct register,” meaning that the hind foot lands in the spot just vacated by the forefoot on the same side. This increases their efficiency while moving through snow.

That’s one of the ways you can tell a coyote track from a domestic dog’s track. Domestic dogs, well-fed and comparatively uncoordinated, don’t need such efficiencies so are rarely precise in their registering, if they register at all. They also tend to have meandering tracks as they are excited to be outdoors and have no fears of wasting energy. Finally, their feet also tend to splay more because they simply have less-strong feet because they don’t spend all day everyday trotting along like coyotes.

So this track, which we followed for a couple of miles on Glacier Point Road was a bit perplexing. But we realized that the foot that failed to direct register was always the left hind foot. And the coyote would occasionally rest and then we would see it direct register and slowly get sloppier until it rested again. We also saw a place where it left the road and there was blood in the snow. At first we thought it was from a kill, but there were no signs of other tracks or fur or anything.

We finally guessed that the poor coyote had injured its foot and had minor bleeding, possibly from something as simple as snow building up and turning to ice that eventually irritated the foot. It also seemed at times to want to leave the road, but this was after a big storm. It would make a brief foray into the soft snow off the groomed cross-country ski trail and then return to the firmly packed road until, finally, it took a right turn and went off into the woods near Bridalveil Creek campground.

Much of that is just guessing, but it is fun to play detective while following an animal through the woods or, in this case, down the ski trail.

Did we correctly piece together the story of this coyote? We’ll never know, but the simple act of trying can deepen your experience of the land you move through and live in.

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A Few More for Fun

Here are a couple more for fun. First a deer track. Deer seem to be rather inefficient walkers in the snow, dragging their feet and sinking deep on their small hooves. But as a general rule, they try to move lower for the winter and they often move in groups, which helps as they can take turns breaking trail. With the huge snows we’ve had this year, a lot of the animals seem exhausted. The deer in the video was alone, at relatively high altitude (about 5500 feet) and seemed very tired. When we drove home, she was lying in the road. It was sad knowing that two more feet of snow were forecast for the next day.

The group of deer in the were lower and and had packed out trails around the river near Wawona and were doing much better.

At the other end of the size spectrum are the mice and voles. We don’t even try to identify species, but it’s impressive to see the distances they cover, almost floating on the snow with their delicate tracks. Mice leave tracks similar to mini-squirrels, often with a tail drag. Voles do not typically drag the tail and are often in a 2×2 pattern. So if there is a tail drag, it’s probably a mouse. If there isn’t a tail track it could be either one.

That said, the deer mouse is more likely to be out in the snow while the vole is more likely to stay snug in the subnivean layer. The last tracks in this gallery are funny ones: the little rodent was going along just fine until it came to a dropoff about a foot high left by the cross-country grooming machine. The critter just walked off the cliff, leaving a big (or little actually) plop in the snow.

The first two sets of tracks pictured below just impress us for how far these tiny guys were willing to walk in the open on the snow with the potential for getting intercepted by a hawk or a bobcat. And where was he or she going? Why walk all the way to the tree just to walk back? Who knows?

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Final Thoughts

Even though the forests can feel quiet in the winter, paying attention to the tracks brings them alive. Even more than in the summer, you can get a sense of who frequents these woods and what the rough proportions are between, say, squirrels and coyotes and fishers. If you live near a place that has undisturbed snow, a tracking outing is a great way to get to know the habitat.

Recommended Books

You can, of course just go out on your own, but having a decent tracking book can help get you started.

For our area, we really like Mark Elbroch, Michael Kresky and Jonah Evans, Field Guide to Animal Tracks and Scat of California (University of California Press: Berkeley, Los Angeles, London, 2012).

The Stokes guide is also quite good, but oriented more toward the East Coast. See Donald and Lillian Stokes, A Guide to Animal Tracking and Behavior (Little, Brown and Company: Boston, Toronto and London, 1986).

For a more compact option for the Sierra Nevada, the wonderful Laws Field Guide to the Sierra Nevada by John Muir Laws (Heyday Press, 2007) has some minimal information on tracks and scat.

Spring visitors to Yosemite, looking around and seeing only deer with no antlers, sometimes ask rangers, “Where are all the bucks?”

People more familiar with deer will know that bucks lose their antlers in late winter and regrow them over the course of the spring and summer. So when you see a deer in March, whether male or female, you won’t see those characteristic antlers.

Pause for just a second to think about how amazing it is that these animals regrow and then shed their antlers every year. Deer antlers are unlike anything else in the mammal world. They are among the fastest growing tissue in the entire animal kingdom. They are not just majestic, but also fascinating to medical science and to casual observers like us! 

And that’s just the beginning. Did you know scientists can get mice to grow antlers? Do you know about the unique antlers of Yosemite’s most famous deer ever? Did you know that some Asian deer don’t have antlers at all, but something much scarier?

Look at these two guys below who stopped by the house on April 26 with just their short spring antlers. We don’t know at this point how large these antlers will get.

A healthy, mature male with excellent nutrition will grow these out to a majestic “rack” with over three feet of “spread” by September. Mule deer average about a quarter to a half inch per day of antler growth throughout spring and summer.

Other members of the deer family (Cervidae) are even more impressive. In a single day, elk can grow an inch of antler and moose can add a full pound. Still, this is nothing compared to the extinct Irish Elk (actually a deer, not an elk). It could grow and regrow antlers up to twelve feet (3.5m) across.

Just how do they do that?

That’s just what scientists trying to understand bone growth, regeneration, and other basic science questions want to know.

Wait, Antlers are Bones?

Yes! Antlers are bones. People sometimes confuse antlers with horns, but they are very different. Horns are mostly keratin, the protein that makes up hair, claws, hooves, feathers and, yes, horns. Horns are found on both males and females, grow continuously, are permanent, hollow, and grow from the base. They are found in cattle, bison, buffalo, sheep and several other mammal families.

Antlers are altogether different. Antlers are unique to deer and only found among males except in reindeer, including caribou. Most uniquely, though, they are shed and regrown every year.

That requires a significant outlay of energy and nutrients for the male deer. Just like other bones of the body, the thickest part of the antlers have a spongy interior that contains bone marrow, which is where the body makes blood cells. In other words, the antlers are full-fledged bones that do all the things bones do.

During the growing phase they are soft and made up mostly of water and protein. They are covered with “velvet” that is rich in nerves and blood vessels. As summer ends, antlers stop growing, mineralize and harden in time for “rutting” season when the bucks use their antlers to compete in pushing contests. The winner is the one who gets to mate.

Wondrous Velvet

The fuzzy velvet that covers a deer’s antlers during the growth phase is how all the nutrients get to those growing bones. Because these growing antlers are mostly water and protein, they are relatively fragile.

So in addition to having a rich blood supply, the velvet is full of nerves and highly sensitive. In fact, it’s so sensitive that deer can be seen gingerly avoiding branches and brush in order to avoid injuring the velvet. This helps ensure they get a nice, symmetrical rack to increase their chances of mating in the fall.

We might think that antlers are a formidable weapon for defense, but that’s only true once they harden and shed their velvet. Their main purpose is to challenge other bucks during the rut and to display dominance, not to fight off coyotes. If a buck in the velvet phase is forced to fight off a predator, he will actually fight with his hooves and protect those antlers from damage. They are too precious to risk in a fight, and too soft and too sensitive to be effective anyway.

It is only late in the season, when the antlers are fully formed and hardened and ready for contests with other bucks that the velvet dies and falls off. And what does a deer do with that discarded velvet? It eats it. Can’t let all that good protein go to waste!

The Life Cycle of a Yosemite Deer’s Antlers

Of course, this cycle is more or less the same everywhere, though the timing might differ a bit here and there due to climate.

• March. Bucks shed antlers as early as January, but rarely. Shedding is most common in March.
• April. New growth starts 2-4 weeks after shedding.
• July. First forking of antlers is achieved. Before this, all bucks will have just a single spike. Once they reach full size, they will begin to harden and mineralize.
• September. Antlers have grown to full size and strength. At this point the velvet dies and bucks then start “horning” brush and trees to scrape it off.
• October or November. Necks swell to prepare for rutting contests.
• November to January. Rutting Season. Mostly a pushing contest where the goal is to drive the rival to his knees. Once achieved, the dominant male “runs” a female for several days until she lets him mate with her. Once that’s done, he starts running another female. This lasts into January, sometimes into February.
• Once the mating season is over, the bucks shed their antlers and the cycle starts all over again.

Notice in the photos below how the bucks sparring in the top photo from September still have thin necks. In the second photo, where they are in it for real, the necks have thickened and are ready for the real contest.

Where Do All the Antlers Go?

The deer population of Yosemite probably numbers in the thousands. If only a thousand bucks are shedding 2,000 antlers every year, where do they all go? You would think that 2,000 antlers shed year after year would start to become a bit of nuisance. Why don’t we see them all the time on hikes?

There are a few reasons. The first is that the deer don’t follow our trails, so a lot of the antlers end up in places humans don’t frequent. In addition, the deer often go to lower altitude to shed antlers. Still we see deer tracks in our area all winter, so they must be shedding antlers in our area.

So after many years, shouldn’t there be antlers everywhere?

Mature, hardened antlers are about 40% protein and 60% minerals. That makes them a great nutritional supplement for squirrels and other rodents who do not have subscriptions to Amazon Prime and can’t get their calcium supplements delivered by UPS. Also, rodents need to gnaw in order to maintain their teeth. When they find an antler, they gnaw on it. Porcupines are particular fans of deer antler, but in our area they only inhabit the lower reaches of the deer’s range. That leaves squirrels as the great recyclers of all that calcium, phosphorous and protein tied up in deer antlers. And thanks to them, the woods are not littered with years of antler accumulation.

What would happen if there were no squirrels? It turns out that we know the answer. The squirrel population of California generally and Yosemite in particular was devastated by disease in the early 1920s. For years at a time into the 1930s, as few as a single pair of squirrels were seen in Yosemite Valley. The grey squirrel almost went extinct in much of California. In 1925, a few years after the collapse of the squirrel population, park naturalist Carl Russell went walking an area where deer were known shed antlers. He found more than two dozen single antlers in less than a mile without leaving the trail. Without the squirrel helpers to break down the antlers, they apparently did start to accumulate in the 1920s.

Antlers and Medical Science

Antlers are the only appendage that any mammal regenerates. They also grow faster than almost any tissue in the animal kingdom and are probably the fastest growing bone in the world. You can see why scientists are interested in antlers. If we understood antlers better, we might conceivably be able to regenerate a lost finger, heal broken bones faster or prevent and reverse osteoporosis.

Scientists have long known that there was something special about the cells at the base of the antler, the pedicle, from which the antler regrows every year. In the 1960s, researchers transplanted pedicle cells to the leg of a deer and it started to grow an antler on the leg! Even more surprising, they have transplanted pedicle cells to the forehead of a mouse and guess what? The result is this somewhat disturbing picture of a mouse with a sort of unicorn in its head. Do not try this at home!

More recently, scientists have discovered the key genes that allow the deer to grow bone so quickly. In 2018, researchers at Stanford identified one gene that promotes the exceptionally rapid growth of antlers and another that promotes the exceptionally rapid hardening of antlers. Both of these genes are present in humans and linked to bone development. Understanding them better could lead to therapies for osteoporosis and other bone diseases.

And that’s not all. There could even be implications for cancer research. Why can’t other mammals regenerate appendages? Nobody knows for sure, but deer commonly suffer from deformities or uncontrolled growth of their antlers. It appears there might be some sort of tradeoff. You can have rapid growth and regeneration, but it might come at the cost of being more susceptible to that other form of rapid growth, cancer. So the study of deer antlers might have clues to what causes runaway cell growth and how to control it.

More Fun Facts About Antlers

• If a deer is injured in the right front leg while the antlers are growing, the right antler will be deformed or stunted. But if the deer is injured in the right hind leg, the left antler will be deformed or stunted.
• Mule deer antlers can weigh over 30 pounds, much of which is calcium.
• To get all the calcium they need for their antlers, deer take it from their own bones, by preference non-weight-bearing bones like ribs. This means they get temporary osteoporosis every year.
• Antlers have been important to humans for thousands of years – they are one of the primary tools used for flintknapping, that is making arrowheads, spearheads and the like from flint and obsidian.
• The number of points on an antler do not indicate the age of the deer. In general, antlers get larger with age up until about 5.5 years old (the buck’s sixth summer) then stabilize. As a deer ages they can get smaller each year.
• Age is only one determinant of antler size. The other big one is nutrition. Calcium is important, but during the growth phase antlers are mostly protein, so protein availability really affects antler size.

And the Really Crazy Stuff

If you’ve made it this far, now we get to the really crazy stuff! Here’s a quick bit about Yosemite’s most famous deer and deer species that don’t grown antlers at all, but something much scarier looking.

Yosemite’s “Rhino Buck”

Unquestionably, the most famous deer in the history of Yosemite was an ancient old buck people called Old Horny. He got his name because he had a third antler growing out of his forehead. Three-antlered deer are rare, but not unheard of. Typically, however, the third antler grows out of the frontal bone like the other two. Old Horny is believed to be unique in that his third antler grew out of the nasal bone.

He was much beloved by visitors in the 1920s who frequently fed him buttered toast, back when feeding the animals was a standard part of a national park visit (please don’t revive that tradition!). When he finally died, it was discovered that he was exceptionally old. His teeth had been ground all the way down to the gums, a sign of extreme old age in a deer.

That’s not a surprise — antler deformities are more common as deer age and Old Horny’s twisted antlers were another testament to his advanced age.

Saber-toothed Deer?

What could be stranger than a three-antlered deer? How about a saber-toothed deer! If you live in parts of Asia where the water deer come from, or in the UK where they are considered invasive, you might know about deer with tusks. For most of us in North America, though, the thought of innocent little Bambi with deadly tusks is a bit unsettling.

How in the world do you end up with a saber-toothed deer? There are in fact several species with tusks. It turns out, that antler size correlates to the size of the animal and, below a certain size, antlers are just not effective fighting tools. All the deer with tusks are under 15kg.

They also live in dense forests or jungle and are solitary rather than herd animals. This is important because antlers allow for bloodless competition among bucks. Herd animals do not want to shed blood, because they do not want to draw predators to the herd. Also, deer with antlers tend to live in open areas where they can display their large antlers from a distance as a dominance display. In tight vegetation, there’s no advantage to a big rack visible across distance and it just gets hung up in the vegetation. So these small, solitary jungle dwellers have tusks.

It turns out that ancient deer may have had both tusks and antlers, but as they evolved, one came to dominate based on the size, habitat and social life of the deer. However, even our nice Bambi mule deer have to potential to grow tusks. On occasion, hunters who kill a mule deer find that in fact it has canines up to an inch long. In other words, the basic genetics for tusks remains latent, it just is not expressed since antlers are so much more useful in the places mule deer live, like Yosemite.

All of that is somewhat theoretical, but it’s the best guess of the scientists who published the wonderfully-named most recent research article on this: “Stabbing Slinkers: Tusk Evolution Among Artiodactyls,” by Doreen Cabrera and Theodore Stankowich in Journal of Mammalian Evolution, Vol. 27, Iss. 2,  (Jun 2020): 265-272.

Wrap Up: Your Turn.

I hope all that deepens your knowledge of our deer, and yours too if you have them near your home. I also hope that the images of the “stabbing slinkers” will not trouble your dreams!

There’s a lot more one could say about antlers, but maybe we already said too much. Our goal with these articles is to expand people’s knowledge and appreciation of the natural world around them. We find these explorations interesting, but maybe you would rather read about different things. If you have ideas for things related to Yosemite nature or history that you would like to read about, let us know by email or in the comments. We would love to read your suggestions!

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Read More

There are countless articles about antlers on everything from the Smithsonian website to hunting blogs. A lot of state departments of wildlife have nice pages too. These are some fun articles as well as some of the more esoteric, academic sources that played into this article.

Fun and not too scholarly:

• What are antlers and why do deer have them? at Wildlife Online. This is a great, detailed, non-scholarly overview with some excellent photos, including photos of sectioned antlers, infrared photos of deer during the antler growth phase and after and lots of interesting stuff.
• Jason Bittel, “Antlers Are Miraculous Face Organs That Could Benefit Human Health.” Smithsonian Magazine, June 12, 2017.
• Richard Grant, “Biggest. Antlers. Ever. Meet the Irish Elk.” Smithsonian Magazine, June 2021.
• Outside/In podcast episode: Holy Scat! Why Antlers Are Freaking Amazing, March 10, 2022.
• Robert A. Pierce II, Jason Sumners, Emily Flinn, “Antler Development in White-tailed Deer: Implications for Management White-tailed deer management.” A nice guide focused on white-tailed deer developed jointly by Missouri University Extension and the Missouri Department of Conservation.
• Similar to the Missouri page, this is nice set of resource pages mostly on white-tailed deer by the Mississippi State University Deer Ecology & Management Lab.

A bit on the more esoteric side:

• Price JS, Allen S, Faucheux C, Althnaian T, Mount JG. “Deer antlers: a zoological curiosity or the key to understanding organ regeneration in mammals?” J Anat. 2005;207(5):603-618.
• Doreen Cabrera and Theodore Stankowich. “Stabbing Slinkers: Tusk Evolution Among Artiodactyls.” Journal of Mammalian Evolution, Vol. 27, Iss. 2,  (Jun 2020): 265-272.
• G. A. Lincoln, “Biology of antlers.” Journal of Zoology (1992) v. 226, pp. 517-528.
• Chunyi Li, John Harris, James Suttie. “Tissue Interactions and Antlerogenesis: New Findings Revealed by a Xenograft Approach.” Journal of Experimental Zoology, v. 290, pp. 18–30 (2001).
• Hanae Armitage, “Genes behind rapid deer antler growth, hardening identified.” Stanford Medicine News Center, October 30, 2018.
• Science Direct AI-generated selection of articles on antler-research (many of which require institutional affiliation to read)