Most hikers might not think of the summit of Half Dome as a unique and vibrant ecosystem, but it is precisely that, as are many other summits in California’s Sierra Nevada mountain range.
The Lyell Salamanders
The most famous and endearing of Half Dome’s year-round residents are the Mount Lyell salamanders, Hydromantes platycephalus. The color of dark chocolate, the Lyell salamander is a member of the Plethodontid family—the lungless salamanders. The Lyell salamanders breathe through their skin and mouth tissues, and this requires a humid environment that will keep these delicate tissues moist They have found this wet environment under the rocks and snowfields of the Sierra Nevada.
Mount Lyell is the highest peak in Yosemite National Park with a summit elevation of 13,120 feet.
These salamanders have lived on Sierra summits for almost 30,000 years, before the last of the glaciers receded from Yosemite Valley. They were unknown until 1915 when two were caught accidentally in a researcher’s mouse trap near Mount Lyell. While scientists have found these salamanders as low as 4,000 feet in elevation, most live above 7,000 feet, with Half Dome’s congress of salamanders living at a summit elevation of 8,839 feet.
The Lyell salamander has a comfortable home atop Half Dome; living beneath the seasonal summit snowfield, under the summit rocks, and deep inside the cracks and fissures that shoot through the Dome.
Curiously, the Lyell salamanders’ nearest relatives within the Hydromantes genus are found far away in Italy and southern France. How it came to be that this genus of salamanders is found only in the Sierra and southern Europe is a mystery.
In the winter, the salamanders retreat into warm underground habitats to avoid the freezing temperatures that they cannot tolerate. Once spring has thoroughly taken hold of the Sierra, the salamanders stir from their slumber.
As nocturnal creatures, they emerge under cover of night to feast on countless insects and spiders. In feeding, the thin-skinned salamanders establish themselves as true predators. Hidden behind a gentle face is the salamander’s food capturing weapon. A long, sticky tongue darts out of the salamander’s mouth and ensnares the night’s feast.
These salamanders have one other important weapon to use during the hunt. Sticky, webbed feet allow the salamanders to explore and hunt on cliff faces. In this vertical world, they can find plenty of insects to feed on and deep, moisture-laden cracks to call home.
Half Dome’s Lyell salamanders do not have many natural predators thanks to the steep granite faces that drop off from all sides of the summit plateau. The mice and marmots who share this space are not regular predators of the salamanders. Instead, the salamanders’ primary enemy lurks in the skies above Half Dome. Ravens and other birds patrol the skies to scoop up the five inch long salamanders when they find the opportunity.
The salamanders do have a few self-defense techniques, however. First among these are toxic skin secretions and a sacrificial tail. When a salamander senses a threat, it will flatten its body to the ground, arch its tail above its body, and release toxins through its skin. The tail secretes many of the toxins, which are slightly poisonous and have a foul taste to discourage predators. The tail also serves as a decoy; if grabbed, it detaches from the salamander’s body and allows the creature to run away. If a salamander loses its tail, the appendage will regenerate within a few weeks. In addition to these defenses, the salamander is a nimble escape artist during the heat of a battle. It will coil its body into a ball and quickly roll downhill or into the crevices of Half Dome’s stacked boulders. As it bounces along, it will often spring out of its ball, flipping through the air to change direction and confuse a predator, and then return to a coiled ball to flee the scene.
Yosemite Valley in the summer is known for being hot and dry, characteristic of its Mediteranean-like climate. During these dry spells, the salamanders retreat once again to their underground dwellings to slip into a state of dormancy called aestivation. As summer transitions to fall, thunderstorms return moisture to Half Dome’s summit, allowing the salamanders to reemerge until autumn’s freezing temperatures and snowfall force them deep below ground until the spring.
While all of this may sound like an idyllic life—living atop Half Dome, eating and sleeping the days away with few natural predators—the salamanders here face a vicious threat to their existence: humans. Some years ago, when camping was still allowed on the summit, campers built rock shelters to create more comfortable sleeping spots and block out the mountain winds. Campers gathered the rocks from the summit plateau, thus disturbing the moist underground homes of the salamanders. For this reason, camping is no longer allowed on the summit; these small, sensitive creatures whose population is quite small and scattered need our respect and protection.
Today, the salamanders still face threats from hikers who unknowingly use the salamanders’ shelters to construct rock cairns—towers of rocks stacked one atop the other for ostensible artistic or navigational purpose. Some of the cairns are over six feet tall and marvels of engineering, but a cairn of any size is a destruction of habitat in this sensitive ecosystem. Park Rangers and volunteers break down the cairns as often as possible, but the tide of self-proclaimed artists and amateur trail builders continues to endanger this threatened species. Instead of leaving a mark on nature, perhaps we all would be better served allowing nature’s beautiful vistas to imprint upon us.
If the Lyell salamander is the most endearing of creatures atop Half Dome, then the yellow-bellied marmot must be the most notorious. These stout, furry rodents regularly steal hikers’ unattended food and chew on the sweat-soaked straps of backpacks.
The yellow-bellied marmot, Marmota flaviventris, is one of the larger members of the squirrel family. The marmot has a coat of thick, brown fur, except for the namesake yellow streak adorning its chest like a knight’s breastplate.
The chubby marmots living on Half Dome can weigh up to 11 pounds, surpassing the size of the average house cat. They are diurnal, meaning active during the day, and this explains the oft-reported sightings by hikers. While the marmots are omnivorous, their diet is mostly limited to grass, leaves, and flowers. Insects and the occasional bird egg supplement this fiber-rich diet. Given a choice, the marmots most likely avoid eating the mildly toxic and foul tasting Mount Lyell salamanders.
In obtaining water, the marmots are also well-adapted to this barren environment. Their primarily plant-based diet provides them with ample hydration. Of course, Half Dome’s human visitors are not so efficiently adapted and should carry up to 3 liters of water for the hike, or risk dehydration.
Lucky hikers will witness a running marmot. Why are they so lucky? Marmots are not graceful runners. A marmot run is more of a quick waddle—their fat stomachs swaying from side to side. Their short legs struggle to move faster while their disproportionately large bodies still lumber along. The marmots are better adapted to their underground burrows, where they spend up to 80% of their lives.
Fortunately for Half Dome’s marmots, there is little need to run. Foxes and coyotes, their usual predators in the Sierra Nevada, are not present on the summit plateau. Eagles, however, do ply the skies above, and the marmots must not grow complacent atop this seeming refuge. When a predator does appear in the air, any marmot who witnesses the threat will let out a sharp whistle to warn the other members of its colony, hence the nickname “whistle-pig.”
Marmots can live for up to fifteen years. They live in colonies of up to twenty individuals. In the spring, the marmots emerge from hibernation and are ready to mate. For the male, this means finding up to four mates in a season, though he will hibernate with only one of them. Some 30 days later the females give birth to a litter that averages four baby marmots, but she can have up to eight pups.
The typical day in a marmot’s life is a day of extended rest. Like most humans, they wake up, poop, and groom themselves. Then they lounge in the sun until mid-morning, when it’s time to find breakfast. After breakfast, they might spend more time basking in the sun or hanging out in their burrow. Dinner takes place in the late afternoon before they retire to the burrow for the night. Observant hikers may see members of a colony playing and grooming each other.
In September, with cooling temperatures and advancing winter storms, Half Dome’s marmots fatten up and prepare for their winter hibernation. For up to eight months the marmots will slumber in their cozy burrows beneath the summit’s boulders.
Hibernation may appear to be a quiet, restful time in a marmot’s life. However, many marmots die in hibernation during the long, dark hours of the winter. Another common source of marmot mortality is the plague. The plague is common among rodents in the High Sierra, where it occurs naturally. This is a good reason never to touch these cute but wild creatures!
Marmots prefer to live in high elevation meadows near the edges of talus fields or forests. Hikers might wonder how marmots came to exist on the summit of Half Dome. Did the marmots’ ancestors walk across a long-gone glacier? Or perhaps a female and a male escaped the talons of a golden eagle and landed on the summit?
The answer is none of these. The marmots found their way to the summit via the same route as today’s hikers. They ascended the low angle granite slabs where the Cables Route is bolted to the rock. If this fact is surprising, consider that the Yosemite Black Bear can ascend technical rock climbing routes that most humans cannot climb with ropes and harnesses! Yosemite’s mammals have evolved with a unique penchant for climbing.
The common raven, Corvus corax, is common to Yosemite Valley, the Sierra Nevada, North America, and many other parts of the world. However, their habitat wasn’t always as large as it is today. Ravens are highly intelligent, surpassing apes, and even humans, in some cognitive tests. The success of the raven is directly tied to the success of humanity, for they have followed our roads and developments, using them as sources of food, water, and shelter, thus expanding their vast habitat.
Ravens are large birds with wingspans stretching up to 25 inches. Their stout bodies and jet-black coats shimmering with iridescence give the ravens an almost ominous feel. And if that does not cause a second-glance, then surely their eerie clicks, crackles, and mimics will cause many a visitor to give them a wide berth.
If ever there were an ideal home for a raven, it must be Yosemite Valley. The massive cliff faces and towering pine trees are a giant playground for the acrobatic ravens who roll, somersault, and dive through the Valley’s famous vistas. Visitors standing on Half Dome can often look over the edge to see a raven or two gliding through the air below or catching a warm thermal to ascend effortlessly above the Valley’s rim.
Ravens typically mate for life. The search for the right partner takes time, sometimes up to three years for eager juveniles ready to mate. Courtship among ravens involves demonstrations of flying, intelligence, and food gathering. After courting, the pair establishes a territory and builds a nest in one of Yosemite’s tall trees or on a cliffside.
The diet of ravens is opportunistic. They eat what they can find. Within a week, a raven’s food could include: squirrel roadkill on the Yosemite Valley Loop, a mouse on Half Dome’s Sub Dome, invasive Himalayan blackberries in the Valley, an abandoned scrap of pizza at the Yosemite Valley Lodge, and spilled trail mix atop Half Dome’s “visor”. In their opportunism, the ravens are no different from many of Yosemite other famous residents: the black bear, the elusive ring-tailed cat, or the “impoverished” rock climber ascending Half Dome’s 2,000-foot-tall Regular Northwest Face.
For many cultures, ravens are a sign of evil, even death—they are to be viewed with suspicion and avoided. What has the raven done to deserve this bad rap? They are incredibly intelligent creatures. They quickly make friends of many humans. Indeed, they can even recognize a unique human face. Perhaps ravens frighten us because their behavior resembles ours so closely. While some cultures steer clear of ravens, some contemporary human residents of Yosemite believe the ravens there carry the spirits of deceased friends and family—a symbol of life after death.
Remember—when you are standing on the summit of Half Dome, and Corvus corax lands next to you, its rattle call punctuating the mountain wind—you can smile and say hello, but don’t let it trick you into surrendering your food, or else you will discover firsthand which species is more intelligent.
Modern-day hikers know there are no trees on Half Dome’s summit, but this was not always the case. The disappearance of Half Dome’s pines is another sad tale of humans altering this landscape for the worse.
When a plucky Scot, who we will meet later, made the first ascent of Half Dome in 1875, there were four patches of pines on the summit with a combined total of seven trees. Three species were present then: Pinus jeffreyi (Jeffrey), Pinus contorta (Lodgepole), and Pinus albicaulis (Whitebark). Of the seven trees, only one survives out of sight and safe from hikers. What follows is an arboreal obituary of sorts.
Pinus jeffreyi, the Jeffrey pine, is also known as “gentle Jeffrey” for its smooth pine cones. Upon sighting a Jeffrey, many a mountain rambler will stick their nose into its bark to inhale the butterscotch scent of its resin.
Pinus contorta, the lodgepole pine, is named for its traditional use by Native Americans in the construction of tipis and lodges. Of course, visitors to Yosemite must remember that the Native Americans of Yosemite Valley, the Ahwahneechee, constructed cedar bark houses and not tipis.
Pinus albicaulis, the whitebark pine, is another alpine pine common to Yosemite. Its strong roots cling to summits and exposed ridges in a state of krummholz, in which a lifetime of fierce winds and winter storms force the tree to grow into a gnarled and twisted dwarf. The whitebark pine’s propagation is dependent on a winged alpine friend to spread its seeds through the mountains—the Clark’s nutcracker, Nucifraga columbiana. The Clark’s nutcracker caches the seeds underground for times of scarcity, but when the nutcracker fails to retrieve the seeds, a clump of whitebark pines is often born.
What disaster caused the deaths of the magnificent, weathered, and gnarled trees that once lived atop the Dome?
Humans. In particular, unprepared campers who cut down the trees for firewood. If this tragedy can teach a lesson, it is this: let us be conscious of seemingly small actions in the present, for they may appear more significant in the future.
Half Dome’s summit is not so barren a place as some might have you believe. In addition to the mentioned animals and trees, there is an abundance of flora scattered around this island in the sky.
There are alpine spiraea—a genus of hardy deciduous shrubs—and there are the delicate wildflowers of potentilla (cinquefoils), erigeron (daisies), eriogonum (wild buckwheat), penstemon (beardtongues), and solidago (goldenrods). A variety of grasses can be spotted by the observant eye as well.
The most seen but least recognized residents of Half Dome are the dark streaks running down its steep face. Some people may know these streaks as the sorrowful tears of Tis-sa-ack, the female protagonist of a legendary Ahwahneechee tale. We will explore her story in the next chapter. As one might guess, the streaks are not hardened tears. They are communities of rock lichens.
A lichen is a composite organism. It is the symbiotic combination of a fungus and a photosynthetic partner (algae or cyanobacteria) growing together. The lichens that form Tis-sa-ack’s tears are crustose, meaning they grow tight and flat against the rock. Several types of lichen live in the streaks, including Lecidea atrobrunnea and Dimelaena thysanota.
Estimates suggest that lichens cover some 6-8% of the earth’s land. They are among the oldest living organisms on the planet, possibly reaching ages of 10,000 years old! As with other long-living organisms, they grow extremely slow. Along the Mist Trail section of the hike to Half Dome, visitors who wish to leave their names etched into the stone scrub off defenseless mosses and lichens. It takes the native lichens and mosses a long time to recover from this eco-graffiti, if ever.
The Human Impact
In the account of his ascent of Half Dome, John Muir wrote:
“For my part I should prefer leaving it in pure wildness, though, after all, no great damage could be done by tramping over it. The surface would be strewn with tin cans and bottles, but the winter gales would blow the rubbish away.”
These words were written more than 100 years ago, and our attitudes towards litter have certainly changed since then. Though Muir was a great defender of Yosemite, I must disagree with the acceptable standards of his day; trampling over Half Dome’s summit does cause considerable harm. It is a majestic and wonderful place to visit, but let us all tread softly through this fragile ecosystem.
What about those tin cans and bottles? They must blow somewhere.
Each autumn, a special event takes place in Yosemite. The event is the annual Yosemite Facelift, a weeklong cleanup effort organized by Yosemite’s rock climbing community and the non-profit Yosemite Climbing Association. The mission is to clean up Yosemite after the busy summer season. As a part of this effort, the National Park Service’s climbing rangers and volunteers rappel off of Half Dome’s cables and remove trash that falls onto the rock ledges below. I once participated in this and we packed out some eighty pounds of garbage in one afternoon from the Half Dome area.
For conservation to work, everyone must participate. Pack out everything that you pack in. Do no harm. Give the landscape and its creatures the respect you would ask to be given to you, or more.