It was early June, and I had just come into Lamar Valley to see every wildlife watcher’s dream: the Junction Butte pack hunting bison on the valley floor. We pulled over the car, set up the scopes and spent the next two and a half hours watching the back-and-forth battle of wolves pushing bison herds and chasing the young, and then the bison mounting a counter charge and causing the wolves to retreat to a safe distance. After many nearly successful attempts by the Junctions, and a well-placed kick from a female bison, the pack moved off to bed down through the heat of the day. Perhaps they would try again later, but this attempt had been thwarted.

Although the chances of witnessing a predation event are relatively low, the details of predator-prey relationships in the park are a focus of the Yellowstone Wolf Project, Cougar Project, elk research and the Elk Calf Study. This team of scientists monitors Yellowstone’s predators and their effect on prey. In 2024, the team spent 4.5 months across the year studying predation. They were able to identify over 260 different kills, 211 of them from wolves, and 56 of them from cougars. While these 267 kills likely don’t cover every single predatory event throughout the year, they act as a very good representation for what Yellowstone’s wolf and cougar diets looked like. Of the carcasses sampled, 82% of all wolf kills were made up of elk and bison and 67.9% of all cougar kills were made up of elk or deer. These studies have also revealed that predators are disproportionately targeting younger prey, as well as female prey.

While those statistics are interesting, consider the implications for what they mean in the context of the ecosystem. Within wildlife biology, there is a concept known as carrying capacity. This concept states that there is a certain number of animals within a species that an ecosystem can support. Here in the park, the current population of wolves is around 100 adult animals, and it’s been fluctuating around that threshold since 2008. This 100-animal population size, or carrying capacity, is influenced by a number of factors, including disease transmission, competition with other wolves, and food availability. For cougars, current estimates put the population somewhere between 34 and 42 individuals, with carrying capacity likely near that range.

If we look at the population graph for wolves over the last 30 years, a very clear early spike can be seen in the early 2000s. This “overshoot” of the carrying capacity is common when a predator is reintroduced to a landscape. Oftentimes, in the absence of predators, and with wildlife management norms of the twentieth century, it was common for prey species, like elk, to overpopulate landscapes, and have few ecological controls. This was the situation in the northern range of Yellowstone in the 1990s when the northern elk herd numbered upwards of 17,000 individuals. With an abundance of food on the landscape due to this overpopulation, wolves were able to quickly reproduce and expand their population to over 170. However, by the late 2000s, elk populations started to return to a more sustainable level, not only because of predators returning to the landscape, but also because of a variety of management actions and circumstances. These included a recovery of bear and cougar populations, late season cow elk hunts outside of the park, a prolonged drought and series of severe winters, and competition with increasing bison herds. As elk populations fell, other ecological stressors, such as increased competition with other predators caused wolf populations to slowly decline and level out to the stable and healthy population we see today.

A beautiful thing about carrying capacities is that in a healthy ecosystem, carrying capacities exist such that predator and prey populations become very closely tied together. In years of abundant plant growth, elk calf survival might be higher than normal, and therefore the prey population could increase. This could cause a connected response of predators with more available food in following years leading to higher wolf and cougar survival and perhaps their population increasing. As the prey population begins to fall once more, the predator population will follow. In a healthy ecosystem, these populations exist in a harmonic balance, oscillating above and below the carrying capacity for their species. The predation and population dynamics of wolves and cougars of Yellowstone teach us that beneath every action, every situation, and every population we find in the park, there is a complex web of relationships, interactions, and interdependence.

It’s this complexity that I find brings me back to wildlife watching. Being out there, watching wolves hunt is an experience unlike anything else I have experienced. The range of emotions that are felt when, for example, you watch a wolf pack sneak off with a newly born bison calf can be overwhelming. The pure excitement for the pack, and honestly some underlying sadness for the life the calf didn’t get to live. But, at least for me, understanding what predation means for the landscape, and health of a wild ecosystem, like Yellowstone, acts as a certain type of centering force. It allows me to refocus on the now, and it’s what keeps me waking up at 3:30am to get out there for the chance to see it all again.

by Kyle Wonders, Yellowstone Forever Institute Lead Field Educator

Feature Photo: Lead Field Educator, YF / Amanda Evans

The post Dance of Survival: Yellowstone’s Predators and Their Prey appeared first on Yellowstone Forever.

As is the case with the musical symphonies, so, too, is it with the elk. They are concertos that revolve around the bulls. No, like symphonies they intricately weave the various notes of the cows and calves in along with those of the elks’ version of the lead violin: the bulls. And as the maternal herds with their calves move across the landscape, the bulls jockey, display, call, rake, scent mark, and oftentimes battle for dominance and the hard-fought right and opportunity to breed, thus passing along the best genes to best ensure the fitness of the herd’s offspring for the rigors of the lives that they will lead when born the following May and June.

Innately knowing or sensing this, the cows are quite choosy about which bull they will breed with. Elk breeding, like that of so many species, is not egalitarian in the least, for there is too much riding on the genetic fusions between the cows D.N.A. and that of the bulls. Knowing this, they risk leisure, limb, and their very lives to fulfil their biological imperative.

The tableau set and the elk grouping underway as of late August, the annual symphony in C-sharp begins in earnest with its sonata. No two elk sound exactly alike, with several factors including size and age in particular shaping their chords, and their respective temperaments and priorities shaping the style and urgency of their notes, all of which come together across the score to create their seasonal soundscape, the sounds of them coming together to breed.

Throughout their amphitheater-like gathering areas, their notes and chords spill out across the land, each with its own purpose. The cows and calves lead off with their muted, familiar chirps and mews, the short-duration, high-pitched chirps casual to signal their physical movements and the slowed down mews elongated and relaxed when they bed down or feed. The bulls share their own mews to the sonata for the same reasons, but they also add their casual bugles as if to say, “Here I am and I’m up and about”. As the various chirps, mews, and locating bugles are interwoven freely, the occasional caesura will sometimes be broken by an elk’s bark, either of alarm or of nervous curiosity, depending upon what they hear, smell, see, or otherwise sense. Squeals, too, of excited spikes ring out their variable and higher pitched, adding them to the melody and texture of the moments. And when nothing is amiss or imminently threatening, the opening sonata gives way to the symphony’s second movement.

For viewers and admirers like me, this second is a slower, quieter movement, the musical equivalent of lento and largo tempos, piano and even pianissimo tempos, slow, stately, and even quite quiet at times. The elk are unhurried in their physical movements as they are with their vocalizations. Chuckling bulls call out to the cows, deeply, slowly, guttural in their desire for acceptance.

But these seeming decrescendos can only last so long as the relentless beat of metronomic time marches on, their biological clocks requiring more attention as the days go on. As the elks’ pheromones kick into synchronized overdrive due to this seasonal grouping, some of the older cows will enter an estrus cycle, which, in turn, sends its irresistible chemical signal straight to the bulls’ brains via their olfactory systems as they take it all in while shadowing the various cows.

Thus begins the scherzo portion of the elks’ symphony. The changed rhythm and variety of their vocalizations punctuate the air, now quavering out further across the expanses of sagebrush with increasing urgency. Andante gives way to adagio, allegro, and even forte as the pace quickens. To their previous chirps and mews, cows add bugling of their own, along with excited estrus calls that rise and fall, the whining sounds of the excited herd approaching its mating frenzy, all interspersed with various growls and grunts throughout. Invisible baton in hand, Mother Nature exhorts tutti to join in and so the bulls do so, but now, instead of locating bugling, the larger bulls offer their display bugles in their attempts to exhibit their worthiness to the cows. And just as the symphonic portion of the rut builds to forte, the elks’ physical movements become increasingly energized, sometimes almost playful but at other times turbulent and even fierce. Beware, humans, for Mother Nature does not include you in its call for tutti. While tempting and even illogically enticing like so many sirens’ calls from across the mythological deep, the invitations are for elk only, and humans who get too close do so at their own very real peril in this time of greatly heightened, hormonally-driven elk behavior.

The finale, as one would expect, is grander still. Its faster, rondo form keep both the players and audience rapt as the behaviors unfold in a panoply of signalling, rutting, chasing, and even battling, the elk harems and the breeding rights to them always at stake. Be it shrouded in morning mist, bathed in the brilliant light of a clement, sunny day, or blurred by autumnal rains or an ominous gray front, the elk orchestra plays on to its inevitable biological and seasonal conclusion. The cows’ chords change only in urgency and frequency in this last symphonic movement, but the bulls add screaming bugle calls to the score at its moments of crescendos. They raise their intensity to challenge other bulls nearby and rake bystanding trees, bushes, and deadfallen branches with their now velvetless antlers, sharpening them for the climactic combats ahead. Risking wearing themselves out, the bulls run to and fro at the slightest provocations or risk of losing a cow to the entreaties of other, proximate bulls. The ultimate reward of finally breeding and thus fulfilling their hoped-for biological destiny at hand, the bulls leave no challenge or even potential challenge unanswered, so much so that they forego most or even all of their nutritional needs. So laser focused on the twin needs of breeding and jealously herding and protecting their respective harems, they dig deeper into their energy and fat reserves, depleting themselves further with each mouthful of pre-winter grass not taken to ensure maximum vigilance.

Copulation itself is necessarily brief and efficient, both climactic biologically and anticlimactic at the same time as they quickly go their separate ways. The cows go back to the comfort and safety of their maternal herds, feeding and fattening up for both the winter ahead and for the biological requirements of the soon-to-be developing embryos inside of them, the bulls back to the next challenge or breeding opportunity, the rondos cycle on, almost frenetically in their pace and urgency. And so it plays out until each cow has been bred or until no more cows cycle into estrus, the breeding bulls fatigue beyond good health and the cows and calves moving on to the other, figurative pastures of their seasonal lives. The seasonal breeding curtain comes down with finality until the next year and the stages are cleared for autumn to give further way to the oncoming winter. The trees still carry much of their autumnal splendor, but the orchestral accompaniment is much reduced to its more normal chirps, mews, and occasional barks.

Thus completes the cycle of the September elk symphony, easing into October and beyond the precious cargo of the next spring’s elk calves inside the now-pregnant cows and growing steadily until their eventual introduction into the world the following May and June. Mother Nature lowers that particular baton for the last time in that orchestra, only to pick up one of her many other batons to guide one or more of the seemingly numberless other symphonies over which she presides, one seasonal cycle leading to another in the relentless march of time. Players and notes change, but Mother Nature’s many beats go on, marking the continuity and variety of the soundscape through the seasons. There are no bows or curtain calls, just other melodies and sights to mark the passage of time, more experiences, and more memories as they play out inexorably across time and space for us to learn from, enjoy, and wonder at in their beauty, harmony, and never-ending symphonic synchronicity.

by Christian Beall, Yellowstone Forever Institute Field Educator

Photos: YF / Matt Ludin

The post Naturalist Notes: September Symphony appeared first on Yellowstone Forever.

The geysers of Yellowstone are one of the biggest (if not the biggest) reasons why millions of people come to Yellowstone National Park every year. For generations these geysers have captured the hearts and imaginations of people from all around the world. In fact, one of the driving forces in establishing Yellowstone as the first national park in 1872 was the uniqueness and abundance of the geysers found within. The world had known about geysers before Yellowstone, but never to the degree and amount that we see even today.

In all, there are about 10,000 thermal features (geysers, hot springs, mud pots, travertine terraces, and fumaroles) within the borders of the park. And of that 10,000 about 500 of them are geysers, making Yellowstone the largest concentration of geysers on the planet.

There are indeed other places on earth where geysers can be found. Some of the more notable locations being Iceland (home to Geysir, the namesake of all geysers), New Zealand, presenting the tallest geyser ever observed (1900-1904) and was recorded at 1500 feet! And lastly, Dolina Geizerov (Valley of Geysers) in Northeastern Russia on the Kamchatka Peninsula, home to the second largest concentration of geysers on the planet.

But, why are there geysers in those locations as well as Yellowstone? What makes these specific areas so special? And what geological ingredients are needed for geysers to form?

The answer is, unfortunately, not simple, but can be simplistically interpreted allowing us all a chance to understand and learn from these features.

There are 3 main things needed for a geyser to form:

1: A special underground plumbing system
2: A large, consistent heat source
3: A substantial supply of water

Now, all of these ingredients can be found all over the earth. But, having the right amount of all three things (in copious amounts) is quite rare. The question that is presented now: How? How do all 3 of these things connect to make a geyser?

Let’s talk about the first ingredient: A special underground plumbing system.

When we say “plumbing system” we are talking about the underground waterways and chambers that make the underside of a geyser. This is where the hot, boiling water that causes a geyser to erupt can be found. This system is unique in that it provides the conditions necessary for water to reach boiling point, encouraging pressure to build and build. But a channel with boiling water is not all that is needed for an eruption. Another feature of these systems is a characteristic called the “constriction”, which allows for the mass buildup of pressure within the plumbing system so that the water may reach its boiling point, eventually exploding into a geyser eruption! This eruption allows for said pressure to be released when the water in those channels gets to the boiling point.

Fun Fact! Old Faithful’s constriction is only about 4 and 1/8th inches wide!

Riverside Geyser in the Upper Geyser Basin

The second ingredient: Heat

Now, the reason why we even have thermal features in the first place is because Yellowstone is home to a very large heat source. A type of volcano, in fact, called a Caldera. This caldera is very close to the earth’s surface (anywhere between 3-5 miles, depending on which part of the park you find yourself) and continually heats the water within geysers and hot springs. This then allows for the water in those plumbing systems to reach boiling point, triggering an eruption to occur.

The last ingredient: Water

Water is one of the most abundant elements on earth and is an integral part of life as we know it. Here in Yellowstone, there is a large collection of water circulating, between the surface of the park and the super-heated rock before the heat source, the magma chambers of the caldera. The water is supplied predominantly by the snow-melt and rain received across the landscape. While the park may experience this kind of precipitation every year, it can take quite a bit of time to appear in the geysers and hot springs. Each section of the park is different and so is each geyser, meaning that water can take anywhere from a few minutes to many centuries before making its way into the plumbing systems of these thermal features.

Great Fountain Geyser in the Lower Geyser Basin

A Special Plumbing System, a Heat Source, and Water. A simple yet useful way to start understanding what it takes to create the geothermal characters that we have all come to know and love here in Yellowstone. There are those other places on Earth where one can find geysers, but that does not make them any less beautiful or rare. Although these three ingredients may, in themselves, be common, finding them in just the right amounts with just the right conditions to create such geological wonders is, indeed, rare.

Not only must the perfect collection of natural elements come together for geysers and other geothermals to exist, but the sense of appreciation and respect for them is just as key to their continued existence. If not for the efforts of those before us, to understand, protect, and educate about these exemplary, awe-inspiring geologic curiosities, we may not have had the chance to properly preserve them so that they may be experienced and enjoyed by visitors from all walks of life today, and every day.

by David Valdivia, Yellowstone Forever Institute 

Feature image: Grand Geyser in the Upper Geyser Basin

The post Naturalist Notes: The Living Earth appeared first on Yellowstone Forever.

June in Yellowstone is often called the season of babies—wobbly-legged bison calves, wide-eyed fox kits, clumsy bear cubs. It is easy to view this time of year through a sentimental lens. And in many ways, it is heartwarming. But look a little more closely, and something deeper begins to emerge: this is not just a season of cuteness—it is a season of recalibration. Yellowstone in June is a landscape fine-tuning itself, adjusting its balance in real time through the presence of its youngest inhabitants.

These animals are more than symbols of spring; they are agents of ecological change. Their birth triggers shifts in behavior, movement, and energy across the park. They are not merely learning from the landscape—they are influencing it, sometimes profoundly.

Take marmot pups, emerging cautiously from their burrow where they have spent the past several weeks. Their presence is more than a mark of survival—predators begin to take notice and alarm calls echo across talus slopes. The pups’ grazing alters plant growth, which in turn affects pollinators and soil structure. One tiny mammal, in their first days above ground, sends quiet ripples outward that shape the ecosystem in subtle and accumulating ways.

Overhead, cliff swallow colonies come alive beneath the eaves of rock outcroppings and bridges. Dozens of mud-cup nests contain chicks whose survival depends not just on the dedication of their parents, but on the synchrony of the system itself. Insect blooms must arrive on time. Temperatures must rise steadily. Water levels must hold. Even large animals, like bison, play an indirect role—stirring bugs into the air with each step. From the outside, it may look like chaos, but at its core, it is coordination.

Then there are the lives we rarely notice at all. Tadpoles wriggle through snowmelt-fed puddles, racing against evaporation to complete metamorphosis. Young long-tailed weasels begin testing their speed and cunning, emerging as tiny, relentless predators. Their actions may be small in scale, but they shape prey populations and ripple upward into larger trophic dynamics. Even the smallest young have a role in maintaining the equilibrium of the whole.

Predators, of course, are tuned into this season as well. Young coyotes and foxes hone their skills on vulnerable prey. Grizzlies target elk calving grounds with precision, altering the behavior of entire herds. The emergence of young is not just a passive event; it is a catalyst that redefines how the ecosystem behaves for weeks, even months.

In this way, June is not just a moment of birth—it is a test of timing, instinct, and adaptation. The park doesn’t simply awaken in spring; it reorganizes itself. With each fledgling, each fawn, each den of kits or pups, Yellowstone is updating its internal systems—revising, responding, evolving. The nursery is not separate from the wild; it is the wild, doing what it has always done: preparing for whatever comes next.

To witness this season is to observe the park thinking. Not consciously, of course, but dynamically—responding to snowpack, temperature, moisture, daylight, and species behavior with precision and subtlety. It is a time of movement and vulnerability, of possibility and risk. And in the quiet moments, if you pay close attention, you may begin to feel it: the whole place humming with the fragile, determined pulse of new life.

Photos:
Feature: NPS / Jim Peaco
Others: NPS / Jacob W. Frank

The post Naturalist Notes: Nursery of the Wild appeared first on Yellowstone Forever.