Sentinels of a Warming World: The Case of the Alpine Marmot

The piercing call of the Alpine marmot has long echoed across high pastures. Today, those calls carry a new note of urgency, as the species faces threats on multiple fronts. In this month’s Lapilli+, science and nature journalist Roman Goergen reports on what researchers know about the state and future of this iconic inhabitant of the Alps, whose decline could anticipate the fate of the ecosystem they help sustain.

The burlap sack on the grass bulges and shifts, tracing the outline of a quarrelsome creature about 40 centimeters (about 15 inches) long. The only thing keeping it from hopping away across the Alpine meadow is the knee of Samuel Ginot. The French biologist, trading his lab at the University of Montpellier for the high peaks this summer, pins down one end of the sack while preparing his instruments. Finally, he loosens the drawstring just enough for a head to appear: a female Alpine marmot, still visibly indignant.

That suits Ginot perfectly, because he’s here to measure how hard this four-kilogram (eight-pound) rodent can bite. He holds a clamp-like device in front of the marmot’s nose and she snaps at it with her distinctive incisors. The bite sends an electrical signal through a cable to a small reader. Ginot jots the result into his palm-sized notebook: 130 newtons (29 pound-force) — roughly the bite force of a red fox.

“I want to learn more about the bite strength of these animals and the role it plays in their social behavior,” Ginot explains. “Do dominant animals bite harder? Are they weaker after hibernation? How do sex, age or season influence bite force?”

From the two ear tags, he can tell this marmot is already known to his colleagues — and that she’s a dominant female, ruling over a territory and extended family. Once released, the marmot darts into one of the many burrow entrances scattered across the green slopes of the Aiguille de la Grande Sassière, at about 2,500 metres (8,200 feet) in the French Alps near the Italian border.

In this narrow valley, where the Ruisseau de la Sassière winds between the peaks, the University of Lyon has run one of the world’s most comprehensive Alpine marmot studies since 1990, monitoring the species across 2,200 hectares. For centuries, these whistle-voiced sentinels have been the animal face of the Alps, immortalized by Goethe and Beethoven. Ginot’s bite-force readings join a trove of data amassed over more than three decades, revealing that the marmots’ world is changing fast. Climate shifts are lowering the survival chances of their young, disrupting social structures and even altering their physiology.

“The health of the marmots reflects the health of the Alps,” says Christophe Bonenfant, a population biologist who has led the University of Lyon research team since 2019. “They are a sentinel species” — and, he warns, may become the face of climate change in the Alps.

Average temperatures in the Alps have risen by about two degrees Celsius (3.6 degrees Fahrenheit) since the late 19th century — roughly twice the global rate. Glaciers are retreating; cliff faces crumble after years of drought. If current trends continue, many of the range’s glaciers could vanish entirely before the century is out.

“The snowline keeps moving higher,” says Nicolas Vernon, a ranger for the Grande Sassière Nature Reserve. “Where there used to be a single meltwater lake, there are now three.”

The Alpine marmot is what scientists call an Ice Age relic. During the Pleistocene, the species lived throughout the lowlands of Europe. As the last glaciation ended and the climate warmed, the cold-adapted species retreated upslope to the high mountains, where a six- to seven-month hibernation allowed them to survive. But adapting to life in the high Alps came at a cost.

“They’ve already survived one episode of climate change — the warming that ended the Ice Age,” says Bonenfant. “The question is whether they can adapt quickly enough this time, with the pace of change we’re seeing now.”

At the Grande Sassière field station, Rebecca Garcia sits on a wooden bench outside the chalet that serves the research team as both quarters and laboratory in the summer. Each year, for two months from mid-May to mid-July, the usually six-person crew works and sleeps here while gathering daily observations across the marmots’ domain. As a technical assistant for the University of Lyon, Garcia coordinates the fieldwork and directs the students who fan out into the study area each morning.

At the edge of the hiking trail that passes the chalet, a male marmot stands with tail held high, waving it vigorously while rubbing his cheeks against the ground to deposit a pungent secretion from his facial glands — a scented warning to trespassers.

Alpine marmots organize into family groups led by a dominant pair and their subordinate offspring. For subordinates with ambitions of their own, the options are stark: strike out to claim a patch of ground, challenge a neighbor or overthrow their own parents. Once in power, the new marmot rulers ensure their genes dominate the family.

Because of their six- to seven-month hibernation, Alpine marmots develop slowly, reaching sexual maturity only after three or four years. Even then, many remain in their natal group as “helpers” to the dominant pair — assisting with rearing the young and sharing body heat in winter to keep the burrow warm. But these finely tuned social mechanisms, honed over millennia, are now being disrupted by a changing climate.

“We’re seeing smaller litters now,” Garcia reports. “In the past, there were four or five pups; now it’s down to three or four. And the mothers are often in poorer condition when they emerge from hibernation.”

The culprit is the snow — or rather, its absence. The winter blanket above the burrows is growing thinner, which paradoxically makes it colder underground because there’s less insulation. Marmots can tolerate temperatures as low as about four degrees Celsius (39 degrees Fahrenheit) in their hibernation chambers. Below that, their bodies must generate extra heat, burning more energy and fat reserves. “Then they come out of hibernation in worse shape and the females give birth to fewer young,” says Bonenfant. It’s a downward spiral the team is determined to track closely, documenting changes in body condition and reproduction year by year.

On her stomach in the grass, biology student Aure Hirigoyen has been lying motionless for three hours in front of a marmot burrow. Her mission today is to catch pups for testing — a tricky assignment. In the first three days after they emerge from the burrow, the young are naïve enough to be scooped up by hand. After that, the researchers have to set live traps: large cages triggered by a weighted plate, baited with molasses and rabbit food.

Today, no traps are needed. Three pups venture out into the open and Hirigoyen tosses a burlap sack over the burrow entrance to block their escape route. Two dart away, but the third ends up in her hands.

At the chalet lab, the pup is anesthetized. Garcia gets to work: weighing it, measuring its body proportions and temperature, and taking samples of blood, feces and fur. Every animal receives a microchip and an ear tag — two for dominants. The family of origin is noted and all data is entered into a meticulous family register. “If we’ve had the animal before, we just update the records,” Garcia explains.

As the pup wakes in a cardboard box, Garcia writes a new number on the whiteboard: 2,302. “The total number of individual marmots we’ve studied here so far,” she clarifies. Within hours, samples and data are on their way to the University of Lyon for Bonenfant’s analysis.

Although Alpine marmots remain common — the International Union for Conservation of Nature (IUCN) lists them as “Least Concern” despite an annual population decline of around 4 percent — the Lyon data show clear negative trends that, in the researchers’ view, warrant close watch. Litters are getting smaller, survival rates for pups are falling and average body size has been shrinking steadily since the early 1990s. For a cold-adapted animal, that’s bad news. “Without natural selection, the drop in body size would be even steeper,” says Bonenfant.

Just beyond the French peaks, less than twenty kilometers (12 miles) from the Grande Sassière study site, lies Italy’s Gran Paradiso National Park. Here, since 2006, behavioral ecologist Caterina Ferrari has been studying the marmots’ Italian cousins — and she’s noticing many of the same social changes as her colleagues in Lyon.

She also notes the beginnings of behavioral adaptation. “Marmots usually live in large families. But as their habitat shrinks, you have to wonder if that social structure is still advantageous. I don’t think it is — there’s no longer enough space and food,” Ferrari says. She expects smaller group sizes and new social patterns to become the norm.

In the Italian Alps, the treeline is climbing higher, and what used to be mountain prairies and alpine pastures are now young forests. “Where I’m working, just a few years ago, there were open meadows, and marmots were everywhere. Now there’s woodland, and I see them moving through bushes or small trees,” she says. “It’s a massive change for a species so well adapted to life on open Alpine grasslands.”

It’s not just temperature driving the change. Many Alpine meadows are human-made landscapes, maintained for centuries by mowing or grazing cattle. As traditional highland farming recedes, pastures grow unchecked, reducing the marmots’ preferred feeding grounds. The new forests also bring new predators: Red foxes now hunt in places once ruled by golden eagles alone, targeting young marmots in particular. Protecting remaining Alpine pastures, Ferrari believes, would be an important first step in helping the species.

Ferrari has watched Alpine marmots shift their range in both directions — higher up the slopes in search of cooler refuges and lower down in search of space. “But go much higher and you eventually reach the summit, where there’s nothing but bare rock — no food, no place to dig burrows,” she explains. Lower down, the problem is the heat. Even in their usual mid-altitude habitats, the animals struggle with thermal stress. On hot days, Ferrari’s team has found, marmots are spending longer hours in their burrows. “We’re even seeing them forage more at night now — but for an animal that’s prey for many predators, that’s a dangerous strategy.”

In the marmots’ traditional highland strongholds, parasites, bacteria and viruses are naturally scarce; many pathogens never make it that far, also points out Markus Ralser, a metabolism biochemist at Berlin’s Charité hospital. But in the valleys, the animals encounter a greater diversity of disease agents and they are poorly equipped to fight them.

Until now, the isolation of the high mountains has shielded the species from many threats. But climate change could tear down that barrier, exposing them to pathogens and invasive species for which they have hardly any defenses. “It doesn’t matter how big your population is — without genetic diversity, you’re more vulnerable to unpredictable new challenges,” Ralser warns.

For now, large colonies of Alpine marmots persist and no one anticipates an imminent collapse. But scientists expect smaller families, altered social structures and a continued retreat into higher altitudes. Hovering over the scene is the threat of an unforeseeable crisis that the species may be unable to withstand. Ralser sees only one sure safeguard at the moment: “Stop climate change.”

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