Of goats and men: How the Galápagos eradicated a non-native species

Celso Montalvo in the Galápagos

Celso Montalvo, who now works as a naturalist with Lindblad Expeditions, shared his experiences with the problematic goat population, growing up in the Galápagos. (Peter Jurich/University of Wisconsin-Madison)

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Biodiversity, Sustainability

AUTHOR’S NOTE: I first learned about invasive goats from the book “Where Are The Galápagos Islands?” by Megan Stine. The book is part of Penguin’s “Where Is?” series for young readers. The author mentions briefly a decadelong project to remove many thousands of goats from the island. Since we in the U.S. rarely think of goats as “invasive,” I was interested to learn more. I discovered the following impressive story about invasive species management on the islands. Enjoy!

When he was a teenager, Celso Montalvo crawled quietly through the volcanic ash on the island of Santa Cruz with his three cousins and uncle, Victor Hugo, armed not with firearms, but with rope. He was either 14 or 15 years old. “I’m not 100% sure, but I remember I was bold and careless for adventure,” he says.

The naturalist and his family usually ate fish on the island. “But sometimes we would have a really honorable highlight to go and hunt the goats,” he says.

The goat that the party had chosen to hunt was an alpha male, surrounded by a harem of females, somewhere near Cerro Dragón, or Dragon Hill.

“I did not know, but it was my initiation,” he recalls. “My right of passage, and this changed my life forever.”

Montalvo did not know that he was responsible for the catch. He had just gotten off a plane from mainland Ecuador hours before and was already very tired. Suddenly, he found himself creeping through the brush and his uncle whispered to him: “Son, you see the alpha male right there? Well, I think you can bring this guy down.”

“There was no excuses allowed,” Montalvo says of a childhood in which he and his cousins were all given chores that would help the community at large. “Your responsibility, whatever they gave you, was to be committed and you will grow into others as you become better.”

Only a teenager and fresh out of the Ecuadorian Naval Academy for the summer, Montalvo was undeterred by the goat. He hunkered down into a burrow while his cousins moved to the other side of the herd and whistled. This scared the goats and the alpha male galloped in his direction.

“I was on the ground and when this goat appeared on the crevice, this thing was not smaller than me anymore,” he says with a laugh. “This thing was huge!”

The goat butted Montalvo right in the chest with its massive horns and Montalvo was immediately in severe pain. The goat then ran away, escaping its capture.

When his cousins asked him what happened — why he was unable to capture the goat for dinner — Montalvo says he cried and made too many excuses. “Immediately, my cousins started to shut down,” he says. “They did not speak to me.”

The hunting party trekked the two hours back to camp empty-handed. No one spoke. His uncle went into the ocean to catch fish for dinner. “The shame that I felt so bad. I did not provide for my family.”

He went to bed that night and had nightmares about goats.


The goats that Montalvo and his family hunted were not native to the islands; they were brought over in the 1700’s by English settlers.

In those hundreds of years they inhabited the islands, they devastated them.

“We knew that goats did not belong to the Galápagos,” Montalvo says. And still, he had to watch them daily devouring all of the vegetation on the islands. “Of course, it breaks your heart. Of course, you want that to be over.”

goats eat vegetation in the Galapagos
Goats eat vegetation on an island in the Galápagos. (Photo courtesy Island Conservation/Josh Donlan)

In 1959 when the islands became a parque nacional, the government took inventory of the islands and their species.

“We needed to see what were our assets to protect and what were the problems,” Montalvo says. The assessment concluded that goats were not only eating all of the native plants, but they were leaving none for other native animals. The goats had become invasive.

Goats will “eat anything if there’s nothing else to eat, but if there’s everything to eat, they’re very selective,” says Karl Campbell, program director for Island Conservation, an organization dedicated to removing invasive species from islands. “It’s like letting a kid go in a supermarket. Somehow, they manage to gravitate toward the candy section.”

In the plant world, ‘candy’ means endemic species in an area with no natural predators. The flora have adapted in a way that loses defenses like spines and toxins.

Struggling to manage the goats on their own, the Ecuadorian government sent out a distress call. “Hunters of the world: come over!”

But that plan backfired. “They shot each other,” Montalvo says, “They got lost and there was finally a heart attack because it was really hot.” 

Then the Army gave it a go. But that was unsuccessful because they could not find all of the goats. And if you don’t kill all of them, Montalvo says, the population will bounce right back quickly.

“We were able to control them, but not to eradicate them.”

“It’s very easy to get the first 95% because they’re naive,” Campbell says. “And you try to keep them naive as long as you can, but that’s not always possible.”


Campbell now lives on the island of Santa Cruz where he works out of the Charles Darwin Research Station. He is the world’s leading goat eradication expert, having completed his Ph.D. in the subject. He is interested in what he calls “active conservation efforts.” Many efforts in the field have results that won’t be seen until years down the line, but invasive species eradication produces results that can be felt in real time. 

“If you look at islands, you’ve got less than 5% of the worlds surface area, but you’ve got around 40% of species that are heading toward extinction,” he says. “If you want to prevent extinctions, have a close look at islands. If you want to prevent extinctions on islands, you should get pretty good at removing invasive species.”

Once an invasive species is removed, a threatened species can come back from the edge of extinction — provided they still have a sustainable environment.

That posed the biggest challenge for the eradication effort. How do you eliminate not just the majority of the goats, but also the ones in hiding, the ones that can rejuvenate the entire population if they’re not also killed?

Eventually, the UN and UNESCO connected Ecuador with New Zealand, which had had some small scale success with goat eradication.

Enter the “Judas goats,” which Campbell describes as “horny but sterile.”

Goats are gregarious by nature and are good at finding others. So in the late 1990s, scientists sterilized about 600 goats on Isabela Island, fitted them with radio collars and let them loose. Then they trailed the Judas goats in a helicopter, rifles in hand, until they were led to the smaller, harder-to-reach populations. From there, they could take out the smaller, stealthier populations.

They were named them Judas goats because they “betray their own kind,” Montalvo says.

“We’re a very Catholic country,” he adds. “They chose that [name] so that we’d understand that that guy is going to work for us.”

The effort had been wildly successful. “We are proud, very proud, and honored to say that we have totally eradicated goats from Santiago Island. And it’s a very large island. Also, we have totally eradicated goats from this northern part of Isabella.

“We fought and we raised millions of dollars. We thought it would take forever. It took probably like three years and one-third of the money we raised.” The total effort cost $1 million.

Montalvo laughs. “The truth is we thought it was just another project that would fail.”


Eradicating an invasive species has more challenges than just with the animals.

“When you start working on inhabited islands, suddenly you start interacting with communities and politics,” Campbell says. “How do you engage with them? How do you fit in with their vision and their goals or actually even help them establish what is their vision and their goals because sometimes there’s disparities within communities.”

For example, some people in a community may look at an invasive species as an important food source. So while eliminating that species may help many, others may not directly see any of those benefits.

“This is a bit that, instead of harmony, actually continues division between communities,” Campbell says. “You want to structure your projects so that the benefits seem to be — and truly are — well divided among the community.”

Campbell says a more holistic approach should be taken when creating an eradication plan, one that puts community members into a leading role. 

“You might have the best idea in the world,” Campbell says, “but if the idea is not coming from them or their ideas haven’t been heard… you’re pretty quickly being told, ‘There’s the door, mate.’”

Island Conservation therefore seeks to establish itself as more of a “technical assistance” program on the islands — one that takes on a supportive role rather than a leading one.

This approach worked on the island of Pinzon in 2012 when they helped eliminate invasive rats. In the 90’s, the California Academy of Sciences hadn’t been unable to collect any giant tortoises due to the rodents’ aggressiveness, but by working with communities to eliminate them, they were able to bring back the giant tortoise population for the first time in 150 years.

“This is a bright spot for conservation,” Campbell says. “We can basically recover species that are on the brink of extinction and get them back to healthy populations so that they’re ready for the next threat — whether it’s a major cyclone or El Niño or La Niña or whatever affects you negatively in these large cyclical patterns.

“It doesn’t matter whether you’re in the U.S. or Europe or anywhere else, your life is impacted by invasive species. If you’re a baseball fan, you’re impacted. Why? Because the trees that are used for your bats are now impacted by abora. Those trees are no longer available and you can’t get bat-length pieces that haven’t been bored (by insects).”


At 5 a.m., the morning after his failed hunt, Montalvo woke up to a tapping on his shoulder. It was his uncle, Victor Hugo. 

“You can do anything you put in your mind as long as you believe in yourself,” he told Montalvo. “I believe you can stop this alpha male.”

Montalvo says that the story played out much in the same way — the trek to Cerro Dragón, hiding in the crevice — except this time, his cousins made him wait longer before they scared the goats. Maybe to increase the intensity, to build up Montalvo’s adrenaline.

“I was not the same kid the day before,” Montalvo says. “That was another kid. I was ready for that goat.”

And finally, he heard his cousins whistling and the goats stampeding. Again, the alpha male trampled its way in Montalvo’s direction. “I needed to embrace the situation, so I run towards the guy,” he says.

Again, there was a painful struggle. Montalvo wrestled with the goat exactly as his uncle taught him: by grabbing onto its horns and heaving it up into the air.

“So I’m rolling on the ground with this,” he says. “This guy’s kicking and everything. I would not let go. I didn’t even care.”

Suddenly, Victor Hugo stopped him and told him to let go of the goat. Once the pain subsided, Montalvo heard his cousins cheering for him. The goat ran away, though this time, it was by Montalvo’s choice, not because he couldn’t capture it.

“This is why you have no excuses,” Victor Hugo said. “We’re here to assist as a family. You have to believe in yourself. Today, you’re providing.”


As an adult, Montalvo is no longer wrestling goats. But he provides in a different way: As a Galápagos naturalist, he gives tours of the islands to visitors from all over the world, telling them about the important measures the government takes to mitigate the threat of invasive species.

However, he says these efforts could not be successful without tourism.

“Many places, people don’t like tourism,” he says. “We are not going to throw open the door, but tourism is greatly involved. Conservation would not work without tourism, that’s for sure. It works here in Galápagos.”

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Biodiversity, biology, ecology, Galápagos, invasive species, Threatened Ecosystem

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