Wolf in snowy landscape with helicopter and people in the background

Daniel Conjanu/The National Parks of Lake Superior Foundation via AP Images

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The Wolves of Isle Royale

Scientists are helping an island's top predator return from the brink

February 2022

By Kimberly Y. Masibay

As you read, think about how changes in predator populations affect other living things in an ecosystem.

A small airplane landed on a remote forested island in Lake Superior known as Isle Royale (I-uhl roy-AHL) in September 2019. The plane carried a very special delivery: one male gray wolf.

A few days earlier, scientists had captured the wolf in the Michigan woods. A veterinarian gave him a checkup, and biologists fitted him with a GPS tracking collar. Then he was flown to this 535-square- kilometer (207-square-mile) island, his new home.

The wolf had a big role to play on the island, which makes up much of Isle Royale National Park. Gray wolves have long been the island’s main predator, hunting animals like moose and beavers. But in recent years, wolf numbers have dropped. That has caused the moose population on Isle Royale to increase by hundreds.

The moose have gobbled up many of the island’s plants, affecting its ecosystem. “There are too many moose,” says Mark Romanski, a biologist with the National Park Service (NPS). “The animals target certain plants at certain times of the year, and it’s changing the forest.”

For the past three years, NPS researchers have teamed up with other scientists to bring new wolves to Isle Royale. They hope these wolves will help reduce the moose population. That will allow the island’s other living things to thrive.

A small airplane took off in September 2019. It landed on a remote island in Lake Superior. It was called Isle Royale (I-uhl roy-AHL). The plane carried a special delivery. It was a male gray wolf.

Scientists had caught the wolf a few days early. He was found in the Michigan woods. A veterinarian gave the wolf a checkup. Biologists fitted him with a collar. It had a GPS tracker. Then the wolf was flown to the island. It covers 535 square kilometers (207 square miles). It was his new home.

The wolf had a big role to play on the island. It’s part of Isle Royale National Park. Gray wolves have long been the island’s main predator. They hunt animals like moose and beavers. But wolf numbers have dropped in recent years. That caused the moose population to rise. The moose have eaten many of the island’s plants. That has affected its ecosystem.

“There are too many moose,” says Mark Romanski. He’s a biologist. He works for the National Park Service (NPS). “The animals target certain plants at certain times of the year. And it’s changing the forest.”

The NPS has worked with other scientists for the past three years. They’re bringing new wolves to Isle Royale. They hope these wolves will lower moose numbers. That will allow other living things on the island to thrive.

Where Is Isle Royale?

Isle Royale National Park is a 45-mile-long island in Lake Superior off the coasts of Minnesota and Michigan. It can be reached only by boat or aircraft.

Think: How might the island’s location affect its animals?

Where Is Isle Royale?

Isle Royale National Park is a 45-mile-long island in Lake Superior off the coasts of Minnesota and Michigan. It can be reached only by boat or aircraft.

Think: How might the island’s location affect its animals?

Out of Balance

Predators are an important part of many ecosystems. When a predator feeds on populations of plant-eating animals, it helps prevent those animals from overeating plants in the ecosystem.

On Isle Royale, moose are some of the ecosystem’s main herbivores. Their diet includes tree bark, twigs, and shrubs. And there’s just one predator on the island built to take down a moose: the gray wolf.

Researchers from Michigan Technological University have been monitoring the wolves and moose on Isle Royale for the past 60 years. During much of that time, there were about 21 or 22 wolves on the island. These wolves would regularly hunt the moose for food. That helped keep the size of the moose herd in check. “The wolves can do a pretty good job,” says Rolf Peterson. He’s a biologist at Michigan Tech who studies the animals of Isle Royale.

But over the past decade, the wolf population on the island has declined because of factors like disease. By 2016, there were just two wolves left. As wolf numbers decreased, the moose population exploded. The moose have overeaten the island’s tree saplings, preventing them from growing into mature trees. That has harmed birds and other animals that depend on the trees for shelter and food.

Predators are an important part of many ecosystems. Some predators hunt plant-eating animals. That helps stop those animals from eating too many plants in the ecosystem.

Moose are some of the main herbivores on Isle Royale. They eat tree bark, twigs, and shrubs. Just one predator on the island is built to take down a moose. That’s the gray wolf.

Scientists from Michigan Technological University visited Isle Royale. They studied the wolves and moose there. They did this for the past 60 years. There were about 21 or 22 wolves on the island for much of that time. These wolves would hunt moose for food. That helped keep the size of the moose herd in check. “The wolves can do a pretty good job,” says Rolf Peterson. He’s a biologist at Michigan Tech.

But wolf numbers on the island have gone down over the past decade. That’s because of things like disease. There were just two wolves left in 2016. Moose numbers shot up as wolf numbers dropped. The moose ate most of the island’s tree saplings. They couldn’t grow into adult trees. That has harmed birds and other animals. They need the trees for shelter and food.

Return of the Wolves

USFWS/COURTNEY CELLEY/NPS

A veterinarian examines the captured wolf’s teeth.

To help the island’s ecosystem, NPS scientists, along with other experts, decided to bring back more of the moose’s main predator. In 2018, they began airlifting healthy wolves from the mainland to Isle Royale. Scientists plan to relocate 20 to 30 wolves to the island over three to five years.

Scientists want the new wolves to form packs. That will benefit the health of all of the wolves on the island. When animals mate, they pass genes to their offspring. If parents are relatives, they are more likely to pass down unhealthy genes that cause health problems. On a small island like Isle Royale, the members of a tiny population of animals eventually become relatives. With each generation, more unhealthy genes can get passed down.

The new wolves are not related to those already on the island. By forming new packs, they could help keep the wolf population healthy for years to come.

NPS scientists and other experts wanted to help the island’s ecosystem. They decided to bring back more of the moose’s main predator. They began airlifting healthy wolves in 2018. They brought them from the mainland to Isle Royale. Scientists plan to move 20 to 30 wolves to the island in three to five years.

Scientists think the new wolves can help all the wolves on the island. That’s because animals mate and pass genes to their offspring. Parents are more likely to pass down unhealthy genes if the animals are relatives. Their offspring can have health problems. This can happen on a small island like Isle Royale. A tiny group of animals eventually become relatives. More unhealthy genes can get passed down with each generation.

The new wolves are not related to those already on the island. Scientists want them to form new packs. That could help keep the wolf population healthy for years to come.

Time to Heal

NPS/SUNY-ESF PHOTOS

Images taken from a remote camera in 2019 show wolves born on the island.

To monitor the wolves, scientists visit the island and look for paw prints and droppings. They use remote cameras to count and identify individuals and GPS collars to track the wolves’ movements. That data helps researchers learn how the wolves are hunting and if they are choosing mates and forming packs.

As early as 2019, researchers discovered that wolf pups had been born on the island. Two additional litters were born in the spring of 2020. But even though there are more wolves on Isle Royale, it’s going to take time to curb the moose population, experts say.

So far, the new wolves are settling in, hunting moose, and having babies. As these predators make a comeback, their presence promises to help all wildlife and native plants on Isle Royale.

Scientists keep track of the wolves. They visit the island. They look for paw prints and droppings. They use remote cameras to count wolves. The GPS collars help track the wolves’ movements. That data helps scientists learn how the wolves are hunting. They also learn whether the wolves are choosing mates and forming packs.

Scientists found wolf pups had been born on the island as early as 2019. Two more litters were born in the spring of 2020. There are now more wolves on Isle Royale. But it’s going to take time to reduce the moose population.

So far, the new wolves are settling in. They hunt moose and have babies. The predators are making a comeback. That could help all wildlife and native plants on Isle Royale.