Canadian Invaders!

Leanne Grieves
Readability
8.25

How does this align with my curriculum?

Beavers are a Canadian symbol. But in South America, they’re considered an invasive species.

If you live in Canada, you probably know a thing or two about beavers. You’ll recognize the beaver from our nickel coin. You may also have seen the large, mud-and-stick lodges and sturdy dams that beavers build. In fact, the beaver was officially recognized as an emblem of Canada in 1975!

But not every country celebrates beavers as much as Canadians do. As we’ll learn in this article, in Argentina and Chile, beavers cause some huge problems. Those problems do not have easy solutions.

Beavers in Canadian history

Beavers are an important part of Canadian history. During the fur trade of the 1600s and early 1700s, they were trapped and hunted for their valuable pelts. At the height of the fur trade, around 200 000 beavers were killed in Canada each year!

By the 1900s, beavers were scarce across North America. In the 1930s, a beaver conservation movement began. Because of this, people stopped trapping and hunting beavers for many years. Eventually, beaver populations grew back to a healthy level.

Beaver in a canoe with Grey Owl,
Beaver in a canoe with Grey Owl, 1931 (Library and Archives Canada [CC BY 2.0] via Wikimedia Commons).

Did you know?

The beaver conservation movement of the 1930s happened largely thanks to Grey Owl, a man who wrote passionately about Canadian wildlife. Some people call him one of Canada’s first conservationists.

Beavers in South America today

In 1946, 25 pairs of beavers were brought to the South American countries of Argentina and Chile. These countries hoped to encourage fur trade there, too. Today, that number has grown to 200 000 beavers.

What’s the difference between beavers in North America and South America?

Beavers (Castor canadensis) occur naturally throughout most of North America. In other words, they are a native species here. 

In North America, beavers have natural predators. Wolves, coyotes and other large predators kill and eat beavers. This way, the number of beavers stays at a healthy level for the ecosystem. 

But the beavers in South America have no natural predators. Because of this, they were able to spread rapidly in peat bogs, grasslands and other environments.

In parts of South America, beavers have become what’s called invasive species. Invasive species are species that cause harm in an area to which they are introduced. Unlike native species, invasive species do not naturally occur in that area.

What is so harmful about beavers?

Beavers use their strong, sharp front teeth (incisors) to cut down the trees they need to construct their dams and lodges. 

Left: Beaver lodge at Six Mile Lake Provincial Park, Ontario
Left: Beaver lodge at Six Mile Lake Provincial Park, Ontario (Public domain image via Wikimedia Commons ).Right: Beaver dam near Wetaskiwin, Alberta (Zeitlupe [CC BY-SA 3.0] via Wikimedia Commons).

North American tree species can often grow back after being cut down by beavers. But South American trees can’t do this. That means beavers are destroying South American forests. 

Beaver dams have also led to flooding in many areas. This can drown and kill old-growth trees in South America, many of which are over 150 years old. The beaver dams are also destroying peat bogs, which are a crucial part of the environment.

Beaver dam in Tierra del Fuego National Park, Argentina
Beaver dam in Tierra del Fuego National Park, Argentina (Anne Dirkse (www.annedirkse.com) [CC BY-SA 4.0] via Wikimedia Commons ).

Many of these South American forests can only regenerate from seeds lying dormant in the ground. When the areas next to beaver dams flood, the seeds drown and die. This means that the area of forest lost to beavers won’t recover.

Beaver dams also can affect the migration of fish, such as trout, which cannot swim around beaver dams. As well, beaver dams can create bogs. This means land animals must now navigate bogs in areas that used to be lush river deltas.

And the impacts are not just environmental. Beaver-related flooding has also destroyed roads and bridges, and contaminated drinking water. The invasive beavers have caused millions of dollars in damage!

What are the solutions?

The government of Chile has dedicated $7.8 million to fight the massive destruction caused by North American beavers. In 2008, Chile and Argentina signed an agreement to get rid of beavers and restore the ecosystems affected by their invasion. In 2017, these governments announced a plan to kill (“cull”) more than 100 000 beavers over ten years.

One option to reduce the number of beavers is to train hunters to quickly and humanely kill the beavers. Other options include encouraging trapping and offering rewards for beaver hunting. These countries might also try to introduce beaver meat as a delicacy. This would encourage people to eat the meat from hunted beavers so that it would not go to waste.

Some animal rights groups oppose these methods. Instead, they are pushing for beavers to be captured and shipped back to Canada. But biologists in Chile argue this would take too much time and money. Also, once the beavers got back to Canada, they might need medical treatments and a period of quarantine. These two things would help ensure these beavers are healthy, and would not introduce new diseases to Canadian beaver populations.

Did you know?

The beaver is the second largest rodent in the world. The largest is South America’s capybara.

Why is all this important?

Beavers in South America have caused a difficult and sensitive problem. Argentina and Chile need to protect their environments and economies from the beavers’ massive destruction.  But the government's solution of killing over 100 000 animals is difficult for many people to accept.

We can learn important lessons from the introduction of North American beavers into South America. Before people move species from one place to another, they must first do some careful research to make sure these moves will not cause problems. People must always strive to balance the costs and benefits of their actions. As this example shows, correcting past mistakes can involve making very difficult decisions.

Starting Points

Connecting and Relating

  • Have you observed beavers or evidence of beavers in your community? 
  • Have you ever eaten beaver meat? Would you be willing to eat beaver meat in order to reduce an invasive species? Explain.
  • Have you experienced an invasive species in your community or region of Canada? What species? Describe the observable impacts of this invasive species.
  •  

Connecting and Relating

  • Have you observed beavers or evidence of beavers in your community? 
  • Have you ever eaten beaver meat? Would you be willing to eat beaver meat in order to reduce an invasive species? Explain.
  • Have you experienced an invasive species in your community or region of Canada? What species? Describe the observable impacts of this invasive species.
  •  

Relating Science and Technology to Society and the Environment

  • Importing beavers into South America was initially an economic decision made to  build the business of fur trade. How has this decision impacted other aspects of society and the environment? How is getting rid of the beaver population still an economic issue? 

Relating Science and Technology to Society and the Environment

  • Importing beavers into South America was initially an economic decision made to  build the business of fur trade. How has this decision impacted other aspects of society and the environment? How is getting rid of the beaver population still an economic issue? 

Exploring Concepts

  • What role do predator-prey relations have in controlling the spread of invasive species? 
  • What other North American plant or animal species have become an invasive species in another country or continent? Note: This will require some research.
  •  

Exploring Concepts

  • What role do predator-prey relations have in controlling the spread of invasive species? 
  • What other North American plant or animal species have become an invasive species in another country or continent? Note: This will require some research.
  •  

Teaching Suggestions

  • Teachers could use this article to present an example of an invasive species that is of Canadian origin.
  • After reading the article, students could complete a Key Ideas Round Robin activity. Students first summarize the key ideas from the article, then form pairs and finally groups of four to negotiate the key idea gained from article. The ready-to-use Key Ideas Round Robin reproducible can be found in [Google doc] and [PDF] formats.
  • Students could also debate the decision to cull the population of beavers in South America using a Pros & Cons Organizer. The ready-to-use Pros & Cons reproducible can be found in [Google doc] and [PDF] formats.
  •  

Teaching Suggestions

  • Teachers could use this article to present an example of an invasive species that is of Canadian origin.
  • After reading the article, students could complete a Key Ideas Round Robin activity. Students first summarize the key ideas from the article, then form pairs and finally groups of four to negotiate the key idea gained from article. The ready-to-use Key Ideas Round Robin reproducible can be found in [Google doc] and [PDF] formats.
  • Students could also debate the decision to cull the population of beavers in South America using a Pros & Cons Organizer. The ready-to-use Pros & Cons reproducible can be found in [Google doc] and [PDF] formats.
  •  

Learn more

The Beaver Slayers of Patagonia (2015)

Video (10:37 min.) interview from Motherboard (Spanish with English subtitles) with beaver hunters in Chile.

North American Beaver Invasion Occupies Forests and Steppes in Southern Chile and Argentina (2015)

Article from Scientific American on the ecological threat that beavers pose as an invasive species in Southern Chile and Argentina.

Beavers

Hinterland Who’s Who by the Canadian Wildlife Federation giving detailed information on the North American beaver.

Beavers

Information about beavers from the Canadian Wildlife Federation.