Keystone Species: Definition, Importance and 17 Examples

Sea otter as Keystone Species

[Updated: 7 August 2020]

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What are Keystone Species?

Ecosystem Importance of Keystone Species

17 Examples of Keystone Species

  1. Grizzly Bears: Forest Gardeners
  2. African Elephants
  3. Sharks; Ocean Cleaners
  4. Sea Otters
  5. Krill
  6. Beavers
  7. Hummingbirds
  8. Parrotfish; Coral Cleaners
  9. Priaire Dogs
  10. Woodpeckers – Tree Surgeons
  11. Gray Wolves
  12. Snowshoe Hare
  13. Starfish (Sea stars)
  14. Figs
  15. Saguaro Cactus
  16. African Termites
  17. California Mussel

What are Keystone Species?

Keystone species are considered the pillars of an ecosystem. They have defined roles that ensure survival of the food-web.

These roles can range from being a keystone predator, prey, producer and as general ecosystem engineers that shape up the whole ecological community.

While experimenting on Starfish at the coastline of California, Robert T Payne realized that some species have a larger role in the ecosystem. Number of those species in the entire ecosystem didn’t matter to the role they played. These came to be known as ‘Keystone species‘.

Sometimes, these are confused with Indicator species.

Ecosystem Importance of Keystone Species

The importance of the keystone species is related to how they interact with other species of the ecosystem. Their presence in the ecological community is essential to maintain the populations of other species that interact with them.

Keystone species importance in ecosystem
This graph shows how important keystone species are to an Ecosystem. Although this is an experimental ecosystem, the idea can truly be applied on the field. As you can see removal of a single predator keystone led to severe loss of biodiversity in the ecosystem.

For example, if a keystone species was to be removed from the chain, the whole ecosystem would come tumbling down. It would trigger a trophic cascade! The elimination of one of the keystone species leads to multiple reactions in the environment as follows.

There will be overpopulation of prey species which were initially being eaten by keystone predator. Additionally, there will be endangerment of animals that used to depend on our keystone prey species for food.

These will look to find other sources of food and the single species they find will get endangered too.

While the loss in quantity of species of a remote ecosystem
may not be of much concern, the loss in biodiversity could have some long-term irreversible effects.

Now that you get what keystone species are and how important they are to maintaining biodiversity, let me show you a few examples of keystone animals and plants in our world. The article also shows you what effect keystone species have on our ecosystem.

17 Important Examples of Keystone Species

Keystones species are often the first to be prioritized by ecologists doing research or authorities for policy-making, and repeatedly covered by media for their conservation status. This makes you think, why are they more important than the other species?

Below are some keystone species examples with their integral roles in the ecosystem. Click on any of these to navigate to details.

1. Grizzly Bears – Forest Gardeners

Grizzly bear as keystone species

Grizzly bears are one of the keystone species because they provide the soil of the forest floor with important nutrients such as nitrogen and phosphorus when they drag their food (salmon carcasses) from the lake into the forest.

The leftovers of their food enrich the soil as well. This helps the flora of the forest.

In a way, these bears play a role as gardeners of the forest as when they dig on the soil to look for food (roots or bulbs),they shallowly dig a widespread area of soil which leads to the organic material on the surface mixing in with the layers below.

This also allows air to penetrate the soil thereby enhancing growth of many wildflowers. Seeds of berries and pine nuts are primarily distributed by these grizzlies.

Moose and elk are some of their preys and these bars keep their population in check by eating away the week species.

Humans have endangered Grizzly bears with hunting, habitat loss due to urban development and introduction of invasive species.

2. African Elephants

Lets just call them architects of the forest. They have the ability to markedly transform the landscape of the environment.

African Elephants as keystone species

They work on the environment by pushing down trees and eating away shrubs which keeps the grasslands in check.

This makes the habitat for mice or the comfortable warm and dry soil for species like zebras and antelopes. When they get attracted to this transformed area, so are their predators, such as lions.

While we’re discussing lions and Africa; African lions are known to be keystone species as well as flagship species.

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When reading about actions like pushing down trees or digging deep holes in the forest floor, it may seem that these elephants are quite destructive to the forest.

You may not believe this but actually these actions are quite beneficial. Pushing down trees creates corridors in the forest which prevent spread of forest wildfires and the deep holes collect water for other animals to drink.

Unfortunately, these keystone species of the African Savanna are also on the list of endangered species and could possibly be extinct by 2025.

3. Sharks – Ocean Cleaners

For as long as sharks have existed, which is like 400 million years, the the ocean has depended upon sharks more than any other animal in the marine ecosystem.

sharks acting as keystone

Sharks prey on individuals of marine life that are weak or sick, and a few also eat carcasses of dead fish present on the ocean floor. Additionally, Sea turtle populations that eat a lot of sea grass are also controlled by sharks.

By doing this, sharks keep a check on the fish populations and ensure that the fish species present are of good health (thereby preventing spread of disease).

P.S: If these dead fish were to stay in the ocean for long, they can become home to harmful bacteria that use up dissolved oxygen in the ocean. We also need not be worried about fewer fish in the ocean because they have a good rate of reproduction.

Without sharks as predators, the whole marine environment of the ocean could shatter completely.

4. Sea Otters

Sea otters are the second smallest mammals present in the ocean of northwest pacific. These mammals are the ones responsible for controlling the coastal marine ecosystem.

Sea otters feed on Sea urchin and are responsible for controlling their populations.

Sea urchin feed on Kelp. If, for some reason, the population of sea urchin was to rise significantly, it would lead to steep decrease in Kelp populations.

Now Kelp is a Giant seaweed that grows in kelp forest near the coast. Kelp forest is a habitat as well as food source for many herbivorous species such as crabs, snails and small fishes.

Imagine if Kelp was gone, how many of these species would lose their habitats and also be more visible to the prey.

Kelp forests are much more beneficial to humans and the environment as well. Their populations reduce the speed at which the waves hit the shore, thereby reducing coastal erosion.

Contrary to popular belief, they don’t have roots like other plant species. They have kelp holdfasts which allow them to cling to rocky shores

But the more major role of Kelp is in their ability to absorb Carbon Dioxide from the environment. Since Carbon Dioxide is one of the greenhouse gasses, this is how Kelp defends climate change and global warming.

P.S: Do not underestimate other plant species in their role against climate change.

5. Krill

Krill as Keystone Species

These are very small crustaceans which perform the role of nutrient carriers. Krill feeds on phytoplanktons which full of nutrients like amino acids, bioflavinoids, antioxidants and carotenoids along with Omega 3,6 fatty acids which are the good kind.

Whales primarily feed on krills, and hence krills provide whales with the essential nutrients.

Whales are not exclusive to eating krills, many other species like fishes, seals and penguins feed on krills. They are also harvested for us humans to eat as well.

6. Beavers

Beaver as keystone species

History suggests that we used to hunt beavers for their fur and for the fact that they would block streams and alter landscapes. At the time, it was thought that this behavior was harmful to the environment.

It was not until recently that we realized that behavior of beavers was actually helpful to other species in the environment. This is because beaver dams made habitats for other species and ideal spawning grounds for aquatic animals like salmon.

The mere fact that we are able to catch salmon for seafood is only because of existence of beaver dams. Beaver dams act like filters, removing the fine sediment from the waters, the filtered water ahead is perfect for salmon to lay eggs.

The beavers would also cause formation of wetlands which actually absorb more carbon from the environment as compared to forests.

SEE ALSO  What is Trophic Cascade? Types and Examples

7. Humming birds – Pollination Patrol!

In Patagonia forest, humming birds (Sephanoides) are responsible for pollination of 20% of local plantations.

humming birds as keystone species

Pollination of some plants is actually exclusive to humming birds, which means that if these birds were to vanish for some reason, the entire forest diversity is at risk.

8. Parrotfish – Coral Cleaners!

Parrot-fish as Keystone Species

Parrotfish are the primary cleaners for the coral reefs. Parrotfish feed on Algae and other parts of coral reefs including some dead materials, which are present on the surface of coral reefs.

Hence, by eating algae, they clean up the surfaces of coral reefs. It is said that just a single parrot-fish can eat up to 5000 Kg of algae in a year!

Algae populations on coral reefs needs to be controlled, because if they were to rise very high the population of corals would be adversely affected.

We cannot let that happen because coral reefs play the role of habitat to thousands of marine animals, almost 25 percent of the entire marine life.

9. Prairie dogs

Prairie dogs as keystone species example

Prairie dog is a small herbivore. This means that prairie dog feeds on plants. This is why a healthy population of Prairie dogs keeps the grass height in check.

This means that there is healthy biodiversity on the grassland which would attract many others including birds, mammals and crustaceans (insects).

Another benefit of this action of prairie dogs is that when grass height is controlled from growing too much, it prevents excessive loss of water from the grassland through evaporation.

This allows groundwater to be conserved and grasses can stay greener for a longer period of time.

Prairie dogs also burrow holes into the ground sometimes which can form water pockets for other animal species to drink water from, and where small animals can seek shelter.

10. Woodpeckers- Tree Surgeons

Woodpecker as Keystone Species Example

Woodpeckers have a habit of making holes in trees. These holes can be used by other bird species to make their nests. Holes in tree trunks can only be made by woodpeckers among the bird species. Even holes formed naturally in the tree trunks aren’t as good as these.

They also keep larvae populations in check. Their beaks can reach into holes where no other species can. When they reach these larvae, they open up the hole for other species to eat out of. This provides easier to access to food for others as well.

Woodpeckers truly act as doctors because they also eat up the pests which are harmful to the forest such as bark beetles. Since woodpeckers stay in their forest area, they keep these pests in check and promote forest health.

11. Gray Wolves (Yellowstone National Park Example)

A known incident was the disappearance or removal of wolves from the Yellow Stone National Park during early 1900’s which led to such negative effects that the authorities have tried to manually tried to introduce them back into the environment. More on this below…

Gray Wolves were initially native to 2/3 of the area of United States. Nowadays, their population has become limited to parts of Alaska and the Greater Yellowstone Ecosystem (one of the last large-sized ecosystems left).

This vast ecosystem has it all; a volcano, mountains, forests, shrubs and various kinds of grasses. Many of the Gray Wolf’s preys like elk, rabbits or birds eat these grasses.

With this many herbivores (plant-eating animals), there is bound to be some competition. This is where gray wolves thrive!

Gray wolves, at the top of the food-chain, prey (eat) and control the populations of these herbivores so the grasses or shrubs don’t get over-eaten and die out.

And this is exactly what happened at the Yellowstone National park!

In 1926, the last pack of wolves got killed because US government wanted to protect elks and other grazing animals.

This led to overpopulation of elks. Elks started to eat a lot more grass than other species. This meant that other species would go hungry because of higher competition.

Soon, others that depended upon grass/vegetation for food, like fish and beavers, started to die out.

Elks ate so much that there was over-grazing and soil erosion of the land!

After realising these catastrophic effects, US government finally reintroduced wolves into the Yellowstone National Park on 12 January 1995.

This brought back the balance which was lost long ago.

12. Snowshoe Hare

Also known as Snowshoe rabbit, this species is native to cold climates in North America.

Snowshoe Hare as Keystone Species

The snowshoe hare, named because of it’s long hind-feet, plays the role of prey to many predators. One of those is the Gray Wolf, which is itself a keystone species!

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Other predators include Canada Lynx, Bobcats, fishers, foxes, Coyote, different kinds of hawks, eagles, crows and even domesticated cats and dogs.

Whew! That’s a long line of predators.

Studies have proven that the population of these predators, especially of the Canada Lynx, is closely tied to the population of snowshoe rabbits.

Since so many predators (vertebrates) depend on snowshoe hares for food, you can imagine the side-effects of snowshoe rabbits going extinct.

Did you know? Snowshoe hares are actually vulnerable to climate change, mainly because of habitat loss.

13. Starfish as Keystone Species

Starfish as Keystone Species Example

A professor of Biology (zoology to be specific), Robert T Payne, researched on species that lived on the coastline in California in 1966.

During his experiments; in one of the trials he removed the apex predator species which was starfish (a.k.a Sea Stars).

When the predatory starfish was eliminated from the trial, entire food web began to have changes. Other species began to vanish, slowly leading to collapse of the entire ecosystem.

When noticing this, Robert realized that some species have a larger role in the ecosystem, no matter how many there were in the marine ecosystem. Hence, they came to be known as ‘Keystone species‘.

14. Figs

Figs as Keystone Species Example

Fig trees, as keystone species, perform the role of providing food to animals and birds. Even though Fig leaves are edible, most of it’s importance comes from it’s fruits.

Fig trees bear fruits throughout the year! When dry seasons come around, these fruits are no less than a gem for other species to survive.

You can imagine the loss if those birds and animals didn’t have fig trees to survive in dry seasons. That’s what makes fig trees a keystone species.

15. Saguaro Cactus

Who would’ve thought that these pricky gems of nature would be responsible for sustaining hundreds, if not thousands, of lives.

Saguaro cactus are exclusive to the desert and play the role of host to their fellow species. It’s branches give perfect support to big birds, like the red-tailed hawk, to make nests where these branches meet the stem.

Some have suggested Saguaro cactus being exclusive to desert is because of them being a dominant plant species.

P.S: Tall Saguaro Cacti are used by big birds as hunting platforms

Smaller birds like Gila woodpecker, gilded flicker, elf owls and purple martins make their homes inside the pulpy flesh of Saguaro Cactus.

Saguaro Cacti aren’t exclusive to helping birds. In dry summer months, Saguaro cactus fruit is the only moist fruit available for animals in the desert.

16. African Termites

Importance of African Termites as keystone species comes from it’s home; Termite Hills/Mounds. These termite mounds survive as long as 60 years and gain heights of up to 30 metres.

That’s like a 50-story building in insect world!

These features attract animals like mongoose and warthogs to safely grow their young inside this mound acting as a habitat. Ironically, predators use the height of the mound as a hunting platform.

That’s not it. Termite mounds greatly increase soil fertility around them. These mounds contain high levels of nitrogen, phosphorus and necessary micro-nutrients like zinc.

This can be proven by the fact that many farmers willingly build termite mounds on their farms to increase fertility.

17. California Mussel

Scientifically known as Mytilus californianus, California Mussels are native species living along the coast of Pacific Ocean.

Mussel beds are definitely a key species. A mature bed grows so large that it can host several species in the marine world. As many as 300 have been identified growing on these beds. Similarly, coral reef is also used as a habitat by a number of animals.

Such organism which are home to many other animals are, at times, known as umbrella species.

These include marine organism like Oysters, Gastropods, Annelid worms and particular species of young octopus. Fine spaces allow them to hide from predators, so healthy species diversity is achieved.

If you you’re still interested, you should read up about gopher tortoise as keystone species as well!

Now that you know quite a bit about of keystone species,

What are your thoughts?

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  1. Keystone predators may increase the biodiversity of communities by preventing a single species from becoming dominant. They can have a profound influence on the balance of organisms in a particular ecosystem. Introduction or removal of this predator, or changes in its population density, can have drastic cascading effects on the equilibrium of many other populations in the ecosystem. For example, grazers of a grassland may prevent a single dominant species of grass from taking over.

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