Estimated Read Time: 6 minutes

Killing in the name of (biodiversity)

Soil, dead deer and a certain feline predator just might be key to sustaining biodiversity.

(yes that’s a grizzly bear, not a cat…but do you even know how hard it is to find a cougar!?)

Maybe you’ve heard: Soil is pretty important.

After all, it’s the foundation of life as we know it: soil’s our primary water filter; it stores 75% of our land-based carbon; it provides the nutrients for almost all life on Earth to exist, including 95% of our food.

So, yeah, soil matters. In fact, it might be the most important component of any ecosystem.

But guess what helps soil be a biodiversity superpower?

You guessed it: deer.

Well, dead deer.

Specifically, deer killed by wild cats.

What? That wasn’t obvious? Okay, let me explain.

Deer have been a plant predator for about 30 million years – helping keep plant growth in line and allowing it to re-generate.

In Canada, we have two species – the whitetail and the mule deer (a literal cousin on the whitetail’s mother’s side) – but every continent is home to some type of deer species, other than the Antarctic and Australia,

But guess which continents aren’t really known for super powerful, life-giving soil? Right: Antarctica and Australia.

Those other four land masses though? Lots of biodiversity-rich soil. Also? Lots of deer!

Unlike many species, deer reproduce easily and are highly adaptable. It’s why they’ve been so successful basically everywhere: from the savannahs of Africa to the jungles of Borneo to right here in Mount Robson.

Sometimes, however, deer are too successful.

When deer over-browse, they hurt plant diversity and take food from other species, like songbirds. As a result, birds can’t replant the native landscape as easily and suddenly entire ecosystems can be altered – water systems change, amphibians stop reproducing, insects multiply, different trees grow and entire food webs are dismantled.

Not

good!

But here’s good news: For about as long as deer have been gardening our planet, wild cats have been, um, gardening deer.

About six different wild cats have evolved to act as the primary deer regulators around the world, including our very own cougar – also known as the mountain lion or puma.

And for many years, that’s about all we assumed these cats did. But new scientific research has shown us that wild felines – and the cougar especially – play a far more important role: Like the beaver, they’re ecosystem engineers.

You see, a healthy adult cougar kills almost 50 deer per year. But even though cougars are big (they’re much larger than a lynx, though smaller than a lion or a tiger) and even if they usually weigh less than 90 kilograms, (they’re stronger than your average George St. Pierre), they aren’t really fighters.

Cougars rely on their famous cat eyes to see long distances in the dark, their claws to climb, their unheralded virtue – patience – to sit in wait, and their ridiculously strong hind legs to jump more than five metres to pounce on their prey, usually killing it with one powerful bite to the back of the skull. (With apologies to the Beastie Boys, there might be something worse to the neck than Mr. Spock.)

Yet one measly cougar can’t eat all the meat on the body of a full-grown deer – they’re not pigs, after all. Nor are they inclined to fight a grizzly or a wolf for the rights to a carcass they can’t fully consume either.

That means, unlike grizzlies or wolves, cougars leave a tremendous amount of food behind. In fact, scientists believe they’ve evolved to kill more than they can eat so they can leave behind food to feed the entire ecosystem.

Studies have found that when a cougar eats, so too do 275 other species, including 39 species of birds and mammals. One cougar kill actually fed – and housed – 24,000 beetles from 215 different species types. That created more food for more species – especially bears and birds – and is probably why all life in the vicinity of that kill weighed more and was found to be healthier for a full eight weeks after the cougar first sat down to dinner.

Talk about

keystone

species.

In fact, of the invertebrates that rely on cougar kills, 40% are endangered. As the cougar loses its range, we lose these insects and the species and processes they help sustain, directly or indirectly, like seed dispersal and nutrient cycling.

But here’s what’s more fascinating and more important:

Even though cougars are found in low density across large landscapes, their ability to travel means that they kill deer across a large swath of land. That means they’re messily eating and leaving behind food across large ecosystems.

The rotting, dispersed carcasses? Those are the nutrients that go into the soil, allowing for it to be our all-powerful, life-giving Overlord.

via GIPHY

That’s right, cougars are literally gardening deer and enhancing soil better than bears or wolves or people.

In fact, 43% of soil outside the Antarctic is enhanced by a similar cat-deer predator-to-prey cycle.

Why just 43% of land? Well, in part, because we’re losing cats from much of their traditional range.

Cougars once existed everywhere south of the boreal forest to the tip of South America, but because, like many predators, we fear cougars and compete with them for the meat of their prey, their range has been mostly reduced to the mountainous west.

As a result, the whitetail deer population has exploded and they’ve evolved from helpful plant predator to unhelpful plant murderer. Without their natural predator and with ever expanding, opened landscapes, whitetail deer have also started marching west and north.

That’s a big problem for the once omnipresent mule deer – who some believe are actually becoming threatened because of whitetail – and even the caribou.

You see, whitetail deer aren’t native to the boreal forest, but they’re starting to settle it as their own, taking out naturally occurring vegetation and spreading invasive species.

Even though whitetail deer are increasingly seen as an invasive species themselves, they actually hate the taste of invasive plants. That means they stick to the native plants and – ironically – that helps invasive vegetation takeover.

With decreasing quality food, biodiversity is stressed and the struggling caribou now have to compete with whitetail for the same food sources. Caribou also have to deal with the predators that the deer have brought along with them, like wolves, who find it easier to kill the weakened caribou than the stronger whitetail.

And because cougars aren’t made for the boreal, they can’t help with this problem – a problem that, again, can be traced, in part, to whitetail losing this natural foe in their original range.

And that brings us to the good news.

Cougars, despite our worst fears, are secretive, nocturnal scaredy cats. They don’t like us and don’t want to see us, but – unlike many large predators – they are adaptable and are willing to live alongside us – if we let them.

And when we find ways to co-exist with cougars, we enable them to take care of bigger problems at the root source.

That means not only can cougars keep an invasive species in check before they seek global domination, they can also drive biodiversity by feeding entire ecosystems, especially that life-giving superhero: soil.

See? I told you the answer to our problems was cougar-killed-deer-fed super soil!

What do you think?

What strikes you most about the cougar/deer relationship?
What feature do you like best of the cougar? The deer? Why?
Do you have cougars and/or deer in your area? What type of deer? If not, where is the closest region they exist?
What is the current estimate of cougar populations in your region, or the region closest to you that contains a populations?
List the characteristics of the cougar and the deer that help them both survive.
What other close predator to prey relationships exist in your region?
What is a keystone species? Give an example of keystone species that you can find in your community.
Explain the nutrient cycle.
Why do people fear cougars? Should they? How can we live alongside cougars?
Define invasive species. What invasive species do you have in your community? Are there programs to alleviate the problem? What else can you do to prevent invasive species, and reduce their existing numbers?
Is the soil in your region healthy? How do you know?
Explain what would happen if the cougar population declined. If the deer population declined. How might that affect you?
Do you believe ecosystems could survive without the relationship between cougars and deer? Why or why not?
What don’t we know much about when it comes to the cougar and deer relationship? About both species in general? How might we find this out?

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