Hunters and other predators played much bigger parts in reducing the Yellowstone elk population than the wolves

Photo by john Cox on Unsplash

Naturalist guide Aaron Bott, who lives and works in the Greater Yellowstone Ecosystem tells us the grizzly bear population is 700-800, maybe even 1000 now. Wouldn't death by bear be a more likely reason the elk numbers went down so dramatically? Older elk would die off, and a lot fewer calves survived to replace them. Thus the 20,000 elk reduced to 5,000 by the late 2000s. But hold your horses. There's more.

The real ambush super predators like mountain lions or cougars had been dying out but recolonized themself without any outside help. Can you picture their sharp teeth and powerful jaws locking onto an elk and those retractable claws, perfect for ripping it to shreds? Their numbers were up by 76% and competing with the wolves.

We know wolves are wily creatures. Why should a pack do the hard work of catching and bringing a calf down when they can track a cougar and steal its dinner? The unfortunate cougar would then have to go off and hunt down another baby elk for the rest of its meal. And just for fun, the bears got in on the act too, robbing twice the number of calves as the wolves snatched from the cats. The big cats don't hang around to fight a bear. The wolves do, though. Finishing off what the bear left is much safer than fighting and getting injured or killed.

So let's look at the stats

Daily Dose of Nature | Yellowstone: Wolves, Willows & Trophic CascadesAaron Bott Slide Screenshot by Author

Wolves contributed, but cougars, mountain lions, and bears were also getting fat and increasing their populations on the elk calves. Even with the added predators, the elk population was still growing.

Do you recall the trophic cascade from Did Yellowstone wolves really bring down 80% of the elk population all on their own? We have to include an essential element, humans.

A trophic cascade is triggered by adding or removing a top predator from an ecosystem, which then has a trickle-down effect on the entire food web. It affects reciprocal changes in populations of predator and prey that result in dramatic changes in the entire structure of an ecosystem. Aaron Bott

A late-season hunt

Back in 1976, Montana State decided to do something about it. They began a late-season hunt from December to February to kill young female elk. Any young female elk stepping over the Yellowstone Park boundary into Montana became fair game for hunters. An average of 965 elk of calf bearing age was shot between 1976 and 1995. Add in 520 kills from the general fall hunt, and what the predators were dining on, you'd think the elk population would be going down fast.

But there were still 20,000 elk when the wolves arrived in 1998. From 1995-2002 the annual late-season hunt killed off between 940 and 2,465, mostly young female elk. Or 5.7% to 18.7% of the population.

Wolves only accounted for eating 1.8% to 6.2% of elk calves.

Photo by christie greene on Unsplash

These figures would lead you to believe that humans were the main drivers of falling elk numbers, right? However, because the hunting seasons focused on young females and not calves, there were still plenty of female babies to replace the culled young. In other words, despite the purpose of the hunting seasons to stop the population from increasing, it continued!

In the 1990s, though, everything began to come together:

• The grizzly population recovered.
• Cougar numbers rose.
• The wolves returned to Yellowstone.

The domino effect; killing off the calves in higher numbers equaled fewer female elks reaching breeding age, which stalled the population increase, and finally, numbers reduced.

Predators galore

In fact, by the early 2000s, Yellowstone saw the highest number of predators ever. To the list above, you can add coyotes and black bears. All these guys had baby elk on tap!

Photo by Delaney Van on Unsplash

The elimination of breeding females and calves resulted in the 80% decrease in the elk population mentioned previously. So much so the state of Montana indefinitely stopped the late-season hunt.

Hunters blame the wolves for depriving them of their family hunts. They are so unhappy they even have bumper stickers. Save an elk, kill a wolf. Yes, wolves contributed but you've also got to include humans, bears and mountain lions in the decline of the elk population.

That said, the wolves of Yellowstone didn't have much of an impact until 2002 when the elk were down to 4,000-5,000. Now they have a greater impact of about 5% on regulating elk numbers. As alpha predators, wolves at the top of the trophic cascade brought many indirect effects into restoring the previously broken ecosystem.

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