Lecture 5 Keystone Species and Trophic Cascade

Who was the person in the “Some animals are more equal than others” video that thought of trophic cascades

Robert Paine

What causes arise from the effects of predation in a trophic cascade?

a series of strong interactions that start at upper trophic levels and cascaded downwards across trophic levels

What does the trophic cascade concept focus on aside from mere species protection?

The functional integrity of species interactions

Why is trophic cascade an important concept?

For conservation of community and ecosystem functions and provides support for the reintroductions of predators

What is a trophic cascade defined as in the outline?

Indirect species interactions that originate with predators and spread downward through food webs

What is top down forcing?

Indirect effects proceed downward across successively lower trophic levels

What Yellowstone was established in (name the year), what was the grey wolf considered as?

1872, considered as competition for game like elk and deer

What did the U.S Congress do to impact wolves and what year?

In 1914, they appropriated funds to destroy wolves (and other animals) inside the park deemed “injurious to agriculture”. People were paid to kill wolves since they would eat livestock. They were hunted, trapped, and poisoned which decimated their numbers in Yellowstone area

When was the remaining wolf population eradicated within Yellowstone?

1926

For roughly how many years where there no resident wolves in the Yellowstone area?

70 years

What year range were wolves reintroduced to Yellowstone?

1995-1997

By best guess estimate how many wolves were there are reintroducing them?

41 ish were relocated from Canada to Yellowstone National Park

What is the Greater Yellowstone Ecosystem?

The area surrounding Yellowstone National Park including National forests and wildlife refugees

What was the big takeaway regarding the size of Yellowstone National Park and the Greater Yellowstone Ecosystem

Yellowstone Park is not big enough to house the wolves since they have territory outside of the park. When compared to others outside the US, its not big enough in most cases.

What was their focus on during the wolf recovery?

Focus on woody plant structure

When there were no wolves for around 70 years, what happened to plant growth.

Plant growth was suppressed by elk browsing without the fear from being hunted by wolves and caused the forest canopy to decrease overall of willow and aspen trees.

What effects did wolf reintroduction have on willow and aspen tree growth?

Plant growth increased in size and density potentially because the wolves hunted the elk.

Aside from lower elk numbers, how else did wolf reintroduction affect elk? What is the specific name for it?

They made a change in their behavior where elk could not stand out in open fields and moved further up the landscape rather than being down in the valleys eating willow and aspen. “Land of fear”.

How was wolf reintroduction partly justified?

By the idea of reversing a trophic cascade

However, the reintroduction of wolves to Yellowstone was what?

An equivalent disturbance to removing them in the first place

What does it mean for wolves to be an equivalent disturbance?

‘What you get may, or may not, be what you had in the first place’ meaning the system was modified over the 70 years without wolves and didn't stand still.

Who coined the term ‘keystone species’ and when?

Robert Paine, latter 1960s