Avoiding Predators

How fear shapes prey behavior even if they aren't eaten

Lethal

Predator eats prey and population drops

Non lethal

Predator scares prey costing them energy being vigilant, hiding, or being in smaller/larger groups

What is a takeaway between lethal vs non lethal effects

In a meta analysis 166 studies found fear was stronger than killing effects concluding that fear can cost prey even when no one is killed

Snowshoe Hare Cycle

Population dynamics of lynx and hare fluctuate every 10 years but the reason is not clear to researchers

What does the data say about the snowshoe hare cycle?

Only 3% die of starvation. But 95% die from predators. When scientists built fences to keep predators out, the population crashes stopped possibly fear and stress are the issue

What is a key takeaway snowshoe and hare

The cycle needs predators to kill hares and maintain population but fear may also drive their population fluctuations in tandem

Two kinds of Defense

1. Before being seen prey has armor or camouflage

2. After being seen prey notices the predator, alert, and flees

Takeaway from defense and fleeing

Fleeing is a decision not a reflex better defended animals wait longer to flee because of armor

When to flee

Flee when staying costs more than going such as the risk of capture going up then flee sooner (can’t outrun predator), if the cost of fleeing goes up flee later (don’t want to lose meal)

Do Groups Lower Vigilance?

Group size has no impact on vigilance because looking up serves other purposes or costs feeding time so groups help prey survive it’s not because they spend more time looking up elk, bison, and prairie dogs demonstrate this

Elk and Wolves in Yellowstone

Wolf reintroduction increased vigilance and lowered feeding time for mother elks with calves and were more vigilant but male bulls had no change/effect

Landscape of fear

Prey live in a “second landscape” of Risk where high risk areas (hills) are where predators hunt and safe areas (valleys) are where prey are for safety and spend more time in moving as predators move around

What shapes the hills

How often prey and predator meet, how lethal predator is, how well vigilance works

Elk Leave Grass

GPS collared elks and found when wolves are present elk stopped being in open grass areas even if food quality was better and chose to hide in trees

Predator tactics on where prey exist

Where its safe depends on who and how the prey is being hunted and the landscape of fear can change depending on predator tactics if Wolves hunt in open grass, so elk hide in trees. But wild dogs hunt in thick trees, so if wild dogs are around, hiding in trees will get you killed.

Elk traded grass for cover. What does that cost the herd, and how would you test it?

It cost the herd good food. I would test it by comparing the health and survival rates of elk in different environments, measuring weight gain and reproductive success in relation to predator presence.

How to test killing vs. fear in hares?

Expose some hares to the sound or cues of a predator without actually killing them and see how their population does in comparison to hares that are just exposed to killing

Vigilance did not follow group size in prairie dogs. What would you measure instead?

I would measure individual vigilance and see how what they’re looking for may contribute to their survival and behavior