The Ecology of FEAR

Fear in the South African Landscape – Augrabies NP

Rock Hyrax

The view away from the Kopje -

Comparison of the lethal and fear approaches

Lethal

- predators kill their prey

- N (population size) - driven systems

- Brownian motion behavior of pred/prey

Fear

- predators scare their prey

- - driven systems: fierce predators and fearful prey

- Sophisticated game of stealth and fear

LW

L

W

W

W

WL

K

The Catch-22 of the lethal approach

Efficient predatorslead to highlyunstable predator-prey interactions

Inefficient predatorslead to extinctionof the predator in variable environments

Incorporating the Ecology of Fear (Brown et al. 1999)

Prey are apprehensive – i.e., they engage in vigilance behavior

MFear (i.e., predation risk) = ---------------- (prey have perfect info)

(k + bu*)

Fear: - w/likelihood of encountering a predator, M- w/predator’s lethality, 1/k

- w/effectiveness of vigilance, b- w/level of vigilance, u*

# pred, #prey, feeding opportunities

Tradeoff:

Too much vigilance miss out on valuable feeding opportunities

Too little vigilance likely killed by a predator

Shift the hump in the prey’s isocline.

Still safety in #s, butreduced vigilance reduces effectiveness

bend down the predator’sisocline.

Predator’s have reduced efficiency because more predators results in greater vigilance in the prey making them harder to catch

Interference or Behavioral Resource Depression

K K*

Implications:

(1) Greater stability in predator-prey interactions – no Catch-22,

(2) Predator regulation is not tied to the number of prey killed

(3) Territoriality in fierce predators may function to protect the catchability of the prey – avoid the “wayward” Mnt. Lion stumbling into your territory

(4) Behavior (e.g., vigilance) is a leading indicator of ecological change

Wolves, elk, and bison in Yellowstone: reestablishing the“Landscape of Fear”

(Laundre et al. 2001 – Can J. Zool. 79:1401)

Wolves reintroduced into the LamarValley of Yellowstone in 1994-1995.

This now becomes a familiar scene – wohoo!!!

...while time spentforaging declines

Vigilance in female elkw/calves increases…

Similarly for bison, however, males and femalesw/o calves no show behavioral shift

1996 2002

1997 versus2001

Three kinds of evidence:

- The changes are much faster than could occur from elk mortality

- Reduced herbivory is restricted to risky habitats

- Elk have exhibited behavioral changes consistent with an Ecology of Fear Hypothesis:

(1) avoid forest edge (scat)(2) increased vigilance and less feeding

These changes have left physiological evidence

Cottonwood trees need wolves in order to establish their populations.......as does willow and aspen.

Predation Risk So what other responses are there?

Red KnotCalidris canutus

Tidal mudflat foragers

Ruddy turnstoneArenaria interpres

Inshore foragers

Differences in predator escape?

• Knots – advanced warning and collective flight maneuvers• Turnstones – little warning, find cover, every turnstone for itself

At the Netherlands Institute for Sea Researchthe animal caretaker kept track of knots’ abilitiesto make 90 degree turns into the aviary…..

> 160 g, knots compromise their flight abilities

Flight performance increases with an increase in the ratio of:

Pectoral Muscle Mass/Body Mass

So how do you increase flightperformance?

Body Building to defy death

Red-eyed tree frog Agalychnis callidryas

What’s the tradeoff?

Early hatchers

Late hatchers

Snakes

Wind

Rain

http://people.bu.edu/kwarken/KWvideo.html