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 L W W L W W L W

Efficient predators lead to highly unstable predator prey interactions The Catch-22 of the lethal approach Inefficient predators lead to extinction of the predator in variable environments K

Incorporating the Ecology of Fear (Brown et al. 1999) Prey are apprehensive – i.e., they engage in vigilance behavior M Fear (i.e., predation risk) = --------------- (k + bu*) (prey have perfect info) 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, but reduced vigilance reduces effectiveness K bend down the predator’s isocline.

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

Behavioral Resource Depression

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 Lamar Valley of Yellowstone in 1994-1995.

This now becomes a familiar scene – wohoo!!!

Vigilance in female elk w/calves increases… ...while time spent foraging declines

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

1996 2002

1997 versus 2001

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 Knot

Calidris canutus

Tidal mudflat foragers

Ruddy turnstone

Arenaria 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 Research the animal caretaker kept track of knots’ abilities to 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 flight performance?

Body Building to defy death

Red-eyed tree frog

Agalychnis callidryas

What’s the tradeoff?

Early hatchers Late hatchers

Snakes Wind Rain

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