The Ecology Book

76

FEAR ITSELF

IS POWERFUL

NONCONSUMPTIVE EFFECTS OF

PREDATORS ON THEIR PREY

M

any descriptions of

ecosystems focus on

predator–prey interactions

in which predators kill and prey are

eaten. However, American ecologist

Earl Werner and others have shown

that the mere presence of a predator

affects the behavior of prey.

Apart from apex predators, all

animals must balance the need to

sleep, reproduce, and feed with the

risks of being eaten. The lethal role

of predators is obvious, but their

nonlethal (nonconsumptive) role

can have an even bigger impact on

an ecosystem. Potential prey are

forced to change their way of life

in order to avoid being killed.

In 1990, Werner studied the

effects of green darner dragonfly

larvae on toad tadpoles. He noticed

that when the predatory larvae

IN CONTEXT

KEY FIGURE

Earl Werner (194 4 –)

BEFORE

1966 American ecologist

Robert Paine conducts a

series of groundbreaking

field experiments to highlight

the crucial effects of a predator

on the community in which

it lives.

1990 Canadian biologists

Steven Lima and Lawrence

Dill analyzed the decision-

making of organisms that are

at the greatest risk of being

preyed on by other creatures.

AFTER

2008 American behavioral

biologist and ecologist John

Orrock teams up with Earl

Werner and others to produce

mathematical models to

explain the nonconsumptive

effects of predatory animals.

prey move on to

other areas even if there is

less food there.

prey spend more time

hiding in sheltered habitats

than feeding in the open.

In the presence of predators ...

Even without preying on

them, predators can cause prey to

fail to thrive.

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