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THE FITNESS OF
A FORAGING ANIMAL
DEPENDS ON ITS
EFFICIENCY
OPTIMAL FORAGING THEORY
E
very plant and animal
on Earth needs resources
to survive. Plants obtain
their nutrients and water from soil,
and sunlight provides the energy
for photosynthesis. Animals
generally have to work harder to
find their food—they have to move,
and this uses extra resources.
Optimal foraging theory (OFT)
proposes that animals try to gather
resources in the most efficient way
to avoid using additional energy.
Searching for and capturing food
takes energy and time. The animal
needs to gain maximum benefit
for minimal effort in order to
achieve optimal fitness. OFThelps predict the best strategy
that an animal can use to achieve
this goal.Foraging theories
The first theory of foraging by
wild animals did not emerge until
the mid-1960s, when Americans
Robert MacArthur and Eric Pianka
examined the question of why,
when a range of food was available
to them, animals often restricted
themselves to a few preferred types
of prey. They argued that natural
selection favored animals whose
behavior maximized their net
energy intake per unit of time spent
foraging. An animal’s foraging time
includes searching for prey and the
killing and eating of the food
(handling time).
These ideas were developed by
American ecologists Ronald Pulliam
and Eric Charnov and Australian
ecologist Graham Pyke. It seems
that OFT works best for mobile
foragers seeking immobile prey, and
some researchers believe it is less
relevant when prey are mobile.Key choices
Animals must choose which types
of food to eat, which is rarely
straightforward. For example,IN CONTEXT
KEY FIGURES
Ronald Pulliam (1945 –),
Graham Pyke (1948–), and
Eric Charnov (1947–)BEFORE
1966 John Merritt Emlen,
Robert MacArthur, and Eric
Pianka outline the concept
of optimal foraging in two
articles published in the
American Naturalist magazine.AFTER
1984 Argentinian–British
zoologist Alejandro Kacelnik
researches the foraging
behavior of starlings to
illustrate the marginal
value theorem (MVT).1986 Belgian ecologist Patrick
Meire investigates prey
selection by oystercatchers.1989 Swiss environmental
scientists T. J. Wolfe and Paul
Schmid-Hempel examine how
the weight of nectar carried
by bees has an effect on the
bees’ foraging behavior.Diets should be broad
when prey are scarce,
but narrow if food
is abundant.
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