EXERCISE 17
Predator - Prey Interactions
Predator-prey interactions have been among the
most intensively studied areas of aquatic biology
during the past several decades. Investigations
have focused particularly on theories of "optimal
foraging," which seeks to describe predator
behavior [e.g., Charnov (1976), Werner and Hall
(1974), and Pyke (1984)], and "predator
mediated community structure" (Hrbacek, 1962;
Brooks and Dodson, 1965; Hall et al., 1976;
Zaret, 1980; Werner and Gilliam, 1984; Sih
et aI., 1985; Kerfoot and Sih, 1987), which
interprets community structure in relation to
predatory activities. Many of these hypotheses
still are speculative, although supporting evidence for some is growing. These concepts form
a useful basis for the study of predator-prey
relationships. The literature on this subject is
extremely large; a few summary articles relative
to limnology are cited in this exercise.
In evaluating predator-prey interactions,
both the predators and prey have physiological
and behavioral characteristics that must be
considered. Major predator characteristics that
can be evaluated include: (1) visual, mechanical,
or chemical detection of prey; (2) how much
energy is required during searching for and
attacking prey; and (3) energy and time expended
OPTION 1
Procedures
in handling, and total or partial consumption of
prey. Evaluation of the ways in which prey
respond to predation requires considerations of:
(1) behavior and energy expended in escape
responses, often by refuge in space and/or time;
and (2) means by which prey adapt and coexist
with predators. The latter coexistence can be
accomplished by camouflage, differences in size,
release of repulsive chemical compounds, frightening displays, evasive movements, morphological structures that impede or prevent consumption, and aggregation in large groups.
Predators and prey respond continuously to
the other's adaptations, which results in constant,
although slow, coevolution and changing interactions. The extent of interactive couplings
can be evaluated by exposing prey to predators
under controlled experimental conditions [e.g.,
Thompson (1978) and Werner (1974)] or by the
introduction of new predators or prey into
established ecosystems [e.g., Langeland (1981)
and Morgan et ai. (1978)]. The latter approach
should not be done without considerable forethought and understanding of ecosystem properties. The former experimental approach will
be used in this exercise to gain insight into some
basic predator-prey interactions.
The objective of this exercise is to compare the feeding characteristics of two predators,
a common fish (bluegill, Lepomis macrochirus) and a dragonfly nymph (Corduliid
241
Predator - Prey Interactions
Predator-prey interactions have been among the
most intensively studied areas of aquatic biology
during the past several decades. Investigations
have focused particularly on theories of "optimal
foraging," which seeks to describe predator
behavior [e.g., Charnov (1976), Werner and Hall
(1974), and Pyke (1984)], and "predator
mediated community structure" (Hrbacek, 1962;
Brooks and Dodson, 1965; Hall et al., 1976;
Zaret, 1980; Werner and Gilliam, 1984; Sih
et aI., 1985; Kerfoot and Sih, 1987), which
interprets community structure in relation to
predatory activities. Many of these hypotheses
still are speculative, although supporting evidence for some is growing. These concepts form
a useful basis for the study of predator-prey
relationships. The literature on this subject is
extremely large; a few summary articles relative
to limnology are cited in this exercise.
In evaluating predator-prey interactions,
both the predators and prey have physiological
and behavioral characteristics that must be
considered. Major predator characteristics that
can be evaluated include: (1) visual, mechanical,
or chemical detection of prey; (2) how much
energy is required during searching for and
attacking prey; and (3) energy and time expended
OPTION 1
Procedures
in handling, and total or partial consumption of
prey. Evaluation of the ways in which prey
respond to predation requires considerations of:
(1) behavior and energy expended in escape
responses, often by refuge in space and/or time;
and (2) means by which prey adapt and coexist
with predators. The latter coexistence can be
accomplished by camouflage, differences in size,
release of repulsive chemical compounds, frightening displays, evasive movements, morphological structures that impede or prevent consumption, and aggregation in large groups.
Predators and prey respond continuously to
the other's adaptations, which results in constant,
although slow, coevolution and changing interactions. The extent of interactive couplings
can be evaluated by exposing prey to predators
under controlled experimental conditions [e.g.,
Thompson (1978) and Werner (1974)] or by the
introduction of new predators or prey into
established ecosystems [e.g., Langeland (1981)
and Morgan et ai. (1978)]. The latter approach
should not be done without considerable forethought and understanding of ecosystem properties. The former experimental approach will
be used in this exercise to gain insight into some
basic predator-prey interactions.
The objective of this exercise is to compare the feeding characteristics of two predators,
a common fish (bluegill, Lepomis macrochirus) and a dragonfly nymph (Corduliid
241