G
ood night,sleep well.” After a good-night kiss,
the parent leaves the child’s room and turns off the
lights. Immediately bogeymen, ghosts, and all man-
ner of fearsome things crawl out of drawers, threaten from
underneath the bed, and creep from behind the curtains.
The child hides under its blankets and pillows, remains
wide-eyed in the darkness, and waits —until merciful sleep
saves the night. Actually, the child’s responses to these more
or less imaginary fears fit effectively within the “ecology
of fear” (Brown et al. 1999). Hiding under or behind ob-
stacles, remaining still, and being vigilant are among the
most frequent adaptive responses to increased predation
risk. Additionally, sociality may influence fear responses
and their effectiveness. Hiding in the parents’ bed might
be an even better strategy for a frightened child. Sociality
and social behaviors influence predation risk. And fear
responses may in turn influence social behaviors such as
breeding. Our objective in this chapter is to describe how
the interaction of fear, sociality, breeding, and foraging pro-
duces adaptive and ecological feedbacks.
Predators have both lethal and nonlethal effects on their
prey. The lethal effects manifest through the predator’s func-
tional response when some number or proportion of the
prey population succumbs to predators (Taylor 1984). The
nonlethal effects emerge as fear responses of the prey to
their predators (Lima and Dill 1990). Sometimes the dra-
matic lethal aspects of predation obscure the drama of the
nonlethal effects induced by the mere presence of predators.
During the last decade, however, antipredatory responses
of prey animals toward direct or indirect cues of a preda-
tor’s presence have received increasing attention (reviews
by Lima and Dill 1990; Lima 1998; Norrdahl and Korpi-
mäki 2000; Ylönen 2001; Owings and Coss chap. 26, this
volume).
The ecology of fear examines the behavioral, popula-
tion, and community consequences of the nonlethal effects
of predators. Predation risk may reduce activity levels, shift
activity from risky to safe places, alter mating behaviors
and reproduction, increase levels of vigilance and appre-
hension, and alter intra- and interspecific competitive inter-
actions (Brown et al. 2001). Furthermore, fear in response
to predation risk may alter life-history characteristics such
as growth rates, dispersal, and age at maturity (see Lima
1998 for review). These fear responses are adaptations that
serve to maximize the prey’s fitness in the face of preda-
tion risk. Predation risk is an activity cost (Brown 1988;
Brown and Kotler 2004) that influences the costs and ben-
efits of foraging, breeding, or engaging in other social
activities.
In this chapter, our aim is to examine fear and its effects
on the foraging, breeding, and social behavior of rodents.
Based on our own research biases, we will often refer to bo-
real voles (MicrotusandClethrionomys) living under rela-
tively dense vegetation, and desert rodents (e.g.,Gerbillus)
exposed to predation in more open environments (fig. 28.1).
All of these rodents share risks from terrestrial predators
(mammals and snakes) and avian predators (hawks and
owls). Different predators pose different challenges and may
present different cues to their rodent prey (Lima and Dill
1990). We begin with a brief description of boreal voles and
desert rodent systems. We then examine predation risk as
an activity cost of foraging, breeding, and social interac-