Temperature Motivation 51the range of stimuli that are effective in eliciting sexual be-
havior” (Domjan, 1994, p. 426). That is, learning shifts the
position of cues on the continuum by increasing their prox-
imity to the female and thereby enhancing the cues’ ability to
release sexual responses.
This shift on the continuum is manifested also by the
change in repertoire of responses that stimuli come to elicit.
Prior to conditioning, local cues elicit weak general search
behavior. After conditioning they may trigger both focal
search and copulatory behavior. Additionally, the strength of
general search behavior is enhanced. For example, approach
behavior is a form of local search behavior. Quails display
approach behavior to a red light only after the cue has been
paired with a sexual encounter (Domjan et al., 1986).
In the introduction we made the point that behavior is a
bidirectional interaction among motivation, learning, and
genetics. Perhaps nowhere is this clearer than in sexual moti-
vation. The work of Domjan and Hollis indicates that experi-
ence strongly influences with which members of our species
we prefer to mate. Because Pavlovian conditioning deter-
mines attractiveness, it also determines which sets of genes
recombine. Because conditioning determines reproductive
success, measured rather directly by sperm and offspring pro-
duction, it also determines what genes are best represented in
the next generation of many vertebrate species. Not only does
the reproductive success that drives evolution influence our
learning abilities, but our learning abilities drive that repro-
ductive success as well.
TEMPERATURE MOTIVATION
Body temperature regulation is essential for the survival of
animal species. Most species are adapted to the temperature
range of their niche, and they can only maintain normal ac-
tivity within a relatively narrow window of body temperature
imposed by their genetic makeup. At extreme body tempera-
tures critical enzymes cannot function, energy metabolism is
compromised, and body systems fail. Thus, animals that fail
to maintain body temperature within the critical range of their
species die. Because of this stringent evolutionary selective
pressure, species have adapted multiple strategies to cope
with the problem of body temperature regulation.
Thermoregulatory Responses
Species utilize both physiological and behavioral means to
cope with the environmental demands of body tempera-
ture regulation. These two categories of processes interact to
provide an adequate temperature regulation strategy in each
species and individual. Specific body temperature regulation
strategies abound in the animal kingdom (e.g., Prosser &
Nelson, 1981; Bartholomew, 1982). In this section we de-
scribe several strategies of thermoregulation that have
evolved. Two broad categories of these strategies are ec-
tothermyandendothermy.Ectothermic animals rely on envi-
ronmental heat for body warming. Endothermic animals use
metabolic heat for body warming. Animals belonging to
these broad groups often display distinct behavioral tenden-
cies because these strategies impose different thermoregula-
tory needs.The Mountain LizardThe South American mountain lizard (Liolamus) is both an
ectotherm and apoikilotherm. Poikilotherms are ectothermic
animals whose body temperature may vary widely at differ-
ent times of the day or year. These animals often maintain
body temperatures that exceed the environmental tempera-
ture during periods of activity, whereas they display rela-
tively cold body temperatures during periods of inactivity. To
accomplish these extremes, poikilotherms rely heavily on
behavioral means to regulate body temperature. For exam-
ple,Liolamusavoids freezing Andes temperatures by staying
in its burrow during the night. Just after sunrise the animal
emerges and moves to a position exposed to direct sunlight
to absorb solar energy until its body temperature shifts from
approximately 5°C to upward of 30°C. Throughout the day
this lizard shuttles between sunlit and shaded microenviron-
ments to maintain this body temperature (Bartholomew,
1982).The Polar BearPolar bears live in and near the Arctic Circle. These large
mammals are endotherms, and they commonly sustain activ-
ity in extreme thermal conditions that range from approxi-
mately 15°C in summer months to –30°C in winter months.
Because of these drastic seasonal environmental demands,
polar bears have adapted strategies that permit the animal to
maintain its body temperature across the full range of envi-
ronmental temperatures in its habitat.
Polar bears are genetically organized to cope with the tem-
perature demands of their niche, and this organization is man-
ifested in physiological adaptations. First, polar bears have a
layer of blubber and fur over much of their bodies. This tis-
sue helps insulate the animal and maintain its body tempera-
ture in winter months. Second, a polar bear’s snout, ears, nose,