Animal Behavior
• What, How, and Why Questions
• Behavior Shaped by Inheritance
• Hormones and Behavior
• The Genetics of Behavior
• Communication
• The Timing of Behavior: Biological Rhythms
• Finding Their Way: ________ and Navigation
• Human Behavior
What, How, and Why Questions
• In studying animal behavior, we can ask what, how, and why questions.
• What questions focus on the ________ that elicit a behavior; such stimuli are the proximate causes of the behavior.
• How questions focus on the development of a behavior and the neural and hormonal mechanisms that underlie a behavior.
• Why questions are concerned with the function and evolution of a behavior; the selective pressures that shape a behavior are considered ________ causes.
Behavior Shaped by Inheritance
• Stereotypic behaviors are performed in the same way every time. If there is little difference in the way different individuals perform the behavior it is said to be species-specific.
• Web spinning by spiders is an example of a complex, ________ behavior that requires no learning or prior experience. This behavior is also ________ to modification by learning.

Behavior Shaped by Inheritance
• Early ethologists studied the behavior of animals in their natural environments. Ethologists were particularly interested in stereotyped, species-specific patterns of behavior.
• The parallel field of comparative psychology focused on learning by animals in laboratory environments.
• Early ethologists asked to what extent behaviors are determined by ________ and to what extent they are modified by experience.
Behavior Shaped by Inheritance
• Early ethologists used deprivation and ________ experiments to determine whether a behavior was inherited.
• In deprivation experiments, animals were reared in conditions devoid of all experience relevant to the behavior being studied.
• If the behavior was displayed in its entirety, then it was described as inherited.
• For example, a young tree squirrel reared in isolation displayed stereotypic burying behavior when given a nut; these observations suggested that burying behavior was inherited in squirrels.
Behavior Shaped by Inheritance
• In hybridization experiments, closely related species that differ in aspects of a behavior are bred to produce hybrid offspring.
• Konrad Lorenz did hybridization experiments with duck species that can interbreed, but rarely do so because of the specificity of their ________ displays.
• In crossbred species, elements of the displays of the parent species were expressed in new combinations.
• Hybrids sometimes showed display components that were part of the repertoire of other species.
• These results showed that motor patterns of courtship displays are inherited.

Behavior Shaped by Inheritance
• ________ are specific stimuli that ________ many inherited behaviors.
• Releasers are usually a simple subset of the sensory information available to an animal.
• For example, a tuft of red feathers, and not the entire bird, is all that is required to elicit aggressive behavior in male European robins.
Behavior Shaped by Inheritance
• In herring gulls, chicks peck at the red dot at the end of their parent's bill, and the parent ________ food.
• Ethologists Niko Tinbergen and A. C. Perdeck hypothesized that the red dot was the releaser for begging in chicks.
• They presented chicks with artificial models of gull heads that differed in color, shape, and presence of the red dot on the bill, and counted pecking responses of the chicks.
• Color or shape of the head made no difference, and chicks also responded to models of bills as long as they had a red dot.


Behavior Shaped by Inheritance
• Early ethologists focused on inherited behavior and also made contributions to the study of learning.
• Tinbergen studied spatial learning in digger wasps by placing pine cones around the entrance of a female's nest, then moving the pine cones a short distance away once she had left the nest.
• Upon returning, the female oriented to the moved pine cones and could not find her nest entrance.
• The female wasp had learned to recognize and use objects in the environment as ________ cues to find her nest.


Behavior Shaped by Inheritance
• Today, behavioral biologists believe that most behaviors develop through an ________ of inheritance and learning.
• For example, begging in herring gull chicks also has a learned component: Over time, gull chicks learn the characteristics of their parents, refine their parental image, and eventually beg only from their own parents.
Behavior Shaped by Inheritance
• ________ is a type of learning in which animals learn, during a critical period, a complex set of stimuli that later act as a releaser.
• Lorenz showed that newly hatched goslings imprint on the image of the first object they see (normally their parent, but under experimental conditions, Lorenz or his assistants), and that subsequent exposure to the object releases the goslings' following behavior.
• A critical period is a time, determined by developmental or hormonal state, during which exposure to certain stimuli produce virtually irreversible effects on behavior.

Behavior Shaped by Inheritance
• The singing behavior of male songbirds is an example of how inheritance and learning interact to produce behavior.
• Young male white-crowned sparrows reared in ________ do not produce their species-specific song when adults.
• For males of this species to produce normal adult song, they must hear the song of their species as nestlings.
• Males memorize this song during the nestling stage and imprint the memory in their nervous system.
Behavior Shaped by Inheritance
• It is also important for young male white-crowned sparrows to hear themselves sing.
• Males deafened after exposure to their species song when they are nestlings, but before they begin to sing, produce abnormal song.



Behavior Shaped by Inheritance
• The ability to learn and modify behavior based on experience is adaptive in many situations.
• In species with ________ generations, opportunities to learn from parents are not available, so inherited behaviors are very important.
• In spiders, for example, offspring cannot learn how to build a web from their parents because young emerge after their parents have died.
Behavior Shaped by Inheritance
• Inherited behaviors also occur when there are opportunities for learning the wrong behavior, when mistakes would be costly or dangerous.
• In ducks, several closely related species may occur in the same pond, and it would be possible for young to learn the courtship behaviors of species other than their own. Thus, many courtship signals in ducks are inherited.
• Inherited behavior patterns for ________ avoidance are also adaptive. The behavior must be performed correctly the first time; there may be no second chance.
Hormones and Behavior
• Differences in behaviors of males and females are an example of genetic influence on behavior.
• Action of the sex steroids on the brain determine sex differences in behavior.
• The sexual behavior of rats differs between males and females.
• Receptive female rats display lordosis, a posture in which the hindquarters are slightly raised.
• Male rats, on the other hand, display mounting and copulatory behavior.
Hormones and Behavior
• Sex steroids present early in life determine which pattern of sexual behavior an adult rat will display.
• For a male rat to display mounting and ________ behavior as an adult, he must be exposed to testosterone around the time of birth.
• When adult, such males will display male sexual behavior when levels of testosterone are high.
• Exposure to estradiol around birth is not necessary for a female rat to have the potential to display lordosis as an adult.
• In adulthood, however, high levels of estradiol are necessary for females to display lordosis.


Hormones and Behavior
• In many songbirds, only males sing, as part of territorial displays and to attract females.
• Although females do not typically sing, they know the song of their species.
• Nestling males hear the song of their ________ and memorize it, but don't try singing until the following spring, when levels of testosterone rise in response to increasing day length.
• By matching their vocal output to the song memorized the previous spring, they gradually refine their song and eventually produce the correct species- specific song.
• At this time, their song is said to be crystallized.
Hormones and Behavior
• In some species, females given ________ implants in the spring produce their species-specific song. This suggests that females learn the song of their species while nestlings and have the capacity to express it, but lack the hormonal stimulus under normal circumstances.
• In canaries, rising levels of testosterone in the spring causes regions of the brains of the adult males to increase in size. This increase in size is due to increases in the numbers of neurons and to growth of individual neurons and their branches.

The Genetics of Behavior
• Behavior has genetic determinants. Genes code for proteins; there are then many complex steps between this starting point and the expression of a behavior.
• There is no behavior for which we know the precise series of steps from gene to behavior.
• Three methods for studying the genetic basis of behavior include hybridization, artificial selection and crossbreeding, and molecular analysis of genes and their products.
The Genetics of Behavior
• In crickets, males produce species-specific sounds by rubbing their wings together.
• Crossing two species produced offspring that expressed songs with elements of the songs of both species.
• Backcrossing F1 individuals with the parental species produced songs closer to the parental species used in the backcross.
• This demonstrates a ________ basis for song pattern in male crickets.
• Female crickets preferred the songs of their own species, and hybrid females preferred the songs of hybrid males.
The Genetics of Behavior
• Artificial selection has been used to produce breeds of domestic animals such as dogs with distinct behavioral, as well as anatomical characters.
• However, most research involving artificial selection has been conducted with organisms with short generation times and large numbers of offspring.
The Genetics of Behavior
• Nest-cleaning behavior in honeybees is an example of a behavior that follows simple ________ segregation.
• The hygienic strain of honeybee uncaps the brood cell of a larva that has died and removes the carcass from the hive.
• The nonhygienic strain leaves dead larvae in the brood cells.
• When bees of hygienic and nonhygienic strains were crossed, all offspring were nonhygienic.
• When the F1 individuals were backcrossed to the hygienic strain, the typical 3:1 ratio expected for a two-gene trait emerged.

The Genetics of Behavior
• Of the nonhygienic offspring, one-third showed no hygienic behavior at all, one-third uncapped cells of dead larvae but did not remove the larvae, and one-third would remove dead larvae if the cells were uncapped.
• This suggests one gene for uncapping and one gene for removal, but these behavior patterns are complex and there is no gene that codes for the entire behavior.
The Genetics of Behavior
• Techniques of molecular genetics have been used to study ________ behavior in male fruit flies.
• The behavior is highly stereotyped and does not require learning.
• Most components of male courtship appear to be controlled by a single gene, fruitless, which is part of a hierarchy of genes involved in sexual differentiation and behavior.

The Genetics of Behavior
• In flies with two X chromosomes (females), the gene sex-lethal is expressed.
• The protein produced by sex-lethal causes the transformer gene to be expressed.
• Fruit flies without the transformer gene develop into males anatomically and behaviorally.
• Anatomical differentiation in males appears to be controlled by the doublesex gene, and the formation of the nervous system that directs male courtship behavior is controlled by the fruitless gene.

Communication
• Communication is behavior that influences the actions of other individuals.
• The displays or signals of communication convey information, and the transmission of this information benefits the sender and the receiver.
• There are five channels of ________ chemical, visual, auditory, tactile, and electric. These channels differ in their effectiveness in different environments.
Communication
• Pheromones are molecules used in chemical communication between individuals.
• Pheromones can convey very specific messages with large amounts of information. An example is the pheromone released by female silkworm moths.
• Territory marking by cats and other mammals provides information on the species, individual identity, reproductive status, size, and when the animal was last in the area.
• Pheromones remain in the environment for a while, in contrast to vocal or visual signals.

Communication
• The speed of diffusion of pheromone molecules is determined by the size and chemical nature of the molecules.
• Sex attractants tend to be small molecules that diffuse rapidly; such messages travel great distances and quickly disappear.
• Scent marking pheromones tend to be large molecules that create relatively localized, long-lasting messages.
Communication
• The advantages of visual signals include ease of production, diversity, flexibility, speed, and a clear indication of the position of the signaler.
• The disadvantages of visual signals include failure to get the attention of the receiver, who may not be focused on the sender, and limitations on the details that can be transmitted.
• Visual communication also works poorly at night and in complex or low-light environments.
Communication
• Unlike visual signals, ________ signals can be used at night or low-light environments. In addition, the receiver does not have to be focused on the sender of an auditory signal to get the message.
• Sound can provide directional information as long as the receiver has at least two receptors with some space between them.
• Communicating with sound works well over long distances; an extreme example is the song of humpback whales, which can be heard hundreds of kilometers away.
• However, visual signals are better than auditory signals at rapidly conveying complex information.
Communication
• Communication by touch is very common among animals, particularly when conditions are poor for visual communication.
• Studies by Karl von Frisch revealed the role of tactile communication in the dance of honeybees.
• A successful forager returns to the hive and communicates by dancing in the dark on a vertical surface within the hive.
• As she dances, her hivemates monitor her movements through touch and interpret her message.
Communication
• If the food source is more than 80 m away, the waggle dance is used to convey information about distance and direction to the food source.
• The round dance conveys information about the distance of food if it is within about 80 m.
• The odor on the bee's body also provides information about the kind of flower to look for.

Communication
• Some fish emit electric pulses and generate electric fields in the water around them. Such signals can be used to detect objects in the environment and to communicate.
• Glass knife fish emit electric signals that convey information about the sex, identity, and position within the dominance hierarchy of the sender.
• Resident individuals adjust the frequencies of their signals to prevent overlap with a new fish introduced into their tank.
The Timing of Behavior: Biological Rhythms
• ________ rhythms are rhythms that are about 24 hours long but do not depend on the cycle of light and dark.
• Animals in constant darkness demonstrate daily cycles of sleep and activity; they are said to have an endogenous (internal) clock.
• A rhythm is a series of cycles and the length of one cycle is the period.
• Any point in the cycle is called a phase; two rhythms that completely match are said to be in phase.
• Rhythms that are shifted so as to be out of phase are described as phase-advanced or phase-delayed.
The Timing of Behavior: Biological Rhythms
• Entrainment is the process of resetting the circadian rhythm by exposure to environmental cues.
• Animals in constant light or dark will not be entrained to the 24-hour cycle of the environment; their circadian clock is described as free-running.
• The free-running circadian rhythm is under genetic control.
• Free-running circadian rhythms of animals can be entrained in the laboratory by short pulses of light or dark every 24 hours.

The Timing of Behavior: Biological Rhythms
• In mammals, the master circadian clock is located in the suprachiasmatic nuclei (SCN).
• The SCN is found only in vertebrates; in some vertebrates, the SCN is the master clock (mammals), and in others the master clock is the pineal gland (birds).
• In some invertebrates (mollusks), the cells driving circadian rhythms are in the eyes.
• In protists and fungi, rhythmicity is a property of individual cells.


The Timing of Behavior: Biological Rhythms
• The clock genes that regulate circadian rhythms are homologous across a wide range of organisms.
• In fruit flies, the genes period (per) and timeless (tim) are clock genes.
• Mutations of the per gene cause flies to have either short or long free-running circadian periods, and mutations of the tim gene result in loss of circadian rhythms.
• The transcription and translation of these two genes have a circadian rhythm, and the rhythm appears to be controlled by negative feedback of the PER and TIM proteins on two other clock genes, clock (clk) and cycle (cyc).

The Timing of Behavior: Biological Rhythms
• This molecular negative feedback loop is the basic model for a clock mechanism.
• Genes produce products that shut down their own expression, with a delay.
• The mammalian clock has a similar circuit design and some homologous genes, but their molecular interactions and functions are different.
The Timing of Behavior: Biological Rhythms
• Day length, or photoperiod, is a reliable indicator of upcoming seasonal changes. Animal species are described as photoperiodic if their behavior or physiology is influenced by day length.
• Some animals, such as those that hibernate, cannot rely on day length as a cue of upcoming seasonal change and instead have endogenous annual rhythms called circannual rhythms.
• Circannual rhythms are usually shorter than 365 days.
• The neural mechanisms of circannual rhythms are unknown.
Finding Their Way: Orientation and Navigation
• Piloting is a simple means of navigation involving the use of landmarks.
• Gray whales use landmarks along the west coast of North America to find their way between the Bering Sea and the coastal lagoons of Mexico.
Finding Their Way: Orientation and Navigation
• Homing is the ability of an animal to return to its nest site or burrow.
• In many animals, homing involves piloting, the use of landmarks in a familiar environment.
• Incredible examples of homing are also found among marine birds that can return home after flying great distances over open ocean with few, if any, landmarks.
• Albatrosses, for example, return to the island on which they were raised after spending 8 or 9 years flying over southern oceans.

Finding Their Way: Orientation and Navigation
• In other species, including homing pigeons, individuals released at a location they have never been before can still find their way home.
• Homing pigeons do not fly randomly until encountering familiar landmarks. Instead, they fly in a fairly direct route to their home loft.
• Experiments have shown that these birds can navigate without visual cues from the landscape. Birds fitted with frosted contact lenses so that they could only see the degree of light and dark could still find their way home.
Finding Their Way: Orientation and Navigation
• Seasonal movement between breeding and nonbreeding grounds is called________
• Many homing and migrating species are able to take direct routes to their destinations, even through environments they have never experienced before.
• Two types of navigation include distance-and-direction navigation (knowing direction to the destination, and how far it is) and bicoordinate or true navigation (knowing latitude and longitude of current position and destination).
Finding Their Way: Orientation and Navigation
• Experiments with starlings showed that naive juvenile birds were using distance-and-direction navigation.
• Experienced adult birds were not disrupted by geographic displacement.

Finding Their Way: Orientation and Navigation
• Biological rhythms may be involved in determining distances for some migratory species.
• Birds held in captivity show increased and oriented activity, termed migratory restlessness, at about the time they would normally migrate.
• The duration of migratory restlessness correlates with the typical duration of migration for the species.
• This suggests that the duration of migratory restlessness could set the distance for migration.
Finding Their Way: Orientation and Navigation
• Animals may use the sun and the stars to determine direction.
• The sun is an excellent compass, provided the time of day is known. Animals can determine time of day from their circadian clocks.
• Clock-shifting experiments have shown that birds are capable of using their circadian clocks to determine direction from the position of the sun.
Finding Their Way: Orientation and Navigation
• In a clock-shifting experiment, a bird is placed in a circular cage from which it can see the sun and sky but no other visual cues.
• After training the bird to expect food from a certain direction, scientists were able to phase-advance the bird's circadian rhythms by 6 hours. Once under normal conditions, the bird looked for food in the wrong direction.
• These birds are using a time-compensated solar compass.


Finding Their Way: Orientation and Navigation
• Many species are active at night, or simply migrate at night, and thus cannot use the sun for directional information. These species appear to use stars for direction.
• Species that rely on stars for directional information can use the North Star, a fixed point that always indicates north, or constellations, collections of stars that move as Earth rotates.
• Animals need to use their circadian clock with the moving constellations.
Finding Their Way: Orientation and Navigation
• Stephen Emlen tested the orientation abilities of birds in a planetarium in which the star patterns were projected on the domed ceiling. The star patterns could be rotated to simulate rotation of Earth.
• Wild-caught birds could orient in the planetarium when the star patterns were either stationary or rotated more quickly than normal.
• These results showed that the birds were using the North Star, the fixed point in the sky, for directional information, rather than the constellations.
Finding Their Way: Orientation and Navigation
• Birds raised in the planetarium under a stationary sky and tested with a stationary sky could not orient well.
• However, birds raised in the planetarium under a rotating sky oriented well when tested with a rotating sky.
• Thus, birds could learn to use constellations for orientation as long as the sky rotated during the time the birds were maturing.
Finding Their Way: Orientation and Navigation
• Use of the sun and stars for directional information is not possible during overcast conditions.
• Some birds, such as pigeons, can orient well under overcast skies, apparently using their ability to sense Earth's magnetic field and thus gain directional information.
• When small magnets were attached to the heads of pigeons and the birds were displaced under overcast skies, they could not find their way back to their home loft.
Finding Their Way: Orientation and Navigation
• It now appears that homing pigeons use the sun when available, magnetic cues when the sun is unavailable, and landmarks when close to home.
• There appears to be considerable ________ in the means by which animals determine direction.
• Other sources of directional information include the plane of polarized light, low-frequency sound, and weather patterns.
Human Behavior
• ________ is the transmission of learned behavior from one generation to another and is characteristic of humans.
• Human behavior is also influenced by genetic factors.
• Some motor patterns appear to be programmed into the human nervous system.
• For example, similar facial expressions are displayed by human populations that have had little or no contact. Blind infants smile and frown although they have never seen these expressions in others.
Human Behavior
• As we acknowledge that human behavior has both learned and genetic components, we also find examples of culture, once thought to be a uniquely human characteristic, in other animals.
• Japanese macaques, for example, developed new methods of food preparation, and these methods were transmitted to other individuals in the population via ________ learning.
• Chimpanzees also display culturally transmitted behaviors including tool using and courtship. Populations have distinct behavioral repertoires or culture.
Animation 52.1 Hormonal Control of Sexual Behavior
Animation 52.2 Circadian Rhythms
Animation 52.3 Time-Compensated Solar Compass
Video 52.1 Three examples of courtship behavior in birds
Video 52.2 Courtship behavior in a male fruit fly, Drosophila melanogaster
Video 52.3 Honeybee waggle dance
Video 52.4 Visual communication in squid