1. Chapter 32: Animal Behavior

2. Genetic Basis of Behavior
The behavior of animals is any action that can be observed and described.
All behavior has a genetic basis, as demonstrated by various experiments.
Lovebirds are small green and pink African parrots; several closely related species differ by the way they build nests.
Hybrids between species have trouble with carrying nest materials.
All behavior has a genetic base in that an animal inherits the anatomy and physiology suitable to performing the behavior.

3. Nest-building behavior in lovebirds
Fischer lovebirds (left) carry strips of nest material in the beak, as do most other birds. Peach-faced lovebirds (right) tuck strips of nest material into their rump feathers before flying back to the nest. Hybrids between these two species try to tuck nest materials into rump feathers but do not push the strips far enough into the feathers and they fall out. After a period of three years, the hybrid birds learned to carry nest materials in their beaks, although they still looked toward their rumps before flying off. These studies support the hypothesis that behavior has a genetic basis.

4. Several experiments have been done with the garter snake, which has two different populations in California.
Inland populations are aquatic and feed underwater on frogs and fish.
Coastal populations are terrestrial and feed mainly on slugs.
In the lab, inland garter snakes refused to eat slugs but coastal snakes ate them.
Hybrid offspring showed an intermediate acceptance of slugs as food.

5. Feeding behavior in garter snakes
The number of tongue flicks by inland and coastal garter snakes is measured in terms of their response to slug extract on cotton swabs. Newborn coastal snakes tongue-flicked more than newborn inland snakes, indicating a genetic difference between the two groups. When snakes eat, their tongues carry chemicals to an odor receptor in the roof of the mouth. Tongue flicks are used to recognize their prey. Apparently, inland snakes do not eat slugs because they are not sensitive to their smell.
These experiments support the hypothesis that the nervous system controls behavior. A genetic difference between the two populations of snakes has resulted in a physiological difference in their nervous systems.

6. ELH is thought to control the egg-laying behavior in Aplysia.
Both the nervous and endocrine systems are responsible for the integration of body systems.
To test whether the endocrine system influenced behavior, the egg-laying behavior of a marine snail Aplysia was examined.
Egg-laying hormone (ELH) causes the snails to lay eggs even without mating.
ELH is thought to control the egg-laying behavior in Aplysia.
ELH was found to be a small protein of 36 amino acids that diffuses into the circulatory system and excites the smooth muscle cells of the reproductive duct, causing them to contract and expel an egg string (this attaches the eggs to a rock). Using recombinant DNA techniques, investigators isolated the ELH gene. The gene’s product turned out to be a protein with 271 amino acids. The protein can be cleaved into as many as 11 possible products, and ELH is one of these.

7. Development of Behavior
Some behaviors seem to be fixed action patterns (FAPs) in which a specific cue sets the behavior in motion.
Experiments with laughing gull chicks show that improvement in motor skills, as well as visual experience, strongly affect development of chick begging behavior.
This suggests that learning, rather than FAPs, may be involved in gull chicks.
Begging behavior refers to the interaction between the chick and the parent feeding it.

8. Pecking behavior in laughing gulls
At about three days, a laughing gull chick grasps the red beak of a parent, stroking it downward, and then the parent regurgitates food.
The interaction between the chicks and their parents suggests that learning, rather than FAPs, may be involved. To test this hypothesis, diagrammatic pictures of gull heads were painted on small cards, and then eggs were collected in the field. The eggs were hatched in a dark incubator to eliminate visual stimuli before the test. On the day of hatching, each chick was allowed to make about a dozen pecks at a model. The chicks were returned to the nest, and then each nest was retested. The tests showed that on the average, only one-third of the pecks of a newly hatched chick strike the model. But one day after hatching, more than half the pecks are accurate, and two days after hatching, the accuracy reaches a level of 75%.

9. The Phenomenon of Learning
Operant Conditioning and Imprinting
Operant conditioning, one of many forms of learning, is the gradual strengthening of stimulus-response (behavior-reward) connections.
Imprinting is another form of learning; chicks, ducklings, and goslings will follow the first moving object they see during a sensitive period after hatching.
B.F. Skinner is well-known for studying operant conditioning in the laboratory. In his simpler experiments, a caged rat happens to press a lever and is rewarded with sugar pellets. Thereafter, the rat regularly presses the lever whenever it is hungry.
The sensitive period for imprinting occurs two to three days after hatching. This means the behavior will only develop during this time.
Englishman Douglas Spalding first observed imprinting, but Austrian Konrad Lorenz is well known for investigating it. He found that imprinting not only served the useful purpose of keeping ducks near their mother, it also caused male birds to court a member of the correct species. Goslings who imprinted on Lorenz courted human beings later in life.
Eckhard Hess found that vocalization before and after hatching was an important element in the imprinting process. Female mallards cluck during the entire time imprinting is occurring. Hess found that mallard ducklings imprinted on humans in the laboratory would switch to a female mallard that had hatched a clutch of ducklings several hours before.

10. Song-Learning in Birds
Song learning in birds is an active area of research.
White-crowned sparrows sing a species-specific song, but males of a particular region have their own dialect; birds were caged into three groups to see how young birds learn to sing from older members of their species.
Birds in the first group heard no singing; when grown, these birds sang a song that was not fully developed.

11. Birds in the second group heard tapes of white-crowns singing; when grown, they sang in a dialect, as long as the tapes had been played during a sensitive period.
Birds in the third group were given an adult tutor; these birds sang a song of even a different species, no matter when the tutoring began.
It appears that social influence, along with genetics, is of great importance in the development of singing.
Neurons that are critical for song production have been located, and they fire when the bird’s own song is played or when a song of the same dialect is played. Apparently, however, the brain of a bird is especially primed to respond to acoustical stimuli during a sensitive period.

12. Song-learning by white-crowned sparrows
Three different experimental procedures are depicted. In the cage on the left, isolated birds heard no singing; the isolated bird sings but its song is not fully developed. In the middle cage, the bird listens to tapes of its song; the bird sings a developed song played during the sensitive period. In the cage on the right, the bird has an adult tutor and sings the song of its social tutor, without regard to the sensitive period. These results suggest both a genetic basis and an environmental basis for song-learning in white-crowned sparrows.

13. Adaptiveness of Behavior
Since genes influence the development of behavior, it can be assumed that behavioral traits are among those subject to natural selection.
Investigators studying survival value of a given behavior seek to discover how a given trait might improve reproductive success.

14. Males can father many offspring because they produce sperm in great quantity; it would be expected that they inseminate as many females as possible.
Females produce few eggs, so choice of mate becomes an important consideration.
Experiments with satin bowerbirds and birds of paradise support these bases for sexual selection.
Sexual selection refers to changes in males and females, due to male competition and female selectivity, leading to reproductive success.

15. Mating behavior in birds of paradise
In birds of paradise, males have resplendent plumage brought about by sexual selection. The females are widely scattered, foraging for complex fruits; the males form leks (groups of males calling, hopping, and shaking their wings) that females visit to choose a mate.

16. Female Choice
Courtship displays are rituals that serve to prepare the sexes for mating; they help male and female recognize each other so that mating will be successful.
Courtship displays also play a role in a female’s choice of a mate.
Female choice can explain why male birds are so much more showy than females; colorful, lengthy plumes might signify health and vigor.
In one example, raggiana birds that required both monogamous parents to raise offspring, males were to be less showy.

17. Male Competition
Evolution by sexual selection can occur either when females have the opportunity to select among potential mates, and/or when males compete among themselves for access to reproductive females.
Only if the positive effects of male competition outweigh the negative effects will the animal have reproductive success.

18. Dominance Hierarchy
Male and female baboons within a troop have separate dominance hierarchies in which a higher-ranking animal has greater access to resources than a lower-ranking animal.
Dominant male baboons generally monopolize females when they are fertile, although males that help rear offspring sometimes have breeding access during less fertile times.
Dominance is decided by confrontations.

19. A male olive baboon displaying full threat
In olive baboons, males are larger than females and have enlarged canines. Competition between males establishes a dominance hierarchy for the distribution of resources.

20. Female choice and male dominance among baboons
Although it may appear that females mate indiscriminately, they mate more often with a dominant male when they are most fertile.

21. Territoriality
A territory is an area that is defended against competitors.
Territoriality includes the type of defensive behavior needed to defend a territory.
Vocalization and displays, rather than outright fighting, may be sufficient to defend a territory.
Red deer stags may actually lock antlers and push against each other to repel challengers.

22. Competition between male red deer
Male red deer compete for a harem within a particular territory. Roaring alone may frighten off a challenger, but outright fighting may be necessary and the victor is most likely the stronger of the two animals.

23. Animal Societies
Some animals are solitary, others live in small groups, and still others organize a society in which members cooperate, a behavior extending beyond mating and parental care.
Social behavior in societies requires communication between members.

24. Communicative Behavior
Communication is an action by a sender that affects the behavior of a receiver.
Chemical communication uses chemical signals, such as pheromones; an advantage is that this form of communication works both night and day.
Auditory (sound) communication is fast and effective, and can be easily modified.
Language is the ultimate auditory communication, but only humans have the ability to produce a large number of different sounds and put them together in many different ways.
Nonhuman primates have at most forty different vocalizations, each having a different meaning. Although chimpanzees can be taught to use an artificial language, they never progress beyond the capability level of a two-year-old child.

25. Use of a pheromone
This male cheetah is spraying a pheromone (found in urine, feces, or anal gland secretions of animals) onto a tree in order to mark his territory. Female moths secrete pheromones from abdominal glands which are detected downwind by receptors on male antennae.

26. A chimpanzee with a researcher
Chimpanzees are unable to speak but can learn to use a visual language consisting of symbols. Some researchers believe chimps only mimic their teachers and never understand the cognitive use of language. Here the experimenter shows Nim the sign for “drink”. Nim copies.

27. Visual communication involves signals used by species active during the day.
For example, defense and courtship displays are exaggerated and are always performed in the same way so their meaning is clear.
Tactile communication occurs when one animal touches another.
Honeybees use a combination of methods of communication, but especially tactile ones, to impart information about food distance and direction.

28. Communication among bees
Honeybees do a waggle dance to indicate the direction of food. If the dance is done outside the hive on a horizontal surface, the straight run of the dance points to the food source. If the dance is done inside the hive on a vertical surface, the angle of the straightaway to that of the direction of gravity is the same as the angle of the food source to the sun.

29. Sociobiology and Animal Behavior
Sociobiology applies the principles of evolutionary biology to the study of social behavior in animals.
It is assumed that a social individual derives more reproductive benefits than costs from living in a society.
Group living protects members from predators and helps in finding food; disadvantages include increased disease and territoriality, and not all members of the group will mate.

30. Altruism Versus Self-Interest
Altruism is behavior that has the potential to decrease the lifetime reproductive success of the altruist while benefiting the reproductive success of another member of the group.
Genetic relatedness appears to underlie altruism; an altruistic act is best targeted at a close relative sharing the same genes.

31. Direct selection is natural selection that can result in adaptation to the environment when the reproductive success of individuals differs.
Indirect selection is natural selection that can result in adaptation to the environment when individuals differ in their effects on the reproductive success of relatives.
Inclusive fitness of an individual includes personal reproduction and reproduction of relatives.

32. Inclusive fitness
A meerkat is acting as a baby-sitter for its young sisters and brothers while their mother is away. Could this helpful behavior contribute to the baby-sitter’s inclusive fitness?

33. Inclusive fitness is measured by the genes an individual contributes to the next generation, either directly by offspring or indirectly by way of relatives.
Many of the behaviors once thought to be altruistic turn out to be examples of indirect selection and are adaptive.

34. Chapter Summary
Various experiments with African lovebirds, California garter snakes, and and the marine snail Aplysia have shown that behavior has a genetic basis, and further that the nervous and endocrine systems control behavior.
The environment influences the development of behavioral responses, and learning occurs.

35. Song learning in birds involves various elements, including a sensitive period during which the bird is primed to learn, and the effect of social interactions.
Since genes influence the development of behavior, it can be assumed that behavioral traits, such as mate choice, are among those subject to natural selection.

36. Evolution by sexual selection can occur either when females have the opportunity to select among potential mates, and/or when males compete among themselves for access to reproductive females.
Territoriality includes the type of defensive behavior needed to defend a territory.
Vocalization and displays, rather than outright fighting, may be sufficient to defend a territory.

37. Animals that form social groups use chemical, auditory, visual, or tactile communication, and communication fosters cooperation that benefits both sender and receiver.
In most cases, individuals of a society act to increase their own reproductive success by helping relatives who share their genes.
Altruistic behavior has a benefit in terms of inclusive fitness.