Chapter 39 Animal Behavior (Sections 39.1 - 39.4)

1. Chapter 39Animal Behavior(Sections 39.1 - 39.4)

2. 39.1 An Aggressive Defense • Bee stings are highly painful and even a single sting can be fatal to someone allergic to honeybee venom • Africanized bees respond aggressively to chemical alarm signals (pheromones); they attack in great numbers, sting with little provocation, and pursue intruders persistently • pheromone • Intraspecific chemical communication signal

3. Hybrid Africanized Honeybees

4. Ecology • Scientists investigate proximate causes of behavior (genetic and physiological factors) and ultimate causes (environmental factors that favored evolution of a behavior) • Interactions among organisms and their environment are part of the study of ecology • ecology • Study of organism–environment interactions

5. 39.2 Behavior’s Genetic Basis • Animal behavior requires a capacity to detect stimuli • Structure of the nervous system determines the types of stimuli an animal can detect, and types of responses it can make • stimulus • Environmental cue that a sensory receptor responds to

6. How Genes Can Influence Behavior • Much variation in behavior within or among species results from inherited differences • Behavior can be influenced by genes that affect the structure and activity of the nervous system, and by genes that affect metabolism or physical traits • Example: Genes that specify beak structure in African seedcrackers determine which species eat large seeds and which species eat small seeds

7. Genetic Variation Within a Species • One way to investigate the genetic basis of behavior is to examine behavioral and genetic differences among members of a single species • Example: Garter snakes of the Pacific Northwest • Snakes in coastal forests prefer to eat banana slugs that are common on the forest floor • Snakes that live inland prefer to eat fishes and tadpoles • When offered a slug, newborn offspring of coastal snakes ate it, but offspring of inland snakes ignored it • Newborn coastal snakes associate slug scent with food

8. Coastal Garter Snake and Banana Slug

9. Genetic Variation Within a Species (cont.) • Example: Fruit fly larvae eat yeast on decaying fruit • 70% are “rovers” (move as they feed) • 30% are “sitters” (stay in one place) • The proximate cause of different behaviors is the gene foraging, which encodes an enzyme for olfactory cues • Dominant allele = rover phenotype • Homozygous recessive = sitter phenotype • The ultimate cause of behavioral variation is natural selection: a rover does best when surrounded by sitters, and vice versa

10. “Rovers” and “Sitters” • Genetic polymorphism for foraging behavior in fruit fly larvae

11. “Rovers” and “Sitters” yeast A Rovers (genotype FF or Ff ) move often as they feed. When a rover’s movements on a petri dish filled with yeast are traced for 5 minutes, the trail is relatively long. B Sitters (genotype ff ) move little as they feed. When a sitter’s movements on a petri dish filled with yeast are traced for 5 minutes, the trail is relatively short. Fig. 39.3, p. 658

12. Genetic Variation Among Species • Comparing behavior of related species can clarify the genetic basis of a behavior • Example: In voles, inherited differences in hormone receptors influence mating and bonding behavior • Most voles are promiscuous, some are monogamous • Brains of monogamous species have many receptors for the hormone oxytocin • Also, males of monogamous species have more arginine vasopressin (AVP) receptors

13. Voles • Vole species vary in mating and bonding behavior, and in the number and distribution of receptors for the hormone oxytocin

14. Oxytocin Receptors in Vole Brains • Monogamous • Promiscuous

15. Human Behavior Genetics • Most human behavioral traits have a polygenic basis and are influenced by the environment • Effects of a single gene among many may show a small statistical correlation between a particular allele and an increased tendency toward a particular human behavior • Animal studies sometimes inspire human studies: Investigators are looking at possible connections between oxytocin and autism, a disorder involving social attachments

16. Key Concepts • Genetic Foundations • Genes that affect the ability to detect stimuli or to respond to nervous or hormonal stimulation influence behavior • Studying behavioral differences within and between species allows scientists to determine the behavior’s proximate and ultimate causes

17. ANIMATION: Hormonal Control of Behavior To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

18. 39.3 Instinct and Learning • All animals are born with the capacity for instinctive behavior – such as the newborn coastal garter identifying a banana slug as food • instinctive behavior • An innate response to a simple stimulus

19. Instinctive Behavior: Cuckoos • A female cuckoo lays her eggs in nests of other birds • When a cuckoo egg hatches, contact with other eggs stimulates a fixed action pattern: the blind hatchling shoves the eggs out of the nest, eliminating the competition • fixed action pattern • Series of instinctive movements elicited by a simple stimulus and carried out with little variation once begun

20. Cuckoos (cont.) • Instinctive behavior: A young cuckoo shoves its foster parent’s eggs out of the nest

21. Cuckoos (cont.) • The cuckoo’s foster parent responds to the simple stimulus of a chick’s gaping mouth with the fixed action pattern of parental feeding behavior

22. Time-Sensitive Learning • A genetic capacity to learn, combined with actual experiences in the environment, shapes most forms of behavior • Learning may occur throughout an animal’s life, or be restricted to a critical period • learned behavior • Behavior that is modified by experience

23. Time-Sensitive Learning (cont.) • Imprinting is a form of learning that occurs during a genetically determined time period early in life • Example: Baby geese follow the large object that bends over them in response to their first peep – usually their mother • imprinting • Learning that can occur only during a specific interval in an animal’s life

24. Imprinting • Nobel laureate Konrad Lorenz with geese that imprinted on him, and a normal imprinting pattern

25. Time-Sensitive Learning (cont.) • Example: Songbirds • A male songbird recognizes his species’ song when he hears older males singing it • Males reared with no model sing a simplified version of their species’ song • Many birds can only learn the details of their species-specific song during a limited period early in life

26. Conditioned Responses • Most animals are lifelong learners: • They learn to associate certain stimuli with rewards and others with negative consequences • Classical conditioning: • An involuntary response to a stimulus becomes associated with a stimulus that accompanies it • Example: Pavlov’s dog salivated at the sound of a bell associated with feeding time

27. Conditioned Responses (cont.) • Operant conditioning: • An animal modifies its voluntary behavior in response to consequences of that behavior • Example: A rat that presses a lever and is rewarded with food presses the lever again; a rat that receives a shock when it enters a particular area avoids that area

28. Other Types of Learned Behavior • Habituation: • An animal learns by experience not to respond to a stimulus that has neither positive nor negative effects • Example: Pigeons in cities learn not to flee from people who walk past them • habituation • Learning not to respond to a repeated stimulus

29. Other Learned Behavior (cont.) • Spatial learning: • Animals learn about landmarks in their environment that help them return home • Social learning: • Animals learn to recognize offspring, competitors, or mates by appearance, calls, odor, or combinations of cues • Observational learning: • Animals learn skills by imitating behaviors it observes in others

30. Social Learning • Male lobsters battle at their first meeting – the loser will remember the winner’s scent and avoid him

31. Observational Learning • A marmoset opens a container using the same method he observed another use

32. Key Concepts • Instinct and Learning • Instinctive behavior can be performed without any practice • Most behavior has a learned component • Even instinctive behavior is often modified over time • Some learning can only occur during a certain portion of the lifetime

33. Video: Ducklings Following

34. Video: Woodpecker Feeding Young

35. 39.4 Adaptive Behavior • Not all behaviors are adaptive; scientists use experiments to test hypotheses about the adaptive value of a behavior • Example: • Starlings place sprigs of wild carrot in their nests • Scientists tested the effect of wild carrot sprigs on the number of blood-sucking mites in nests • Results: Nests with wild carrots had significantly fewer mites than those with no greenery

36. Starling Nest Decorating Behavior