Albia Dugger • Miami Dade College

Chapter 43Animal Behavior

43.1 Alarming Bee Behavior

• Africanized honeybees (“killer bees”) have an aggressive defensive response to threats

• They have a greater response to alarm pheromones – signal molecules that are released into the environment and influence the behavior of others of the same species

• Africanized bees are less particular about where they establish a colony and are more likely to abandon their hive

Africanized Honeybees

Animal Behavior

• Scientists study both proximate and ultimate causes of animal behavior – coordinated responses to stimuli

• Proximate causes are the genetic, developmental, and physiological mechanisms that make a behavior possible

• A behavior’s ultimate causes are its adaptive significance and evolutionary history

Video: The Vanishing Honeybee’s Impact on Our Food Supply

43.2 Behavioral Genetics

• Much variation in behavior within or among species results from inherited differences

• Genes that affect the nervous and endocrine systems cause animals to differ in which stimuli they perceive and how they respond to them

Variation Within a Species: Snakes

• Garter snakes and food preferences:• Coastal garter snakes prefer to eat banana slugs• Inland garter snakes ignore banana slugs• Hybrids have an intermediate response

• Inland snakes lack a genetically determined ability to associate the scent of slugs with food

Coastal Garter Snake and Banana Slug

Variation Within a Species: Flies

• Foraging behavior in fruit flies:• 70% of wild fruit flies are “rovers,” 30% “sitters” • Genotype at the foraging (for) gene determines whether a

fly is a rover (FF or Ff) or a sitter (ff)• The for gene encodes an enzyme (PKG) active in

intercellular signaling pathways • Learning and memory are also affected

Figure 43-3 p774

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.

Genetic Variation Among Species

• Pair-bonding in prairie voles:• Prairie voles mate for life• Mountain voles are promiscuous• Prairie voles have more oxytocin receptors than mountain

voles• Prairie voles injected with a drug that blocks action of

oxytocin dumped their partners

Figure 43-4a p775

Figure 43-4b p775

B PET scan of a monogamous prairie vole’s brain with many receptors for the hormone oxytocin (red).

Figure 43-4c p775

C PET scan of a promiscuous prairie vole’s brain with few hormone receptors for oxytocin.

Human Behavior Genetics

• Nearly all human behavioral traits have a polygenic basis and are influenced by the environment

• Animal behavior studies help researchers understand human behavioral disorders

• Example: Oxytocin’s role in animal bonding suggests that impaired oxytocin production or reception may contribute to autism

Take-Home Message:

How do genes influence behavior?

• Behavioral differences within a species can arise from allele differences.

• Differences between closely related species can also have a genetic basis.

• Most human behaviors are complex, polygenic traits. Studies of genetic differences can shed light on predispositions to particular behaviors.

43.3 Instinct and Learning

• Instinctive behavior is inborn and can be performed without any prior experience

• A fixed action pattern is a series of instinctive movements, triggered by a specific stimulus, that (once started) is carried to completion without further cues

Cuckoo Bird: Instinctive Behaviors

• The cuckoo bird is a social parasite that lays its egg in other birds’ nests• The newly hatched cuckoo eliminates competition by

instinctively rolling other eggs out of the nest• The foster parents instinctively respond to the cuckoo’s

open mouth by feeding it

Cuckoo Bird: Instinctive Behaviors

Time-Sensitive Learning

• Learned behavior• Behavior that is altered by experience• Some instinctive behavior can be modified by learning

(such as avoiding unpalatable prey)

• Imprinting• A form of learning that occurs during a genetically

determined time period• Example: Baby geese follow the first large object that

bends over them

Konrad Lorenz and Imprinted Geese

Time-Sensitive Learning

• A genetic capacity to learn, combined with actual experiences in the environment, shapes most forms of behavior

• Example: To learn to sing normally, a male sparrow must hear a male “tutor” of his own species during his first 50 or so days of life – he must also practice their song to perfect it

Conditioned Responses

• Classical conditioning• An animal’s involuntary response to a stimulus becomes

associated with another stimulus presented at the same time

• Example: Salivation in Pavlov’s dogs

• Operant conditioning• An animal modifies its voluntary behavior in response to

consequences of that behavior• Example: Reward of food for pressing a lever

Other Types of Learned Behavior

• With habituation, an animal learns not to respond to a stimulus that has neither positive nor negative effects

• Example: Pigeons in cities learn to ignore people walking past

• Animals learn landmarks in their social environment, and recognize mates, offspring and competitors

• Example: Once male lobsters have fought, the loser recognizes and avoids the winner

Social Learning in Lobsters

Observational Learning

• With observational learning, one individual imitates the behavior of another

• Example: Marmoset monkeys learned to open a container using their hands or teeth, depending on which method they had previously observed

Observational Learning

Take-Home Message: How do instinct and learning shape behavior?

• Instinctive behavior can initially be performed without any prior experience, as when a simple cue triggers a fixed action pattern. Even instinctive behavior may be modified by experience.

• Certain types of learning can occur only at particular times in the life cycle.

• Learning affects both voluntary and involuntary behaviors.

43.4 Environmental Effects on Behavioral Traits

• Phenotypic plasticity refers to the ability of an individual to express different phenotypes in different environments

• Many animals show behavioral plasticity; their behavioral traits are altered by environmental factors

• Example: Woolly bear caterpillars normally don’t eat leaves with a high concentration of alkaloids – when parasitized by fly larvae, they prefer to alkaloid-rich foods

Diets of Wooly Bear Caterpillars