Chapter 51 Behavioral Ecology

The modern scientific discipline of behavioral ecology Extends observations of animal behavior by studying how such behavior is controlled and how it develops, evolves, and contributes to survival and reproductive success

The scientific questions that can be asked about behavior can be divided into two classes Those that focus on the immediate stimulus and mechanism for the behavior Those that explore how the behavior contributes to survival and reproduction

What Is Behavior? Behavior Is what an animal does and how it does it Includes muscular and nonmuscular activity Figure 51.2 Dorsal fin Anal fin

Learning is the modification of behavior Is also considered a behavioral process Learning is the modification of behavior Based on specific experiences Learned behaviors Range from very simple to very complex

Proximate and Ultimate Questions Proximate, or “how,” questions about behavior Focus on the environmental stimuli that trigger a behavior Focus on the genetic, physiological, and anatomical mechanisms underlying a behavioral act Ultimate, or “why,” questions about behavior Address the evolutionary significance of a behavior

Ethology is the scientific study of animal behavior Particularly in natural environments

A fixed action pattern (FAP) Fixed Action Patterns A fixed action pattern (FAP) Is a sequence of unlearned, innate behaviors that is unchangeable Once initiated, is usually carried to completion A FAP is triggered by an external sensory stimulus Known as a sign stimulus

In male stickleback fish, the stimulus for attack behavior Is the red underside of an intruder Figure 51.3a (a) A male three-spined stickleback fish shows its red underside.

When presented with unrealistic models As long as some red is present, the attack behavior occurs Figure 51.3b (b) The realistic model at the top, without a red underside, produces no aggressive response in a male three-spined stickleback fish. The other models, with red undersides, produce strong responses.

Proximate and ultimate causes for the FAP attack behavior in male stickleback fish Figure 51.4 ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreases the chance that eggs laid in his nesting territory will be fertilized by another male. BEHAVIOR: A male stickleback fish attacks other male sticklebacks that invade its nesting territory. PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback.

Imprinting is a type of behavior That includes both learning and innate components and is generally irreversible Imprinting is distinguished from other types of learning by a sensitive period A limited phase in an animal’s development that is the only time when certain behaviors can be learned Ducks following their mother

There are proximate and ultimate causes for this type of behavior Figure 51.5 BEHAVIOR: Young geese follow and imprint on their mother. PROXIMATE CAUSE: During an early, critical developmental stage, the young geese observe their mother moving away from them and calling. ULTIMATE CAUSE: On average, geese that follow and imprint on their mother receive more care and learn necessary skills, and thus have a greater chance of surviving than those that do not follow their mother.

Behavior that is developmentally fixed Genetic Component Behavior that is developmentally fixed Is called innate behavior and is under strong genetic influence Many animal movements Are under substantial genetic influence These types of movements Are called directed movements

Kinesis A kinesis Is a simple change in activity or turning rate in response to a stimulus

Sow bugs Become more active in dry areas and less active in humid areas Figure 51.7a Dry open area Moist site under leaf (a) Kinesis increases the chance that a sow bug will encounter and stay in a moist environment.

Taxis A taxis Is a more or less automatic, oriented movement toward or away from a stimulus

Many stream fish exhibit positive rheotaxis Where they automatically swim in an upstream direction Direction of river current (b) Positive rheotaxis keeps trout facing into the current, the direction from which most food comes. Figure 51.7b

Many features of migratory behavior in birds Migration Many features of migratory behavior in birds Have been found to be genetically programmed Figure 51.8

Animal Signals and Communication In behavioral ecology A signal is a behavior that causes a change in another animal’s behavior Communication Is the reception of and response to signals

Animals communicate using Visual, auditory, chemical, tactile, and electrical signals The type of signal used to transmit information Is closely related to an animal’s lifestyle and environment

Chemical Communication Many animals that communicate through odors Emit chemical substances called pheromones

When a minnow or catfish is injured An alarm substance in the fish’s skin disperses in the water, inducing a fright response among fish in the area Figure 51.9a, b (a) Minnows are widely dispersed in an aquarium before an alarm substance is introduced. (b) Within seconds of the alarm substance being introduced, minnows aggregate near the bottom of the aquarium and reduce their movement.

Habituation (“cry-wolf” effect) Is a loss of responsiveness to stimuli that convey little or no information

Spatial learning is the modification of behavior Showed how digger wasps use landmarks to find the entrances to their nests Figure 51.14 CONCLUSION A female digger wasp excavates and cares for four or five separate underground nests, flying to each nest daily with food for the single larva in the nest. To test his hypothesis that the wasp uses visual landmarks to locate the nests, Niko Tinbergen marked one nest with a ring of pinecones. EXPERIMENT Nest When the wasp returned, she flew to the center of the pinecone circle instead of to the nearby nest. Repeating the experiment with many wasps, Tinbergen obtained the same results. RESULTS The experiment supported the hypothesis that digger wasps use landmarks to keep track of their nests. No Nest Based on experience with the spatial structure of the environment After the mother visited the nest and flew away, Tinbergen moved the pinecones a few feet to one side of the nest.

Cognitive Maps A cognitive map Is an internal representation of the spatial relationships between objects in an animal’s surroundings Hard to distinguish whether animal is using landmarks or a true cognitive map.

Associative Learning In associative learning Animals associate one feature of their environment with another Classical conditioning is a type of associative learning In which an arbitrary stimulus is associated with a reward or punishment (dog and bone) Operant conditioning is another type of associative learning In which an animal learns to associate one of its behaviors with a reward or punishment Trial and error learning

Cognition and Problem Solving Cognition is the ability of an animal’s nervous system To perceive, store, process, and use information gathered by sensory receptors Problem solving can be learned By observing the behavior of other animals

The genetic components of behavior Natural Selection Natural selection favors behaviors that increase survival and reproductive success The genetic components of behavior Evolve through natural selection Behavior can affect fitness Through its influence on foraging and mate choice

Optimal foraging theory Foraging Behavior Optimal foraging theory Views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food

Energy Costs and Benefits Reto Zach Conducted a cost-benefit analysis of feeding behavior in crows The crows eat molluscs called whelks But must drop them from the air to crack the shells Correlated with a fewer number of drops, indicating a trade-off between energy gained (food) and energy expended

Mating Behavior and Mate Choice Is the product of a form of natural selection called sexual selection In many species, mating is promiscuous With no strong pair-bonds or lasting relationships

In monogamous relationships One male mates with one female In a system called polygyny One male mates with many females The males are often more showy and larger than the females In polyandrous systems One female mates with many males The females are often more showy than the males

Paternity and the needs of the young Influences parental care and mating behavior In species that produce large numbers of offspring Parental care is at least as likely to be carried out by males as females Figure 51.26 Eggs

Sexual Selection and Mate Choice In intersexual selection Members of one sex choose mates on the basis of particular characteristics Intrasexual selection Involves competition among members of one sex for mates

Mate Choice by Females Male zebra finches Are more ornate than females, a trait that may affect mate choice by the females Figure 51.27

Male Competition for Mates Male competition for mates Is a source of intrasexual selection that can reduce variation among males Figure 51.30

Many social behaviors are selfish Natural selection favors behavior Concept of inclusive fitness can account for most altruistic social behavior Many social behaviors are selfish Natural selection favors behavior That maximizes an individual’s survival and reproduction

On occasion, some animals Altruism On occasion, some animals Behave in ways that reduce their individual fitness but increase the fitness of others This kind of behavior Is called altruism, or selflessness

Altruistic behavior can be explained by inclusive fitness The total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables close relatives to produce offspring

Hamilton’s Rule and Kin Selection Hamilton proposed a quantitative measure For predicting when natural selection would favor altruistic acts among related individuals The three key variables in an altruistic act are The benefit to the recipient The cost to the altruist The coefficient of relatedness (the probability that two relatives may share the same genes) Natural selection favors altruism when the benefit to the recipient Multiplied by the coefficient of relatedness exceeds the cost to the altruist This inequality Is called Hamilton’s rule

Kin selection is the natural selection That favors this kind of altruistic behavior by enhancing reproductive success of relatives An example of kin selection and altruism Is the warning behavior observed in Belding’s ground squirrels

Altruistic behavior toward unrelated individuals Reciprocal Altruism Altruistic behavior toward unrelated individuals Can be adaptive if the aided individual returns the favor in the future This type of altruism Is called reciprocal altruism

Social Learning Social learning Forms the roots of culture Culture can be defined as a system of information transfer through observation or teaching That influences the behavior of individuals in a population

Social Learning of Alarm Calls Vervet Monkeys: Infant monkeys give undiscriminating alarm calls at first But learn to fine-tune them by the time they are adults

Human behavior, like that of other species Is the result of interactions between genes and environment However, our social and cultural institutions May provide the only feature in which there is no continuum between humans and other animals