Chapter 51Behavioural Ecology

Studying behaviour• Humans have probably studied animal

behaviour– for as long as we have lived on Earth

• As hunters– knowledge of animal behaviour was essential to

human survival

• The modern scientific discipline of behavioural ecology– extends observations of animal behaviour by

studying how such behaviour is controlled and how it develops, evolves, and contributes to survival and reproductive success

• Concept 51.1: behavioural ecologists distinguish between proximate and ultimate causes of behaviour

• The scientific questions that can be asked about behaviour can be divided into two classes– those that focus on the immediate stimulus and

mechanism for the behaviour– those that explore how the behaviour

contributes to survival and reproduction

What Is behaviour?• Behaviour– is what an animal does and how it does it– includes muscular and nonmuscular activity

Figure 51.2

Dorsal fin

Anal fin

• Learning– is also considered a behavioural process

Proximate and Ultimate Questions• Proximate, or “how,” questions about behaviour– focus on the environmental stimuli that trigger

a behaviour– focus on the genetic, physiological, and

anatomical mechanisms underlying a behavioural act• e.g. How does day length influence breeding in birds?

– increased day (environmental stimuli) length triggers hormone production associated with reproduction like singing & nest building

• Ultimate, or “why,” questions about behaviour– address the evolutionary significance of a

behaviour• Why did natural selection favour this type of

behaviour?

• Proximate & ultimate causation are linked• e.g. many animals breed during spring & summer

because of warmth of seasons– abundant food supply may increase chances of

offspring surviving

Ethology• Ethology is the scientific study of animal behaviour

– particularly in natural environments

• Karl von Frisch, Konrad Lorenz, & Niko Tinbergen• What are the questions that must be answered to

understand any behaviour?1. What is the mechanistic basis of the behaviour, including

chemical, anatomical, physiological mechanisms?2. How does development of an animal influence behaviour?3. What is the evolutionary history of the behaviour?4. How does behaviour contribute to survival & reproduction

(fitness)?

Behaviours typically studied by ethologistsFixed Action Patterns

• A fixed action pattern (FAP)– is a sequence of unlearned, innate behaviours

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 behaviour– 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

behaviour occurs

Figure 51.3b

(b) The realistic model at the top, without a red underside, produces no The realistic model at the top, without a red underside, produces no aggressive response in a male three-spined stickleback fish. Theaggressive response in a male three-spined stickleback fish. Theother models, with red undersides, produce strong responses.other models, with red undersides, produce strong responses.

• Proximate and ultimate causes for the FAP attack behaviour in male stickleback fish

Figure 51.4ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreasesthe chance that eggs laid in his nesting territory will be fertilized by another male.

Behaviour: 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 stimulusthat releases aggression in a male stickleback.

Imprinting• Imprinting is a type of behaviour– 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 behaviours can be learned

• An example of imprinting is young geese– following their mother

• Konrad Lorenz showed that– when baby geese

spent the first few hours of their life with him, they imprinted on him as their parent

• There are proximate and ultimate causes for this type of behaviour

Figure 51.5

Behaviour: 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.

• Conservation biologists have taken advantage of imprinting– in programs to save the whooping crane from

extinction

Figure 51.6

• Concept 51.2: Many behaviours have a strong genetic component

• Biologists study the ways both genes and the environment– influence the development of behavioural

phenotypes• nature-versus-nurture issue is not about whether

genes or environment influence behaviour– how are both involved?

• Behaviour that is developmentally fixed– is called innate behaviour and is under strong

genetic influence

Directed Movements• 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

• Pill 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

Figure 51.7b

Direction

of river

current

(b) Positive rheotaxis keeps trout facing into the current, the direction from which most food comes.

Migration• Many features of migratory behaviour in birds– have been found to be genetically programmed

Figure 51.8

• e.g. blackcap = warbler – range from Cape Verde Islands to N. Europe

• behaviour = N. Europe populations migrate at night

-CVI populations do not migrate-NE pop. exhibit migratory restlessness

when held in captivity• experiment = cross German with CVI

blackcaps• result = 40% of offspring show migratory

restlessness• conclusion = must be under genetic control

Animal Signals and Communication• In behavioural ecology– a signal is a behaviour that causes a change in

another animal’s behaviour• 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

• common among mammals & insects• often relate to reproductive behaviour

– context is important• e.g. honey bee hive

– inside hive pheromones maintain social order

– outside triggers mating with queen

• 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 thebottom of the aquarium and reduce their movement.

Auditory Communication• Experiments with various insects

– have shown that courtship songs are under genetic control

Charles Henry, Lucía Martínez, and ent Holsinger crossed males and females of Chrysoperla plorabunda and Chrysoperla johnsoni, two morphologically identical species of lacewings that sing different courtship songs. EXPERIMENT

SONOGRAMS Chrysoperla plorabunda parent

Vibration volleys

Standard repeating unit

Chrysoperla johnsoni parent Volley period

crossed with

Standard repeating unit

The researchers recorded and compared the songs of the male and female parents with those of the hybrid offspring that had been raised in isolation from other lacewings.

Volley period

The F1 hybrid offspring sing a song in which the length of the standard repeating unit is similar to that sung by the Chrysoperla plorabunda parent, but the volley period, that is, the interval between vibration volleys, is more similar to that of the Chrysoperla johnsoni parent.RESULTS

The results of this experiment indicate that the songs sung by Chrysoperla plorabunda and Chrysoperla johnsoni are under genetic control.CONCLUSION

Standard repeating unit

Volley period

F1 hybrids, typical phenotype

Genetic Influences on Mating and Parental behaviour• A variety of mammalian behaviours– are under relatively strong genetic control

• Research has revealed the genetic and neural basis

– for the mating and parental behaviour of male prairie voles

– arginine-vasopressin (AVP)

Figure 51.11

• Concept 51.3: Environment, interacting with

an animal’s genetic makeup, influences the development of behaviours

• Research has revealed– that environmental conditions modify many of

the same behaviours

Dietary Influence on Mate Choice behaviour• One example of environmental influence on behaviour– is the role of diet in mate selection by Drosophila

mojavensis

• Laboratory experiments have demonstrated– that the type of food eaten during larval development

influences later mate choice in females

Figure 51.12

William Etges raised a D. mojavensis population from Baja California and a D. mojavensis population from Sonora on three different culture media: artificial medium, agria cactus (the Baja host plant), and organ pipe cactus (the Sonoran host plant). From each culture medium, Etges collected 15 male and female Baja D. mojavensis pairs and 15 Sonoran pairs and observed the numbers of matings between males and females from the two populations.

EXPERIMENT

When D. mojavensis had been raised on artificial medium, females from the Sonoran population showed a strong preference for Sonoran males (a). When D. mojavensis had been raised on cactus medium, the Sonoran females mated with Baja and Sonoran males in approximately equal frequency (b).

RESULTS

The difference in mate selection shown by females that developed on different diets indicates that mate choice by females of Sonoran populations of D. mojavensis is strongly influenced by the dietary environment in which larvae develop.

CONCLUSION

100

75

50

25

0Artificial Organ pipe cactus Agria cactus

Culture medium

With Baja males

With Sonoran males

(b)

Pro

porti

on o

f m

atin

gs b

y S

onor

an fe

mal

es

(a)

• Therese Markow and Eric Toolson proposed– that the physiological basis for the observed

mate preferences was differences in hydrocarbons in the exoskeletons of the flies

Figure 51.13

Social Environment and Aggressive behaviour• Cross-fostering studies in California mice and white-footed mice– have uncovered an influence of social

environment on the aggressive and parental behaviours of these mice

– California mice – monogamous, highly aggressive, extensive parental care

– white-footed mice – not monogamous, little parental care

Influence of cross-fostering on male mice

Table 51.1

Learning• Learning is the modification of behaviour– based on specific experiences

• Learned behaviours– range from very simple to very complex

Habituation• Habituation– is a loss of responsiveness to stimuli that

convey little or no information

Spatial Learning• Spatial learning is the modification of behaviour– based on experience with the spatial structure

of the environment

• In a classic experiment, Niko Tinbergen– showed how digger

wasps use landmarks to find the entrances to their nests

After the mother visited the nest and flew away, Tinbergen moved the pinecones a few feet to one side of the nest.

Figure 51.14CONCLUSION

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.

NestNo Nest

Cognitive Maps• A cognitive map– is an internal representation of the spatial

relationships between objects in an animal’s surroundings

– how do you distinguish between animal using landmarks & one using cognitive map?• e.g. corvids – store food in caches from which bird can

retrieve food later• pinyon jays & Clark’s nutcrackers store nuts in as

many as thousands of caches• can relocate caches • can also keep track of food quality

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

Figure 51.15

Before stimulus

Influx of water alone

Influx of alarm substances

Influx of pike odor

Day 1 Day 3

Control group

Control group

Experimentalgroup

Experimental group

Rel

ativ

e ac

tivity

leve

l

• Operant conditioning is another type of associative learning– in which an animal learns to associate one of its

behaviours with a reward or punishment

Figure 51.16

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• cognitive ethology – examines connection between

animal’s nervous system & it’s behaviour• how animal’s brain represents objects in environment

– many animals (including insects) capable of distinguishing “same” & “different” objects

• animals have substantial ability to process information

• problem solving behaviour highly developed in primates & dolphins, some birds especially crows, ravens, jays

• Problem solving can be learned– by observing the behaviour of other animals

Figure 51.17

Genetic and Environmental Interaction in Learning• Genetics and environment can interact– to influence the learning process

• Some songbirds have sensitive period for developing their songs– individuals reared in silence performed abnormal songs,

but if recordings of proper songs were played early in life of bird, normal songs developed

• Canaries exhibit open-ended learning where they add new syllables to their song as they get older