what do i do? i study behavior i look at an animal’s adaptations to its environment i study...

What do I do?

I study behavior

I look at an animal’s adaptations to its environment

I study Evolution

Animal BehaviorAnimal Behavior

Observe a behavior, ask 2 Observe a behavior, ask 2 questions?questions?

1) Why does animal have this 1) Why does animal have this behavior?behavior?

2) How does animal carry out this 2) How does animal carry out this behavior?behavior?

Animal BehaviorAnimal Behavior

Why?Why? Ultimate causationUltimate causation = evolutionary basis = evolutionary basis

for existence of behaviorfor existence of behavior How?How?

Proximate causationProximate causation = immediate cause = immediate cause and/or mechanisms underlying behaviorand/or mechanisms underlying behavior

What is Behavioral What is Behavioral Ecology?Ecology?

1) The study of how an animal’s 1) The study of how an animal’s behavior contributes to its survival behavior contributes to its survival and reproductionand reproduction

OROR

2) How natural selection has 2) How natural selection has shaped the evolution of behaviorshaped the evolution of behavior

The ultimate questions

Behavioral ecology Behavioral ecology emphasizes evolutionary emphasizes evolutionary

hypotheseshypotheses Behavioral EcologyBehavioral Ecology: Study of how : Study of how

organisms increase Darwinian fitness organisms increase Darwinian fitness through optimal behavior through optimal behavior

If you can optimize behavior, then:If you can optimize behavior, then: behavior must be genetically influencedbehavior must be genetically influenced behavior is subject to natural selectionbehavior is subject to natural selection

Cost/Benefit Approach

B > C

How does a behavior benefit an individual?

Benefit (and cost) in terms of reproductive success!!

Critical part of the adaptationist program is that all traits have negative and positive effects on an individual’s reproductive success (I.e. costs and benefits). In order to be selected for, a trait must confer more positive (benefit) than negative (cost).

Two main methods:

ExperimentationComparative studies

How do we test adaptationist hypotheses

The Experimental MethodThe Experimental Method

Example : Eggshell Removal by Gulls:

Black-headed Gulls: parents always pick up the freshly hatched eggshell, and carry it away from the nest.

Why? Although the young and eggs are well camouflaged, the inside of the eggshell is white and very conspicuous.

hypothesis eggshell removal behavior is adaptive because it reduces the risk of predation.

Benefit: reduces predation

Cost: virtually no energy or time cost in moving the egg shell, but the parent must leave the new nestlings unattended.

Can you think of a test of this hypothesis?

Test: •put out cryptic eggs (n = 150) in artificial nests on the ground.

•Next to some (randomly distributed) put some broken egg shell.

•Check "nests" frequently, and record which are preyed on.

The Comparative MethodThe Comparative Method

1. Comparison among individuals of 1. Comparison among individuals of the the same speciessame species

2. Comparison between closely 2. Comparison between closely related related species in different species in different environmentsenvironments


1. Comparison among individuals of the 1. Comparison among individuals of the same species same species

E.g. Comparing individuals that hang out in groups vs. those that are solitary


2. Comparison between closely related 2. Comparison between closely related species in different environmentsspecies in different environments

Must be careful of divergent and convergent evolution!!!

(need to know an accurate phylogeny)

Behavioral Ecology deals Behavioral Ecology deals with many topics including:with many topics including:

foraging strategiesforaging strategies Predator/prey dynamicsPredator/prey dynamics Optimal foragingOptimal foraging

communicationcommunication alternative reproductive strategiesalternative reproductive strategies mating systemsmating systems

Sexual selectionSexual selection Parental careParental care

social systemssocial systems

Optimal means maximize Optimal means maximize benefit and minimize costbenefit and minimize cost

organisms should maximize organisms should maximize reproductive successreproductive success

Sometimes it is difficult to easily Sometimes it is difficult to easily see what the benefit of behaviors see what the benefit of behaviors could be…could be…

Why are animals social? Why group?

Costs of groupingCosts of grouping

Increased conspicuousnessIncreased conspicuousness Increased disease/parasitesIncreased disease/parasites Increased competition for resourcesIncreased competition for resources Increased risk of infanticide or Increased risk of infanticide or

brood brood parasitismparasitism

1) Increased conspicuousness

Black-tailed prairie dogs: larger colonies have greater # parasites

2) Increased parasitism

Benefits of groupingBenefits of grouping

Detection and Defense against Detection and Defense against PredatorsPredators

Finding foodFinding food Cooperative defense of territoryCooperative defense of territory ThermoregulationThermoregulation

1. Detection and Defense against Predators

1. Get in a crowd 2. Watch together

3. Defend as a group

b) Feeding efficiency

Examples: lions, orcas

c. Defend a territory together

e.g. Pallid Bats

d. Thermoregulation – huddle to stay warm

Non-social Highly social

Ground squirrel sociality

. .

N

Windhoek

Study site

Female Social GroupsFemale Social Groups

1-3 adult females and up to 9 subadults of 1-3 adult females and up to 9 subadults of either sexeither sex

One female social group in a burrow clusterOne female social group in a burrow cluster

Female philopatry and male-biased Female philopatry and male-biased dispersaldispersal

Share sleeping burrows and a feeding rangeShare sleeping burrows and a feeding range

Litter size is 1-2, with no male parental care Litter size is 1-2, with no male parental care

Males live in ALL MALE BANDS

• number up to 19 males • together throughout the year• live separately from female groups• form temporary sub-bands•NOT TERRITORIAL

Why do males live in groups?

1. Enhanced thermoregulation

0 5 10 15 20 250

5

10

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Mal

e gr

oup

size

Minimum temperature ( C) o


1. Enhanced thermoregulation

2. Aggregations around females

-3 -2 -1 0 10

1

2

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Days from oestrus

Mea

n in

tera

ctio

ns/h

22

30

27

21

18

-5 -4 -3 -2 -1 0 1 2 3 4 50

2

4

6

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10

(5)

(9)

(11)

(17)

(25)

(41)

(28)(20)

(11)

(12)

(10)M

ean

grou

p si

ze

Days from estrus

*

**

* *

*


1. Enhanced thermoregulation2. Aggregations around females3. Information exchange

Information Exchange

Predictions:

1. Older males would be better at finding females

Dominant (= older) males were more likely to find estrous females than subordinate (younger) males

(Spearman’s Rank Correlation, P < 0.025)


Predictions:

1. Older males would be better at finding females2. Younger males should prefer to associate with

older males in order to find females


Predictions:

1. Older males would be better at finding females2. Younger males should prefer to associate with older

males in order to find females3. Also predicts males that tend to hang out in larger

groups would have more information and thus be able to find more estrous females


1. Enhanced thermoregulation2. Aggregations around

females3. Information exchange

4. Enhanced predator avoidance

a) Vigilanceb) Mobbing

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erc

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s ingle

grouped

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Mobbing!!

• Less exposure time

• Dilution effect

Individuals in larger groups are at less risk

Prediction - Group size:

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5

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25

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Group size

Ave

rag

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(min

)

Mobbing duration, per capita

Spearman’s, P<0.01Larger groups have less exposure time

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1

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Group size

Mo

bb

ers

Number of mobbers

Spearman’s, P<0.05Larger groups can benefit from the dilution effect

So Benefit to groupingSo Benefit to grouping

But what about the costs again…for But what about the costs again…for males what would be the greatest males what would be the greatest cost, in terms of reproductive cost, in terms of reproductive success, with hanging out with other success, with hanging out with other males?males?

Competition for females

The evolution of mating systems

What are the important factors?

2 major factors:

(1) Distribution of resources in time and space(2) Male parental care – is it needed for offspring survival?

(1)Distribution of resources in time and space

a) Spatial distribution of resources:Would this be important to males or females?

Female distribution theory!

Males respond spatially to what females are doing!

b. Temporal distribution of resources – degree of asynchrony of female estrus

How could this affect the mating system?

Complete synchrony = monogamySlight asynchrony = territorialityHigh asynchrony = dominance hierarchy

(2) Parental Care

Factors influencing mating systems

Is it needed?

Lots of variability.

Types of mating systems

Balance between environmental factors and phylogentic constraints!

Non-social

Highly social

Monogamy to polygyny to polyandry

No male parental care!

1) Defense polygyny (territoriality)

2) Non-defense polygyny (dominance hierarchy)

3) Competitive searching (scramble competition)

Male Mating Strategies

Cape ground squirrel - how do males determine access to females

More infoMore info

Linear dominance hierarchy amongst Linear dominance hierarchy amongst malesmales

estrous lasts about 3.1 hoursestrous lasts about 3.1 hours no synchrony in breeding within or no synchrony in breeding within or

between social groupsbetween social groups females can breed throughout the females can breed throughout the

yearyear

Remember males are not territorialRemember males are not territorial

Therefore can’t be defense polygynyTherefore can’t be defense polygyny

Older males (more dominant) are better at finding females than are younger (subordinate) males

So maybe we have So maybe we have competitive searchingcompetitive searching going on!!!! going on!!!!

BUT

0 1 2 3 4 5 6 70

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Annual number of Mates

Fre

quen

cy

Male Cape ground squirrels mate success:

Average = 2.3 females per year

Dominance vs. mate Dominance vs. mate successsuccess

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Med

ian

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Rank

Can we conclude it is non-defense Can we conclude it is non-defense polygyny?polygyny?

NONO

1 2 3 4 5 6 7 8 9 100

1

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Fre

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Number of mates per estrus

Female Cape ground squirrels:

Polyandry????Polyandry????

Sperm competitionSperm competition

Sperm compete in the reproductive Sperm compete in the reproductive tract of femalestract of females

Studying mating systems and Studying mating systems and reproductive strategiesreproductive strategies

Really looks at behavioral Really looks at behavioral adaptations and directly assesses adaptations and directly assesses how they affect reproductive success how they affect reproductive success

And that looks directly at And that looks directly at natural selection!!!natural selection!!!

what do i do? i study behavior i look at an animal’s adaptations to its environment i study...

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