Territoriality

Question 1

evolutionary game theory

• what is it?
• why do we need it?

Answer 1

application of game theory to interaction-dependent strategy evolution in populations

the costs and benefits of actions depend on behaviour of other individuals in the population

Question 2

key components of a game-theoretic model

Answer 2

players
= participants in game (2-player of multiple-players)

payoffs
= costs + benefits of actions

actions
= option an animal can choose

decision mechanisms
= single or repeated, simultaneous or sequential

Question 3

evolutionary stable strategy (ESS)

Answer 3

set of behaviours adopted by all players
that cannot be invaded by any alternative strategy
that is initially rare

Question 4

Hawk-Dove game

- rules

Answer 4

2 animals meet
- both want access to a resource value V

play Hawk
= attack opponent + may gain full V
BUT has cost of injury, C

play Dove
= don’t fight

Question 5

Hawk-Dove game

- Payoff matrix

Answer 5

2 doves
= V/2

focal Dove vs Hawk
= 0

focal hawk vs dove
= V

focal hawk vs hawk
= (V/2) - C

Question 6

if v/2 < C then what’s the best strategy?

Answer 6

frequency dependent:

only doves in population
-> play hawk

only hawks in population
-> play dove
(at least you don’t pay the -ve cost) (0 > -ve)

Question 7

if V/2 > 2C then what’s the best strategy?

Answer 7

always play hawk

- cannot lose

Question 8

Hawk-Dove game

- ESS

Answer 8

p that an individual plays Hawk

p* = V/2C
when V/2C

Question 9

Hawk-Dove game

- cichlid fish example

Answer 9

if asymmetry in fighting ability
-> contest ends in early phases

if individuals matched
-> contest ends in final phase (costs escalate -> dangerous fighting)

Question 10

Hawk-Dove game

- golden orb weaver spider example

Answer 10

males mate only once + guard against rivals

mated males won contests against virgin males (even if physically inferior) (virgins give up as can find another female)

contests between mated males = high freq of injury

Question 11

ideal free distribution
Fretwell 1972
- 2 rules

Answer 11

> every individual is free to choose where to go

> no limit to no. of competitors

Question 12

ideal free distribution

- predicted pattern

Answer 12

1st arrivals go to rich habitat

more competitors lower the rewards per individual by resource depletion

at a point poor habitat will be equally attractive

SO the 2 habitats should be filled so that the rewards per individual are the same in each

Question 13

ideal free distribution

- sticklebacks

Answer 13

add 2x as much food to side B of tank

still had 2 fish left at side A
(not 0)
-> although those at B may be getting 2x as much food.. they’re competing with 2x fish

no. of fish is in proportion to the amount of resources available

Question 14

what is the main point of ideal free distribution?

Answer 14

all about individual choice in a population in terms of distribution

Question 15

resource use by waders

- 2 predictions for distribution

Answer 15

surface distribution model
= equal densities over total surface
- only depends on amount of individual space

ideal free distribution model
- depends on space and richness for feeding

Question 16

resource use by waders (Red knots)

- conclusion if resources are fixed

Answer 16

ideal free distribution model

Question 17

resource use by waders

- why aren’t resources fixed over time?

Answer 17

depletion by predators

reproduction of prey

emigration and immigration of prey to + from different patches

Question 18

resource use by waders

• experiment
• results

Answer 18

exclude waders from some patches
-> after 13 days compare prey densities between excluded + control sites

inside enclosure
- prey densities increased

outside
- densities decreased

Question 19

resource use by waders

- what does the experiment show?

Answer 19

if you force individuals to not distribute themselves
-> it will effect the prey

predators modify their own environment in a way that affects resource availability

Question 20

dispersal

• natal
• adult
• what happens after the dispersal stage?

Answer 20

young animals leave home

adults change sites to find better feeding location, mate or breeding territory

animals often stay in/return to the same location for rest of life

Question 21

dispersal

• why disperse?
• cost
• benefit
• costs + benefits are often…? which leads to..?

Answer 21

> forced to
benefits of dispersing exceed its cost

mortality

outbreeding

sex-specific
-> sex difference in dispersal propensity

Question 22

dispersal influences population structure via?

Answer 22

emigration

immigration

Question 23

what are meta-populations?

Answer 23

group of populations separated by space but consist of the same species

made up of sources and sinks

drives connectedness
- more related populations in if they have more movement between

Question 24

conservation importance using meta-populations

Answer 24

suitable habitats are rapidly fragmenting globally

efforts should focus on sources
- can supply multiply sinks and doesn’t depend on another population for individuals

Question 25

territory

- define

Answer 25

an area defended by an individual against the intrusion of others

e.g. mating or resource-rich habitat

Question 26

dragonflies + damselflies patrol and defend their territories

Answer 26

body mass didn’t predict the outcome of fights

but fatter males won more fights than lean fat males
-> able to sustain fights + aerial chases for longer

Question 27

how large should a territory be?

Answer 27

based on economic defendability
= optimal size where max difference between benefits and costs

benefit increases with territory size
cloys of maintaining territory also increases rapidly

Question 28

territory area vs cost/benefit model

• optimal territory size
• used to generate predictions e.g…?

Answer 28

where slope of costs + benefits are equal

smaller territories are expected in better habitats

Question 29

degree of territoriality varies with resource abundance

e.g. New Holland honeyeater

Answer 29

territory size decreases with the abundance of nectar-producing Banksia flowers

more resource rich
-> easier for individuals to get the most out of the area they’re defending

Question 30

population regulation

- density-dependent factors

Answer 30

population growth rate decreases as population size + crowding increase

e.g. effects of food supply + potential breeding sites

Question 31

population regulation

- density-independent factors

Answer 31

influence populations independently from population size

e.g. the effects of weather + catastrophic events

Question 32

migration

- what are the characteristics of seasonal environments?

Answer 32

polar regions + temperate climate

seasonal environments in tropics e.g. grasslands, wetlands

Question 33

migration in insects e.g. Monarch butterflies

Answer 33

spring, adults leave Mexico

mating occurs + females lay eggs in north Mexico/south Texas

caterpillars hatch + develop into adults that move north

autumn, all adults move to Mexico

Question 34

benefits of migration

Answer 34

avoid seasonal decline of resources

continue foraging using long daylight hours

Question 35

costs of migration

Answer 35

starvation + death
- by flying over water or deserts

predation
- e.g. Eleonora falcons time their breeding to coincide with migration of passerine birds

Question 36

how do animals find their way when migrating?

Answer 36

inexperienced
- clock + compass strategy

experienced
- map-based navigation

Question 37

clock + compass strategy

Answer 37

fly in direction A for x days
-> then direction B for y days

only need an inherited migratory direction + a circannual clock + 1 compass e.g. sun

Question 38

map-based navigation

Answer 38

experienced migrants can achieve few m precision over 5000km

olfactory map - homing pigeons

landmarks - pigeons