Territoriality Flashcards
evolutionary game theory
- what is it?
- why do we need it?
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
key components of a game-theoretic model
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
evolutionary stable strategy (ESS)
set of behaviours adopted by all players
that cannot be invaded by any alternative strategy
that is initially rare
Hawk-Dove game
- rules
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
Hawk-Dove game
- Payoff matrix
2 doves
= V/2
focal Dove vs Hawk
= 0
focal hawk vs dove
= V
focal hawk vs hawk
= (V/2) - C
if v/2 < C then what’s the best strategy?
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)
if V/2 > 2C then what’s the best strategy?
always play hawk
- cannot lose
Hawk-Dove game
- ESS
p that an individual plays Hawk
p* = V/2C
when V/2C
Hawk-Dove game
- cichlid fish example
if asymmetry in fighting ability
-> contest ends in early phases
if individuals matched
-> contest ends in final phase (costs escalate -> dangerous fighting)
Hawk-Dove game
- golden orb weaver spider example
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
ideal free distribution
Fretwell 1972
- 2 rules
> every individual is free to choose where to go
> no limit to no. of competitors
ideal free distribution
- predicted pattern
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
ideal free distribution
- sticklebacks
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
what is the main point of ideal free distribution?
all about individual choice in a population in terms of distribution
resource use by waders
- 2 predictions for distribution
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
resource use by waders (Red knots)
- conclusion if resources are fixed
ideal free distribution model
resource use by waders
- why aren’t resources fixed over time?
depletion by predators
reproduction of prey
emigration and immigration of prey to + from different patches
resource use by waders
- experiment
- results
exclude waders from some patches
-> after 13 days compare prey densities between excluded + control sites
inside enclosure
- prey densities increased
outside
- densities decreased
resource use by waders
- what does the experiment show?
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
dispersal
- natal
- adult
- what happens after the dispersal stage?
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
dispersal
- why disperse?
- cost
- benefit
- costs + benefits are often…? which leads to..?
> forced to
benefits of dispersing exceed its cost
mortality
outbreeding
sex-specific
-> sex difference in dispersal propensity
dispersal influences population structure via?
emigration
immigration
what are meta-populations?
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
conservation importance using meta-populations
suitable habitats are rapidly fragmenting globally
efforts should focus on sources
- can supply multiply sinks and doesn’t depend on another population for individuals
territory
- define
an area defended by an individual against the intrusion of others
e.g. mating or resource-rich habitat
dragonflies + damselflies patrol and defend their territories
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
how large should a territory be?
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
territory area vs cost/benefit model
- optimal territory size
- used to generate predictions e.g…?
where slope of costs + benefits are equal
smaller territories are expected in better habitats
degree of territoriality varies with resource abundance
e.g. New Holland honeyeater
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
population regulation
- density-dependent factors
population growth rate decreases as population size + crowding increase
e.g. effects of food supply + potential breeding sites
population regulation
- density-independent factors
influence populations independently from population size
e.g. the effects of weather + catastrophic events
migration
- what are the characteristics of seasonal environments?
polar regions + temperate climate
seasonal environments in tropics e.g. grasslands, wetlands
migration in insects e.g. Monarch butterflies
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
benefits of migration
avoid seasonal decline of resources
continue foraging using long daylight hours
costs of migration
starvation + death
- by flying over water or deserts
predation
- e.g. Eleonora falcons time their breeding to coincide with migration of passerine birds
how do animals find their way when migrating?
inexperienced
- clock + compass strategy
experienced
- map-based navigation
clock + compass strategy
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
map-based navigation
experienced migrants can achieve few m precision over 5000km
olfactory map - homing pigeons
landmarks - pigeons
