Territoriality, Habitat Selection, and Aggression
Territoriality
•
When is it beneficial?
1. When limited resources are clumped and
ephemeral?
2. When limited resources are uniformly distributed in
time and space?
Environmental factors and territory size in
kites
• Research question: What factors affect the size of
a territory? (Dunk & Cooper 1994)
• Hypothesis: The density of resources and the
density of competitors affect territory size
• Prediction: Territory size will decline with an
increase in resource density or competitors
Environmental factors and territory size in
kites
• Methods:
– White-tailed kites (Elanus leucurus)
– Uniquely marked individuals
– Recorded feeding territory size
– Estimated abundance of food items
(voles)
– Estimated abundance of avian
competitors for food (hawks, kites,
falcons, and owls)
Environmental factors and territory size in
kites
• Results:
– Territory size declined with
increasing competitor abundance
– Territory size declined with
increasing number of voles
Habitat Selection
• Most animals have habitat preferences
• Natural selection has lead to the evolution of
species matched to particular environments
• Conclusion:
– Both competitor abundance and
food density affect territory size
in kites
Kirtland’s warbler
Habitat Preferences
• Endangered
• Breeds only in jack pine
N lower peninsula - MI
• Nests exclusively beneath
young jack pines (5-20ft)
• Well-drained, sandy soils
Conspecific density can influence
reproductive success in a preferred habitat.
Good
Fair
Poor
x
x
x
x x
x
x
x
x
x
x
x
x
x x
x x
x
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The reproductive
success of individuals
in highly preferred and
less preferred habitats
may be the same (on
average) if the density
in preferred habitats is
high.
Resource availability and the presence of others influence habitat
selection
• Ideal free distribution model assumes:
– Individuals attempt to maximize fitness
– Habitat locations differ in resources
– Fitness is negatively density-dependent
– Individuals are equal competitors
– Individuals are free to move at no cost
Habitat preference in aphids
• Territorial poplar aphid
• Each spring, 1000s of
females compete to form
galls on the midribs of poplar
leaves
• Preferred position is at the
base of a large leaf
• Inferior competitors must
make the best of their bad
situation
– Smaller, unoccupied leaf?
– 2nd gall on larger, occupied leaf?
The ideal free distribution model
• IFD predictions:
1. Individuals will settle in habitats
based on the relative fitness
payoffs: the number of individuals in
each habitat will be proportional to
habitat quality
2. All individuals will have the same
fitness no matter where they settle
Habitat preference in aphids
• The reproductive success of the second colonist on
medium and large leaves is essentially the same as
that of a single aphid on a small leaf
parthenogenic
Since habitat preferences are adaptive, individuals inhabiting
prime real estate usually have greater reproductive success
• Source habitats
– Better quality
– Better competitors
– Population grows
• natality>mortality
• Sink habitats
–Poorer quality
–Poorer competitors
–Population declines
• natality<mortality
–Population replenished via
immigration from source
habitats
(Dias 1996)
Conspecific attraction
• Conspecific attraction
– Individuals prefer to settle near others
• Two hypotheses:
1. Allee effect: when population size is low, fitness
increases with density
2. Conspecific cueing: the presence of another is a cue to
a high-quality location
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Allee Effect
Why might it be advantageous for animals to choose to live in
an area with a higher density of conspecifics?
1. Mate access
•
•
Why might it be advantageous for animals to
choose to live in an area with a higher density of
conspecifics?
it can be difficult to find a mate at low population densities
2. Cooperative defense
•
“more eyes”, Selfish herd, Dilution effect
3. Cooperative feeding
•
learning about resources, eavesdropping on the location of food
•
group hunting - access to larger prey
4. Environmental conditioning / habitat alteration
•
Why did focal males prefer the occupied bush?
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Conspecific cueing in American redstarts
• Research question: How do male American
redstarts select habitat patches? (Hahn & Silverman
2006)
• Hypothesis: Conspecific cueing is used to find and
settle on territories
• Prediction: Newly settling birds (yearlings and
immigrants) will use the presence of singing males
as a cue to the location of high-quality habitat for
settling, while returning males will not
Conspecific cueing in American redstarts
• Methods:
– American redstart (Setophaga ruticilla)
– Captured and banded birds on 12 plots
– Six treatment plots played conspecific song
– Six control plots played no song
– Surveyed each plot four times per week to record the
arrival of males, along with their age and status
(returning or immigrant)
Conspecific cueing in American redstarts
• Results:
– New immigrants strongly
preferred playback plots
– Returning adults and yearlings
showed no preference
• Conclusion:
– Conspecific attraction is an
important mechanism for habitat
selection for older immigrant
males
The density and behavior of conspecifics can affect
an individual’s:
•
Territory size
•
Habitat selection
•
Fighting behavior
Conspecific cueing in American redstarts
• Why might returning adults
not show a preference for
plots with calling males?
• and yearlings?
Why don’t animals simply
to try to kill their rivals?
Now a female is watching
Let’s play a game!
•
•
You are all male elephant seals. Let’s battle!
•
You will interact with 5 other students one at a time
•
Each time, you decide whether to fight or flee
•
If you both fight determine the winner by playing rock-paper-scissors
•
Winner: 10 points
•
Loser: -10 points
•
•
•
If one of you fights and the other flees
•
Fighter wins 10 points
•
Fleer: wins 0 points, no cost
•
If you both fight determine the winner by playing rock-paper-scissors
•
Winner: 50 points
•
Loser: -10 points
If one of you fights and the other flees
•
Fighter wins 50 points
•
Fleer wins 0 points
If you both flee, play rock-paper-scissors.
If you both flee, play rock-paper-scissors.
•
Winner: 10 points
•
Loser: wins 0 points, no cost
•
Winner: 30 points
•
Loser: 0 points, no cost
Now you are all male elephants with huge
tusks
•
•
•
The decisions of opponents and resource value
affect fighting behavior
If you both fight determine the winner by playing rock-paper-scissors
•
Winner: 10 points
•
Loser: -50 points
• Hawk-dove model
– Game theory model used to understand variation in
fighting behavior
– Assumes two strategies: hawk (fight until victory or injury)
and dove (never fight but uses low-cost display)
– Payoffs for an individual depend on the strategy of the
opponent, along with the benefits and costs of fighting
– Predicts an evolutionary stable strategy (ESS): both hawks
and doves exist in a population with equal fitness
If one of you fights and the other flees
•
Fighter wins 10 points
•
Fleer wins 0 points, pays no cost
If you both flee, play rock-paper-scissors.
•
Winner: 10 points
•
Loser: wins 0 points, pays no cost
Hawk-Dove Model
Hawk
Dove
Opponent Opponent
Hawk
Payoff
Dove
Payoff
0.5 (B-C)
0
B
0.5 B
Hawk-Dove Model
Hawk
Dove
Opponent Opponent
•
What would happen if a
hawk tries to invade a
population of all doves?
Hawk
Payoff
0.5 (B-C)
B
Dove
Payoff
0
0.5 B
Hawk-Dove Model
•
What would happen if a
dove tries to invade a
population of all hawks?
•
assume C > B
Hawk-Dove Model
Hawk
Dove
Opponent Opponent
Hawk
Payoff
0.5 (B-C)
•
What would happen if a
dove tries to invade a
population of all hawks?
B
•
Dove
Payoff
0
0.5 B
Hawk
Dove
Opponent Opponent
Hawk
Payoff
0.5 (B-C)
B
Dove
Payoff
0
0.5 B
what if B > C?
The decisions of opponents and resource value
affect fighting behavior
• Sequential assessment model
– Game theory model used to understand fighting
– Individuals can exhibit many different strategies, not just hawk
and dove
– Individuals assess the relative fighting ability of their
opponent
– The predicted ESS behavior: fight as long as the potential
benefit of winning exceeds the cost of continuing to fight
– Low-cost behaviors should be used early in fights
– Fights between evenly matched opponents will last longer than fights
between unequally matched opponents
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Salamander fights for mates
• Research question: What affects the duration of
fights between male salamanders? (Verrell 1986)
• Hypothesis: The size (value) of a female affects
male fighting behavior
• Prediction: Males will fight longer for larger
(more fecund) females
From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press
Salamander fights for mates
• Methods:
– Red-spotted newts
(Notophthalmus
viridescens)
– Staged encounters
between size-matched
males over a female
– Recorded the duration
of wrestling between the
males
Salamander fights for mates
• Results:
– The duration of wrestling was
positively correlated with
female body length
• Conclusion:
– The value of a resource
affects fighting duration in
red-spotted newts
If you had to bet on who will win
a fight, the territory owner or an
intruder, which one would you
bet on?
a. Territory owner
b. Intruder