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20 Cards in this Set

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territoriality is aggressive defense of home range or some other area
Disadvantages to aggression
-potential for wounding or death during fights
-aggression is conspicuous and can attract predators
-aggression is costly in terms of time and energy(muscular exertion; costly morphological structures such as armor, weapons or oranaments)
-aggression may cause physiological stress
-"aggressive neglect" or other inadvertent damage to aggressive individual's own reproductive success
ex. Austrawlian magpies fight so much they fail to feed offspring or defend them from predators
ex.male elephant seals and other pinnipeds often crush some of their own young while fighting with other males
Aggression favored only when it gains a resouce necessary for reproductive success(either through increased survival or increased breeding success)
1. resource must be limiting(must be competition)
2.resource must be defensible
3.The fitness benefits gained must exceed the fitness costs of aggression. (aggression is only favored by selection if it increases reproductive success in some manner)
selection tends to increases benefit:cost ratio by reducing the cost of aggressive acts
-makes aggression more profitable and allows the frequency or intensity of aggression to increase without an increase in fitness costs.
Morphological modification
defensive and offensive capabilities
-large body size, big teeth, "armor" protection, strong claws
Behavioral modification
-ritualization means that aggressive acts are largely exercises in communication, rather than actual combat.
-ritualization popssible because it is not necessary, in many cases, for the animals to actually fight in order to determine who is going to win.
-selection will favor mophology and behavior that communicate level of aggression and combat value
-ritaulization produces aggressive displays
Appeasement behaviors
-they reduce the level of aggression of the winner, usually permitting the loser to escape without further damage
-these displays often the opposite of aggressive displays - Darwin's "principle of antithesis"
animals determine the likely outcome of a fight ASAP, and then quit immediately if they are going to lose. If individuals repeatedly encoutner each other, a Dominance Hierarchy is set up
Ex of dominance/subordinance displays
mountain sheep horn display
-honest communication because the signal(horn size) indicates combat ability
most species hold one form of territory or another
Home range
all the areas an animal usues, but a territory is a defended, exclusive part of the home range
Classification of territories
Type A
Type B
Type C
Type D
A:large, exclusive area with everything the animals needs; territory=home range
B:an area containing only some of what the animal needs(ex nest site, some of food supply) Territory<home range
C:nest site only, in colonial species
D:mating site only(leks)

-most real territories are intermediate)
Rules of territory
-territory implies defense
-territoriality is a form of aggression
-territory is a resource that is limiting to reproduction
-its defense must be feasible and economical
-costs of defense must be less than the fitness benefits
Ex of economics of territoriality
-golden-winged sunbirds
-territory defense depended on the quality of the resource being defended(flowers containing nectar) and the number of competitors
-the birds are territorial if it increases their energy intake
-the cease to be territorial when the behavior is "uneconomical"
Territory size is quite plastic, depending on circumstances
ex. pomarine jaegers eat lemmings, territory size depends on lemming density
Ex factors influencing territoriality
1. pied wagtails:defend a stretch of riverbank about 600m long. The rate of food acquisition in territory holders is less than for nonterritorial flocking birds. But territory is a hedge against snowy weather. After a snowstorm, riverbanks may be the only food source and 600m is the necessary length of riverbank
2.Tawny owls:territory does not change much in food rich and food poor years. what does change is the number of offspring - pairs of owls hold a territory large enough to see them through bad years
When there is competition for territories one would predict that the good habitats should fill up first, and then the animals should move into the less desirable areas.
-when these also fill,additional animals may become NONTERRITORIAL "floaters"
exs of "floaters"
-rufous-collared sparrows
-wood warblers
-great tits
-artic ground squirrels
In some species nonterritorial birds may breed but are less successful than territory holders even though they avoid the costs of defending territories (great tits)
-therritoriality is beneficial
Interspecific territoriality
-less common than intraspecific territoriality
-greatest competitiors are likely to be conspecifics
-evolves under the same rules that govern intraspecific territories
-limiting, economically defensible resources
-interspecific territoriality and aggression often seen when two species compete for the same food resourves(raptors, chipmunks, bell miners, psyliid bugs and lerps)