Unit 2: Social Behavior Flashcards
social behavior
the interactions between individuals of the same species
benefits of social behavior
- survival -> lower likelihood of predation
- feeding -> easier to find food; safer to feed
- mating -> easier to find/attract mates
calf defense by
musk oxen
the benefits of living in groups include
- less energy expended on vigilance
- decreased vigilance -> decreased food handling COST (in terms of time)
Leks are a good example of
the benefits (for some individuals) of group living
reproductive displays among sage grouse draw in more females when
multiple males are involved
density - dependent factors like [–] and [–] make group living [–]
density - dependent factors like predation and competition make group living costly
close association with conspecifics alllows
rapid infection of parasites and diseases
large groups can also mean
increased competition for food
The trade-off between risk and reward leads to
optimization
intermediate-sized baboon groups had
the least stress and the smallest food travel distance
territoriality has [–] but can mitigate [–] encounters
territoriality has energy costs but can mitigate agonistic encounters
territory
area defended against the intrusion of other
territoriality is used to protect resources such as
- food
- mate
- offpsring
territoriality is
transient or permenant
territoriality requires
active defense, territorial animals are mobile
dominace hierarchies maintain social order when
defending a territory is impractical
dominance hierarchies are defined by
social rank rather than space
first ranked individuals
dominate all other
territoriality is hard to maintain when
there is high population density, resource transcience, need to live in group
Social interactions can be categorized as + or - for the
donor and the recipient
cooperation and selfishness favored by
natural selection (benefit donor)
spitefulness is
never favored (no benefit)
altruism is a
- special case
- reduces direct fitness of the donor but increases inclusive fitness
altruistic
donor = losses (-)
reciever = gain (+)
spiteful
- donor = losses (-)
- reciever = losses (-)
cooperative
donor = gain (+)
reciever = gain (+)
selfish
donor = gains (+)
reciever = losses (-)
coefficents of relatedness describe
the likelihood that two individuals will share the same alleles
natural selection favors traits that increase
inclusive fitness (direct + indirect)
Total fitness of a gene responsible for a particuar behavior =
inclusive fitness
indirect fitness =
B x r
B = benefit
r = relatedness
inclusive (total) fitness =
direct + indirect fitness
altruism will evolve where:
C/B < r
C = cost to donor
B = benefit to recipient
r = coefficent of relationship
Hamilton’s Rule
Br > C
Wild turkey coalitions demonstrate
the benefits of altruistic behavior
LEK
- gathering of males to perform courtship displays
- more males -> more females pay attention
Wild turkey leks =
2+ males
indirect fitness benefit of LEK
associated males are full or half sibs (coefficent of relationship ave = 0.42)
offspring produced: dominant male (ave) = 6.1, solo male (ave) = 0.9
cost to a single male to join lek = 0.9
indirect fitness benefit = B x r = 6.1 x 0.42 = 2.6
“Helpers at the nest” increase their
inclusive fitness when likelihood of individuals success is low
one of the costs associated with kin selection is described as
“Parent/Offspring Conflict”
Parent/offspring conflict
parent and offspring differ over optimal level of parental investment
parent’s dilemma
current reproductive effort vs future efforts
Parental investment may be
an “actractiveness” factor in mate choice
fitness of an individual progeny generally increases with
parental expenditure
parental optimum differs from
the optimum for individual progeny, setting up a conflict of interests between parents and progeny
In belding’s ground squirrels, females
risk death more often than would be expected
females are more likely to be related to
their co-foragers
eusocial groups exhibit the
highest level of organization
eusocial groups
- large number of non-reproductive individuals
- several adults living together in groups
- overlapping generations
- cooperation in nest building and brood care
- reproductive dominance by one or a few individuals, including the presence of sterile castes
eusociality is limited among
insects to isoptera (termites) and hymenoptera (ants, bees, wasps), and to one mammal, the naked mole rat
naked mole rat eusociality
- live in large colonies, presided over by a queen
- only thr queen and a few select males breed
- rest of the colony – all members of the same family – work together to raise young and maintain the colony
- wild colonies range in size from 20 to 300 individuals, with an average colony consisting of 75 individuals
in bees relatedness is skewed by
haploidy/diploidy sex determination
bees
females are
diploid
bees
males are
haploid
bees
dominated by
a queen, only the queen breeds
bees
sterile worker caste =
female
bees
reproductive cast =
male and female
bees
caste determined by
nutritioon during larval development
bees
because of haplodiploidy in bees, sisters have [–] of their genes (on average)
75%
bees
because female share [–] the same genes from their father and an average of [–] from their mother, the average coefficent of relatedness among workers is [–], much higher than mammal sibilings
because female share 100% the same genes from their father and an average of 50% from their mother, the average coefficent of relatedness among workers is 75%, much higher than mammal sibilings
