A group of individuals of the same species that is organized in a cooperative manner, extending beyond sexual and parental behavior.
Are there costs and benefits to living in a society?
most mammalian social systems are arrange matrilinearlly; mothers and their offspring may stay together and groups are this composed of mothers, daughters, aunts, and nieces
Because of the prevalence of polygyny, and associated tendency for males to disperse as they reach maturity, adult males are generally not related to other adults in the group. Males leave before they reach the age of maturity (sexually) and fathers leave before their daughters reach the age of maturity
Most complex social organizations are in what species?
Carnivores, Cetaceans, and Primates
Tend to be large and have large brains
Social terrestrial species
tend to forage above ground in open habitats during the daytime
When a mammal emits an alarm call, the caller is more likely to fall prey to the predator. The predator might abandon the hunt since they've been detected (caller is selfish) Other individuals may benefit (altruism)
Behavior that is potentially costly to the individual but beneficial to others
Cooperative Rearing of Young
is not common but it does occur in social carnivores and some rodents
Cooperative Rearing of Young in Carnivores (Lions)
Among carnivores, lionesses
share the nursing of cubs in the pride, and subordinate wolves
regurgitate food for the alpha female and her litter.
Cooperative Rearing of Young in Carnivores (Meerkat)
In mongooses and meerkats, subordinate females help rear the young of the dominant females.
Degrees of cooperation
The degree of cooperation
ranges from none to complex coalitions and alliances. In some species, kinship is important but in others coalitions among nonrelatives are also common, as in hamadryas baboons and chimpanzees.
Barbary Macques Bonding
male Barbary macaques have a better chance of bonding with each other when at least one is hauling
around an infant. the infant is used as a social tool-- the males however also have high stress levels because the children can get annoying
Agonistic buffering hypothesis
where males control their
relationships with other males in
the group using infants in what
are called triadic male-infant
The epitome of social organization is referred to as?
1. Cooperative care of the young
2. Reproductive castes with non-reproductive members
caring for reproductive nest mates
3. Overlap between generations such that offspring assist
parents in raising siblings
Organisms that have reached the level of Eusociality
the naked mole rat
Naked mole rat
the "queen" reproduces, mother and young are fed
(but not nursed) by male and female adults of the worker caste,
another caste kept the young warm . males of this caste bred with the queen.
Benefits of Mammals Living In a group
Benefits from Physical factors Protection against Predators Finding and Obtaining food
Benefits from Physical factors
White-footed mice frequently form communal nests in winter to huddle and conserve energy. Also Bats .
This benefit does not necessarily lead to organized social groups.
Protection Against Predators
Detection of and communication about danger is more rapid
when individuals are in groups and predator deterrence may be
enhanced by mobbing and group defense.
Many eyes hypothesis
individuals in large groups spend less time watching for predators and more time doing other activities such as eating.
Many eyes hypothesis ground squirrel
predators could approach within 3 m of solitary individuals but no closer than 300 m to grouped individuals before waves of alarm calls swept through the colony
Musk oxen form lines of defense
against wolf attacks.
African Wild Dogs
African wild dogs are cooperative
breeders living in packs of up to
20. Some will stay back and
protect the pups while the rest
Minimum pack size is 5,
more than that and some can stay
back. This minimum group size is
Finding and Obtaining Food
Wolves and lions are able to capture large species of prey - such
as moose or Cape Buffalo - that would not be possible for individuals.
Optimum Hunting Size
Optimum group size in lions varies depending on the prey they take - 2 lions in the case of eating Thomson's gazelle.
a behavior passed from one generation to the next
through the process of learning.
Big Horn Sheep reason for grouping
in bighorn sheep the locations of feeding areas and migration routes are remembered by older members of the band and this information is transferred to subsequent generations via tradition
Group Defense of Resources
Lion prides, wolf packs and African wild dogs are all territorial
and will defend resources to the death. In most cases the largest
Assembling Members for Location of Mates
males of several species defend small territories and display to attract females for copulation. Examples include hammer-headed bats, topi, and fallow deer.
Division of Labor Among Specialists
This feature is rare in mammals and is found only in naked mole rats.
Richer Learning Environment for Young:
This suggested to be very important for primates and cetaceans.
Dependence on learning provides for greater behavioral plasticity, but it requires a long period of physiological and psychological dependence
How much time do offspring spend with their parents?
Large brained and highly social
species of primates and dolphins spend as much as 25% of their
lives being dependent on parents and other relatives
Costs of Mammals Living In a group
Increased Intraspecific Competition for Resources Increased Chance for Spread of Diseases and Parasite Interference with Reproduction
Increased Intraspecific Competition for Resources
Agonistic behavior per individual increases as group size increases Foraging per day increases as a function of group size
Increased Chance for Spread of Diseases and Parasites
Members of dense colonies are much more at risk of spreading
parasites or disease simply based on density and proximity.
Interference with Reproduction
Parental care that is misdirected to
non-offspring (suckling the wrong
baby) and killing of young by
non-parents are the biggest costs
in this category
Prairie dog colonies
In prairie dog colonies the amount of agonistic behavior per individual increases as a function of group size
Frugivorous primate colonies
Among frugivorous primates, the amount of time spent foraging per day increases as a function of group size and potentially sets an
upper limit of group size.
Trouble Identifying Young
Many species who live in large
groups have the challenge of
identifying their young when
returning from a foraging trip.
Most mammalian movements occur in a relatively small area
such as when an individual acquires resources within its home
includes trips outside the
home range, usually in search of mating opportunities or suitable
habitat. This type of movement includes natal dispersal.
means leaving the site of birth or
social group (emigration), traversing unfamiliar habitat, and
settling into a new area and/or social group (immigration).
Natal Dispersal in Mammals
In many species of mammals, members of one sex disperse
while the other sex are philopatric (breeding near the place they were born). Among mammals it is usually the male that disperses.
Causes of Dispersal at Proximal Level
an individual may be forced out by its
parents or as an involuntary response to increased testosterone
levels associated with sexual maturation
Causes of Dispersal at ultimate level
the reasons may not be so immediately apparent
Ultimate cause of Dispersal
the avoidance of inbreeding
It manifests itself through reduced reproductive success and
survival of offspring from closely related parents compared to
offspring of unrelated parents.
It is caused by increased homozygosity of the inbred offspring
and the resulting expression of deleterious recessive alleles.
Hamadryas Baboon Natal dispersal
hamadryas baboon males usually leave the natal group around sexual maturation. They usually transfer to a neighboring group with age peers or brothers. Several years later,
they may again transfer to a third group. This pattern of nonrandom
followed by random movement minimizes the chances of mating with kin
Inbreeding effects depend on
The ultimate effects of inbreeding depend on past population
size and mating patterns
Populations that have survived episodes of inbreeding in the past
may tolerate current inbreeding with relatively few ill effects. This is likely because deleterious recessive alleles already have been
selected out of the population i.e Cheetah
Northern Elephant Seal Inbreeding
At the turn of the last century it was estimated that there were only
between 20 and 50 northern elephant seals remaining. Now there are about 160,000 and growing at 6% per year. This suggests a severe genetic bottleneck and a minimal amount of genetic diversity.
Reason for dispersal (reduce Competition)
with conspecifics for food, shelter, or mates. Most mammals are polygynous and males may be forced to disperse as they compete for access to females
Does inbreeding hypothesis predict which sex should disperse?
No. While the inbreeding hypothesis predicts that one sex should
disperse it does not predict which sex.
Does competition hypothesis predict which sex should leave?
Yes, the male should disperse in a polygynous species
The reproductive success of males depends on?
the number of females they can mate with and so are likely to range farther than females searching for mates.
Lion Dispersal Pattern
males leave (usually
before 4 years old), to become nomads or form coalitions that take
over new prides. Competition with other males is important as
most departures occur when a new coalition takes over. Some
males do leave voluntarily.
A coalition controls a pride until a new one takes over or they
leave to take over another pride (usually before their daughters
start mating). New coalitions usually kill all of the young cubs so
breeding males usually stay until their cubs are old enough.
What plays a role in lion dispersal patterns?
Male-male competition, mate acquisition, protection of young cubs, inbreeding avoidance
Testosterone in Belding's Ground Squirrels
dispersal appears to be the prenatal
effects of testosterone on the male embryo during development
and the attainment of critical body mass after birth.
matings between members of different populations within
a species leads less-fit offspring. . Members of a population may possess adaptations to local
conditions that are potentially lost through outbreeding.
Two areas may differ in temperature, humidity, or types of food
and if each population is genetically adapted to these conditions
they would be better off mating with individuals with those same
More cooperative behavior is predicted in philopatric species and
especially within the philopatric sex.
Belding's Ground Squirrels relative
In Belding's ground squirrels,
females are philopatric and
engage in altruistic alarm calling,
whereas males who disperse
away from relatives do not make
alarm calls. This suggests an optimal
inbreeding strategy in which
matings between close relatives
are avoided, but matings with
Belding's ground squirrel
more distant relatives are favored.
Groups with female dispersal
Pikas,kangaroo rats, chimpanzees, African wild dogs and whitelined
Dispersal in Pikas
Most juvenile pikas stay in their natal patch for life but individuals occasionally disperse both within and between patches of talus Of those that move 100 m or more,
most were females
isolated patches of rock debris
choosing a place to live, which
does not necessarily imply a conscious choice or that individuals
make a critical evaluation of all of the factors. More often the
choice is an automatic reaction to key aspects of the environment
Limitations of Choices of Habitats
Choice of a habitat may be limited by:
• accessibility (islands versus mainland)
• behavior patterns (i.e., prefer trees to grasslands)
• allelopathic agents (plant toxins)
• abiotic factors (temperature, moisture, light, nutrients)
Determinants of Habitat Preference
1. Genes and the Environment (Nature versus Nurture)
Genes and the Environment (Nature versus Nurture)
If two animals reared from birth under identical environments
differ in habitat preference when adults, the conclusion would be
that the differences resulted from hereditary factors
Nature vs Nurture study results
After this series of experiments it was concluded that:
1. The choice of grassland by grassland deer mice is predetermined genetically.
2. Early grassland experience can reinforce this innate preference
but is not a prerequisite.
3. Early experience in either forest or grassland did not reverse the
4. Twenty generations of lab rearing resulted in a reduction of
hereditary control over habitat choice.
5. Lab raised stock retained the capacity to "imprint" on early
grassland experience but not forest. .
He concluded that learned responses were primary basis of
restriction and that genetics was secondary.
Nature vs. Nurture study participants
three types of mice:
1) Wild caught in grassland
2) Offspring of wild-caught parents
3) Grassland mice reared in the lab for 20 generations
Sheep habitat Home
Sheep habitats consist of stable, long-lasting grass
communities that exist in small patches where knowledge of
location and predator avoidance is crucial.
Moose and Deer Habitat Home
Moose and deer are more pioneer species and continuously
colonize newly formed successional habitats that are formed by
Migratory movements take an animal out of its home range and
habitat type and is triggered by proximal cues, such as photoperiod,
that are linked to ultimate factors, such as shortage of resources
Migration new info
Used to be defined by round trip but now one-way travel also counts
Bats and Migration
As the only flying mammals bats might be expected to
show long distance migrations like birds but that is not generally
true. Bat wings are very effective for slow maneuverable flight
but not long distance migrations.
Bats migration and Hibernation
Most bats hibernate.
Some bat species do migrate - most often to and from caves used
as hibernation sites. Some little brown bats migrated over 200 km
from hibernation caves in Vermont to summering sites in
Most species of baleen whale spend their summers at
high latitudes feeding on plankton in the highly productive waters
and then migrate to sub-tropical to tropical waters for the winter.
What drives Catecean migration?
Food supply does not drive this migration, but it is suggested that it
is to minimize heat loss in the newborns
Many species of seals and sea lions migrate thousands of kilometers each year from island breeding and molting sites to feeding areas.
Northern elephant seal migration
Northern elephant seals make two round-trip migrations per year
travelling up to 21,000 km during the 250-300 days they are at-sea.
Males migrate further than females.
Large ungulates migrate impressive distances as well.
Barren ground caribou herds move migrate 1000+ km between
wintering and summering grounds.
a process by which most species return to a home range, nest
site or den
Most of what is known about homing comes from studies on what species?
Birds but enough has been done on mammals to show that they
use the same mechanisms. Most mammal research has been done on bats and mice.
In order for homing to occur an animal must have
- a sense of direction (some form of compass)
- a sense of location (understand where it is starting from)
Distant landmarks have been demonstrated to be used by some
Best ways to use piloting
This approach would
be best suited for use within the home range such as when grey
squirrels locate a food cache
Requirements for piloting
requires a mental map of
the terrain but does not require a compass. In principal it could be
used for longer trips
Another way to maintain direction
Another way to maintain direction is to use the sun or stars as a
compass and maintain a constant angle to it while traveling. This
requires an internal clock to compensate for the sun moving at about 15° per hour
Many organisms use geomagnetic cues. Marine Species follow the magnetic lineation in the seafloor, which are predominantly north-south. Other lineations oriented primarily east-west intersect these
north-south lines; these east-west lines correspond to fracture zones
across the spreading ridges
What causes marine mammal strandings?
Many marine mammal
strandings have been associated with changes in the earth's
magnetic field possibly due to solar flares or areas of magnetic
Scale color denotes
how old the seafloor is in millions of years.
Factors Affecting Spatial Ability
Mammals are assumed to have a cognitive map, sex differences in spatial ability
- a representation of
the geometric relationships among a home site, terrain surrounding
the home site, goals to be visited, and the terrain surrounding those
Where would a map be stored in the brain
The grates differences in sex spatial ability is seen in?
polygynous or promiscuous
mating systems, and especially those with scramble competition
Size of Hippocampus differences
males of polygynous species have hippocampi that were 11% larger than females whereas in monogamous species the difference was only 2% (no data for humans).