The questions to answer for this week’s attendance to be counted are at the end of this document.
Start by watching this video:https://www.youtube.com/watch?v=BHtAcA2CMYU&t=836s (Links to an external site.) orhttps://www.youtube.com/watch?v=BHtAcA2CMYU (Links to an external site.)whichever works
Primates as a group are social animals; with the possible exception of the orangutan, all of the higher primates live in groups of at least a mating pair and their sub-adult offspring
The strongest ties are usually between a mother and her offspring
Primates, especially the apes, have a long period of childhood dependency
Learning occurs within the group throughout childhood through observation and imitation and peer group interactions
Communication is both verbal and non-verbal
GROUP SIZE AND COMPOSITION
The factors which regulate the size of a group are complex but the most important determinant is the richness and distribution of the food supply in the area where each species lives
PRIMATE GROUPS VARY IN THE FOLLOWING INTER-RELATED CHARACTERISTICS:
- overall size (how many individuals are in the group)
- ratio of males to females
- types and strengths of ties between individuals
- types and strengths of dominance orders
- male or female migration (who leaves the group when they reach maturity and who stays: in some species young males leave, in other species young females are the ones who leave the group they were born into to join another group)
TYPES OF GROUPS AS CHARACTERIZED BY MALE/FEMALE RATIOS:
- multi-male groups where sex ratios are more or less equal;
- “harem” groups with one adult male and several females, often these are separate units within larger groups
- pairs with offspring
Troops are lead by an alpha individual. Most primates have alpha male leaders but some, especially lemurs, have alpha females. In gibbons and siamangs, both adults in the nuclear family group are leaders.
STABILITY AND COHESIVENESS OF THE GROUP IS THE GOAL OF GROUP INTERACTIONS; THEREFORE THE INDIVIDUALS NEED TO HAVE WAYS TO COMMUNICATE WITH EACH OTHER AND DEFUSE TENSIONS. BEHAVIOR SHOULD BE PREDICTABLE AND EVERY MEMBER OF THE GROUP SHOULD KNOW THE RULES IN ORDER FOR THE GROUP TO SURVIVE AND SUCCEED
GROOMING IS THE MOST IMPORTANT SOCIAL INTERACTION BECAUSE IT REINFORCES SOCIAL BONDS, REDUCES TENSION, AND HELPS CLARIFY DOMINANCE. GROOMING IS ONE INDIVIDUAL TOUCHING ANOTHER, IT CAN OCCUR BETWEEN TWO INDIVIDUALS OR IN A GROUP.
Watch these short videos
https://www.youtube.com/watch?v=OALXV8Jlevo (Links to an external site.) Snow monkeys, a type of macaque, are the only primates (except for humans of course) that live outside of tropical or sub-tropical environments. These are the monkeys at the Central Park Zoo.
Most commonly, mothers groom their children, subordinate individuals groom more dominant ones, friends groom each other, but grooming can occur between anyone and can be a group activity.
EXAMPLES OF SPECIES LIVING IN DIFFERENT TYPES OF GROUPS:
SAVANNAH BABOONS (Old World Monkeys)
Terrestrial monkeys living on the savanna but they seek trees or rocks at night for protection from predators
They eat grass, roots, seeds, fruits, blossoms, insects, and occasionally hunt or stalk small animals; they forage together as a group
Most have multi-male groups but some species (geladas and hamadryas baboons) have harem units within the overall group; the overall group size can be quite large
The male hierarchy is strong and well-enforced, especially under conditions of environmental stress (there is an alpha male and several beta males, who are subordinate friends of the alphaâ€”the alphaâ€™s posse)
There is a separate female hierarchy
Bonds between males and females, in addition to mothers and siblings, can be consortship (mates) and friendship
There is very apparent sexual dimorphism with males much larger than females
COLOBUS MONKEYS (Old World Monkeys)
Arboreal monkeys – quadrupedal (run along branches, leap between them, use tails for balance [not for grasping])
They eat leaves, leaves, and more leaves, with the occasional fruit, seed, or insect
Their social structure is groups with one male and several females and children, the extra males form all male groups (bachelor bands)
There is a male hierarchy and a separate female hierarchy
They are slightly sexually dimorphic
GIBBONS (lesser apes)
Arboreal apes who brachiate (review this term from last weekâ€™s class)
They eat leaves, fruits, and blossoms for the most part
They live in pair groupsâ€”one male, one female, and their children, until the children reach maturity. They live within a family territory that they defend against other families using verbal calls.
There is very little sexual dimorphism in size.
CHIMPANZEES (great apes)
They eat fruit, leaves, and a little of a lot of other things, including meat and insects
Their groups are multi-male multi-female that both come together and split apart; their group composition is fluid with periods of fission and fusion
Individuals forage by themselves within the communityâ€™s range; if a food source is particularly abundant many individuals might forage together
There is an alpha male who usually has friends to back him up
Males are extremely territorial and communally defend their territory against outsiders using physical violence
There is some sexual dimorphism
Groups need leaders in order to ease tensions between members and to help with group cohesion. The leader of a group is the Alpha (from the first letter in the Greek alphabet). Alphas get to be leaders by asserting their dominance over other members of the troop. They can assert their dominance by physical domination or by forming alliances with other individuals, but usually it is a combination of the two. An Alpha needs friends to help support his positon and authority.
Watch these videos about chimps
Watch this video of a Ted talk about alphas. The person giving the lecture is Franz deWaal, a Dutch scientist who has studied both chimpanzees and bonobos.
Questions for this week: What are the roles of alpha individuals in primate groups? What, according to deWaal, is the prime benefit that an individual male chimpanzee gets from being the alpha?
Here is an amusing video that we would have watched in class. Watch it if you have time. Itâ€™s the record of a trip the British comedian John Cleese (he was one of the Monty Python group) took to Madagascar to visit lemurs.