Today we're going to be looking specifically
at primates, not at behavioral theories or terminologies.
We have two goals:
Describe the physical characteristics of
Describe the general features of
Question we're going to answer today:
What makes a primate?
|How do we come up
with a definition of the order primates? It is difficult because there's
quite a range of differences in characteristics. For instance, there is a
two-to-three-thousand-fold size difference between largest and smallest
Primate Anatomy A
definition from 1873, written by St. George Mivart:
"Unguiculate, claviculate, placental mammals, with
orbits encircled by bone; three
of teeth, at least at one time of life; brains
always with a posterior lobe and calcarine fissure; the innermost digits
of at least one pair of extremities opposable, hallux with a flat nail or
none; a well-developed caecum; penis pendulous;
testes scrotal; always two pectoral mammae."
A link to
the Oxford English
Dictionary (Available only to UM-affiliated users, sorry)
Seriously though, they're not very physically specialized. Not when
compared to say a giraffe or a platypus! There are some defining
are very visual. Compared to other mammals, the eyes have moved more to
the forepart of the head. This gives good binocular vision.
Teeth: Incisors, canines, and molars. (The
three kinds referred to in the definition.) Diversity of tooth types is
because of diversity in diet. The canine teeth rip food and get it into
mouth, while molars grind the food to prepare it for digestion. Felines,
who have a less-varied diet, have less varied teeth.
Brain: A lot of development in the neo-cortex which
implies heavier reliance on learning and memory. Also, olfactory bulb is
rather reduced, especially in the ones with bigger neo-cortex. Older
primates, like the prosimians, have a larger olfactory bulb but a smaller
neo-cortex. More recent developments have a smaller olfactory bulb and
Fairly generalized so
it can be used for many different modes of locomotion. Skeletal
proportions have great variation among species, mostly related to
Ecology and Behavior
Worldwide geographic distribution: Primates are fairly widely
distributed; on 5 out of the 7 continents (Not Australia or Antarctica.)
They're more restricted now than before, mostly due to climate changes-
they're basically a tropical order. Mostly they're found in the rain
forests of SE Asia, west-central Africa, and South America. Exceptions:
Barberry Macaque in N Africa, Japanese Macaque in Japan, and some
Habitat types: These differences in
habitat are caused by differences in rainfall, going from highest to
Primary forest: Tall trees with a dense, multi-level
Secondary forest: Spots where primary forest has
disturbed so it doesn't have tallest trees- more dense understory due to
more light getting in.
Gallery forest: Develops along
waterways in drier areas.
Woodland: Trees are sparser and
shorter, with more shrubbery.
Savannah: Made up of grass and
scattered trees (pretty dry here).
Within any given habitat, there
Microhabitats: These are smaller divisions
within the same habitat: You might have altitudinal gradience where two
species live in the same habitat but at different altitudes. Also, within
a forest, they might use different levels of the canopy: Highest is the
emergent trees (up to 300ft tall) that poke out above canopy. Next comes
the main canopy, which has a lot more horizontal branches and vines and
things. The main story comes next, with more trunks and vines, and
we find the ground. Certain species may specialize in one particular
height level, rarely venturing out of it. (This type of microhabitat is
also known as vertical distribution)
Patterns Most mammals are nocturnal: they sleep during the day.
Primates on the other hand are mostly diurnal. The holdouts are the
prosimians (the less-developed primates who also have smaller
neo-cortexes.) All apes are diurnal. All monkeys except the 'night
are diurnal. Some monkeys could be called crepuscular maybe, but not
Primates, being 'unguiculate,' not only have nails or claws, but usually
flat nails instead of claws. This is because hands and feet have become
modified for grasping.The exception is the prosimians; they still have
The Classifications a.k.a Different ways to
Quadrapedalism; May be arboreal(african
monkeys) or terrestrial (macaques and baboons). A specialized
form called knucklewalking is seen in african apes, gorillas, chimps, and
Leaping; Seen in squirrel monkeys. Vertical
leaping from a clinging position on a trunk is seen in the prosimians
as the tarsiers and indries (who still have claws).
Suspensory climbing; Hanging down from hands from branches.
Orangutans do this. Gibbons do a special type of suspensory travel; they
Bipedalism: Examples are us; also
chimps and spider monkeys do it. Mostly they bipdedal (if that's a word)
for shorter distances or when carrying something, but don't use it as
their primary mode of movement.
'...well-developed caecum...' This is a sac
in the digestive system which comes off at the top of the large intestine
but leads nowhere. Its harbors bacteria used in the digestion of some
nutrients that we can't break down, such as cellulose or complex
carbohydrates. Bacteria in the caecum digests this stuff for us.
Gross dietary categories
frugivore fruit-eater: orangutans
folivore leaf eater: leaf-eating monkeys
insectivore insect eater: tarsiers
gummivore gum eater (saps and gums from injuries to trees):
tamarins and marmosets
omnivore animal & plant eater
faunivore animal eater (includes insectivores) but this category
also includes invertebrate-eaters
herbivore plant eater (includes leaf and fruit eaters)
*Note if we say an animal is one of these types it doesn't mean that's
all they eat! Some animals have stricter diets than others.
Spacing systems-- Nomadic-migratory vs. Philopatry
Many animals move around quite a bit. Primates don't move so much. They
are called philopatric which means they stay in the same place. This is
Ścause they live in such a complex environment; they need to know where
find food, sleeping areas, and predators. Therefore they stick around
within an area that they know. Maybe an animal will move to another
territory once when it reaches adulthood, but that's usually it.
How far they go in one day; day range (often measured in
How far they go in a longer period of time (like a year); home
The area in home range which is used most; core area (area)
If they actively defend their home range, then it's called a
territory and if they don't, then it's just called a home range.
Examples: Gibbons have territory and they defend it. They move
quickly, so their day rage is pretty long, but their territory is
relatively small since they do defend it. The orangutan moves more slowly
so its day range is shorter. Its home range, not being a territory, is
pretty big, however. When undefended, home ranges often overlap quite a
Social Groups: Solitary vs. Gregarious
Mostly, primates are social animals. Most mammals aren't. Holdouts, as
usual, are the prosimians many of whom are solitary. Monkeys and apes are
almost all in groups, the prototypical example being baboons who live in
huge groups. An exception is the orangutan who is a solitary beast.
A Classification of Social Group Types
Note that these often correspond to mating system classifications.
Noyau: Animals have overlapping home ranges, and the sexes don't
live together. There's no territoriality. Each female has a home range
while males have larger home ranges that cover several female ranges.
is the system seen in orangutans. Usually goes with a promiscuous mating
Monogamy: One territory for each pair and their offspring.
An example is the gibbons. Goes hand-in-hand with the monogamous mating
Polyandry: Each territory has one female and many males.
Guess which mating system they use.
Multi-male group: (Should really be called multi-male,
multi-female group, since each territory has many of both sexes.)
are an example. Usually a promiscuous mating system.
One-male group: Such as the leaf-monkey. Usually a
polygynous mating system. The leftover males form bachelor herds who raid
periodically to take power and women from aging reigning males.
Fission-fusion society: This type is less common, but can
seen in chimps, bonobos, and spider monkeys. A group has shared
All the members are friendly to each other and work to keep non-group
members out, but they don't travel toge ther as a group. They have
subgroups that join and split almost constantly.
Hamadryas baboons: This category is used almost just to
describe their systems, so they got the naming of it. It is a complex
hierarchical system, with several levels. The basic unit is a one-male
unit, with accompanying females, but the units co mbine into larger
called clans. These are made up of related males' groups who merge for a
while to forage and socialize, but don't share women. Clans will
merge to form troops who share common sleeping sites, often on
Sometimes a troop will move as unit to a new location, but usually during
the day they split into clans. A similar system is seen in the golden
monkey and proboscis monkey, but it hasn't been so well described.