Modern Primates and Primate Behavior

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Modern Primates and Primate Behavior

• A Survey of Living Primates
• Anthropoids

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Anthropoids (Monkeys, Apes, and Humans)

• The anthropoid (humanlike) primates include
  monkeys, apes, and humans.
• Although there is much variation among
  anthropoids, there are certain features that,
  when taken together, distinguish them as a group
  from prosimians.
• Generally larger body size
• Larger brain (in absolute terms and relative to
  body weight)
• Reduced reliance on the sense of smell, as
  indicated by absence of rhinarium and other
  structures.
• Increased reliance on vision, with forward-facing
  eyes placed at front of face.
• Greater degree of color vision.
• Back if eye socket formed by a bony plate.

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• Blood supply to brain different from that of
  prosimians.
• Fusion of the 2 sides of the mandible at the
  midline to form one bone (in prosimians and
  tarsiers they are joined by fibrous tissue).
• Less specialized dentition, as seen in absence of
  the dental comb and some other features.
• Difference with regard to female internal
  reproductive anatomy.
• Longer gestation and maturation periods.
• More mutual grooming.

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• Suborder Anthropoidea is further divided into two
  infraorders
• Platyrrhini (NWM) flat-nosed
• Platyrrhini means flat nose and the noses of
  the Central and South American monkeys have
  widely spaced nostrils separated by a broad
  septum.
• Catarrhini (OWM) monkeys, apes, and humans
  downward-facing nose
• If you compare this with a typical OW catarrhine
  nose (nostrils close together and facing
  downward) you will see that they are comma
  shaped and close together.

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Whitehead et al. 2005
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Which one is Catarrhini (OWM) and Platyrrhini
(NWM)
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Dental Formula

• NW and OW primates have different dental
  formulas, that is, the number of each type of
  tooth in each quadrant of the mouth.
• OW have 2 incisors, 1 canine, 2 premolers
  (bicuspids), and 3 molars
• It is written as 2.1.2.3 ? 2 32
• 2.1.2.3
• Some NW anthropoids have 4 extra premolars
• 2.1.3.3 ? 2 36
• 2.1.3.3
• Other NW anthropoids have 4 fewer molars
• 2.1.3.2 ? 2 32
• 2.1.3.2

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• Moreover, because NW monkeys are almost entirely
  arboreal, they have evolved long limbs, an some
  have clawlike nails.
• Several species also have a prehensile tail
  giving them 5 grasping limbs
• NO OW monkey has this adaptation
• Finally, two groups of platyrrhines, the
  marmosets and tamarins, normally give birth to
  twins.

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Howler Monkey Note the prehensile tail
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• The OW primates are divided into two
  superfamilies.
• The monkeys of Europe (now limited to Gibraltar),
  Africa, and Asia make up superfamily
  Cercopithecoidea
• All OWM
• Apes and humans are in the superfamily
  Hominoidea, which are then divided into three
  families.
• Hylobatidae
• Pongiade
• Hominidae

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The Superfamily Hominoida

• Contains the larger, tailless primates.
• The hominoidsapes and humansare generally
  larger that the monkeys and have larger brains,
  both relatively and absolutely.
• Their brains also have neocortexes, meaning that
  the hominoids are more intelligent as I have
  already defined.
• Finally, a series of traits make the hominoids
  good suspensor climbers and hangers.
• The traits behind this ability are a flexable
  shoulder joint, a shoulder blade that is farther
  back than in monkeys, and a stronger color bone
  (clavicle) for added support.

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Family Hylobatidae

• Includes the gibbons and siamangs of Southeast
  Asia and Malaysia.
• There are 14 gibbon species and the closely
  related siamang are today found in the
  southeastern tropical areas of Asia.
• These animals are the smallest of the apes, with
  long, slender body weighing 13 pounds in the
  gibbon and 25 pounds in the siamang.
• The most distinctive structural feature of
  gibbons and siamamgs is related to an adaptation
  to brachiation.

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• Sometimes referred to as the lesser apes they
  are noted for their brachiating mode of
  locomotion
• They have extremely long arms, long permanently
  curved fingers, short thumbs, and powerful
  shoulder muscles.
• This highly specialized locomotor adaptation may
  be related to feeding behavior while hanging
  beneath branches.
• The diet of both species is composed mainly of
  fruit.
• However, both (especially the siamang) eat a
  variety of leaves, insects and flowers.
• They also have unusual social organization for
  primates.
• Male and female hylobatids form monogamous pair,
  though not necessarily a permanent one.

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Grey Gibbon (Hylobates muelleri)
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Siamangs (Hylobates syndactylus)
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Pongidae, (great apes)

• There are 4 species within the family
• Orangutan
• Orangutans (Pan pygmaeus) are represented by two
  subspecies found today only in heavily forested
  areas on the Indonesian islands of Borneo and
  Sumatra.
• As a result of human predation, they are an
  endangered species.
• Orangutans are slow cautious climbers whose
  locomotor behavior can best be described as
  four-handed, referring to the tendency to use
  all your limbs for grasping and support.

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• They are mostly arboreal, however, they do
  sometimes travel quadrupeadally on the ground.
• Pronounced sexual dimorphism (males 200 lbs
  females 100 lbs).
• In the wild they lead solitary lives, although
  adult females are usually accompanied by one or
  two dependent offspring.
• They are primarily frugivorous, but bark, leaves,
  insects, and meant (on rare occasions) may also
  be eaten.

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Orangutan (Pongo pygmaeus)
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Gorilla

• Gorillas (Gorilla gorilla) are the largest of all
  living primates.
• They are limited to forested areas of western and
  eastern equatorial Africa.
• Generally, there are three recognized subspecies
• Western lowland gorilla
• Eastern lowland gorilla
• Mountain gorilla
• However, molecular data suggests that only one of
  these, the western lowland gorilla is perhaps
  sufficiently genetically distinct to warrant a
  separate species.

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• The western lowland gorilla is among the most
  numerous with perhaps a population size of
  110,000.
• Systematic studies of the free-ranging WLG did
  not begin until the mid-1980s thus knowledge
  about social structure and behaviors is still in
  its infancy.
• In general, it appears that their social
  structure is simi8alr to that of mountain
  gorillas, but groups are smaller and somewhat
  less cohesive.
• The eastern lowland gorilla is found near the
  boarder of the DRC and numbers about 12,000.

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• The mountain gorilla probably have never been
  numerous and number about 600
• Live in groups consisting of 1 (or sometimes 2)
  large silverback males, a variable number of
  adult females, and their offspring.
• Silverback refers to adult males with white hair
  across the saddle of their back (12-13 years)
• Typically, but not always, both males and females
  leave their natal group as young adults.
• Females join other groups while males may live
  alone for a while, or they may join an all male
  group before eventually forming their own group.

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• Gorillas exhibit marked sexual dimorphism with
  males (400 lbs) weighing twice as much as females
  (100-200 lbs).
• As a result of their weight, gorillas (especially
  males) are primarly terrestrial and adopt a
  semiquadrupedal (knuckle-walking) posture on the
  ground.
• All gorillas are almist exclusively vegetarian.
• MT gorillas concentrate primarily on leaves,
  pith, and stalks.
• WLG eat the same foods but also eat considerably
  more fruit.
• Not the myth of the killer ape.

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Right Western Lowland Gorilla
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Chimpanzee (Pan troglodytes)

• Chimps are probably the best known of the all the
  NHP
• Chimp are found in equatorial Africa from the
  Atlantic Ocean in the west to Lake Tanganyika in
  the east.
• Chimps are in many ways structurally similar to
  gorillas, with corresponding limb proportions and
  upper-body shape.
• This similarity is due to commonalities in
  locomotion when on the ground (quadruped knuckle
  walking).
• However, ecological adaptation of chimps and
  gorillas differ, with chimps spending more time
  in the trees.
• Moreover, while gorillas are typically placid and
  quiet, chimps are highly excitable, active, and
  noisy.

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• Chimps are smaller than orangutans and gorillas,
  but they do exhibit sexual dimorphism, just not
  as much as orangutans and gorillas. Males just
  over 100 lbs and females around 80 lbs.
• In addition to knuckle walking, chimps (in
  particular young) may brachiate while in the
  trees.
• On the ground, they frequently walk bipedally for
  short distances when carrying food or other
  objects.
• They eat a variety of food items, including
  fruit, leaves, insects, nuts, birds eggs,
  berries caterpillars, and small mammals.

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• They live in large fluid communities of as many
  as 50 individuals or more.
• At the core of a chimp community is a group of
  bonded males.
• While this relationship is not always peaceful or
  stable, these males use each other to defend
  their territory.
• Adult females tend of forage alone or in the
  company of their offspring.
• Their social behavior is complex and individuals
  form lifelong attachments with friends and
  relatives.
• The bond between mother and child is strong
  lasting their whole lives
• Chimps live to their mid-30s early 40s

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Chimpanzees (Pan troglodytes) organize themselves
into complex social structures, requiring
considerable intelligence.
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Bonobos (Pan paniscus)

• Are found only in an area south of the Zaire
  River in the DRC.
• They are among the least studied of the great
  apes.
• There are no accurate counts but it is believed
  that their numbers are around 10,000 to 20,000
• They are sometimes called pygmy chimpanzee
  because of their strong resemblance but smaller
  size.
• However, this title is a misnomer because in fact
  bonobos exhibit several anatomical and behavioral
  differences from chimps.

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• Physically
• They have a more linear body build
• Longer legs relative to arms
• A relatively smaller head
• A darker face from birth
• Tuffs of hair on the side of the face.
• They are more arboreal than chimps and appear to
  be less excitable and aggressive.
• Physical violence both within and between groups
  are uncommon.
• These groups are centered around female bonding
  not male like chimps.
• Bonobo sexuality is different than in chimps.

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