Bio Anthropology Chapter 6-7

Maturation, Learning, and Behavior

1. A more efficient means of fetal nourishment, longer periods of gestation, reduced numbers of offspring (with single births the norm), delayed maturation, and extension of the entire life span. 2. A greater dependence on flexible, learned behavior. 3. The tendency to live in social groups and the permanent association of adult males with the group. Except for some nocturnal species, primates tend to associate with other individuals. 4. The tendency toward diurnal activity patterns. This is seen in most primates. Lorises, tarsiers, one monkey species, and some lemurs are nocturnal; all the rest (the other monkeys, apes, and humans) are diurnal.

Anthropoid (Monkeys, Apes, and Humans) traits

1. Larger average body size 2. Larger brain in absolute terms and relative to body weight 3. Reduced reliance on the sense of smell, as indicated by the absence of a rhinarium and reduction of olfactory-related brain structures 4. Increased reliance on vision, with forward-facing eyes placed more to the front of the face 5. Greater degree of color vision 6. Back of eye socket protected by a bony plate 7. Blood supply to the brain different from that of lemurs and lorises 8. Fusion of the two sides of the mandible at the midline to form one bone (in lemurs and lorises, they're two distinct bones joined by cartilage at the middle of the chin) 9. More generalized dentition, as seen in the absence of a dental comb 10. Differences in female internal reproductive anatomy 11. Longer gestation and maturation periods 12. Increased parental care 13. More mutual grooming

diurnal

Active during the day.

frugivorous

Having a diet composed primarily of fruit.

omnivorous

Having a diet consisting of many kinds of food, including plants, meat, and insects.

anthropoids

Members of the primate infraorder Anthropoidea (pronounced "an-thro-poid´-ee-uh"), which includes monkeys, apes, and humans.

ischial callosities

Patches of tough, hard skin on the buttocks of Old World monkeys and chimpanzees.

estrus

Period of sexual receptivity in female mammals (except humans), correlated with ovulation. When used as an adjective, the word is spelled "estrous."

the order Primates includes all primates. But at the next level down, the suborder, primates are divided into two smaller categories: Strepsirrhini (lemurs and lorises) and Haplorhini (tarsiers, monkeys, apes, and humans). Therefore, the suborder distinction is more specific. At the suborder level, the lemurs and lorises are distinct as a group from all the other primates. This classification makes the biological and evolutionary statement that all the lemurs and lorises are more closely related to one another than they are to any of the other primates. Likewise, humans, apes, monkeys, and tarsiers are more closely related to one another than they are to the lorises and lemurs. READ10

READ10

Lemurs and lorises greater olfactory capabilities (compared with other primates) are reflected in the presence of a relatively long snout and a moist, fleshy pad, or rhinarium, at the end of the nose. Many other characteristics distinguish lemurs and lorises from the other primates, including eyes placed more to the side of the face, differences in reproductive physiology, and shorter gestation and maturation periods. Lemurs and lorises also have a unique derived trait called a "dental comb", formed by forward projecting lower incisors and canines. These modified teeth are used in grooming and feeding. READ11

READ11

Some are mostly arboreal, and others, such as ring-tailed lemurs, are more terrestrial. Several species, such as ring-tailed lemurs and sifakas, live in groups of 10 to 25 animals composed of males and females of all ages. Indris are among the few primates that live in "family" units composed of a mated pair and dependent offspring. In addition, several nocturnal species are mostly solitary. READ12

READ12

New World monkeys rely on a combination of fruits and leaves supplemented to varying degrees with insects. Most are quadrupedal; but some, such as spider monkeys (see Fig. 6-9), are semibrachiators. Howlers, muriquis, and spider monkeys also have prehensile tails that are used not only in locomotion but also for hanging from branches. Socially, most New World monkeys live in groups composed of both sexes and all age categories. Some (such as titis) form monogamous pairs and live with their subadult offspring. READ13

READ13

Common affiliative behaviors include reconciliation, consolation, and simple amicable interactions between friends and relatives. Most such behaviors involve various forms of physical contact, such as touching, hand-holding, hugging, and, among chimpanzees, kissing. In fact, physical contact is one of the most important factors in primate development, and it's crucial in promoting peaceful relationships and reinforcing bonds in many primate social groups. READ21.

READ21

Reproductive strategies, and especially how they differ between the sexes, have been a primary focus of primate research. The goal of these strategies is to produce and successfully rear to adulthood as many offspring as possible. Primates are among the most K-selected of mammals. By this we mean that individuals produce only a few young, in whom they invest a tremendous amount of parental care. Contrast this pattern with r-selected species, where individuals produce large numbers of offspring but invest little or no energy in parental care. Good examples of r-selected species include insects, most fishes, and, among mammals, mice and rabbits. READ22

READ22

Brachiation, or arm swinging, is a suspensory form of locomotion, and the body moves by being alternatively suspended by one arm or the other. (You may have brachiated as a child on "monkey bars" in playgrounds, although these would more appropriately be called "ape bars.") Because of anatomical modifications at the shoulder joint, apes and humans are capable of true brachiation. However, only the small gibbons and siamangs of Southeast Asia use this form of locomotion almost exclusively. Brachiation is seen in species characterized by arms longer than legs, a short, stable lower back, long curved fingers, and shortened thumbs. READ6

READ6

As these traits are seen in all the apes, it's believed that although none of the great apes (orangutans, gorillas, bonobos, and chimpanzees) habitually brachiates today, they probably inherited these characteristics from brachiating or climbing ancestors. Some New World monkeys, such as spider monkeys and muriquis, are called semibrachiators, since they practice a combination of leaping and some arm swinging. READ7

READ7

cusps

The bumps on the chewing surface of premolars and molars.

Strepsirrhini

The primate suborder that includes lemurs and lorises.

Haplorhini

The primate suborder that includes tarsiers, monkeys, apes, and humans.

olfaction

The sense of smell.

cercopithecines

The subfamily of Old World monkeys that includes baboons, macaques, and guenons.

arboreal

Tree-living; adapted to life in the trees.

quadrupedal

Using all four limbs to support the body during locomotion; the basic mammalian (and primate) form of locomotion.

Human Activities

virtually all nonhuman primate populations are now impacted by human hunting and forest clearing. These activities severely disrupt and isolate groups, reduce numbers, reduce resource availability, and eventually can cause extinction.

Apes and humans share the following characteristics that separate them from monkeys:

1. Generally larger body size (except for gibbons and siamangs) 2. No tail 3. Shorter and more stable lower back 4. Arms longer than legs (only in apes) 5. Anatomical differences in the shoulder joint that facilitate suspensory feeding and locomotion 6. Generally more complex behavior 7. More complex brain and enhanced cognitive abilities 8. Increased period of infant development and dependency

Dentition and Diet

1. Lack of dietary specialization. This is typical of most primates, who tend to eat a wide assortment of food items. In general, primates are omnivorous. 2. A generalized dentition. Primate teeth aren't specialized for processing only one type of food, a trait related to a general lack of dietary specialization.

How many nonhuman primates are there approximately?

230

Lemurs size range from:

5 inches to 2 to 3 feet

altruism

Actions that benefit another individual but at some potential risk or cost to oneself.

nocturnal

Active during the night.

Old World primates are found in:

Africa, India, Southeast Asia (including numerous islands), and Japan

affiliative behaviors

Amicable associations between individuals. Affiliative behaviors, such as grooming, reinforce social bonds and promote group cohesion.

adaptive niche

An organism's entire way of life: where it lives, what it eats, how it gets food, how it avoids predators, and so on.

behavior

Anything organisms do that involves action in response to internal or external stimuli; the response of an individual, group, or species to its environment. Such responses may or may not be deliberate and they aren't necessarily the results of conscious decision making.

Lorises

Are nocturnal. There are at least eight loris species, all of which are found in tropical forest and woodland habitats of India, Sri Lanka, Southeast Asia, and Africa. Also included in the same general category are six to nine galago species, also called bush babies , which are widely distributed throughout most of the forested and woodland savanna areas of sub-Saharan Africa. Locomotion in some lorises is a slow, cautious, climbing form of quadrupedalism. All galagos, however, are highly agile vertical clingers and leapers. Some lorises and galagos are almost entirely insectivorous, while others also eat fruits, leaves, and other plant products. Lorises and galagos frequently forage alone, but feeding ranges can overlap, and two or more females may feed and even nest together. Females also leave young infants behind in nests while they search for food (referred to as parking), a behavior not seen in most primate species.

brachiation

Arm swinging, a form of locomotion used by some primates. Brachiation involves hanging from a branch and moving by alternately swinging from one arm to the other.

Body Size

As a rule, larger animals require fewer calories per unit of weight than smaller animals because larger animals have less surface area relative to body mass than smaller animals. Since body heat is lost at the surface, larger animals can retain heat more efficiently, so they need less energy overall. It may seem strange, but two 10-pound monkeys require more food than one 22-pound monkey.

Dispersal

As is true of most mammals, members of one sex leave the group in which they were born about the time they become sexually mature. Male dispersal is the most common pattern (for example, ring-tailed lemurs, vervets, and macaques). However, female dispersal occurs in some colobus species, hamadryas baboons, chimpanzees, and mountain gorillas. In species where the basic social structure is a mated pair, offspring of both sexes either leave or are driven away by their parents (for example, gibbons and siamangs). Dispersal may have more than one outcome. When females leave, they join another group. Males may do likewise, but in some species (for example, gorillas), they may live alone for a time or they may temporarily join an all-male "bachelor" group until they're able to establish a group of their own. The common theme is that individuals who disperse usually find mates outside their natal group. This has led primatologists to conclude that the most valid explanations for dispersal are related to two major factors: reduced competition between males for mates and, more importantly, the decreased likelihood of close inbreeding.

Diet

Because the nutritional requirements of animals are related to both body size and BMR, all three have evolved together. Therefore, when primatologists study the relationships between diet and behavior, they consider the benefits in terms of energy (calories) derived from various food items against the costs (energy expended) of obtaining and digesting them. While small-bodied primates focus on high-energy foods, larger ones don't necessarily need to. For instance, gorillas eat leaves, pith from bamboo stems, and other types of vegetation, and they don't need to use much energy searching for food, since they're frequently surrounded by it. Some monkeys, especially colobines (colobus and langur species), are primarily leaf eaters. Compared with many other monkeys, they're fairly large-bodied. They've also evolved elongated intestines and pouched stomachs that enable them, with the assistance of intestinal bacteria, to digest the tough fibers and cellulose in leaves.

Bonobos

Bonobos are more arboreal than chimpanzees, and they're less excitable and aggressive. While aggression isn't unknown, it appears that physical violence both within and between groups is uncommon. Like chimpanzees, bonobos live in geographically based fluid communities, and they eat many of the same foods, including occasional meat derived from small mammals. However, bonobo communities aren't centered around a group of males. Instead, male-female bonding is more important than in chimpanzees and most other nonhuman primates. This may be related to bonobo sexuality, which differs from that of other nonhuman primates in that copulation is frequent and occurs throughout a female's estrous cycle, so sex isn't linked solely to reproduction. In fact, bonobos are famous for their sexual behavior, copulating frequently and using sex to defuse potentially tense situations. Also, sexual activity between members of the same sex is common

life history traits

Characteristics and developmental stages that influence reproductive rates. Examples include longevity, age at sexual maturity, and length of time between births.

Chimpanzees

Chimpanzees are probably the best known of all nonhuman primates, even though many people mistake them for monkeys. Often misunderstood because of zoo exhibits, circus acts, and movies, the true nature of chimpanzees didn't become known until years of fieldwork with wild groups provided a more accurate picture. Today, chimpanzees are found throughout much of equatorial Africa. However, within this large geographical area, their range is very patchy, and it's becoming even more so with continuous habitat destruction.

colobines

Common name for members of the subfamily of Old World monkeys that includes the African colobus monkeys and Asian langurs.

sexual dimorphism

Differences in physical characteristics between males and females of the same species. For example, humans are slightly sexually dimorphic for body size, with males being taller, on average, than females of the same population.

sensory modalities

Different forms of sensation (e.g., touch, pain, pressure, heat, cold, vision, taste, hearing, and smell).

Limbs and Locomotion

Erect posture, flexible-generalized limb structure, prehensile hands (5 digits on hands and feet, opposable thumb, nails, sense of touch), and tactile pads.

True or False: Apes and humans are classified separately

False: Apes and humans are classified together in the same superfamily, Hominoidea

Gorillas

Gorillas (Gorilla gorilla) are the largest of all the living primates. Today, they are restricted to forested areas of western and eastern equatorial Africa. Gorillas exhibit marked sexual dimorphism. Males may weigh as much as 400 pounds, while females weigh around 150 to 200 pounds. Adult gorillas, especially males, are primarily terrestrial, and like chimpanzees, they practice a type of quadrupedalism called knuckle walking.

matrilines

Groups that consist of a female, her daughters, and their offspring. Matrilineal groups are common in macaques.

Distribution of Resources

Leaves can be abundant and dense and therefore support large groups of animals. Insects, on the other hand, may be widely scattered, and the animals that rely on them usually feed alone or with only one or two others. Fruits, nuts, and berries occur in clumps in dispersed trees and shrubs. These are most efficiently exploited by smaller groups of animals, so large groups frequently break up into smaller subunits while feeding. Such subunits may consist of onemale-multifemale groups (for example, some baboons) or matrilines (for example, macaques). Species that feed on abundantly distributed resources may also live in one-male groups, and because food is plentiful, these one-male units are able to join with others to form large, stable communities (for example, howlers and some baboons). To the casual observer, these communities can appear to be multimale-multifemale groups. Some species that depend on foods distributed in small clumps are protective of resources, especially if their feeding area is small enough to be defended. Some live in small groups composed of a mated pair (siamangs) or a female with one or two males (for example, marmosets and tamarins). Lastly, foods such as fruits, nuts, and berries are only seasonally available, and primates that rely on them must eat a wide variety of items. This is another factor that tends to favor smaller feeding groups.

hominoids

Members of the primate superfamily (Hominoidea) that includes apes and humans.

intelligence

Mental capacity; ability to learn, reason, or comprehend and interpret information, facts, relationships, and meanings; the capacity to solve problems, whether through the application of previously acquired knowledge or through insight.

Activity Patterns

Most primates are diurnal, but galagos, lorises, aye-ayes, tarsiers, and New World owl monkeys are nocturnal (note that these groups have very large eyes relative to their body size). Nocturnal primates tend to forage for food alone or in groups of two or three, and many hide to avoid predators.

dental formula

Numerical device that indicates the number of each type of tooth in each quadrant of the upper and lower jaws.

Orangutans

Orangutans (Pongo pygmaeus) are represented by two subspecies found today only in heavily forested areas on the Indonesian islands of Borneo and Sumatra. The name orangutan which means "wise man of the forest" in the language of the local people. But despite this somewhat affectionate-sounding label, orangutans are severely threatened with extinction in the wild due to poaching by humans and continuing habitat loss on both islands. Orangutans are slow, cautious climbers whose locomotion can best be described as four-handed—referring to their use of all four limbs for grasping and support. Although they're almost completely arboreal, orangutans sometimes travel quadrupedally on the ground, walking on their fists. Orangutans exhibit pronounced sexual dimorphism; males are very large and may weigh more than 200 pounds, while females weigh less than 100 pounds. In the wild, orangutans lead largely solitary lives, although adult females are usually accompanied by one or two dependent offspring. They're primarily frugivorous, but they may also eat bark, leaves, insects, and (rarely) meat.

territorial

Pertaining to the protection of all or a part of the area occupied by an animal or group of animals. Territorial behaviors range from scent marking to outright attacks on intruders.

ecological

Pertaining to the relationships between organisms and all aspects of their environment (temperature, predators, nonpredators, vegetation, availability of food and water, types of food, disease organisms, parasites, etc.).

territories

Portions of an individual's or group's home range that are actively defended against intrusion, especially by members of the same species.

Predation

Primates, depending on their size, are vulnerable to many types of predators, including snakes, birds of prey, leopards, wild dogs, and other primates. Their responses to predation depend on their body size, social structure, and the type of predator. Typically, where predation pressure is high and body size is small, large communities are advantageous. These may be multimale-multifemale groups or congregations of one-male groups.

Evolution is not a goal-directed process. Therefore, the fact that lemurs appeared earlier than anthropoids doesn't mean that lemurs "progressed" to become anthropoids. Living primates aren't in any way "superior" to their evolutionary predecessors or to one another. Actually, the only species that represent final evolutionary stages of particular lineages are the ones that become extinct. READ1

READ1

All Old World monkeys are placed in one taxonomic family, Cercopithecidae. In turn, this family is divided into two subfamilies: Cercopithecinae (the cercopithecines) and Colobinae (the colobines). Most Old World monkeys are arboreal, but some (such as baboons) spend a great deal of time on the ground and return to the trees for the night. They have areas of hardened skin on the buttocks called ischial callosities that serve as sitting pads, making it possible to sit and sleep on tree branches for hours at a time. The cercopithecines are more generalized than the colobines. They're more omnivorous, and as a group, they eat almost anything, including fruits, seeds, leaves, grasses, tubers, roots, nuts, insects, birds' eggs, amphibians, small reptiles, and small mammals (the last seen in baboons). The majority of cercopithecine species, such as the mostly arboreal guenons and the more terrestrial savanna and hamadryas baboons, are found in Africa. The many macaque species (including the well-known rhesus monkeys), however, are widely distributed across southern Asia and India. Colobine species have a narrower range of food preferences and mainly eat mature leaves, which is why they're also called "leaf-eating monkeys." The colobines are found mainly in Asia, but both red colobus and black-and-white colobus are exclusively African. READ14

READ14

A silverback male may tolerate the presence of one or more young adult "blackback" males (probably his sons) in his group. Typically, but not always, both females and males leave their natal group as young adults. Females join other groups; and males, who appear to be less likely to emigrate, may live alone for a while or may join up with other males before eventually forming their own group. All gorillas are almost exclusively vegetarian. Mountain gorillas concentrate primarily on leaves, pith, and stalks, while western lowland gorillas eat more fruit. Unlike mountain gorillas (which avoid water), western lowland gorillas also frequently wade through swamps while foraging on aquatic plants READ15

READ15

Chimpanzees are smaller and less sexually dimorphic than orangutans and gorillas. A male chimpanzee may weigh 150 pounds, but females can weigh at least 100 pounds. In addition to quadrupedal knuckle walking, chimpanzees may brachiate. When on the ground, they frequently walk bipedally for short distances, especially when carrying food or other objects. Chimpanzees eat a wide variety of foods, including fruits, leaves, insects (for example, ants and termites), birds' eggs, and nuts. Moreover, both males and females occasionally take part in group hunting efforts to kill small mammals such as young bushpigs and antelope. Their prey also includes monkeys, especially red colobus. When hunts are successful, the members of the hunting party share the meat. READ16

READ16

Many primate societies are organized into dominance hierarchies, which impose a certain degree of order by establishing parameters of individual behavior. Although aggression is frequently used to increase an animal's status, dominance hierarchies usually reduce the amount of actual physical violence. Lower-ranking individuals are unlikely to attack or even threaten a higher-ranked one; what's more, dominant individuals are usually able to exert control simply by making a threatening gesture. READ17

READ17

In many lemur species, females are the dominant sex. Moreover, in species that form bonded pairs (for example, indris and gibbons), males and females are codominant. All primates learn their position in the hierarchy. From birth, an infant is carried by its mother, and it observes how she responds to every member of the group. Just as importantly, it sees how others react to her. Dominance and subordination are indicated by gestures and behaviors, some of which are universal throughout the primate order (including humans), and this gestural repertoire is part of every youngster's learning experience. READ18

READ18

Primates (and other animals) also communicate through displays, which are more complicated, frequently elaborate combinations of behaviors. For example, the exaggerated courtship dances of many male birds, often enhanced by colorful plumage, are displays. Chest slapping and tearing vegetation are common gorilla threat displays. READ19

READ19

Even though most nonhuman primates are arboreal and live in forest or woodland habitats, some Old World monkeys (for example, baboons) spend much of the day on the ground. The same is true for the African apes (gorillas, chimpanzees, and bonobos). Nevertheless, all nonhuman primates spend some time in the trees, especially when sleeping. READ2

READ2

Within primate societies, there is an interplay between aggressive behaviors, which can lead to group disruption, and affiliative behaviors, which promote group cohesion. Conflict within a group frequently develops out of competition for resources, including mating partners or food. Instead of actual attacks or fighting, most intragroup aggression occurs in the form of various signals and displays, frequently within the context of a dominance hierarchy. The majority of tense situations are resolved through various submissive and appeasement behaviors. However, conflicts aren't always resolved peacefully; in fact, they can have serious and even fatal consequences. For example, high-ranking female macaques frequently intimidate, harass, and even attack lower-ranking females to keep them away from food. Dominant females consistently chase subordinates away from food and have even been observed taking food from their mouths. Eventually, these actions can cause weight loss and poor nutrition in low-ranking females, which in turn can reduce the reproductive success of these females because they're less able to rear offspring to maturity simply because they don't get enough to eat. READ20

READ20

Biologists use what's called a dental formula to describe the number of each type of tooth that typifies a species. A dental formula indicates the number of each tooth type in each quadrant of the mouth (Fig. 6-7). For example, all Old World anthropoids (monkeys, apes, and humans) have two incisors, one canine, two premolars, and three molars on each side of the midline in both the upper and lower jaws, for a total of 32 teeth. This formula differs from that of the New World monkeys in that there's one less premolar (see Fig. 6-7 for a comparison of the dental formulae for modern humans and New World monkeys). Some New World monkeys (marmosets and tamarins) have lost their third molars but still have three premolars in each quadrant of the dentition. READ3

READ3

The overall lack of dietary specialization in primates is reflected in the lack of specialization in the size and shape of the teeth, because tooth shape and size are directly related to diet. For example, carnivores typically have premolars and molars with high, pointed cusps adapted for tearing meat; but herbivores, such as cattle and horses, have premolars and molars with broad, flat surfaces suited to chewing tough grasses and other plant materials. Most primates have premolars and molars with low, rounded cusps, a pattern that enables them to process most types of foods. READ4

READ4

Vertical clinging and leaping, another form of locomotion, is characteristic of some lemurs and tarsiers. As the term implies, vertical clingers and leapers support themselves vertically by grasping onto trunks of trees or other large plants while their knees and ankles are tightly flexed. By forcefully extending their long hind limbs, they can spring powerfully away either forward or backward READ5

READ5

Lastly, all the apes, to varying degrees, have arms that are longer than legs, and some (gorillas, bonobos, and chimpanzees) practice a special form of quadrupedalism called knuckle walking. Because their arms are so long relative to their legs, they support the weight of their upper body on the back surfaces of their bent fingers READ8

READ8

DNA differences between chimpanzees and humans range from 2.7 percent to 6.4 percent READ9

READ9

displays

Sequences of repetitious behaviors that serve to communicate emotional states. Nonhuman primate displays are most frequently associated with reproductive or agonistic behavior. Examples include chest slapping in gorillas and, in male chimpanzees, dragging and waving branches while charging and threatening other animals.

dominance hierarchies

Systems of social organization wherein individuals within a group are ranked relative to one another. Higher-ranking animals have greater access to preferred food items and mating partners than lower-ranking individuals. Dominance hierarchies are sometimes called "pecking orders."

Basal Metabolic Rate (BMR)

The BMR concerns metabolism, the rate at which the body uses energy to maintain all bodily functions while in a resting state. It's closely correlated with body size, so in general, smaller animals have a higher BMR than larger ones. Consequently, smaller primates, such as galagos and marmosets, require an energy-rich diet high in protein (insects), fats (nuts and seeds), and carbohydrates (fruits and seeds). Some larger primates, which tend to have a lower BMR and reduced energy requirements relative to body size, can do well with less energy-rich foods, such as leaves.

empathy

The ability to identify with the feelings and thoughts of another individual.

metabolism

The chemical processes within cells that break down nutrients and release energy for the body to use. (When nutrients are broken down into their component parts, such as amino acids, energy is released and made available for the cell to use.)

social structure

The composition, size, and sex ratio of a group of animals. The social structure of a species is, in part, the result of natural selection in a specific habitat, and it guides individual interactions and social relationships.

stereoscopic vision

The condition whereby visual images are, to varying degrees, superimposed. This provides for depth perception, or viewing the external environment in three dimensions. Stereoscopic vision is partly a function of structures in the brain.

Gibbons and Siamangs

The eight gibbon species and closely related siamangs are the smallest of the apes, with a long, slender body weighing 13 pounds in gibbons and around 25 pounds in siamangs. Their most distinctive anatomical features are adaptations to feeding while hanging from tree branches, or brachiation. In fact, gibbons and siamangs are more dedicated to brachiation than any other primate, a fact reflected in their extremely long arms, long, permanently curved fingers, short thumbs, and powerful shoulder muscles. (Their arms are so long that when they're on the ground, they have to walk bipedally with their arms raised to the side.) Gibbons and siamangs mostly eat fruits, although they also consume a variety of leaves, flowers, and insects. The basic social unit of gibbons and siamangs is an adult male and female with dependent offspring. Although they've been described as monogamous, in reality, members of a pair do sometimes mate with other individuals. As in marmosets and tamarins, male gibbons and siamangs are very much involved in rearing their young. Both males and females are highly territorial and protect their territories with elaborate whoops and siren-like "songs," lending them the name "the singing apes of Asia."

natal group

The group in which an animal is born and raised. (Natal pertains to birth.)

Primates

The mammalian order of primates, which includes lemurs, lorises, tarsiers, monkeys, apes, and humans.

rhinarium

The moist, hairless pad at the end of the nose seen in most mammalian species. The rhinarium enhances an animal's ability to smell.

neocortex

The more recently evolved portion of the brain that is involved in higher mental functions and composed of areas that integrate incoming sensory information.

core area

The portion of a home range containing the highest concentration and most reliable supplies of food and water. The core area is defended.

behavioral ecology

The study of the evolution of behavior, emphasizing the role of ecological factors as agents of natural selection. Behaviors and behavioral patterns have been favored because they increase the reproductive fitness of individuals (i.e., they are adaptive) in specific environmental contexts.

hemispheres

The two halves of the cerebrum that are connected by a dense mass of fibers. (The cerebrum is the large rounded outer portion of the brain.)

Tarsiers

There are five recognized tarsier species , all of which are restricted to islands of Southeast Asia, where they inhabit a wide range of habitats, from tropical forest to backyard gardens. Tarsiers are nocturnal insectivores that leap from lower branches and shrubs onto small prey. They appear to form stable pair bonds, and the basic tarsier social unit is a mated pair and their young offspring. Tarsiers are highly specialized (derived) animals that have several unique characteristics. In the past, primatologists believed that tarsiers were more closely related to lemurs and lorises than to other primates because they share several traits with them. However, they actually present a complex blend of characteristics not seen in any other primate. One of the most obvious is their enormous eyes, which dominate much of the face and are immobile within their sockets. To compensate for the inability to move their eyes, tarsiers, like owls, can rotate their heads 180°. A tarsier's eye is about the same size as its brain!

True or False: Almost all primates are, at least to some degree, quadrupedal

True

True or False: Lemurs are found only on the island of Madagascar and adjacent islands off the east coast of Africa

True

True or False: primates have remained quite generalized

True. This means that primates have retained several ancestral (that is, primitive) mammalian traits that some other mammals have lost over time.

binocular vision

Vision characterized by overlapping visual fields provided by forward-facing eyes. Binocular vision is essential to depth perception.

Some of these basic mammalian traits are:

body hair, a relatively long gestation period followed by live birth, mammary glands, heterodonty (that is, different types of teeth, including incisors, canines, premolars, and molars), the ability to maintain a constant internal body temperature through physiological means, increased brain size, and a considerable capacity for learning and behavioral flexibility.

Are large lemurs diurnal or nocturnal?

diurnal

Tiny lemurs eat:

insects

intragroup

intragroup Within the group, rather than between groups (intergroup).

Large lemurs eat:

leaves, fruits, buds, bark, and shoots

Are tiny lemurs diurnal or nocturnal?

nocturnal

New World primates are found in:

southern Mexico, Central America, and parts of South America.