27 Primate Social Organization

Ms. Kiran Singh and Prof. A.K. Kapoor

Contents:

1.  Introduction.

2. Why Anthropologists are concerned with primates.

3. Evolution of primates.

4. Classifications of Primates:

5. Features of the Anthropoids: Monkeys, Apes and Humans.

6. Primate Behavior:

7. Few Social factors that influence social structure.

8. Distributions of the resources:

9. Evolution of Behaviour

10.  Primate Cultural Behaviour.

11.  Factors Influence social structure.

Learning Objectives:

• Students will learn about the primates features.
• Students will be able to learn about primate social organization.
• Student will be able to identify the characteristics of primates.

1. Introduction

Primates cannot be defined as one or even a few traits share in common because they are not so specialized. So human have special interest in the group of animals known as the primates. In addition it includes ourselves to prosimians, monkeys and apes. Human are the part of the nature and the primates are our closest relatives.

Order primates of class Mammalia includes lemurs, tarsiers, monkeys, apes and human. Non-human primates live primarily in sub-tropical and tropical regions of Africa, Asia and South America. In the size they range from mouse lemur at 30grams (1 ounce) to the mountain gorilla at 200 killograms (441 pounds).

2. Why the Anthropologist are concerned to primates?

Anthropology is the study of human being in space and time. Anthropology has four branch that is physical anthropology, Social anthropology, Archaeology anthropology and linguistic anthropology. Physical anthropology is deal with biological origin, evolution, and genetic variation. In Primatology is sub branch of physical anthropology. In this anthropologist are more concerned about the ways of living of primate behavior.

3. Evolution of Primates:

The first primates –like mammals are referred to as proto-primates. They were about resemblance to squirrel and tree shrews in size and appearance. The surviving fossil evidence mostly from North – Africa) is very fragmentary. The oldest known primate-like mammal with a relatively robust fossil records is Plesiadapis (although some primatologist do not agree that plesiadapis was proto primates). Approximately primates have been dated 55 million years ago. Plesiadapiforms had some features of teeth and skeleton in common with true primates. They were found in North America and Europe in the Cenozoic going by the end of the Eocene.

The true first primates were found in the Africa, Asia, and North America in the Eocene Epoch. These early primates were resemble to the present day prosimians such as lemurs. Anthropoids monkeys evolved from prosimians during the Oligocene epoch. By the 40 million years ago, evidence indicates that monkeys were present in the new world (south America) an dold world (Africa and Asia). New World monkeys are also called Platyrrhine a references to their broad noses.

Fig. 1. Howler monkey are native to south America

Old world monkeys are called Catarrhine. Because their nose are narrow. At the time of platyrrhines arose. The continent of south America and Africa had drifted apart. New world monkeys appeared for the first time about 30 millions years ago. The evidence suggest that Africa is most likely continent of the origin. Therefore its believed that due to this reproductive isolation, new world and old world monkeys underwent separate adaptive radiations over milions of years. Old world monkeys include aboreal and ground dwelling , whereas new world monkeys are aboreal.

Apes evolved from catarrhines in Africa through the Cenozoic during the Miocene epoch since 25 millions ago. Apes are generally larger than monkeys and do not have a tail. Traditionally primates has been explained as the results of an adaptation to arboreal living. While other mammals were adapted to the ground-dwelling lifestyle and even in marine environment. The primates. Apes are more intelligent than monkeys as they have relatively larger brains in proportionate to body size.

4. Classifications of Primates:

Primates  are  divided  into  two  smaller  categories  that  is Strepsirhini  (lemurs  and  lorsises)  and Haplorhini (tarsises, monkeys, apes and humans.)

5.  Features of the Anthropoids: Monkeys, Apes and Humans.

1.      A large average body size.

2.      Larger brain in absolute terms and relative to the body weight.

3.      Reduced reliance on olfaction, indicated by the absences of a rhinarium and other structures.

4.      Increase reliance on vision with forward facing eyes placed more to the front of the face.

5.      Greater degree of the color division.

6.      Back of eye socket protected by a bony plate.

7.      Blood supply to brain different from that of lemur and lorises.

8.      Fusion of the two sides of the mandible at the midline to form one bone.

9.      More generalized dentition absence of the dental comb and some other features.

10.  Differences in female internal reproductive anatomy.

11.  Longer gestation and maturation periods.

12.  Increased parental care.

13.  More mutual grooming.

Features of Hominids: Apes and Humans

1.      Generally body size is larger (exception in gibbons and siamangs).

2.      Tail is absence.

3.      Short trunk

4.      Longer arms then legs (only in apes).

5.      More complex behavior.

6.   Anatomical differences in the shoulder joint (related to an adaptation for suspensionary feeding locomotion).

7.      More complex brain and enhanced cognitive abilities.

8.      Increased period of infant development and dependency.

Hominids apes are found in Asia, Africa. Small body gibbon and siamangs were live in southeast Asia. Orangutan subspecies live on the island of Borneo and sumatra. Gorilla,chimpanzee, bonobos were occupied in area of western, central and eastern Africa.

6. Primate Behavior:

The main aim of primatologist is to determine how primate behavior influences the reproductive fitness and how ecological factors have shaped these behaviors. Primates are among the most social of animals, social behavior occurring in social groupings, even some may think of social behavior like feeding and mating.

Social Behavior:

Primates pass through the following developmental stages. 1. Infant, a time during which a primate is dependent on its mothers. 2. Juvenile, during which it is mature animals. It has been observed that primate juvenile period is a time of great learning this learning period is not only from parents, also from interaction with other members of animal group. Also observed that many social skills which are necessary for life necessity are learned during this period. During early adulthood that the secondary sexual characters begins to develop, for instances increased in male body size , long robust canines in comparison to the females. This play important roles in the behavior of those species possessing sexual dimorphism. This extended periods of development and growth is one of the hall mark of the orders of primates. Primates are socially organized animals who travels, eat and live together in groups. There are few species that are more solitary than other, such as orangutans, tarsiers, galagos. It has been found that primates possess many different ways of expressing themselves socially. Like hugging, touching, grooming, mounting, lip-smacking, vocalizing. Three fundamental types of social organization can be distinguished:

1.      Neighbourhood and solitary,

2.      Pair living,

3.      Group –living species

1. Neighborhood system: Fact of the solitary species is the general activity and particularly the movement of different individuals are not synchronized. In social animals in which two individuals synchronize their activity in space and time. The term solitary elements of the social systems. Its neither necessary nor useful to introduce mating systems terminology to characterize social organization. That.is dispersed polygamy. The social diversity of the solitary primates are 1. Extent of range overlap with the members of the same and opposite sex,2. Occurrences of sleeping groups and their sexual composition.
2. Primates in pairs: Permanent association of one adult male and female defines pair living species. Thus, there is not only coincidence of male and female ranges but also synchronized spatial association between the pair. Males and females ranges overlap closely and are neither consistently associated during the period of activity or always sleeping together.
3. It’s has been reported that majority of the primates lives in bisexual group with > 3 adults. This set them to apart from other mammals in which permanently bisexual groups are much less common. Variations in the numbers of adult males is the most striking features of the primate group composition with far reaching consequences for many aspects of male and females behavior. It was identified the number of females in group and their degree of reproductive synchrony as important determinants of the outcome of the dichotomy.

7.  Few Social factors that influence social structure.

Body size: Among the living primates, body size is extremely diverse, ranging from dwarf mouse lemurs about 2.5 ounces to male gorilla at around 260 pounds.

Basal Metabolic Rate (BMR): The Body metabolic rate concern the metabolism the rate which the body uses the energy at a resting state to maintain all body functions. Metabolism is closely correlated to the body size, so in general smaller animals have a higher BMR than the larger ones do. For eg. Galgos,, tarsier, marmosets, and tamarins they consume fats (nuts and seeds) carbohydrate (fruits and seeds). While larger primates tends to have lower BMR and reduced energy requirements relative to the body size, can do well with less energy rich foods like leaves.

8. Distributions of the resources:

Different kinds of foods are distributed in different ways. Leaves can be plentiful an dense will support large groups of animals. Insects on other hands are distributed to the widely scattered. Species that subsist on abundantly distributed resources may also live in one-male-multifamily groups. The reasons is these groups are ready to join and availability of plenty foods. For instances howler monkeys.

9.    Evolution of Behaviour

A major goal of primatology is to determine how behaviours influence reproductive fitness and how ecological factors have shaped the evolution of these behaviours. Because primates are among the most social of animals, social behaviour is a major topic in primate research. Technically, what we are talking about is the study of primate social structure

A social structure is defined as the composition, size, and sex ratio of a group of animals. Social structures guide individual interactions and social relationships. The subject is broad, including all aspects of behaviour that occur in social settings

10. Chief characteristics of primate

The Primates have characteristics of their own. They differ from the species population both in character and passing through an accelerated phase of transformation and equilibrium Anthropological approach to human and nonhuman primate behaviour and cognition predicts biological specializations for social life. Focusing on nonhuman primates, its describe how the primate brain might implement social functions by co-opting and extending pre existing mechanisms that previously supported non social functions.

These specializations for social behaviour reflect a rich evolutionary heritage of adaptation to group life. Like humans, many other primates also live in large groups characterized by patterns of primate behaviour are the following:

• grooming,
• imitative
• cooperative foraging,
• differentiated affiliative relationships,
• ritualized courtship
• mating behavior, and
• competitive interactions structured by social dominance.
• Not surprisingly, the ability to deftly navigate the social environment has observable consequences for reproductive success in some primates.

Anthropological approach to the study of primate social behaviour is powerful in the extent to which it is encompassing and holistic. By presenting the evolution of social behaviour through a lens of social functions, and have provided evolutionarily parsimonious lines of reasoning and evidence, along with tractable avenues for future changes.

Being in Social group is important for Primates:

The costs of competition are offset by the benefits of predator defense provided by associating with others. Groups made up of several adult males and females are advantageous in areas where predation pressure is high, particularly in mixed woodlands and on open savannas. Leopards are the most significant predator of terrestrial primates. Where members of prey species occur in larger groups, the chances of early predator detection and avoidance are increased simply because there are more pairs of eyes looking about. There really is safety in numbers.

Social group

There are advantages: facilitation of reproduction; predator avoidance and defence; help with foraging for food; help with learning; and a division of labor: males and females do slightly different things. Savannah baboons are an excellent example of these advantages. Social evolution (sociality) has occurred among several forms of life, but by no means all Social life, to have evolved at all, must have enhanced the chances of individual organisms to survive and reproduce.

Dominance

Many primate societies are organized into dominance hierarchies, which impose certain degree of order by establishing parameters of individual behaviour. Although aggression is frequently a means of increasing one’s status, dominance usually serves to reduce the amount of actual physical violence. Not only are lower-ranking animals unlikely to attack or even threatening a higher-ranking one, but dominant animals are usually able to exert control simply by making a threatening gesture.

Communication

Communication is universal among animals and includes scents and unintentional, autonomic responses and behaviours that convey meaning. Such attributes as body posture convey information about an animal’s emotional state. Moreover, autonomic responses to threatening or novel stimuli, such as raised body hair (most species) or enhanced body odour (gorillas), indicate excitement. All nonhuman animals use various body postures, vocalizations, and facial expressions to transmit information. But the array of communicative devices is much richer among nonhuman primates, even though they don’t use language the way humans do. Communication is important, because it makes social living possible. Through submissive gestures, aggression is reduced and physical violence is less likely. Likewise, friendly intentions and relationships are reinforced through physical contact and grooming. Indeed, humans can see ourselves in other primate species most clearly in their use of nonverbal communication, particularly because some of their gestures and facial expressions carry the same meaning as ours do.

Primates depends for the food on their specific environment

In many cases, primate more adjusted to their physical environment sources of subsistence and livelihood; starting from the pure and simple parasitic habit for the food who depend mostly on nature for the sources of subsistence.

Aggressive Interactions

Within primate societies, there is interplay between aggressive behaviours, which can lead to group disruption, and affiliative behaviours, 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 aggression occurs in the form of various signals and displays, frequently within the context of a dominance hierarchy. Therefore, the majority of tense situations are resolved through various submissive and appeasement behaviours. However, not all conflicts are resolved peacefully. Competition between males for mates can result in injury and even death. Females also compete with each other, frequently for resources, and especially low-ranking females may starve when food supplies are short .

Chimpanzee facial expressions

Affiliation and Altruism

As you’ve just seen, even though it can be destructive, a certain amount of aggression helps maintain order within groups and protect resources. Fortunately, to minimize actual violence and to defuse potentially dangerous situations, there are much behaviour that reinforce bonds between individuals and enhance group stability. Common affiliative behaviours include reconciliation, consolation, and simple amicable interactions between friends and relatives. These involve various forms of physical contact; in fact, physical contact is one of the most important factors in primate development, and it’s crucial in promoting peaceful relationships in many primate social groups.

Grooming

Grooming is one of the most important affiliative behaviours in many primate species, although grooming occurs in other animal species, social grooming is mostly a primate activity, and it plays an important role in day-to-day life. Because grooming involves using the fingers to pick through the fur of another individual to remove insects, dirt, and other materials, it serves hygienic functions. But it’s also an immensely pleasurable activity that members of some species (especially chimpanzees) engage in for long periods of time.

Altruism, behaviour that benefits another while involving some risk or sacrifice to the performer, is common in many primate species, and altruistic acts sometimes contain elements of what might be interpreted as compassion and cooperation.

Female and Male Reproductive Strategies

Primates are among that individuals produce only a few young, in whom they invest a tremendous amount of parental care. Primates are completely helpless at birth, and because they develop slowly, they’re exposed to expanded learning opportunities within a social environment. This trend has been elaborated most dramatically in great apes and humans, especially the latter. So human and primate relatives (and presumably in our more recent ancestors) is a strategy in which at least one parent, usually the mother, makes an extraordinary investment to produce a few “high-quality,” slowly maturing offspring.

Sexual selection

Sexual selection in primates is most common in species in which mating is polygynous and there is considerable male competition for females. In these species, sexual selection produces dimorphism with regard to a number of traits, most noticeably body size. Conversely, in species that live in pairs (such as gibbons) or where male competition is reduced, sexual dimorphism is either reduced or nonexistent. For this reason, the presence or absence of sexual dimorphism in a species can be a reasonably good indicator of mating structure.

10. Primate Cultural Behaviour

One important trait that makes primates, and especially chimpanzees, attractive as models for behaviour called cultural behaviour. Although many cultural anthropologists and others prefer to use the term culture to refer specifically to human activities, most biological anthropologists consider it appropriate to use the term in reference to nonhuman primates too.

One of the most significant events in human evolution was the development of language; already described several behaviours and autonomic responses that convey information in primates. But although we emphasized the importance of communication to nonhuman primate social life, we also said that nonhuman primates don’t use language the way humans do. The view traditionally held by most linguists and behavioural psychologists has been that nonhuman communication consists of mostly involuntary vocalizations and actions that convey information solely about the emotional state of the animal (anger, fear, and so on).

11.  Factors influence Social Structure Body Size

As a general rule, larger animals require fewer calories per unit of weight than smaller animals because they have a smaller ratio of surface area to mass than smaller animals. Since body heat is lost at the surface, larger animals can retain heat more efficiently, and so they require less energy overall.

Diet

Since the nutritional requirements of animals are related to the previous two factors, all three have evolved together. Therefore, when primatologists study the relationships between diet and behaviour, 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 are frequently surrounded by it.

Predation

Primates, depending on their size, are vulnerable to many types of predators, including snakes, birds of prey, leopards, wild dogs, lions, and even 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.

Relationships with Other, Non predatory Species

Many primate species associate with other primate and non primate species for various reasons; including predator avoidance. When they share habitats with other species, they exploit somewhat different resources.

Dispersal

Dispersal is another factor that influences social structure and relationships within groups. As is true of most mammals, members of one sex leave the group in which they were born their natal group about the time they reach puberty. Male dispersal is the most common pattern in primates (ring-tailed lemurs and macaques, to name a few. Female dispersal is seen in some species, baboons, chimpanzees, and mountain gorillas. This commonality has led primatologists to conclude that the most valid explanations for dispersal are probably related to two major factors: reduced competition for mates particularly between males and, perhaps even more important, the decreased likelihood of close inbreeding.

Distribution and Types of Sleeping Sites

Gorillas are the only nonhuman primates that sleep on the ground. Primate sleeping sites can be in trees or on cliff faces and their spacing can be related to social structure and predator avoidance.

Activity Patterns

Most primates are diurnal, but several small-bodied prosimians and one new world monkey owl monkey are nocturnal. Nocturnal primates tend to forage for food alone or in groups of two or three, and many hide to avoid predators.

Summary:

Primate social organization is complex since there are different kinship. Sex, age, rank, dominance represented in groups. Relationships are frequently cross-cut by subgroups composed of long and short term alliances. This increased complexity. For instances, grooming alliances may not have only short term consequences, long term are also established when males groom a pregnant or lactating female an activity which magnify receptivity by the female when she resumes sexual cycling. Mating in mammalian system are found to be in majority in among the primates. It include the monogamy, in which males and females typically mate with the only one members of the opposite sex and roughly equal variances. Also reported by the researchers that among primate polygamy system also exists. That is when males roam widely in search of the receptive females. So it can be said that both partners mate with the several partners. Females defense polygyny exists among primates. To sum up there is variation within species and sometimes even within population, in mating and social organization patterns or both. Dominance: reproductive success also hypothesis for high ranking females who have greater access to food than subordinate females do. This is because they obtain more energy for the production and care of offspring.

Conclusion: The social organization of group –living primates has been more intensely studied than that of other primates, so the variation of the group size and composition, as well as the underlying mechanisms, are comparatively well-understood.

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