Social Organization in Mammals.....

1. SOCIAL ORGANIZATION
IN ANIMALS

2. Outlines -
 Term – Social organization
 Advantages of grouping
 Association – types of social groups
 Leadership
 Social facilitation
 Social dominance
 Social order

3. The term social organization includes:
 Physical structure : the size of the group and its composition in
respect to age, sex and degrees of relatedness of group members.
 Social structure : all of the relationships among individuals in the
group and their consequences for spatial distribution and
behavioural interactions.
 Group cohesion : the duration of association of the members of the
group and the frequency of fission in which one or more members
leave the group.

4.  The first social relationship is often with the mother. Newly hatched
chicks are attracted to hen by warmth, contact, clucking and
body movements. Chicks rapidly learn the characteristics of their
environment on the first day of life (Bateson, 1964; Broom, 1969a).
 The set of brain processes involved in this rapid learning, sometimes
called imprinting, develop in course of interaction with stimuli
received from the environment of the young chick (Bateson and
Horn, 1994; Bateson, 2003).
 The attachment of mother is further strengthened as her voice and
her detailed appearance are recognized.

5. Advantages of grouping -
 All animal groups, whether aggressions, flocks, or the ‘true societies’ result in
the individuals that are part of them being better off than they would be on
their own.
 Allee and co-workers (1938) used simple experiments to show how even
loose aggregations can benefit the individuals that compromise them.
 They showed that water fleas do not survive in alkaline water, but the
respiratory products of a large group of them are sometimes sufficiently acid
to bring the alkalinity down to viable levels. Thus, a group can survive
whether a few individuals could not.

6.  Flocks of birds and schools of fish exemplify groups that are much more
than simple aggregations because there is often a high degree of social
interaction between individuals.
 One of the most obvious advantages of a cohesive group whose
members respond to each other’s behaviour is protection against
predators.
 Elgar (1989) reported that birds and mammals spend less time in vigilance
and more time in feeding, the bigger groups they are in.

7. A) Vigilant meerkat keeping watch
for predators while the rest of the
group feed.
B) Starlings normally fly in loose flocks
(left), but when under attack by a
peregrine falcon, they fly as close
together as possible (right).

8.  Another advantage is utilizing food resources found by other animals.
 Krebs et al. (1972) showed that when one member of a tit flock finds a
food item, the others rapidly alter their searching strategies and
concentrate their attention both on the general area and the type of
niche in the trees where the food was found.
 Nelson (1980) argues that a group of birds diving together confuse the fish
that they are more easily caught.
 Lions, hyaenas and Cape hunting dogs are all examples of predators that
hunt together.

9.  Experiments indicate that the hormonal cycle of mammals is affected by
the presence of males, this is concerned with stimulation and
synchronization of breeding.
 Animals maintain their breeding rate below the maximum. The regulatory
mechanism is present in their social system.
 Social group have good communication and interaction between
individuals. They communicate by means of olfactory, tactile and
acoustic signals.

10. ASSOCIATIONASSOCIATION
 In groups of social animals, it is common for animals to associate,
i.e. they spend time closer to one another than the mean group
inter-individual distance.
 Within herds, it is often found that discrete pairing through mutual
selection of each other’s company is a common social strategy,
which operates to the advantage of both, particularly in agonistic
situations involving other, dominant animals.
 The stable unit is made up of a number of subgroups of related
individuals.

11. This stability of social relationship requires :
Recognition between individual animals. E.g Sense of smell is used
by cows to recognize other cows (Vomero-nasal organ).
Established social positions
Memory of social encounters that establish social status
Memory of observations of the behavior of social group members

12. Types of social groups -
A) The caste system of social insects - e.g bees, ants, termites and wasps.
The queen honey-bee secretes a pheromone (queen substance), which
both suppresses the ovaries of the workers and prevents them from rearing
new queens.
The development of worker termites is controlled by pheromones produced
by the king and queen.
B) Territory in the social organization of vertebrates – e.g during the breeding
season, great tits are strongly territorial and vigorously defend the area
around their nest against other great tits. But during the winter they group into
large flocks both members of their own species and of others such as blue tits
and nuthatches

13. A male pied flycatcher defends a territory
against other males. The female chooses a male
on the basis of the quality of his territory and the
suitability of the nest site it contains. Males that
had a low density of birch trees in their territories
and nest sites high up in the trees with thick trunks
giving safety to the nest were the ones that
obtained mates first.

14. CATTLE
 Domestic cattle in a free range situation move from place to place
in groups in which individuals maintain close proximity to one
another (Philips, 2002).
 Dairy and beef cattle often lie in groups and grazing animals often
stand within a few metres of one another, seldom moving out of
view of the rest of the herd.
 Animals that were reared together as calves where more likely to
associate when adult (Leaver, 1978).
 The animals in the suckler herd often allogroomed and spent most
of their walking time together (Benham, 1982b, 1984).

15. SHEEP
 Ewes and lambs during the first 4 weeks of the lamb’s life are found
to stay within 10 m of each other for over 50% of the time.
 The formation of ‘weaner’ flocks breaks this social bond and a new
social organization has to be developed with the formation of small
groups, in which inter-animal distances are low.
 The size of subgroups increases with age from weaning up to 4
months old; this is unrelated to the size of paddock or space
available to the animals.
 Normal adult flocking behaviour appears to be established by 15
months of age.

16. Three characteristic flock structures (Arnold, 1977; Lynch et al., 1992) –
A tightly knit flock.
A flock widely dispersed but with uniform spacing between
individuals.
A flock split into subgroups but that remains a social entity with
membership of subgroups continually changing.
When resting, sheep occupied an area of 10 sq.m / sheep.

17.  Distance to nearest neighbor is one attribute of social arrangement;
the cohesion of all members of a flock is another. This cohesion
varies with environmental factors.
 The average distance between neighbouring sheep when grazing
varies from 4 to more than 19 m; the greater distances are for hill
breeds of sheep and the smallest for Merinos.
 Four classes of dispersion-
Merinos < lowland breeds < hill breeds < mountain breeds

18. HORSES
 Two horses encountering each other for the first time show much mutual
exploratory behaviour. Exploratory behaviour at introduction involves an
investigation of the other’s head, body and hindquarters using the
olfactory sense.
 Horses show a form of social order when they live in groups, and a social
hierarchy becomes established within these groups.
 The older and larger animals are usually found to be high in dominance
order. Stallions do not necessarily dominate geldings or mares but have a
significant role in defence of the group (McDonnell, 2002).
 Social dominant horses are sometimes found to have more aggressive
temperaments than the others.

19.  The stallion attempts to herd a group of brood mares together. The
normal size of a ‘harem’ amongst horses is about 7 to 8 mares.
 The colts tend to form a bachelor group after splitting off from the
herd at the age of about 1 – 2 years. Fillies may or may not join this
group.
 The stallion will round up the mares on the periphery of his herd or
‘harem’, but will ignore or repel fillies.
 Stallions in winter form bachelor groups.

20. PIGS
 The social organization of groups of pigs is known to include the
establishment of various friendly relationships and a social hierarchy
(Jenson and Wood-Gush, 1984).
 For the social hierarchy to function properly, the size of a group and
the space allocated to it are important.
 Pigs in an established group are quickly able to recognize an alien
in a group, but pigs are not territorial (Jenson, 2002).
 Visual and olfactory cues seem to be the principal differentiating
features of pigs for each other.

21. PRIMATE BEHAVIOUR
 The long period of parental care in primates gives an opportunity to learn
complex social behaviours.
 To reduce unnecessary conflict, social primates use ritualistic display and
appeasement behaviours. Grooming, facial expression, body posture and
sexual presentation are all important in different species.
 In some monkeys and apes, alliances form between individuals. These are
often used to increase social status within the group.
 The complexity of social structure is related to ecological niche and
taxonomic group.
 Total number of possible relations can be obtained by the mathematical
formula, n(n-1)/2 where, n= no. of individuals in group.

22. LEADERSHIPLEADERSHIP
 Leader : the individual that is in front during an orderly group progression.
 Leadership among sheep is often provided by an old ewe: older animals are
more likely to lead, and the status of the animal in the social hierarchy may
not be a determining factor.
 Types of leadership in cattle –
I. Leadership during movement to and from locations of eating, drinking and
sleeping. This establishes movement order.
II. Leadership in the initiation of grazing and resting.
III. Leadership in direction during grazing activity.

23.  Sato (1982) observed that the summer time lowering of grazing and
the development of association frequently caused heifers to
behave less as followers and to show dispersive grazing formations.
 Under free range conditions, the older grazing stock can transfer to
their offspring information about seasonal pathways, areas of good
pasture and watering places if this familial bond is not disrupted
before weaning.

24. SOCIAL FACILITATIONSOCIAL FACILITATION
 Social facilitation is more likely where there is adequate association,
ability to communicate and react, a potential for mimicking activities,
similarity of motivational state and suppression of intra-species
aggression.
Examples –
a. Increased likelihood of pecking by a chick where another chick is seen
or heard pecking.
b. Cows in a field which are more likely to start grazing or lying if others in
the herd do so (Bentham, 1982a). The amount consumed may also be
affected by social facilitation.

25. SOCIAL DOMINANCESOCIAL DOMINANCE
 Schjelderup-Ebbe was one of the first to develop the concept of a social
dominance hierarchy, using his work on flocks of hens (1935). He observed that a
definite ‘peck order’ developed amongst a group of hens, one gradually
emerging as dominant in the sense that she could displace all others.
 In linear hierarchy, no bird is seen to peck an individual above it in rank.
 Among primates, A may dominate B and B may dominate C but A does not
necessarily dominate C.
 Stags – antlers are shed during April – males rise on their hind legs and box with
their hooves. Fighting with the new antlers increases until about mid-September,
when the male herds breakup. Oestrous females are attracted to displaying stags,
who defend their group of females rather than any particular area.

26. SOCIAL ORDERSOCIAL ORDER
 This can result in maximal group-bonding and minimal aggression,
creating social stability (Schein and Fohrman, 1955).
 Social interactions in the development of a ‘peck order’ usually involve
aggressive acts like biting, butting or pushing.
 A social hierarchy is not an inviolable structure, it is merely the state of
settled-out relationships between individuals.
 Dominant animals have probably been aggressive in the past to obtain
their dominant positions, but a dominant animal need not be aggressive
subsequently (Reinhardt and Reinhardt, 1982).

27.  Relationships are the result of learning, with many different factors being
involved in the formation of a relationship. Once learned, dominance
relationships can persist for a long time (Syme and Syme, 1979).
 Social dominance is not usually exerted when social animals are grazing
or are resting. In horses, subordinate animals deliberatively avoid moving
too close to dominant animals and dominant animals frequently threaten
subordinates while eating.
 Social dominance is exhibited in competition for supplementary feed
given in a restrictive place or at water troughs in cattle, sheep and horses.

28.  Jenson (1984) observed that confinement and semi-confinement
decreases the social activity and leads to unsettled dominance
relationships combined with high aggression levels.
 Taking pigs as an example, aggression does not increase with increasing
group size unless resources are limiting (Turner and Edwards, 2004). Pigs in
large groups may form subgroups or restrict their space use to certain
areas.
 Beattie et al. (1996) found that pigs showed more locomotor behaviour
such as running and jumping when more floor space was provided in
enriched pens.

29. REFERENCESREFERENCES
An Introduction to Animal behaviour, 4th
edition – Aubrey
Manning and Marian Stamp Dawkins
Domestic Animal Behaviour and Welfare, 4th
edition –
D.M.Broom and A.F.Fraser
Animal Behaviour, 2nd
edition – Dr. M.M.Ranga