For Students of Biological Sciences BS Zoology

1. NAVEED AKHTAR
A S S I S T A N T P R O F E S S O R O F Z O O L O G Y
SOCIAL BEHAVIOR

3. What is social behaviour?
 Social behavior is behavior among two or
more organisms within the same species, and
encompasses any behavior in which one member affects
the other.
 Social behavior typically refers to any interactions among
members of the same species, but it also applies to
animals of different species, excluding predator-prey
interactions
 Social behaviour help animals to adapted in variety of
environments
 Social behavior has evolved independently in many
species of animals; invertebrates as well as
vertebrates have complex social organizations

4. Why Animals need Social Behaviour?
 Animal social behaviour, the set of interactions
that occur between two or more individual animals,
usually of the same species, when they form
simple aggregations, cooperate in sexual or parental
behaviour, engage in disputes over territory and
access to mates, or simply communicate across space
 Sets of consistent social relationships produce social
systems or social organizations that can be variations
on monogamous or polygamous themes of
reproduction and involve various types of helpers in
cooperative relationships.

5.  The nature of any social system is ultimately
determined by ecological and social circumstances,
demography, and kinship.

6. Types of Social Behaviour

7. LIVING IN GROUPS
 Animal populations are often organized into groups.
 A group of animals may form an aggregation for
some simple purpose, such as feeding, drinking,
or mating.
 Several Drosophila flies on a piece of rotting fruit
is an example of an aggregation
 A true animal society is a stable group of individuals
of the same species that maintains a cooperative
social relationship

8.  This association typically extends beyond the level of
mating and taking care of young
Advantages and Disadvantages of Group
Development
 Protection from predators by altering other
members of group from intruder
 Cooperative Hunting and capture of prey increase
the feeding efficiency of predators.
 The ability to gain protection from the elements (e.g.,
huddling together in cold weather) and during the
processes of mate finding and rearing of young

10.  Davison of Labor
 The social insects, living in groups has resulted in the
evolutionary division of labor, with specific
individuals performing specialized tasks (e.g.,
defense, food procurement, feeding of young)
 Disadvantages of Group Development
 Competition for limited recourses
 Crowded conditions attract diseases and parasites
 Large social groups attract more predators

11. 1. Agonistic Behaviour

13. Examples

14. Agonistic Behaviour in Birds

17. 2. Altruistic Behaviour
 .

18. What is Altruistic Behaviour ?
 In altruism,an individual gives up or sacrifices some of its own
reproductive potential to benefit another individual.
 Altruism is defined as displaying selfless concern for the well
being of others, caring for those close to them without thought
of individual reward?
 Altruism refers to an individual acting in a way that will
decrease its own survival chances, but improve the survival
chances of another individual.
 Example:
 One individual of a group of crows gives an alarm call to warn
other individuals of the group of an approaching predator,
even though the call may attract the predator to the sender of
the signal

19.  Example:
 Altruism In Elephants
 Elephants have the longest gestation time of any land
animal -22 months - meaning that the bond between
mother and baby is particularly strong.
 Experienced mothers in a herd often show care and
concern for new mothers who need extra help with their
babies.
 The expert will take turns looking after the new baby,
guiding it with their sensitive trunks, giving time for the
new mother to gain energy so she has enough quality
milk for her offspring.

21.  Diploid workers share, on the average, threefourths
of their genes with their full sisters.
 If they reproduced, they would share only half of
their genes with hypothetical offspring.
 Thus, female honeybees may have more genes in
common with their sisters than they would with their
own offspring.
 The workers may pass more genes to the next
generation by helping their mother produce more
full sisters, some of whom may become reproductive
queens, than if they produce their own young

25. 2. Kin selection
 Kin selection‖ was coined by Maynard Smith
 Also known as Inclusive Fitness Theory
 Kin selection is an evolutionary strategy that favors
the reproductive success of an organism relative even
at cost of their own survival and reproduction
 Here, an individual has the tendency to help its relatives
 Altruism may be a result of kin selection, in which aiding
one‘s relatives enhances the spreading of genes shared with
relatives.
 William Hamilton (1936– ) proposed the idea of kin
selection to explain how selection acting on related animals
can affect the fitness of an individual.
 In this way, a gene that a particular individual carries may
pass to the next generation through a related animal.

26.  An individual‘s fitness is therefore based on the
genes it passes on, as well as those common genes its
relatives pass on.
 A genetically based tendency to be altruistic could
therefore be passed on by the individual carrying it
or by a relative who also carries it.
 Obviously, for kin selection to work, individuals of a
group must be able to identify relatives, as can small
groups of primates and social insects.

28. MATING SYSTEM

29. Choice of Mate
 Why, for example, do some animals choose a single
mate for life, while others mate with a single partner
each breeding season, but switch partners across
breeding seasons?
 And, why, for that matter, do some mating systems
involve a male (or female) having two (or more)
opposite-sex partners during a single breeding
season?

30. 1. Different Mating Systems

31.  1. MONOGAMOUS MATING SYSTEMS
 In monogamous systems, one male and one female
are paired for at least one breeding season. In some
animals, such as the prairie vole, these associations
can last much longer, even a lifetime.
 As such, we can have animal societies in which pairs
mate only with one another during season 1, but in
subsequent years find new mates (serial
monogamy)— indeed, this sort of mating system is
very common in territorial animals.

32.  Example: Long-term monogamy in the oldfi eld mouse
 Importance of Monogamy
 ―Male-assistance hypothesis,‖ where males that remain with a
female to help guard and rear their young will have more and
healthier offspring.
 Social monogamy can also be advantageous for the female: she has
help from a social partner in raising her offspring, but she can also
mate with other males who may be genetically ―better.‖
 Disadvantages
 The disadvantage for the male in this scenario is that he is most
likely helping to raise offspring that are not his own
 The disadvantage for the female is that the male may abandon her –
and her offspring – if he detects that she has mated with another
male.

34.  2. POLYGAMOUS MATING SYSTEMS
 Polygamy is defined as a mating system in which either
males or females have more than one mate during a
given breeding season/cycle.
 Polygamy includes
 Polygyny in which males mate with more than one
female per breeding season
 Because males mate with many females and they defend
females from mating attempts by other males, the mating
system of these wasps is referred to as female defense
polygyny
 LEKS. One type of polygyny is lekking, or arena mating

35.  This type of polygyny has been studied in birds,
mammals, amphibians, fi sh, and insects. It occurs
when males set up and defend small arenas called
leks—temporary territories specifi cally for mating—
that contain no apparent resources (food or shelter,
for example)
 Females come to these leks and select mates from
among the males present.

37.  Polyandry, in which females mate with more than
one male per breeding season.
 Pipefishes, a relative of seahorses exhibit polyandry
where females compete for access to males. In both
pipefishes and seahorses, males receive the eggs
from the female, fertilize them, protect them within a
pouch, and give birth to the offspring

38. A battle-scarred male northern elephant
seal among his harem of females and pups

39.  Polygamy can be also be subdivided temporally, in
that polygamy can be simultaneous or
sequential. Simultaneous polygamy refers to the
case in an individual maintains numerous mating
partners in the same general time frame, whereas
sequential polygamy involves individuals forming
many short term pair bonds in sequence during a
given breeding season

40.  3. PROMISCUOUS MATING SYSTEMS
 Promiscuous mating systems occur when females
mate with multiple males, and males mate with
multiple females.
 When polyandry and polygyny are occurring in the
same population at the same time a breeding system
is said to be promiscuous. There are two very
different kinds of promiscuity, which vary
dramatically as a function of the presence or absence
of pair bonds between mating individuals.

41.  In one form of promiscuity, both males and females
mate with many partners and no pair bonds are formed
 For example, a male may defend a territory that contains
food, and females may visit such territories, obtain food,
mate with a male, and then repeat this sequence many
times
 For example, during their estrous period, female Barbary
macaques (Macaca sylvanus) search for new male mating
partners after each copulation, and males use female
signals to gauge sexual receptivity, which has the effect of
minimizing the chances that a female will mate with just
one male

42.  In the second type of promiscuous breeding system,
polygynandry, several males form pair bonds with
several females simultaneously

43.  SPERM COMPETITION
 In many polyandrous and promiscuous breeding
systems, there is a great deal of variation in
reproductive success between individuals. With
respect to males, a few individuals may obtain the
vast majority of matings in a population, and many
males may fail to obtain even a single mating
opportunity
 the direct competition between the sperm of
different males to fertilize a female‘s eggs—on
mating success

45.  Define and distinguish among serial monogamy,
serial polygyny, simultaneous polygyny, promiscuity
with pair bonds, and promiscuity without pair bonds

46. Lecture # 3
EUSOCIALITY: DIVISION INTO CASTES

48. What is eusociality?
 The most extreme form of social organization is called
‗eusociality‘ and is characterized by;
 Reproductive division of labour, where some members
of the group lose their reproductive capacity altogether
and become members of a worker ‗caste‘.
 The term "eusocial" was introduced in 1966 by Suzanne
Batra, who used it to describe nesting behavior
in Halictine bees.
 Although sterile themselves, their efforts increase the
reproductive output of the colony as a whole through
helping members of the reproductive caste.

49.  Eusociality is distinguished from all other social systems
because individuals of at least one caste usually lose the
ability to perform at least one behavior characteristic of
individuals in another caste.
 Examples:
 It is associated with a high degree of relatedness between
members of all the different castes and with an overlap
between generations.
 Eusociality exists in
certain insects, crustaceans and mammals. It is mostly
observed and studied in the Hymenoptera (ants, bees,
and wasps) and in Isoptera (termites).

50.  Until quite recently, eusociality was associated
exclusively with the social insects, but then Jarvis
(1981) described true eusociality in a
mammal – the naked mole rats
 Naked mole rats are the longest-living rodent species
 They live in large groups in which a single queen
and usually somewhere between one and three males
are the only individuals that mate and reproduce in
the entire colony.

51.  Non reproductive male and female naked mole rats,
which live much shorter lives than reproductive
naked mole rats, undertake a wide variety of
cooperative behaviors, such as digging new tunnels
for the colony, sweeping debris, grooming the queen,
and defending against predators

52. Naked Mole Rats

62. Territoriality

63.  The home range of an animal is the area where it
spends its time; it is the region that encompasses
all the resources the animal requires to survive and
reproduce.
 Competition for food and other resources influences
how animals are distributed in space.
 Individuals are nomads, constantly wandering,
rarely returning to the same place with any regularity

64.  Territoriality is typically defined as the occupation
and defense of a particular area.
 Territories can provide their owners with exclusive
access to food, mates, and safe haven from predators,
and are typically vigorously defended from intruders.
 Such defense can be costly, in terms of both time and
energy. Models of territoriality consider both the
costs and benefi ts of owning a territory. When the
benefi ts are greater than the costs, territory defense
is economically feasible and will be favored by
natural selection