Advantages of Sociality
|Figure 38-11 Mixed herd of topi and
on the savanna of
Living together may be beneficial in
many ways. One obvious benefit for
social aggregations is defense, both
passive and active, from predators.
Musk-oxen that form a passive defensive
circle when threatened by a wolf
pack are much less vulnerable than an
individual facing the wolves alone.
As an example of active defense, a
breeding colony of gulls, alerted by the
alarm calls of a few, attack predators en masse;
this collective attack is certain
to discourage a predator more
effectively than individual attacks.
Members of a town of prairie dogs,
although divided into social units
called coteries, cooperate by warning
each other with a special bark when
danger threatens. Thus every individual
in a social organization benefits
from the eyes, ears, and noses of all
other members of the group. Experimental
tests using a wide variety of
predators and prey support the notion
that the more animals there are in a
group, the less likely an individual
within the group will be eaten.
Sociality offers several benefits to
animals reproduction. It facilitates
encounters between males and
females, which, for solitary animals,
may consume much time and energy.
Sociality also helps synchronize reproductive
behavior through the mutual
stimulation that individuals have on
one another. Among colonial birds the
sounds and displays of courting individuals
set in motion prereproductive
endocrine changes in other individuals.
Because there is more social stimulation,
large colonies of gulls produce
more young per nest than do small
colonies. Furthermore, parental care
that social animals provide their offspring
increases survival of the brood
(Figure 38-12). Social living provides
opportunities for individuals to give aid
and to share food with young other
than their own. Such interactions within
a social network have produced some
intricate cooperative behavior among
parents, their young, and their kin.
Of the many other advantages of
social organization noted by behaviorists,
we will mention only a few in this
brief treatment: cooperation in hunting
for food; huddling for mutual protection
from severe weather; opportunities
for division of labor, which is especially
well developed in the social
insects with their caste systems; and
the potential for learning and transmitting
useful information through the
|Figure 38-13 Japanese macaque washing
sweet potatoes.The tradition
began when a
named Imo began washing
sand from the
potatoes before eating them.
of the troop
imitated the behavior.
|Figure 38-12 An infant yellow baboon
(Papio cyanocephalus) “jockey rides” its
Later, as the infant is
the mother-infant bond weakens
infant will be refused rides.
Observers of a seminatural colony
of macaque monkeys in Japan recount
an interesting example of acquiring
and passing tradition in a society. The
macaques were provisioned with
sweet potatoes and wheat at a feeding
station on the beach of an island
colony. One day a young female
named Imo was observed washing the
sand off a sweet potato in seawater.
The behavior was quickly imitated by
Imo’s playmates and later by Imo’s
mother. Still later when the young
members of the troop became mothers
they waded into the sea to wash their
potatoes; their offspring imitated them
without hesitation. The tradition was
firmly established in the troop (Figure
Some years later, Imo, an adult,
discovered that she could separate
wheat from sand by tossing a handfulof sandy wheat in the water; allowing
the sand to sink, she could scoop up
the floating wheat to eat. Again, within
a few years, wheat-sifting became a
tradition in the troop.
Imo’s peers and social inferiors
copied her innovations most readily.
The adult males, her superiors in the
social hierarchy, would not adopt the
practice but continued laboriously to
pick wet sand grains off their sweet
potatoes and scout the beach for single
grains of wheat.
Social living also has some disadvantages
as compared with a solitary
existence for some animals. Species
that survive by camouflage from
potential predators profit by being dispersed.
Large predators benefit from a
solitary existence for a different reason,
their requirement for a large supply of
prey. Thus there is no overriding adaptive
advantage to sociality that inevitably
selects against the solitary way
of life. It depends on the ecological