Many animals find safety in numbers by living in large groups.
Bison live in herds. Tuna and many other fish species form large
schools. Geese and other birds form flocks as they migrate from
one place to another when the seasons change. Aphids cluster
together on stems.
|This meerkat in the Kalahari Desert of
stands guard atop a
ready to call out a warning if predators
Living in a group helps animals defend themselves against
predators in several ways. lone animals must rely only on their
own senses, but an animal in a group benefits by having lots of
other animals’ eyes, ears, and noses on the alert for danger. An
animal in a group also has a smaller chance of being the unlucky
individual picked out by a predator.
In addition, a group of animals fleeing from a predator can
create confusion. This makes it harder for a predator to focus on
one animal to catch. A school of fish will split in two to avoid a
predator, and then quickly regroup behind it. A herd of zebras
can become a dazzling display of black and white stripes, making
it more difficult for a lion to see where one zebra ends and another
begins. Starlings clump together when a hawk approaches.
This makes it harder for the hawk to single out one bird.
Animal groups may be made up of just one species. Striped
coral-reef catfish, for example, travel in a dense, ball-shaped
school when they are young. Many seabirds nest in crowded colonies
on islands and gang up on trespassing predators.
Animals may also form mixed groups, such as the herds of
hoofed animals that migrate across Africa’s plains. There, shaggy
horned animals called gnus form herds of up to one million animals.
Traveling along with them are tens of thousands of zebras
Groups of animals also may work together to drive off a
predator. One of the most famous examples of group defense is
the circle formed by musk oxen. Musk oxen are huge, shaggy
cattle that live on the broad, snowy lands of the Arctic known as
the tundra. Females and young live in herds year-round. Males
join these herds for part of the year.
If wolves attack a herd, musk oxen form a circle with their
calves in the middle and their horns facing out. The wolves face
a wall of horns backed up by hundreds of pounds of muscle. Musk
oxen also will rush out and try to hook a wolf with their horns. Scientists have seen other animals, such as gnus and white rhinos,
form defensive circles.
Zebras do not form circles, but small herds do work together
to foil predators. If a pack of hyenas creeps up on a herd, a male
zebra charges at them, ready to bite and kick. The females and
young gather together and move away. Often a female known
as the lead mare guides them. Wild horses also behave in this
way. Other animals, such as elephants and cattle, approach and
threaten predators that come near their herds.
Large African monkeys called baboons also live in groups.
They sometimes work together to drive off predators. Scientists
have seen males of one species of baboon ganging up on leopards
and dogs to chase them away. A smaller monkey, the red colobus,
also teams up with other males to defend their group when
chimpanzees attack. The male monkeys get between the females
and their young and the chimps. They leap onto the chimps and
Many species of small, burrowing mammals cooperate
against predators, too. These animals alert each other to danger.
Meerkats are weasel-like animals that live in dry lands of southern
Africa. When they leave their burrows to look for food, a
few animals stand guard. The guards climb onto a rock or
a termite mound and stand on their hind legs. They scan
the skies for eagles and hawks. They also keep an eye out for hungry
jackals. If a predator appears, the guards call quickly and sharply.
This is the signal for everybody to dive into the burrows.
North American prairie dogs, which are related to squirrels,
also live in burrows. The burrows cover a huge area of land
known as a prairie-dog town. Prairie dogs do not post guards.
Yet, because there are so many prairie dogs, someone in the town
is likely to spot a hawk or a coyote. Prairie dogs that spot danger
will give a danger call. At this signal, everybody scurries underground