8 Animals in Groups-High

Animals in Groups FOCUS Question How does living in a group help vertebrates survive?

Animal Groups A group of vervet monkeys are feeding in a grassy area when they hear a low grunt. They quickly look up and run to the nearest bush. The grunt came from another vervet warning them that an eagle was nearby. Living in a group, or being social, helps many vertebrate species survive. A group may eat, sleep, move, and nest together all year long or for just part of the year. A group may have a few members or millions. Not all vertebrates live in groups. But for those that do, being social has powerful benefits. Wowser! Vervet monkeys have different warning calls for different predators.

Dinnertime! Being social can make it easier to get food. Some species use cooperative hunting. For example, Harris's hawks team up to hunt rabbits and other animals. During a hunt, each hawk does something different. One bird may spot the prey while another forces it out of bushes. One hawk may block an escape route while another catches the prey. In an elephant family, the leader is an older female. She is called the matriarch. She can remember many places where the plants they eat grow. When food becomes hard to find in one place, she leads her group to another place.

Better Safe Than Sorry Living in a group can protect members from predators. Zebras live in large herds. With many animals watching for danger, it's easier to stay safe. And since each zebra can spend less time watching, it has more time to eat. Moving as a group can help animals stay alive by confusing their predators. Minnows are fish that swim in large schools. Fish that hunt them have a hard time picking a single minnow to chase. If a predator gets close, the school may split into two groups or quickly swim in all directions.

Meerkats live in groups of up to fifty (see cover). They stay safe in underground burrows. But some must leave their burrow each day to find food. Group members take turns watching for predators when the group is out. If the guard, or sentinel, spots danger, it barks to warn the others. Group behavior also helps animals protect their young. Crows bother and even attack birds of prey that hunt young birds. This behavior is called mobbing. Musk oxen stand in a close circle facing out if a wolf pack is near. The calves stay inside the circle.

Move as a Team Traveling in a group makes it easier for some vertebrates to get where they're going. When geese fly in a V-formation, they fly just behind and to the side of the bird ahead of them. They also beat their wings in time with the bird in front. This way of flying lowers the wind resistance— the force acting against the geese as they fly. As a result, the birds use less energy. They can fly for a long time before needing to rest. Science in Your World During bike races, riders often line up to lower wind resistance and save energy. Like geese, they take turns leading.