In nature, animals often gather into groups. You may even see this near your own neighborhood—a flock of doves on a telephone wire, a small herd of deer, a school of baby catfish near the shore of a pond, a gathering of turkeys near the edge of a cornfield, a pair of ducks in a marsh, a large flock of geese in flight, or sea lions gathered along a beach. Some animal groups occur in the wilderness, far from most people—packs of wolves, drifting herds of buffalo, traveling troops of monkeys, or families of elephants looking for food or water. It is certain that these animals are purposely grouping together, because if they weren’t, we’d instead see them scattered more individually across the landscape.
Biologists believe that animals form groups for numerous reasons. A group of animals has many more eyes, ears, and noses than an individual. So compared to one turkey, a flock of turkeys probably has an enhanced ability to see or smell a predator. A group of animals can effectively defend a territory from intruders of their own kind. For example, a pair of eagles can team up and chase another eagle away from their nesting area.
Groups of animals can divide up a task and accomplish things they could never accomplish individually (see in part Patterns 6 and 7). Several members from a pride of lions can go out and hunt large, dangerous prey such as water buffalo. During the hunt, some lions can chase while others wait to pounce. Meanwhile, other pride members remain back with the family, protecting the cubs from hyenas and other lions.
By congregating, animals can pass on knowledge through generations. Some fish species learn when or where to travel by following the experienced group members. Similarly, bobcat cubs will learn how to hunt from their mother before going off on their own.
Forming groups often gives animals quite an advantage. But being a member in a group has its downsides as well. It can hinder the acquisition of resources—one buffalo inside a large herd might be insulated from predators, but the grass in the middle of the herd isn’t as good as the ungrazed grass on the edge. A pride of lions might cooperate to take down an animal, but if the pride is large and exceedingly hungry, there might not be enough food to go around, and some of the lions might not get a share of the meal.
In other cases, the needs of the group members don’t match up. One bird in a migrating flock might be particularly tired and hungry, and ready to descend, but the other members of the flock might wish to fly many more miles before the next rest. Staying with the group too long could mean certain death for that individual. Some members of the monkey troop might want to feast on figs in the tree canopy, while others are in need of protein and would rather pick for ants and beetles off the ground.
Animals indeed form groups for good reasons, but in doing so, they face a conundrum. How can they enjoy the benefits of their group while minimizing the downside of being in that group?
Animals are keen, both to the positives and the negatives that come with grouping, so they often limit their group size. They may also choose to group and then divide based upon changing conditions. This occurs, for example, with Canada geese. These birds often migrate together in large numbers. This probably helps them navigate and stay safe during rest stops. But when it comes time to breed, they separate off into pairs and generally create their own nesting territories—which probably helps them to obtain food to raise chicks.
African elephants also form groups that later disband. Their matriarchal family groups might contain about a dozen individuals. But sometimes a family will socialize and bond with another family. A handful of families can congregate, forming a clan. Under certain conditions or stressful situations, these elephant clans coalesce even further and form herds of hundreds. The main foundation of all these groupings is the small matriarchal family unit. The small family unit never breaks up, but the other groups break up after they form.
This pattern of congregating and then separating has been termed “fission-fusion.” It means that animals form groups, but they also disband. This fission-fusion behavior is present in many species, from pronghorn antelope to killer whales to baboons.
Further, the predominant pattern in this fission-fusion behavior is that the larger the grouping, the less time individuals spend within that grouping. Why would this be?
One primary factor seems to be that, as groups become larger and larger, the members simply don’t have enough in common to hold them together for as long. Individuals within larger groups don’t have the same territorial memories, the same social bond strength, the same culture, and the same genetic lineage.
It is important to recognize that group fission occurs when group costs outweigh benefits; this implies that when they decide to divide, individuals are sometimes choosing to forego significant group benefits because they are outweighed by even larger group costs.
If animals form groups, you might wonder who gets to lead the group. Who decides when and where the group will go? How do animal groups make decisions? Are some individuals compelled to go along with unfavorable decisions? Who should the group’s decisions yield the most benefit for?
Group Decision Making continues…