For human’s, living in a family group is normal. When we reach maturity sometime usually after 18 years old, we leave the family group, establish our own territory, and may begin a new family. The same is true for many animal species.
Some animals live in groups as it helps them find and hunt food easier. Wolves are the perfect example of this. However, one of the main reasons for group living is to protect themselves from predators. Living together also helps small mammals keep warm at night, while birds group together to fly in a V formation to allow them to migrate great distances.
Whether it is a small family group of parents and offspring, a large extended family, or a herd of several related groups, living in a community has its advantages. Naturally, some species live solitary lives, and we look at these benefits and the reasons why many animals live in groups.
Benefits to Group Living
Perhaps the most famous example of a North American group living is the wolf. The gray wolf, often referred to simply as a wolf, can be found in Northern US states and Canada. There are several subspecies of gray wolf, including:
- Great Plains wolf: native to Rocky mountains, midwestern US, East, Northeast, and Southwest Canada. The population is stable.
- Mackenzie Valley wolf: native to Northern Rockies, Alaska, Western and Central Canada. The population is stable.
- Eastern wolf: native to Eastern Canada. The population is threatened but stable.
- Arctic wolf: native to the Canadian Arctic and Northern Greenland. The population is stable.
- Red wolf: native to North America but found only in North Carolina in two wildlife refuges. There are only 100 wild individuals. They were officially extinct in the wild in the 1980s, but breeding programs with captive animals have reintroduced them into protected areas.
Wolves have a strict group hierarchy. Only the dominant male and female will reproduce, but all members of the group help with rearing the young. When traveling, the pack leader will either be the dominant male or female, with the other dominant wolf towards the rear to protect the weaker members.
Hunting is variable in packs. Some wolves will hunt individually for small prey such as rabbits, while several individuals will hunt together for larger prey like elk and caribou. When the prey animal is brought back to the pack, the dominant pair eat first, followed by lower ranking individuals. Subordinate members will take a piece and move away from the group to prevent their share being taken by a higher ranking member.
During weaning, pups will share their mother’s food, but as they mature, they will be encouraged to feed from the carcass with the other group members or to hunt small prey animals for themselves.
Living in a group means wolves are better able to bring down large prey animals, which provides more food for the group. A large family unit also means there are more individuals able to help with the care of the cubs, which ensure better chances of survival.
Another benefit to living in a group is the conservation of body heat. We see this best in prey animals such as rabbits. They live in large groups with complex underground burrows. The night-time temperature can drop within these burrows, so group members will sleep huddled together for warmth. A mother will give birth to her litter and then seal the nesting chamber. During this time, the littermates remain close together to maintain a stable temperature.
Locomotion can be thought of as a group effort rather than based on each individual. When birds migrate, they travel in a uniform ‘V’ formation. This is not just a coincidence. The lead bird creates a slipstream in the air currents, giving less turbulence for the birds behind. Every so often, another individual will trade places with the lead bird so they can rest in the smooth air currents.
This method of travel means the birds are expending less energy during the flight and can travel longer distances, tiring less frequently than birds travelling alone.
One of the biggest advantages of living in a group is protection from predators. Herds of deer and wild horses will take turns watching for danger, giving nearby members time to graze or rest. If an individual senses danger, they will call the group who can react quickly. Having lots of individuals looking for danger gives a better chance of survival than a single animal who would be vulnerable while resting or foraging for food.
Living in a group also decreases the chances of being predated. Since a large group has so many members, the weakest are always most at risk. Healthy individuals have a greater chance of avoiding predators in a large community than a small group with a handful of members.
This is best observed in schooling fish living in the open ocean. They do not have the protective crevices of fish living in coastal regions or coral reefs, so they have adapted a different form of defense against predators.
Species such as the Atlantic herring can number thousands of fish in a single school. When predators are nearby, the school will begin swimming in concentric circles, forming a huge ball called a bait ball. The purpose of this is for protection and fish will try to push their way into the centre of the ball where it is safest.
Predatory animals such as sharks, dolphins, and seals will use sudden bursts of speed through the middle of the bait ball in an attempt to catch fish. However, sharks can often be seen gliding slowly through the middle of a bait ball as if trying to catch the fish off-guard. The fish move seamlessly, creating a tunnel with the shark passing through the center.
The bait ball puts off some predators due to the sheer size. A large ball of thousands of fish can be quite intimidating, especially for juvenile predators who are inexperienced hunters.
The orca, or killer whale, is perhaps one of the most intelligent hunters on the planet. They are found in all oceans of the world, having adapted to different climates with apparent ease.
In the frigid waters of Northern Canada, orcas have learned a new way of hunting. A pair or small group (pod) will chase a seal in the hopes of catching them in open water. If a seal manages to haul out onto an ice floe, they may think they are safe. However, recent research expeditions have observed orcas working together to create small waves with the intention of rocking the ice floe and forcing the seal back into the water.
Orcas are apex predators, meaning they have no natural predators themselves, so they do not need to hunt in groups. They live in groups, called pods, mainly for the protection of the young. Orcas are highly social creatures, but they usually catch fish to eat for themselves. A small number of orcas, such as those who live in colder regions, will hunt seals and other whales and share the carcass, as it can provide nourishment for several individuals.
Benefits to Solitary Living
While the advantages of living in a group may be obvious, many species live solitary lives, only coming into contact with another member of their species for reproduction.
Generally, most solitary animals will begin to reject their juvenile offspring when they are ready to mate again. Living alone means it is not beneficial to have the previous year’s offspring to care for while also caring for a newborn.
The main advantage to living alone is that the animal only needs to find food to sustain itself, and in the case of females, their offspring during the weaning process. There is less competition for food resources for solitary animals compared to those who live in groups.
An added benefit of a solitary lifestyle is the decrease in the risk of disease transmission. Living in a large group means the transmission of infection or parasites is common, but living alone greatly reduces this risk. If a solitary animal dies of an illness or infection, the chances are another of their species will not come across them for some time. In these cases, the animal will have begun to decompose, and the bacteria or virus will have died due to lack of a healthy host.
The great white shark lives alone for most of the year, only forming a group during the breeding season. As soon as the mating season is over, the individual sharks will return to their solitary lives. When a great white gives birth, she may prey on her own young, so they must swim away quickly to survive.
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