Numerous animal species, including humans, are social organisms that live in groups. For these species, living in groups provides benefits they would not obtain as individuals. In other words, group behavior in these species contributes to the group's survival rather than only benefiting the individual.
In this article, we will discuss group behavior in the biological sense- its definition, its advantages, disadvantages, the different types, and some examples.
What is Group Behavior in Biology?
Let's start with the definition of group behavior.
Group behaviors involve groups of organisms engaging the same behavior at the same time and generally benefit the survival of the group.
Group behavior is opposed to individual behaviors, which involve single organisms carrying out behaviors that benefit themselves.
Cooperative social behaviors are the type that tends to benefit groups the most, though three other behaviors are also recognized:
Altruistic behaviors benefit the receiving individual(s) while being detrimental to the donating individual(s).
Egoistic behaviors are detrimental to the receiving individual(s) but beneficial to the donor(s).
Revengeful behaviors are detrimental to both donors and receivers
Cooperative behaviors are beneficial to both the receiving individual and the donor. So, you can see why cooperative social behaviors are vital to the proper functioning of groups!
Group Behavior Benefits and Detriments
There are benefits and disadvantages to group living. So, let's talk about this.
Organisms living in groups can have decreased levels of predation since potential predators can become overwhelmed or even confused by large groups of prey animals. Even if the level of predation remains constant, the "dilution effect" created by the presence of more individuals decreases the risk of predation for each individual.
Larger groups also have more individuals keeping watch for the presence of predators. Larger groups, however, have a more difficult time hiding from predators.
The dilution effect is used to describe how the greater the size of the group of prey species, the lower the chance of predation for individuals of that group.
Group living also means more individuals are available to forage or hunt for food, though this increases intraspecific competition for and depletion of resources. Group living (and therefore, group behavior) can also increase the risk of spreading disease due to so many individuals living close to one another.
Advantages | Disadvantages |
Increased protection for predators | Increased risk of being spotted by predators if in large groups |
Increased hunting efficiency | Increased intraspecific competition for resources |
Increased movement efficiency | Increased risk of infection |
Access to mates | Increased sexual competitions |
| Increased risk of offspring being killed by the group |
Table 1: advantages and disadvantages of group behavior.
Types and Examples of Group Behavior Biology
There are generally considered to be four types of group behavior in animals:
Anti-predator behaviors
Foraging/hunting behaviors
Increased movement efficiency
Benefits to social interactions.
Group Behavior in Animals: Anti-predator Behavior
As stated above, living in groups can provide some protection from predation. Large groups of prey may be able to physically overwhelm potential predators.
For example, groups of giant river otters (Pteronura brasiliensis) can physically repel or even kill yacare caiman (Caiman yacare), attempting to prey upon them, something they could not do alone. Larger groups may also confuse potential predators through sensory overload.
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Figure 1: Giant river otters (left) are able to repel attacks by yacare caiman (right) due to coordinated group defensive behavior
Another way large groups can minimize predation is by having more individuals keep watch for predators.
Meerkats (Suricata suricatta), for example, live in large groups that are constantly on the lookout for potential dangers, for which they will produce an alarm call if sighted, alerting the rest of the group.
Lastly, when groups are very large, even constant rates of predation may still result in decreased chances of predation for individuals, though the chances are not uniform throughout the group. Vulnerable individuals and those along the group's periphery have much higher chances of being predated.
Let's look at another example. The white-nosed coati (Nasua narica) is a mammal species related to raccoons and native to Central America, Mexico, and limited portions of the southern United States (Arizona, New Mexico, and Texas). These coatis live in groups and forage for fruits, insects, and small vertebrates.
The major predators of coatis are jaguars (Panthera onca) and mountain lions (Puma concolor), which they encounter throughout their range and account for over half of all coati predation.
A study found that lone coatis were significantly more likely to be predated by jaguars and pumas than those in groups. Group living provides coatis with numerous protections from predation by these cats, ranging from mitigation (increased vigilance and alarm calling) to defensive (overwhelming and even attacking the cats).
Figure 2: White-nosed coatis (left) are capable of defending themselves from predatory attacks by big cats, such as the jaguar (right), thanks to living in groups.
Group Behavior in Animals: Hunting and Foraging Behavior
Having more individuals in a group means that more energy can be focused on foraging for food (e.g., fruits, nuts, and vegetables) or cooperative hunting.
Foraging in groups can increase the food resource yield and decrease the time needed to forage. In addition, it can allow for important learned behaviors to be passed on to the next generation from older individuals.
For example, olive baboons (Papio anubis) teach young individuals how to forage for food. Moreover, male baboons occasionally watch over juveniles to allow their mothers a chance to forage unburdened!
Group living also allows for cooperative "pack hunting" behavior. Predators such as chimpanzees, lions, wolves, whales, and possibly even one crocodile species participate in pack-hunting behavior. Pack hunting involves small groups of predators working together in groups to subdue prey species. This allows these predators to subdue larger prey species than they would be capable of subduing alone.
The African lion (P. leo) is well known as a pack hunter, where female lions hunt in groups to take down a wide variety of prey species. In a few areas, particularly Chobe National Park in Botswana, groups of lions have learned to coordinate to take down the largest living terrestrial mammals-African elephants (Loxodonta africana) (Fig. 3).
Adult African elephants are far too large for any single predator, of any living species, to prey upon. But in large groups, these lions have learned how to gradually wear down and prey upon these gargantuan mammals.
Figure 3: In some areas, groups of African lions (left) have learned how to prey upon African elephants (right).
Group Behavior in Animals: Increased Movement Efficiency
Living in groups allows organisms to coordinate movements better on a large scale. This is achieved through the monitoring of the movements of neighboring individuals. Animals such as flocks of birds, schools of fish, and some insects have increased movement efficiency due to group coordination.
Take the starlings, for example. Starlings are birds of the Sturnidae family distributed worldwide in most habitats. Starlings flock together in groups called murmurations while flying. These starlings remain together and in sync by monitoring the movements of the nearest seven other starlings.
This allows thousands of starlings to coordinate their movements so efficiently that they remain just inches from each other, moving very quickly without collisions. The reasons starlings move in these massive murmurations are not entirely understood. However, it is hypothesized that it may reduce chances of predation by raptors or as a way to invite other starlings to a night roosting location.
Figure 4: A murmuration of starlings.
Group Behavior in Animals: Benefits to Social Interaction and Structure
Life in groups can have many benefits to social interactions and structures. Some examples of benefits include increased emotional satisfaction and bonding, mutual cleaning, and a more stable lifestyle. However, animals that naturally live in groups tend to only thrive within a group and may suffer mental and physical health issues if placed in isolation.
Bonobos (Pan paniscus), for example, are some of the closest living relatives of humans and, like humans, are highly social animals that live in groups. Even among other Great Apes, bonobos have unique and complex social behaviors.
One of the most notable features of bonobo social behaviors is the general lack of aggression and only mild conflict that occurs between individuals and groups, even between males. This is unique among primates, including humans. Bonobos also frequently engage in sexual activity as a social practice rather than an exclusively reproductive practice.
Group living has allowed bonobos to develop these complex social behaviors.
Great apes are any members of the Hominidae family, which includes chimpanzees, bonobos, orangutans, gorillas, and humans.
Figure 5: Two bonobos engaging in social interaction. Source: Wikimedia Commons, Public Domain.
Group Behavior Biology - Key takeaways
- Group behaviors are those that involve groups of organisms engaging in them at the same time and generally benefit the survival of the group.
- Cooperative social behaviors are the type that tends to benefit groups the most, though there are three other recognized-altruistic, egoistic, and revengeful behaviors.
- Group living has both advantages and disadvantages. Group behavior increases the chances of survival through decreased predation, increased resource acquisition, and more. But group living can also increase the spread of disease, intraspecific competition, and more.
- There are generally considered to be four types of group behavior in animals: anti-predator behaviors, foraging/hunting behaviors, increased movement efficiency, and benefits to social interactions.
References
- Figure 4: Starling murmuration (https://commons.wikimedia.org/wiki/File:Starling_Murmuration_(22224258175).jpg) by Airwolfhound (https://www.flickr.com/people/24874528@N04) is licensed by CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0/deed.en).
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