Packs (zoology)
Packs, in zoology, refer to organized social groups formed by certain species, primarily for activities such as traveling, hunting, feeding, and rearing young. Unlike herds, packs exhibit a stable composition and a social hierarchy, known as dominance hierarchies, where individuals rank based on their status within the group. This hierarchy often influences access to resources, with dominant individuals benefiting from greater food access and breeding opportunities, while subordinates typically engage in appeasement behaviors to avoid conflict. Various animal species, including wolves, lions, hyenas, and certain primates, exhibit pack behavior, employing different hunting strategies that leverage group dynamics to enhance their success in capturing prey. While the nutritional intake per individual may not necessarily increase with larger pack sizes, the advantages of cooperative hunting, defense against predators, and shared knowledge for rearing young contribute to the pack’s stability and effectiveness. Packs often consist of family units, promoting social bonds and cooperative care for offspring, thereby ensuring greater survival rates and the transfer of skills across generations.
Packs (zoology)
Packs occur when animals gather in highly organized social systems for traveling, hunting, feeding, and sleeping, usually with bonds of attachment between all members. These social units tend to be fairly stable in composition in comparison to most herds. This stability results in a social hierarchy, commonly called a dominance hierarchy, in which individuals are ranked in order of the number of other animals below them. Dominance hierarchies are maintained by dominant animals threatening subordinates, but fights are rare. Generally, subordinates engage in appeasement behaviors or avoid the dominant individual(s) altogether.
Dominance characteristics can be linked to body size, age, or weaponry, but in some packs, dominance is inherited. This is common in baboon and macaque monkey troops, and in hyena clans, and is dependent upon the mother’s rank. Females can move up in status when a younger sister is born; however, several subordinates can form a coalition to challenge an individual above them in status.
Advantages to dominant animals are many. Greater access to food is one common benefit, and in some packs, only the dominant pair breeds while the subordinates help to rear their young. Costs to dominants are that they are frequently challenged and run a greater risk of being killed or injured.
Packs and Predation
Predatory methods differ among species that form packs. Lions, who do not display endurance running, rely on stalking their prey and then rushing. During the rushing phase, lions will target any individual that appears to be slower or weaker than others in the prey herd. This tactic, also used by wolves, requires the predator to approach the prey very closely prior to rushing. In contrast, African wild dogs are known as coursers, chasing their prey for many miles until they can either drive it into other pack members or exhaust it. Hunting success in these dogs is very high. Hyenas vary their hunting tactics based on prey species. For attacks on wildebeest, they rush the herd, run for a while, stop to choose a target, and then resume the chase. As the chase continues, more and more hyenas join, and they generally take down their prey when it turns or runs into a lake or stream. They rely upon sheer numbers to overwhelm their target.
Theoretically, the formation of packs allows individuals within the group to exploit more food resources than they would be able to do on their own. In some pack species, this is the case: Cooperative hunts of lions are more successful than those by solitary lions, and there is some evidence to suggest the same for African wild dogs and hyenas. However, cooperation does not necessarily increase the amount of food available for each member of the pack. In some cases, the nutritional intake per individual decreases with an increase in the size of the pack. Nonetheless, packs may be more able to protect their kills from predators and thus may be more capable of consuming prey completely than could one individual. Packs may also be more successful at driving other packs off from a kill; lions are known for relying on the kills of hyenas for up to half of their food. Hyenas form clans of up to sixty individuals, but these clans break up when food is scarce. Similarly, lions may form larger prides when food is common, but may split into pairs or threesomes as food becomes scarce.
Packs and Rearing of Young
If food per individual is not increased with increasing pack size, then other reasons must be present for the establishment and continuation of a pack. Suggested benefits include better defense of cubs against infanticide by outside coalitions of males that take over the pack (common in lion prides), higher reproductive success because all pack members share in feeding the offspring, and providing food for young while they grow to maturity, thereby ensuring that offspring will survive.
Rearing young in a group can benefit the young because of opportunities to learn from more than one adult and from older adults. Wolves communicate and share knowledge across generations in their packs. Group rearing of the young can also provide the young with practice in certain tasks that later prove important when the offspring are on their own. Cooperative hunting can provide young with the opportunity to learn hunting skills from their elders. Generally, this benefit occurs in longer lived species that produce only a few young per year per female.
The formation of packs tends to occur in groups where kin form the nucleus of the association. Dominance hierarchies are common in such packs and serve to stabilize the relationships among group members. Benefits are then realized in terms of hunting larger prey, spreading food resources between the older and younger generation, help in rearing young from all or most members of the pack, and dissemination of skill learning from adults. In a few packs, associations can serve an anti-predatory function or can allow the defense of resources that would otherwise be taken by some other species or group.
Principal Terms
Antipredator Benefits: Benefits that come from actions that protect individuals from being killed
Carnivores: Animals that eat the flesh of other animals
Dominance Hierarchies: Ranks of individuals within a group
Bibliography
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