Meerkats are highly social animals inhabiting the arid landscapes of southern Africa. They live in groups called mobs, cooperating to forage, guard against predators, and care for young. Despite this cooperation, meerkats exhibit extreme aggression, including lethal violence, within their own groups. This behavior, counterintuitive for a communal species, reveals complex social dynamics and reproductive strategies.
Meerkat Social Structure
Meerkat groups typically range from 5 to 50 individuals, though larger aggregations have been observed. At the core of each mob is a strict social hierarchy, dominated by an alpha male and an alpha female, who usually monopolize reproduction. Subordinate members, often offspring of the dominant pair or unrelated individuals, play various roles such as babysitting, foraging, and acting as sentinels to watch for threats. This cooperative breeding system means that most group members contribute to raising the dominant pair’s offspring, even if they do not reproduce themselves.
The social structure is characterized by constant competition, particularly among females, for reproductive opportunities and access to resources like food and safe burrow sites. Dominant females maintain their position through physical prowess, vocalizations, and intricate social interactions. This hierarchy is not static; subordinate females may attempt to challenge the alpha pair’s authority, leading to power struggles that can reshape the group’s dynamics. The group’s survival and reproductive success are closely tied to the dominant pair’s ability to control breeding within the mob.
Reasons for Intragroup Killing
Intragroup killing in meerkats stems from intense reproductive competition and resource scarcity. Dominant females frequently commit infanticide, killing the offspring of subordinate females to eliminate rivals and ensure their own pups receive maximum care and resources. This maximizes the dominant female’s reproductive success, as her litter benefits from increased helper-to-pup ratios and reduced competition for food.
Subordinate females often face reproductive suppression, involving direct aggression, forced exile, or infanticide of their pups by the dominant female. Eviction, especially of pregnant subordinates, is a common tactic, and the stress of being cast out can lead to miscarriage. Outside the group, evicted individuals face high risks of starvation or predation, with minimal chances of joining another established group. Subordinate females can also commit infanticide, killing pups of other subordinates or even the dominant female to improve their own offspring’s survival prospects.
Competition for limited resources, such as food, water, and suitable burrow locations, can escalate aggression within a meerkat group. High population density or environmental stress, like periods of low rainfall, can exacerbate these aggressive behaviors and contribute to more frequent intragroup conflicts. While within-group violence is common, violent encounters with rival meerkat groups over territory can also result in fatalities, though these are less frequent than infanticide.
The Evolutionary Perspective
The persistence of behaviors like infanticide and expulsion in meerkats is understood through an evolutionary lens, focusing on reproductive success. From the dominant female’s perspective, suppressing other females’ reproduction ensures her genes are disproportionately passed on, maximizing her individual fitness. This behavior reduces competition for resources among pups and increases available helpers for her own offspring, enhancing their survival rates.
Subordinate females, despite aggression and reproductive suppression, often remain in the group because living alone is more perilous due to increased predation risk and difficulty finding food. Their presence provides indirect fitness benefits through kin selection, as they are often related to the dominant pair and help raise individuals sharing some of their genes. This system of reproductive control and resource allocation has evolved to thrive in challenging environments where resources are scarce and cooperation is essential for group survival.