SOCIAL SYSTEM
Courtesy of Marko Laakkonen
Packs
Banded mongooses are gregarious animals, unlike many of the other species in the Herpestidae family, which are solitary. They form multi-male/multi-female packs (De Luca and Ginsberg, 1999) larger than a single-family unit (Rood, 1975), which can range from 4-58 individuals (De Luca and Ginsberg, 1999, Rood, 1986, Neal, 1970). An analysis of a pack of 32 individuals revealed that 17 members were adults, 7 were half-grown juveniles, and 8 were young too small to leave the den (Neal, 1986). Members of the pack may be related or unrelated depending on how the pack was formed and how long the members have been together (see below). Some females remain in their natal packs for their entire lives. It is not yet known whether males remain in their natal packs or disperse after reaching adulthood (Rood, 1986). Within the group is a dominant male and female, each of which lead the group in foraging, indicate when to retreat from predators, and lead mobbing attacks against predators. Most or all adults in the pack raise the young communally by sharing the responsibility of babysitting the pups. The caregivers in the pack are oftentimes referred to as “escorts” (Neal, 1986).
Packs form when evicted or voluntarily dispersed individuals come together. In one study of eviction and dispersal in banded mongoose packs in Queen Elizabeth National Park, Uganda, pack fission occurred through two methods: eviction by intense aggression and voluntary dispersal into new packs. Both males and females participate in the eviction process, with males attacking members of both sexes while females only attack other females. Generally, the dominant members of the groups are the aggressors. The evicted or dispersed members then form new packs with evicted or dispersed mongooses from other groups. Establishment of home ranges by the new pack often results in intense fighting with other groups, favoring the more, well-established pack. Packs do not associate with one another and encounters between different groups are highly aggressive (Cant et. al., 2001).
Dominance Hierarchy
There has been little research discussing the dominance hierarchy in banded mongooses. Although it is known that each pack contains a dominant alpha pair (De Luca and Ginsberg, 1999, Rood, 1986), it remains unclear how this dominancy is established. Dominance amongst group members seems to be relatively independent of sex (Kingdon, 1977). According to Rood, the alpha male and female are the oldest members of the group (1986). One study analyzed the dominance rank of banded mongooses by quantifying the number of times supplantations occurred at food, the number of times individuals had feeding priority in a pack, and the number of times an individual led a pack. The study concluded that male dominance was not related to age or body condition. Age correlated with body condition in females, but body condition did not affect a female’s position within the dominance hierarchy (De Luca and Ginsberg, 1999).
Although this study revealed a linear dominance hierarchy within banded mongooses, the presence of a hierarchy did not produce drastic differences in resource allocation, adult survival, or reproduction in either males or females. The dominant individuals in the group did not regularly enforce their dominance through reproductive suppression or other means. This lack of dominance reinforcement may be due to the low ecological constraints present in banded mongoose populations, which result in low contest competition between individuals for resources. Because of the low ecological restraints, dominant individuals do not accrue much benefit from denying subordinates access to food. In fact, this behavior would actually be energetically costly. Dominant individuals do not have much leverage for suppressing lower-ranked individuals because dispersal is always a viable option. The lack of influence of dominance on resource allocation, survival, and reproduction suggests that contest competition for resources does not play a large role in influencing the social organization of banded mongooses. As a result, banded mongooses live in a relatively egalitarian social system (De Luca and Ginsberg, 1999).
This egalitarian social system, however, is present only when there are low ecological restraints. Ties between members are no longer equal when resources run low, specifically when group size becomes too large that it will hinder the reproductive success of the dominants. For example, female eviction always occurs during oestrus. This occurrence suggests that competition between breeding females may play a role in regulating the number of pups born into a group. These findings reveal that subordinates may not always be beneficial and that low resources may be one circumstance in which dominants may exert their power in order to protect their own reproductive interests (De Luca and Ginsberg, 1999).
Why live in packs?
Banded mongooses live in packs because the benefits of group living outweigh solitary life. First of all, living in large social groups provides banded mongooses with predator protection. According to Rood, predation risk is the most significant influence in pack formation. their predators include eagles, snakes, jackals, and other large predators. In social groups, banded mongooses have a better capability of detecting and harassing predators as well as rescuing pack members from predators. Traveling in large groups allows the mongooses to utilize the “selfish herd” effect, whereby a group of animals have greater predator protection because of the increased numbers of eyes to look out for predators. If a mongoose senses danger, it releases an alarm call that will notify the rest of the group to run for cover. Banded mongooses are also known to clump together into a large mass in the presence of a predator, confusing the predator and making it more difficult for the predator to focus on catching a single mongoose out of the whole bunch. There have also been instances when a group pursues a martial eagle after it snatches a pack member, causing it to release the captive banded mongoose (Rood, 1983). In addition, having large groups allow banded mongooses to have more sentinels to look out for predators near the termite mound and to prevent predators such as snakes from entering it. Secondly, living in groups allows the banded mongooses to develop a division of labor among pack members. The sharing of responsibilities can be seen in the communal raising of young. While the pack forages for food, a helper stays behind to baby-sit the pups that are too young to leave the den. Other pack members bring insects back to the termite mound for the young. Taking turns caring of young gives mongooses the ability to raise young while also giving every member a chance to forage as well. Babysitting young and having enough time to forage would be energetically demanding if it were shared between only two parents in a single-family unit.
Similar to other mammals that form packs, however, the benefits of living in a group outweigh solitary life only to the extent where there are enough resources for all members. Evicted banded mongooses tend to come from very large packs. In these cases, it can be inferred that reducing group size was needed to secure enough resources for group members. Mongooses that voluntarily leave their group are thought to do so in order to gain increased access to mates or to prevent inbreeding. Therefore, group size is dependent on the availability of food and resources.
| General Description | Habitat and Habitat Utilization | Social System | Social Spacing | Social Relationships | Social Cooperation | Summary | References |
* This web site was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2005