Dispersal
Facts in this section taken from (Doolan and MacDonald, 1996, Zoology: 240)
Emigration from the natal burrow plays a central role in shaping meerkat sociality. Breeding opportunities are limited before dispersal due to inbreeding avoidance, but the costs of dispersal are high. Whether a meerkat disperses depends on its current or future fitness opportunities in the burrow balanced against the chances of reproducing after emigration. Dispersal is greatest immediately before or at the beginning of the mating season. Rates of dispersal are highest for animals who become adults while their same sex parent still occupies the alpha position. These facts point to reproductive competition as the drive for dispersal, because reproductive opportunities are at their highest during the breeding season, and inbreeding avoidance in meerkats is strong.
Meerkats who remain in the natal burrow gain indirect fitness benefits because they serve as helpers to the dominant pair, to which they are closely related. They also stand a chance to inherit the alpha position in the future. Females are more likely to gain breeding status in their natal burrow than are males, a fact that explains why more males than females disperse. However, meerkats that don’t disperse sacrifice energy through the same helping behavior that brings them indirect fitness, and they seldom gain direct fitness.
Meerkats who disperse can gain breeding opportunities four different ways. They can immigrate to a band as a subordinate and wait to attain the alpha position. They can join a band that lacks the same sex breeder and fill the position. They can start a new band with other dispersing meerkats. Or, they can immigrate to a band and overthrow the same sex breeder. All strategies potentially incur large costs. Predation is a high risk during dispersal, as the meerkats do not have a burrow in which to retreat. Also, attack from same-sex conspecifics in the band to which they immigrate is likely. Immigrating meerkats represent an increase in reproductive competition whether or not they challenge the same-sex dominant.
To reduce the costs of dispersing, meerkats go on prospecting forays to assess the neighboring bands while still retaining membership of their natal band. In doing so, they decrease the risk of predation by becoming familiar with the foreign areas, and they can better determine the probability of immigrating successfully. They analyze scent marks and shadow bands to determine band composition and fighting capabilities of band members. Even after successful immigration, meerkats may make forays back to their natal burrow to continue evaluating the benefits of membership in a foreign band.

Another way to reduce the costs of dispersal is to immigrate in coalitions. There are more eyes to look for predators, and groups have a much better chance than individuals of taking over a band. Males disperse in groups more often than females. They often leave with kin, affording themselves indirect fitness, though they also form temporary coalitions with dispersing males from other bands. Because they must support the costs associated with motherhood, females cannot afford the costs of ousting dominant females of foreign bands. For this reason, they do not need to immigrate in groups. Also, subordinate females often do not leave of their own volition. Expulsion by the alpha female can lead to immigration for subordinate females (Clutton-Brock et al., Dec 1998). For more information about subordinate female expulsion, please see the section entitled “Reproductive Suppression.”

 

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This web site was completed by Katie Fitzpatrick in partial fulfillment of the requirements for Dr. Verna Case’s Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2004.

Please direct all comments and questions to Katie Fitzpatrick at kafitzpatrick@davidson.edu