The Mating System of the Dwarf Mongoose - Obligate Monogomy

"Dwarf mongooses, like other cooperative breeders, face a classic trade-off between reproducing early in a small group in which their reproductive success and annual survival are relatively low, and reproducing later in larger groups in which their annual survival and eventual reproductive rates will be higher" (Rood, 1990). This problem has been traditionally addressed by performing a cost-benefit analysis of the inclusive fitness benefits for individuals that stay in the population versus the direct benefits that they receive by either dispersing to start a new mongoose pack or by staying in the group and helping with the raising of new mongooses.

The mating system of the dwarf mongoose is classified as an obligate monogamy mainly because within a mongoose pack, the dominant male and female are the primary reproducers but they require the help of subordinates to successfully raise offspring. Only on rare occasions did a solitary pair successfully raise offspring and when they did, the numbers of mature offspring were much smaller than normal (Creel, 1991). When pairs do not have the support of subordinates in reproducing, they rarely attempt this feat. In 237 pack years of observation, only 12 pairs attempted to mate by themselves and of these 12 pairs, only one pair was able to raise any offspring. They were successful in raising only one juvenile to adulthood. Thus, it is evolutionarily favorable to reproduce as a group and not as an individual monogamous pair. Rood, in 1990 also showed that larger packs have a greater number of surviving young than small packs despite a constant number of breeding individuals, one alpha pair, probably due to an increased litter size at birth (Rood, 1990).

The alpha pair, which constitute the primary breeding individuals within the population head a group consisting of adult offspring born within the group (4-5 individuals) who serve as reproductive helpers for several years after birth, juveniles born in the current mating season (4-5 individuals) and immigrants (from other packs that hope to eventually attain breeding status) (Rood, 1983). The hierarchy in the dwarf mongoose pack is primarily based on age, as the oldest members in a group are usually the group's founders (Rood, 1980). In the Serengeti, the natural habitat of the mongoose, the breeding season usually coincides with the rainy season between November and May. During the rainy season, the food resources are more available and thus, the alpha female is able to gain energy for reproduction. Studies of the dependence of reproduction on adequate resources, have demonstrated that if insufficient rain falls at the beginning of the rainy season in September, the mongooses will delay their breeding until December instead of November (Rood, 1983). When resources are adequate, the alpha female will produce approximately three litters of 2.88 individuals (range of 1-6 in observed packs) (Rood, 1983).