Citation [122 page book available in hard copy at Lulu "dot" com]
Jones CB (2020) Female mantled howler monkey (Alouatta palliata
palliata: Primates, Atelidae) life-history strategies—a “major transi-
tions” approach to mammalian social evolution. Lulu.com.
Abstract: Howler monkeys [Alouatta spp.] are wholly herbivorous. Based on earlier work by the present author [1978; 1980], the "age-reversed" dominance system is described whereby young adult mantled howler females are dominant to older females; middle-aged females are dominant to old females and are subordinate to young females; and, old females are subordinate to young and middle-aged females. The dominance system is characterized by "temporal division-of-labor" ["age polyethism"] whereby "social foraging" exhibits work [foraging, in the present case] graded by age, with old female "workers" ["helpers"] engaged in most foraging activities for variable plant resources, young females accounting for least. Adult female life-history parameters are described based on a "life table" and shown to correspond to patterns of temporal environmental cycles, in particular, the 6-month pattern of rainfall which females can "track" relative to "generation time." To my knowledge, this is the first demonstration of "temporal division-of-labor" in primates. Cooperatively-breeding primates/mammals exhibit, by definition "reproductive division-of-labor," the first stage of "complex sociality" in mammals. Reproductive division-of-labor is absent in mantled howler monkeys. Social mole-rats have been shown to exhibit both temporal and reproductive division of labor.
References
Jones CB (1978) Aspects of reproduction in the mantled howler monkey (Alouatta palliata Gray). Unpublished Ph.D. dissertation, Cornell University, Ithaca, NY.
Jones CB (1980) The functions of status in the mantled howler monkey (Alouatta palliata Gray): intraspecific competition for group membership in a folivorous Neotropical primate. Primates 21: 389-405.