Social organisation and mating system of the narrow-striped mongoose (Mungotictis decemlineata)
Final Report Abstract
Due to their diverse adaptive abilities concerning ecology and behavior, Carnivorans represent a suitable group to study social evolution patterns of mammals. The Malagasy carnivores (Eupleridae) offer great potential to study the pace and mechanisms of social evolution of carnivores in a comparative perspective due to their long isolation on the island of Madagascar for more than 20 million years. The aim of this project was to investigate social organization, life-history and genetic characteristics of the Malagasy narrow-striped mongoose (Mungotictis decemlineata). This study was carried out in Kirindy Forest/CNFEREF, a seasonal dry forest in Western Madagascar. With inter-specific comparisons as a basis, we summarized and evaluated the state of knowledge on the social systems and life-history traits of herpestids and euplerids and put them into relation with predictions of socio-ecological theory. Including a pilot study, we individually marked 63 narrow-striped mongooses and analyzed the composition of social units with regard to sex and age of individuals, as well as their home range size and distribution. Additionally, we collected spatial, demographic and behavioral data in order to analyze sex ratios, mortality, and reproductive intervals and success, litter size and dispersal patterns within the study population. Hypotheses on social organization were tested with behavioral data on nutrition, predation and mating behavior. Thus, we were able to collect a significant data pool on a representative number of social units during the research period. The composition of groups, their temporal and spatial distribution, and particularly the patterns of spatial overlapping ranging areas revealed a type of gregarious sexual segregation that had not been observed among carnivores before. We also carried out genetic analyses based on mitochondrial DNA and microsatellite analyses to analyze the determinants of the composition and stability of social units as well as characteristics of the mating system. For these analyses, we used tissue samples of radio-collared individuals collected in the field. We identified a matrilineal population structure within female social units. These results supported our notion that males tend to disperse more than females. This finding was also reflected by the fact that females in same-sex units were in 88% of the cases more closely related to each other than expected by chance. In contrast to this, 82% of male dyads within their units were unrelated. This result as well as the variability in association patterns over several years suggest that possible benefits of kin selection is not the decisive factor for the evolution of this type of organization in M. decemlineata. Compared to Herpestidae, we found interesting characteristics of social organization in M. decemlineata as an indicator for a more complex form of sociality than described for most Herpestidae species, but these show clear differences compared to social systems of other group-living Herpistadae species. For example, we were not able to observe cooperative parental care in M. decemlineata. Further studies need to be carried out to bring more insight into the identification of the mechanisms of reproductive competition among females and its consequences for the composition of social units as well as determinants of reproductive success of males and females. In contrast, predation pressure appears to be an important factor driving the evolution of groups in these relatively small carnivores. In this context further interesting research questions arise with regard to the significance of ecological circumstances in Madagascar and their impact on the evolution of local mammalian taxa.
Publications
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(2014) Social systems and life-history characteristics of mongooses. Biological Reviews 89:173-198
Schneider TC & Kappeler PM
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(2016) Genetic population structure and relatedness in the narrow-striped mongoose (Mungotictis decemlineata), a social Malagasy carnivore with sexual segregation. Ecology and Evolution
Schneider TC, Kappeler PM & Pozzi L
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(2016) Gregarious sexual segregation: The unusual social organization of the Malagasy narrow-striped mongoose (Mungotictis decemlineata). Behavioral Ecology and Sociobiology
Schneider TC & Kappeler PM
