Demographic parameters and events in wild moustached tamarins (Saguinus mystax)

This paper examines demographic events in the context of population structure and genetic relationships in groups of wild moustached tamarins (Saguinus mystax). We used a combination of long-term behavioral observations and genetic data from a total of eight groups from a population in northeastern Peruvian Amazonia. The mean group size was 6.0 (range=4–9), including 2.5 adult males and 1.8 adult females. Within-group relatedness was generally high (r=0.3), and most nonbreeding individuals were either natal or closely related to the respective same-sex breeder. The mean annual persistence of adults in the groups was 70% and 68% for males and females, respectively, and the reproductive tenure of one breeding pair lasted for at least 6 years. Migrations predominantly occurred after stability-disrupting events such as the immigration of new individuals and/or the loss of breeding individuals, or when groups were rather large. Migrations of both breeding and nonbreeding males and females occurred. Our results show that the hypothesis of Ferrari and Lopes Ferrari [Folia Primatologica 52:132–147, 1989] that tamarins live in smaller and less stable groups with lower relatedness compared to marmosets does not generally hold true. In contrast, we found that tamarin groups can consist of predominantly related individuals, and are stable as well. It is also apparent that a single demographic event can produce a chain of subsequent complex demographic changes.

This paper examines demographic events in the context of population
structure and genetic relationships in groups of wild moustached
tamarins (Saguinus mystax). We used a combination of long-term
behavioral observations and genetic data from a total of eight groups
from a population in northeastern Peruvian Amazonia. The mean group
size was 6.0 (range=4–9), including 2.5 adult males and 1.8 adult females.
Within-group relatedness was generally high (r=0.3), and most nonbreeding
individuals were either natal or closely related to the respective
same-sex breeder. The mean annual persistence of adults in the groups
was 70% and 68% for males and females, respectively, and the
reproductive tenure of one breeding pair lasted for at least 6 years.
Migrations predominantly occurred after stability-disrupting events such
as the immigration of new individuals and/or the loss of breeding
individuals, or when groups were rather large. Migrations of both
breeding and nonbreeding males and females occurred. Our results show
that the hypothesis of Ferrari and Lopes Ferrari [Folia Primatologica
52:132–147, 1989] that tamarins live in smaller and less stable groups
with lower relatedness compared to marmosets does not generally hold
true. In contrast, we found that tamarin groups can consist of
predominantly related individuals, and are stable as well. It is also
apparent that a single demographic event can produce a chain of
subsequent complex demographic changes.

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