Sources of variation in social tolerance in mouse lemurs (Microcebus spp.)

Abstract

Background Social tolerance strongly influences the patterns of affiliation and aggression in animal societies. However, not much is known about the variation of social tolerance in species living in dispersed social systems that combine solitary foraging activities with the need of coordinating social interactions with conspecifics on a regular basis. This study aims to investigate the sources of variation in social tolerance within a Malagasy primate radiation with dispersed social systems, the mouse lemurs ( Microcebus spp.). Six mouse lemur species were selected as model species that belong to three different taxonomic clades, live in two types of forest environments (dry and humid), and differed in this study with respect to their reproductive activity. Six male–female and six male–male dyads of each species were tested temporarily in a standardized social encounter paradigm in Madagascar to collect data on joint use of space, non-agonistic body contacts, aggression rates, the number of conflicts and the establishment of intra- and intersexual dominance. Results Male–female dyads of the six species differed significantly in the frequency of affiliative and agonistic behaviors. In contrast, the variations between male–male dyads could not be explained by one parameter only, but clade membership, forest type, reproductive state as well as species were all suggested to be partially influential. Only one species ( Microcebus mamiratra ) showed signals of unambiguous female dominance in all male–female dyads, whereas the others had no or only a few dyads with female dominance. Conclusions Variations in social tolerance and its consequences are most likely influenced by two factors, ecology (via forest type) and physiology (via reproductive activity), and only to a lesser extent by clade membership. The study suggests that mouse lemur females have higher aggression rates and more agonistic conflicts with males when females in the population are reproducing, at least in resource-rich humid forests. The study confirms a high degree of social plasticity between species in these small solitary foragers that supports their taxonomic distinctiveness and requires further scientific attention. Electronic supplementary material The online version of this article (10.1186/s12898-019-0236-x) contains supplementary material, which is available to authorized users.

Past environmental changes affected lemur population dynamics prior to human impact in Madagascar

“…Field work took place between August and October 2017 (dry season). Mouse lemurs were captured by hand near the trees that they used during nighttime activity 66 (see Supplementary section 2.1.1 for details). A total of 46 mouse lemur samples were obtained for genomic analyses, which included 14 M. arnholdi from Mahasarika and 32 from Fantany.…”

Whatisn'tsocial tolerance?The past, present, and possible future of an overused term in the field of primatology

“…BST can be measured at the individual level, such as the time an individual spends cofeeding with a conspecific (e.g., de Waal & Luttrell 22 ), at the dyadic level, such as the time a dyad spends cofeeding (e.g., Hare et al 2 ), or at the group level with group-level paradigms such as the proportion of a group gathered to cofeed (e.g., DeTroy et al 48 ). As an outcome of interest, BST is usually analyzed and discussed on the dyadic, group, or even species level (e.g., Rina Evasoa et al 46 ). It is important to note that BST as a group trait in contrast to social tolerance as a structural construct is not tied to any further assumptions concerning the social style of the group or any covariation of other traits.…”

“…The most commonly used measures are aggression rates, 4,40,46,49 aggression severity, 46,49 and counter-aggression (i.e., retaliation by the recipient of aggression). 28,40,50 This category forms the basis for the phylogenetic approach of measuring social tolerance, 13 and both phylogenetic and socio-ecological approaches treat this selection of measures as mutually codependent 13,31,39 with the occurrence of one variable indicating the presence of the others.…”

“…Some studies do not differentiate between mild and severe aggression and consider high rates of general aggression indicative of socially intolerant relationships. 46,57,58 Other authors have made a distinction between mild and severe aggression and consider only high rates of severe aggression to characterize low SST; high rates of mild aggression, on the other hand, are considered to be characteristic of high SST 22,40,41,[59][60][61] as mild aggression would have less severe consequences in societies with higher SST. 22 We will discuss this discrepancy in more detail in the later section on "The possible future."…”

“…Attributes of the dominance hierarchy are either global measures of the dominance hierarchy, such as the hierarchy steepness or linearity, 28,49 or measures of dyadic dominance relationships between two individuals, 46 most often based on the outcomes of conflicts. 28,46,49 While the behaviors these measures are based on are often the same as those mentioned in the previous category, the outcome of interest and the level of analysis is different. Depending on whether social tolerance is viewed as distinct from or synonymous with egalitarianism, the presence of clearly established (formalized)…”