Spatiotemporal association patterns in a supergroup of Rwenzori black‐and‐white colobus (Colobus angolensis ruwenzorii) are consistent with a multilevel society

Spatiotemporal association patterns in a supergroup of Rwenzori black‐and‐white colobus (Colobus angolensis ruwenzorii) are consistent with a multilevel society:

Progression capturing 141 individuals on August 17, 2017, with a duration of 01:01:12 hh:mm:ss (calculated optimal window size Δ = 228 s, 141 nodes; mothers and infants separated to individual nodes following analysis for better visualization of group composition; modularity score = 0.891). Dark blue nodes denote adult males, light blue nodes denote sub‐adult males, red nodes denote adult‐females, small gray nodes denote infants, and larger gray nodes denote all other individuals; sub‐adult females, pubescent males, juveniles. Edge thickness represents the strength of the connection between two nodes; the thicker the edge, the closer the individuals in the progression.

Abstract

Primates display broad diversity in their social organization. The social groups of a few primate species are organized in a multilevel fashion, with large groups composed of multiple, core one‐male units (OMUs). A characteristic of multilevel societies is that the higher levels can include hundreds of individuals. The Rwenzori black‐and‐white colobus (Colobus angolensis ruwenzorii) in the montane forests of Rwanda form supergroups and have been suspected to exhibit multilevel social organization. Here we present the first data on the “anatomy” of a supergroup numbering 500+ individuals. We identified subgroups within the supergroup based on progression data, extracting the social network structure from the time‐stamped spatiotemporal distribution of passing individuals identified to age–sex class, and selecting an optimal time window for each network using the two‐step approach developed by Uddin, Choudhury, Farhad, and Rahman (2017). We detail the existence of core units—multi‐male units (MMUs) with a mean of 1.7 adult males and 3.1 adult females, as well as OMUs, all‐female units and bachelor units composed of adult and sub‐adult males. More than two‐thirds of units are MMUs. These grouping patterns conform to a multilevel society with predominantly multi‐male core units, a social system that has recently also been described for a population of the same taxon in Uganda. Individual identification will be required to corroborate these interpretations.