Group Size of a Permanent Large Group of Agile Mangabeys (Cercocebus agilis) at Bai Hokou, Central African Republic

Abstract

White-eyelid mangabeys (genus Cercocebus) live in groups of highly variable size. Because of their semi-terrestrial behaviour and preference for dense forest habitats, re-liable data on group size are scarce. During a 5-month study, we collected 17 group counts on a habituated group of agile mangabeys (C. agilis) at Bai Hokou in the Central African Republic. We found a stable group size of approximately 135 individuals. This permanent large grouping pattern is known to occur among several populations of white-eyelid mangabeys and is congruent with extreme group sizes reported in mandrills at Lopé in Gabon.

How Many for Lunch Today? Seasonal Fission-Fusion Dynamics as a Feeding Strategy in Wild Red-Capped Mangabeys (Cercocebus torquatus)

“…However, it fits in well with the large groups reported of C. atys [Range and Noë, 2002;Range, 2006;McGraw et al, 2011] and C. agilis [Devreese et al, 2013]. The age-sex composition also differed from that of the 'C troop' of C. torquatus [Mitani, 1989[Mitani, , 1991.…”

“…We made 10 video recordings of 3 medium-sized parties (see the section 'Measuring parties and fission-fusion dynamics'). Age-sex composition was defined using sexual maturation criteria according to Devreese et al [2013]: adult males were fully grown with descended testicles, subadult males were fully grown without descended testicles, adult females were fully grown with sexual skin present and/or long nipples, juveniles were not fully grown individuals of either sex that foraged independently, and infants were the smallest individuals without the red cap on the head and completely associated with their mother.…”

“…Further studies are expanding our knowledge of the socio-ecology of the genus Cercocebus [Cooke, 2012;Devreese et al, 2013;McCabe et al, 2013;Fernández, 2016] and their fellow clade members, the genus Mandrillus [Astaras et al, 2007;Bret et al, 2013;Hongo, 2014]. In particular, researchers note considerable variety in terms of group size and composition in both genera.…”

“…Sooty mangabeys (C. atys) in the Taï National Park, Ivory Coast, live in groups as large as 115 individuals composed primarily of adult females and juveniles [Range and Noë, 2002;Range, 2006;McGraw et al, 2011]. A permanent group of approximately 135 C. agilis individuals is also known in Bai Hokou, Central African Republic [Devreese et al, 2013]. Mandrills (Mandrillus sphinx) in Lope National Park, Gabon, form groups as large as 800 members made up primarily of females and their offspring [Abernethy et al, 2002].…”

Range extension of the agile mangabey (Cercocebus agilis) and of the mandrill (Mandrillus sphinx) in eastern Gabon evidenced by camera traps

“…The agile mangabey ( Cercocebus agilis ) is a medium‐sized, omnivorous Old World monkey from the large Cercopithecidae family that inhabits the dense humid tropical forests of central Africa. Although mainly arboreal, the species is often found on the ground in groups of highly variable size, from 10 to 50 individuals to over 200 individuals (Devreese et al, 2013; Quris, 1975). The geographical distribution of the species is vast, ranging from western Cameroon to the Central African Republic and north‐eastern Democratic Republic of Congo, but its limits are unclear, particularly for its westernmost isolated populations (Maisels et al, 2020).…”