Distribution of dorsal carriage among simians

Abstract

We surveyed the literature and obtained information from primate researchers and zookeepers to study the distribution of dorsal carriage among 77 simian species including New and Old World monkeys and apes in relation to arboreality and terrestriality, birth (litter) weight relative to maternal weight, and presence or absence of distinct natal coat colors. All New World monkeys are arboreal and commonly carry their infants dorsally. Conversely, arboreal Old World monkeys do not use dorsal carriage, and only some predominantly terrestrial Old World monkeys do so. Whereas lesser apes (which are highly arboreal) do not use dorsal carriage, arboreal as well as more terrestrial great apes commonly carry their infants dorsally. These findings indicate that simple arboreality or terrestriality is inadequate to explain dorsal carriage by monkeys. Infants of small- to medium-sized New World monkeys have relatively high birth weight compared with maternal weight, and are most likely to be carried dorsally than ventrally even on the first postnatal day. In contrast, infants of large-bodied New World monkeys are carried ventrally first and then dorsally up to the end of their second year, albeit increasingly infrequently. Among Old World monkeys, no association was found between mode of infant transport and birth weight relative to maternal weight, but some terrestrial Old World monkeys displaying dorsal carriage tend to do so with older infants, indicating that such behavior enables the mother to transport the infant with lower energy expenditure. Among terrestrial Old World monkeys, infants with distinctive natal coat colors are rarely carried dorsally until the natal coat color changes to adult coloration: infants with distinctive coat colors clinging to the backs of carriers could be highly visible and thus vulnerable to predation. Dorsal carriage by mothers may prolong the affiliative mother-infant relationship.

The sun‐tailed monkey (Cercopithecus solatus): first report of mother‐infant dorsal carrying behaviour in a forest guenon, Gabon

“…First, Gaguie's body mass represented around 15% of her mother's body mass when the behaviour started (Table 1), which is intermediate to the other infants in the study group, and also under the threshold of 30% given by Nakamichi & Yamada (2009) for simian species, great apes excluded. In these species, mothers bear their infants dorsally when they become older and heavier, because otherwise it would require too much energy, thus allowing the mothers more time to consolidate affiliative relationship (Nakamichi & Yamada, 2009).…”

“…In these species, mothers bear their infants dorsally when they become older and heavier, because otherwise it would require too much energy, thus allowing the mothers more time to consolidate affiliative relationship (Nakamichi & Yamada, 2009). In our case, either the infant body mass is not a relevant factor for explaining why dorsal carrying behaviour started or this threshold is not relevant to C. solatus.…”

“…This maternal investment can persist up to several months and aims at decreasing the risk of infant mortality (Altmann & Samuels, 1992;Kappeler, 1998). After a period of ventro-ventral carrying behaviour, infants of some species, predominantly of terrestrial Old World simians, may then be carried dorsally (Nakamichi & Yamada, 2009). However, what drives this behaviour remains unclear.…”

“…However, what drives this behaviour remains unclear. Two factors have received particular attention by Nakamichi & Yamada (2009): first, birth weight relative to maternal weight, assuming that a species with higher birth weight uses dorsal carriage more commonly because it consumes less energy than ventral carriage; second, the presence or absence of distinct natal coat colours, assuming that infants with distinctively coloured natal coats are rarely carried on the mother's back because it would make both the mother and the infant more visible and vulnerable to predation.…”

“…In guenons, infants are usually carried ventrally (Orbell, Brosse & Bussi, 1991;F€ orster & Cords, 2002;Nakamichi & Yamada, 2009). The only two species in which infants are carried dorsally, and only occasionally, are the savannahdwelling, semi-terrestrial species: vervet (Chlorocebus aethiops) (Gartlan, 1969) and patas monkey (Erythrocebus patas) (Galat-Luong, 1994).…”