What makes a pair bond in a Neotropical primate: female and male contributions

Abstract

Pair living and pair bonding are rare in mammals, and the mechanisms of their maintenance remain a puzzle. Titi monkeys, a ‘textbook example’ for ‘monogamous’ primates, have strong pair bonds and extensive male care. To investigate mechanisms of pair-bond maintenance, we studied seven wild groups of red titis ( Plecturocebus cupreus ) in Peruvian Amazonia over a period of 14 months. We analysed pair bonds by measuring proximity, grooming and approaches/leaves within pairs, and collected data on intergroup encounters. Females contributed to grooming more than males, especially during infant dependency, when most of the grooming within pairs was done by females. Females were also more active in controlling proximity between pair mates, making most of the approaches and leaves. Males, on the other hand, invested more in territorial defences. They participated in more intergroup encounters than females and were more active during these encounters. Our data is most consistent with the ‘male-services’ hypothesis for pair-bond maintenance, where a female contributes more to the proximity and affiliation maintenance while a male provides beneficial services.

Multimodal pair‐bond maintenance: A review of signaling across modalities in pair‐bonded nonhuman primates

“…Conversely, white‐handed gibbon ( Hylobates lar ) males invest more than females (Palombit, 1996). Furthermore, in titi monkeys ( Callicebus cupreus ), females invest more in proximity maintenance and allogrooming than males, particularly in the presence of infants, potentially because males are too busy with infant carrying duties (Dolotovskaya, Walker, & Heymann, 2020). Prolonged resting in physical contact requires joint commitment and relatively little energy expenditure, and is markedly exhibited by many pair‐bonded species (e.g., pale fork‐marked lemurs, Phaner pallescens , Kappeler, 1997; red‐bellied lemurs, Eulemur rubriventer , Overdorff & Tecot, 2006; Singletary & Tecot, 2019; titi monkeys, C. cupreus ; Bales, Mason, Catana, Cherry, & Mendoza, 2007).…”

Genetic monogamy and mate choice in a pair-living primate

“…Coppery titis are only the second primate species and the seventh pair-living mammal with no evidence of EPP found in a study with an adequate sample size (the study on Bornean gibbon was based on just four infants from four family groups 9 , Table 1 ). The absence of EPP in titis is not unexpected, as they are consistently pair-living, pair mates spend most of the day within a few meters from each other, sleep together at night and engage in frequent joint visual displays and duetting at the territorial borders 50 − 54 . This high level of proximity and coordination should make mate guarding easy and effective enough to prevent EPC.…”

“…Study individuals belonged to 14 family groups (Supplementary Table S1 , Fig. 1 ), seven of which (Groups 1–7) were also subject to behavioral studies conducted in June–December 2017 and June–December 2018 51 , 77 , 78 . Between the periods of behavioral data collection, the groups were monitored for 2–3 days per month, and genetic samples were collected continuously from the beginning of the study until September 2019.…”

Genetic monogamy and mate choice in a pair-living primate

“…Coppery titis are only the second primate species and the seventh pair-living mammal with no evidence of EPP found in a study with an adequate sample size (the study on Bornean gibbon was based on just four infants from four family groups 37 , Table 1). The absence of EPP in titis is not unexpected, as they are consistently pair-living, pair mates spend most of the day within a few meters from each other, sleep together at night and engage in frequent joint visual displays and duetting at the territorial borders 36,[38][39][40][41] . This high level of proximity and coordination should make mate guarding easy and effective enough to prevent EPC.…”

“…Study individuals belonged to 14 family groups (Supplementary Table S1, Fig. 1), seven of which (Groups 1-7) were also subject to behavioral studies conducted in June-December 2017 and June-December 2018 38,70,71 . Between the periods of behavioral data collection, the groups were monitored for 2-3 days per month, and genetic samples were collected continuously from the beginning of the study until September 2019.…”