Observations of a daytime birthing event in wild titi monkeys (Callicebus oenanthe): implications of the male parental role

Comportamiento reproductivo de Plecturocebus caquetensis (Pitheciidae: Callicebinae), Caquetá-Colombia

El mono tití del Caquetá (Plecturocebus caquetensis) es un primate críticamente amenazado debido a la pérdida de su hábitat. En los últimos años han incrementado los estudios sobre ecología, pero poco se conoce sobre su comportamiento reproductivo. Aquí reportamos los primeros registros del comportamiento reproductivo y el nacimiento de una cría de P. caquetensis en dos grupos en un fragmento de bosque en el departamento del Caquetá - Colombia en octubre de 2013. También registramos el ataque de Pithecia milleri al macho adulto con cría. Estos registros representan un aporte para el conocimiento de la historia natural de esta especie en peligro de extinción.  

Observations of infant conflict and avoidance in San Martin titi monkeys (Plecturocebus oenanthe)

Conflict between caregivers and infants typically centers on disagreements over the amount and frequency of care provided. Prior research has identified many variables that impact patterns of mother-infant conflict. These include wide-ranging factors such as individual temperament, reproductive status, and availability of resources. By contrast, no studies have investigated the variables that influence father-infant conflict. To better understand the nature of caregiver-infant conflict in a species with obligate biparental care, I observed two groups of San Martin titi monkeys inhabiting disturbed secondary forest fragments in the San Martín region of Peru. Using instantaneous focal sampling of infants, I recorded physical conflict between infants and caregivers and instances of infant avoidance (leaving the infant) by adult males. I summarized data as the percentage of records in which these activities occurred for each focal day and report the estimates for caregivers. I further calculated mean percentages by month of infant age to assess the relative timing of infant conflict, for each group and age/sex class, and infant avoidance by males. Percentages of conflict and avoidance were markedly higher in the larger group living in a smaller habitat than in the other group. This pattern occurred across all age/sex classes. In both groups, the greatest amount of infant conflict occurred with siblings. I discuss the substantial variation in conflict and avoidance in relation to the various socioecological conditions that may have played a role. This study provides an in-depth description and exploration of parent-offspring and sibling conflict, which has not been examined previously in this species.

The evolution of pair-living, sexual monogamy, and cooperative infant care: Insights from research on wild owl monkeys, titis, sakis, and tamarins

"Monogamy" and pair bonding have long been of interest to anthropologists and primatologists. Their study contributes to our knowledge of human evolutionary biology and social evolution without the cultural trappings associated with studying human societies directly. Here, we first provide an overview of theoretical considerations, followed by an evaluation of recent comparative studies of the evolution of "social monogamy"; we are left with serious doubts about the conclusions of these studies that stem from the often poor quality of the data used and an overreliance on secondary sources without vetting the data therein. We then describe our field research program on four "monogamous" platyrrhines (owl monkeys, titis, sakis, and tamarins), evaluate how well our data support various hypotheses proposed to explain "monogamy," and compare our data to those reported on the same genera in comparative studies. Overall, we found a distressing lack of agreement between the data used in comparative studies and data from the literature for the taxa that we work with. In the final section, we propose areas of research that deserve more attention. We stress the need for more high-quality natural history data, and we urge researchers to be cautious about the uncritical use of variables of uncertain internal validity. Overall, it is imperative that biological anthropologists establish and follow clear criteria for comparing and combining results from published studies and that researchers, reviewers, and editors alike comply with these standards to improve the transparency, reproducibility, and interpretability of causal inferences made in comparative studies.

Evidence of Placentophagia and Mother-Infant Cannibalism in Free-Ranging Macaca mulatta tcheliensis in Mount Taihangshan, Jiyuan, China

Placentophagia or the consumption of the afterbirth is reported in many primate species, whereas cannibalism is a relatively rare event. Based on our field observations over the course of 3 years, we present evidence of placentophagia and mother-infant cannibalism in a free-ranging population of the Taihangshan macaque, Macaca mulatta tcheliensis, in the Mt. Taihangshan area, Jiyuan, Henan, China. We documented 1 case in which a mother consumed the afterbirth of her infant. In a second instance, we observed a fresh placenta discarded on the ground by an unknown individual. We also present a description of the first documented instance of mother-infant cannibalism in the same group of free-ranging rhesus macaques.

Parturition and potential infanticide in free-ranging Alouatta guariba clamitans

Parturition is a key process of mammalian reproduction that is rarely documented in New World monkeys because it often occurs at night. However, diurnal births have been recorded in several species. In howler monkeys (Alouatta spp.) they have often been observed during prolonged resting periods. Similarly, infanticide is a behavior observed quite infrequently. Infanticide in howler monkeys is often inferred from infant deaths or disappearances after group takeovers by nonresident male(s). Here we report the first observation of parturition and birth-related behaviors in the brown howler monkey (Alouatta guariba clamitans) and the likely attack on the infant that caused its death. The mother was a multiparous female that lived in a ca. 3-ha Atlantic forest fragment in southern Brazil with nine group mates. The behavior ("all occurrences") sampling method was used to record birth-related behaviors and social interactions. The parturition occurred during the day of 27 October 2013 during a feeding session. The female showed no sign of contraction or birth delivery posture. Parturition began apparently after matrix rupture and release of the amniotic fluid. Expulsion of the newborn occurred between 1 and 3 min later (the exact moment of delivery was not observed). Then, the female held and licked the newborn and began to ingest the placenta and the umbilical cord. The other group members continued feeding and had no interaction with the parturient during the preparturition and parturition events. The infant died ca. 35 days later as a consequence of injuries to his forehead and face, potentially caused by a conspecific bite. Because the adult and subadult males chased the female in the day that the infant's wounds were detected, we believe that one of them might have been the aggressor. We discuss this putative case of infanticide in light of the potential motivation of each male.

Primate pelvic anatomy and implications for birth

The pelvis performs two major functions for terrestrial mammals. It provides somewhat rigid support for muscles engaged in locomotion and, for females, it serves as the birth canal. The result for many species, and especially for encephalized primates, is an 'obstetric dilemma' whereby the neonate often has to negotiate a tight squeeze in order to be born. On top of what was probably a baseline of challenging birth, locomotor changes in the evolution of bipedalism in the human lineage resulted in an even more complex birth process. Negotiation of the bipedal pelvis requires a series of rotations, the end of which has the infant emerging from the birth canal facing the opposite direction from the mother. This pattern, strikingly different from what is typically seen in monkeys and apes, places a premium on having assistance at delivery. Recently reported observations of births in monkeys and apes are used to compare the process in human and non-human primates, highlighting similarities and differences. These include presentation (face, occiput anterior or posterior), internal and external rotation, use of the hands by mothers and infants, reliance on assistance, and the developmental state of the neonate.

Female sociality during the daytime birth of a wild bonobo at Luikotale, Democratic Republic of the Congo

Parturition is one of the most important yet least observed events in studies of primate life history and reproduction. Here, I report the first documented observation of a bonobo (Pan paniscus) birth event in the wild, at the Luikotale Bonobo Project field site, Democratic Republic of the Congo. The nulliparous mother's behaviour before, during and after parturition is described, along with reactions of other community members to the birth and the neonate. Data were collected through focal-animal observations, and the events postpartum were photo-documented. The behaviour and spatial distribution of party members were recorded using scan samples. Parturition occurred during the late morning in a social context, with parous females in close proximity to the parturient mother. Placentophagia occurred immediately after delivery, and the parturient shared the placenta with two of the attending females. I compare this observation with reports of parturition in captive bonobos, and highlight the observed female sociality and social support during the birth event. Plausible adaptive advantages of parturition occurring in a social context are discussed, and accrued observations of birth events in wild and free-ranging primates suggest that females may give birth within proximity of others more frequently than previously thought. This account contributes rare empirical data for examining the interface between female sociality and parturition, and the evolution of parturitional behaviours in primates.