Parturition and potential infanticide in free-ranging Alouatta guariba clamitans

Variation in placentophagy in golden snub-nosed monkeys (Rhinopithecus roxellana) reflects nutritional constraints

Golden snub-nosed monkeys show inconsistent frequency of placentophagy between wild and captive populations, with almost all births in the wild but around half of the births in captivity accompanied by the female's consumption of placenta. This aligns with nutritional demands-driven placentophagy, as captive populations are generally under less nutritional constraints for breeding females than the wild population. Placentophagy is probably adaptive in the wild and under positive selection due to nutritional benefits to both mothers and infants.

A report of stillbirth and subsequent maternal cannibalism observed in a free-ranging group of Japanese macaques at Awajishima, Japan

How primate mothers interact with their dead infants has attracted much attention from primatologists. In particular, the care given to infant corpses has been well documented, and some researchers have employed quantitative analyses to explore the underlying mechanisms of this behavior. In contrast, instances of maternal cannibalism, another striking response to dead infants, are relatively uncommon and the factors contributing to this phenomenon remain unclear among primates. Here, we report a new case of stillbirth and subsequent maternal cannibalism that occurred in a free-ranging group of Japanese macaques residing on Awajishima Island, Japan. In the observed case, a multiparous female gave a stillbirth in the winter of 2022. The newborn appeared premature due to the lack of hair and unformed limbs, and the unseasonal birth. Initially, the mother cared for the newborn by licking and holding the body, but she suddenly began consuming the entire corpse, except for the parts around the head. This is the first case of maternal cannibalism by a multiparous mother of free-ranging Japanese macaque. We compared this case with those previously reported in Old World monkeys, and discussed the possible link between stillbirth, maternal care, and cannibalization towards deceased infants. In order to understand how primates comprehend the concepts of "death" and how their maternal relationships have evolved, it would be important to focus not only on maternal care toward dead infants but also cannibalism that could occur at the end of the caregiving.

Birth of a wild black howler monkey (Alouatta pigra) at an anthropogenic site

We present the first description of a diurnal live birth of a wild black howler monkey (Alouatta pigra). The mother formed part of a group of five individuals inhabiting an anthropogenic setting in the tropical lowlands of southeast Mexico. A total of 7 h and 50 min passed from the rupture of the amniotic sac early in the day to the crowning of the infant from the birth canal. The delivery of the infant lasted ~ 3 min. We describe the event while referencing images and time points in a supplementary video recording. We place our findings in the context of the available reports of live births in the Alouatta genus, time of day, birth duration, and group activity budget on the day of the birth. While primates tend to give birth at night to reduce complications from group interactions, the observed birth took place during the day, which may have been possible due to an alteration in group time allocation. Our report provides in-depth details of the events of a birth and important information regarding the natural history of the black howler monkey.

Necropsies disclose a low helminth parasite diversity in periurban howler monkeys

Primate-parasite interactions are often investigated via coprological studies given ethical and conservation restrictions of collecting primate hosts. Yet, these studies are inadequate to recover adult helminths for taxonomic identification and to accurately assess their prevalence, intensity, abundance, and site of infection. Fresh carcasses found in anthropogenic landscapes come as informative and reliable alternatives. In this study, we identified the helminths of brown howler monkeys (Alouatta guariba clamitans) and their sites of infection, and measured their prevalence, intensity, and abundance of infection. We necropsied 18 adult males, 11 adult females, and 7 juvenile males that died in conflicts with the anthropogenic environment (domestic dog attacks, n = 11; electrocutions and road-kills, n = 10 each; unknown, n = 5) in periurban landscapes of southern Brazil between 2013 and 2019. We found three nematodes (Trypanoxyuris minutus, Dipetalonema gracile, and Parabronema bonnei) and one cestode (Bertiella cf. studeri), a diversity estimated to account for a sampling completeness of 99%. Prevalence ranged from 3% for P. bonnei to 100% for T. minutus. Mean abundance ranged from 2 (D. gracile and B. cf. studeri) to 55,116 (T. minutus) and mean intensity of infection ranged from 4 (B. cf. studeri) to 55,116 (T. minutus). Trypanoxyuris minutus sex ratio was strongly male-biased. The intensity of infection with T. minutus was higher in juvenile males and adult females than in adult males. The low parasite diversity and the helminths' mode of transmission are compatible with howlers' arboreality and folivorous-frugivorous diet. The howlers were not infected with soil-transmitted helminth parasites of humans and domestic animals on the ground and probably did not eat invertebrates to complement the diet. Given the lack of evidence of howler health problems, we suggest that the causes of death of the necropsied howlers are the major threats to the long-term conservation of the species at the study periurban landscapes.

Assessing the influence of biotic, abiotic, and social factors on the physiological stress of a large Neotropical primate in Atlantic forest fragments

Wildlife physiological responses to environmental and human-related stressors provide useful clues on animal welfare. Non-invasive biomarkers, such as fecal glucocorticoid metabolites (fGCM), allow researchers to assess whether variations in habitat quality, behavior, and climate influence the animals' physiological stress. We examined the role of fragment size, ambient temperature, ripe fruit availability and consumption, percentage of records moving, sex, female reproductive state, and group composition as predictors of the level of fGCM in adult brown howler monkeys (Alouatta guariba clamitans) inhabiting three small (<10 ha) and three large (>90 ha) Atlantic Forest fragments in southern Brazil. We collected bimonthly behavioral data and fecal samples from adult individuals over three years, and used a multimodel inference framework to identify the main predictors of fGCM. We found that the mean (±SD) fGCM in the study groups ranged from 57 ± 49 ng/g to 93 ± 58 ng/g, which were within the known range for howler monkeys. We found 10 best models including five of the 17 tested variables. Sex and reproductive state were the only variables included in all these models. We found that fGCM was higher in nursing females (mean ± SD = 104 ± 73 ng/g) than in non-nursing females (64 ± 55 ng/g) and males (53 ± 40 ng/g, P < 0.05) and that it decreased with increasing ripe fruit consumption and minimum temperature. However, fragment size did not predict fGCM concentration (groups in small fragments = 71 ± 58 ng/g vs. groups in large fragments = 63 ± 54 ng/g, P > 0.05). We conclude that factors related to the energetic balance of individuals play major roles in modulating the physiological stress of brown howler monkeys. Future studies should investigate the consequences of higher levels of stress hormones on howler monkey health and demography.

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.