American Journal of Primatology最新文献

Parasitism is one of the primary causes of biotic stress in several taxa, and behaviors resembling self-medication have been documented in numerous species. Anointing involves the application of chemical substances derived from animals, plants, mud, soils, and minerals, often emitting a pungent odor, onto an animal's body. We examined the circumstances surrounding 34 bouts of anointing with millipedes in a group of blond capuchin monkeys (Sapajus flavius) inhabiting an Atlantic Forest fragment in northeastern Brazil. Over 412 h of observation, we collected behavioral data through photographs, video recordings, and ad libitum field notes. We collected and identified the millipedes to the species level. We tested three non-mutually exclusive hypotheses on the function(s) of this behavior: self-medication, social bonding, and opportunistic use. We analyzed data in R using nonparametric tests due to low sample size. Anointing occurred at a rate of 8 episodes every 100 h. Millipedes used during anointing are from species that produce benzoquinone. The behavior was more frequently observed in the inferior strata, during midday, while the group is mostly foraging, in periods of higher rainfall, when millipedes emerge from the ground, and during the high fruit productivity season, when the capuchins' activity budget is less constrained. Although anointing occurred at similar rates in solitary and social contexts, adult males were more actively engaged in anointing bouts, indicating sex difference in this behavior, and a possible social function. The observed pattern suggests anointing is a multifunctional behavior, combining elements of self-medication, opportunity, and social interaction.

Behavioral contagion is spread across animal species and is thought to promote social cohesion and group synchronization. While yawn contagion has been extensively studied, scratch contagion remains comparatively under-researched, particularly in wild populations. We investigated whether yawn and scratch contagion occurred in a wild group of Ecuadorian white-fronted capuchins (Cebus aequatorialis, N = 16) at La Hesperia Cloud Forest Reserve in Ecuador. We assessed whether scratching or yawning were more likely to occur after observing a conspecific (i.e., the trigger) scratching or yawning (i.e., triggering event) compared to a control condition. We further examined whether this effect was modulated by the (a) individual characteristics of the trigger and the partner (sex, age category, and social centrality), and (c) dyadic-level variables (sex and age similarity, social bond strength). Our results showed that the probability of scratching was significantly higher in individuals that observed the triggering event, as compared to individuals that did not observe it. However, scratch contagion was not modulated by any of the individual or dyadic predictors included in our models. No yawning events were recorded during the study period. Our findings contribute to understanding scratch contagion in wild primates and underscore the need for further exploration of social factors influencing behavioral contagion.

Stable isotope analysis is a widely used tool in primate ecology for investigating diet and environment, with numerous studies focusing on chimpanzees. However, few studies have used this method to explore the dietary niche of chimpanzees in comparison to other primates or examined intra-individual dietary variability. This limitation hinders the understanding of the comparability of stable isotopic data with the wealth of behavioral observational data in primate ecology. We report the carbon and nitrogen stable isotope ratios of hairs from wild eastern chimpanzees (Pan troglodytes schweinfurthii) and four other primate species (Cercopithecus mitis, Cercopithecus ascanius, Allochrocebus lhoesti, and Colobus guereza) in the Kalinzu Forest Reserve, Uganda. Bulk analysis revealed that both plant foods and chimpanzees in Kalinzu exhibited lower carbon stable isotope ratios than expected for the region's rainfall. Inter-species comparison of bulk stable isotope ratios and preliminary compound-specific nitrogen stable isotope analysis of amino acids revealed that chimpanzees in Kalinzu have a lower degree of faunivory than the sympatric monkeys. Furthermore, ultra-fine sectioning of a hair sample was conducted to investigate dietary variation over daily to weekly timescales. In one adult male chimpanzee, carbon and nitrogen stable isotope ratios fluctuated by more than 1‰ within approximately 10 days. These findings highlight the importance of recognizing uncontrolled ecological variability and hidden intra-individual dietary changes when interpreting stable isotope data in relation to behavior and environmental traits.

Maternal care is ubiquitous in mammals, yet its degree and duration vary across taxa. In primates, mothers provide extended care for young and follow similar developmental transitions in the mother–infant relationship, yet at different paces of change. Since ecological pressures shape life-history traits including female reproductive rate and timing of infant independence, research is needed on mother–infant relationships in wild populations exposed to energetic constraints and predation risk. Assamese macaques (Macaca assamensis) of the study population are seasonal breeders living in an unpredictable environment, where fluctuating food availability imposes energetic challenges on mothers and infants. We quantitatively describe how maternal care and offspring independence develop throughout infancy. Using continuous focal observations on 59 infants, we model the nonlinear age-trajectories of mother–infant proximity and transitions from dependent to independent feeding and locomotion, and estimated sex differences in these trajectories. Newborns were fully dependent on their mothers for feeding and transport, with mothers maintaining close proximity. A transitional phase emerged between 1 and 3 months of age, marked by reduced maternal proximity and increasing infant independence. During the second half of infancy, infants achieved near-complete locomotor and feeding independence, while residual proximity and body contact persisted. No sex differences were detected in the mother–infant relationship trajectory. Collectively, the timing of maternal investment aligns with the breeding strategy of this seasonal species, with females balancing investment in current and future reproduction. This study establishes a baseline for examining how ecological variability affects the timing and pace of mother–infant behavioral transitions.

Jumlah spesies yang terancam punah terus mengalami peningkatan, sehingga semakin menegaskan pentingnya estimasi populasi yang ada dalam penyusunan rencana konservasi yang efektif. Salah satu aspek krusial dalam estimasi populasi adalah kemampuan untuk mengkonfirmasi keberadaan suatu spesies selama survei (kemampuan deteksi). Meskipun sensor audio-visual, seperti kamera jebak dan pemantauan akustik pasif (Passive Acoustic Monitoring-PAM), telah berkembang sebagai alat yang penting dalam pemantauan primata, namun penelitian secara sistematis yang membandingkan efektivitas deteksi kedua metode ini masih sangat terbatas, khususnya pada hutan yang cukup rapat dengan visibilitas rendah dan pada spesies yang sulit ditemukan. Dalam penelitian ini, kami membandingkan pemantauan berkelanjutan selama 40 hari menggunakan sensor audio-visual (kamera jebak, N = 19; PAM, N = 7) dengan metode transek titik berbasis manusia yang dilakukan melalui tiga kali kunjungan survei (N = 20) pada populasi monyet dare (Macaca maura) di dua tipe habitat: hutan (N = 10) dan area terbuka (N = 10). Dengan menggunakan model okupansi untuk membandingkan probabilitas deteksi (p), hasil menunjukkkan bahwa kamera jebak (p = 0,63 ± 0,04) dan PAM (p = 0,79 ± 0,08) memiliki kinerja lebih baik dibandingkan transek titik (p = 0,33 ± 0,07), tanpa dipengaruhi oleh tipe habitat. Setelah waktu survei disetarakan antar metode, ndeteksi lebih tinggi pada transek titik untuk survei yang berlangsung kurang dari satu hari. Namun, kamera jebak dan PAM menunjukkan kinerja setara setelah dua hari survei (p value < 0,05). Menariknya, kombinasi kedua sensor audio-visual menghasilkan tingkat keterdeteksian tertinggi (p = 0,87 ± 0,05). Temuan ini menegaskan efektivitas sensor audio-visual dan mendukung pendekatan multi-metode dalam pemantauan primata di hutan tropis. Secara keseluruhan, penelitian ini berkontribusi pada desain protokol pemantauan yang lebih efektif bagi spesies primata, yang sangat penting dalam perencanaan strategi konservasi.

Activity patterns reveal important information about how primates cope with challenging ecological conditions. This study investigates behavioral variation in white-handed gibbons (Hylobates lar) living at the ecological extreme of their range in a heterogeneous landscape in western Thailand. We spent 13 months studying 4 groups at Khao Nang Rum Wildlife Research Station in Huai Kha Khaeng Wildlife Sanctuary, where gibbons are found living in both evergreen and savannah habitats, both of which we describe as poor-quality habitat. Given specific phenological properties (e.g., predominance of deciduous species) of the savannah habitat, we predicted that food resources would be less available in the savannah habitat compared to the evergreen habitat, making the savannah an even lower quality habitat for these frugivorous apes. The evergreen habitat produced more fruit and young leaves throughout all three seasons, and more flowers during the wet season, compared to the lower-quality savannah habitat. We furthermore predicted that habitat type would drive differences in activity budget. Gibbons in both habitats exhibited high rates of resting behavior (50.1% evergreen, 52.3% savannah), possibly in response to a particularly dry year. However, while activity budget differed between habitats, group identity was a better predictor of this variation. Specifically, compared to evergreen gibbons, savannah gibbons spent more time feeding (28.9% vs. 22.5%) and less time vocalizing (4.2% vs. 12.1%), but this varied between the two savannah groups with one group spending more time traveling (7.7% vs. 3.6%) and less time resting (50.0% vs. 58.4%) than the other group. We suggest that gibbons at this poor-quality site, and specifically in the even lower quality savannah habitat, are responding to the availability of specific key resources within their home ranges and that groups in the savannah habitat are employing unique strategies in response to the relative scarcity of fruit resources compared to the evergreen habitat.