The Ontogeny of "Twitter" Calls in White-Faced Capuchins (Cebus imitator): Usage, Context, and Acoustic Structure.

In stark contrast to our own highly plastic communicative abilities, nonhuman primate vocalizations were historically considered fixed and innate, with very little ability to learn or modify vocal signals. However, recent studies indicate that primate vocalizations do show evidence of developmental plasticity, most notably in their context and usage. We build on these studies by investigating developmental changes in one of the most common calls of white-faced capuchins (Cebus imitator), the twitter.

Conditional benefits of social integration in wild female geladas.

While strong maternal relationships have been linked with improved offspring survival in many mammals, maternal sociality appears to provide little protection against infanticidal males. Here, we evaluated whether maternal social integration predicts offspring survival to adulthood in geladas (), a non-human primate that faces frequent alpha male takeovers coupled with high rates of infanticide. Mothers that formed stronger grooming relationships with their female and male groupmates showed higher offspring survival on average.

Intestivirid Acquisition Increases Across Infancy in a Wild Primate Population.

Intestivirids (order Crassvirales, family Intestiviridae), viruses that infect Bacteroidales bacteria in the mammalian gastrointestinal tract, have been identified as a highly abundant component of the healthy human virome that may shape patterns of human health and disease through direct action on the microbiome. While double-stranded DNA bacteriophages called crAssphages (Carjivirus communis) that infect bacteria in the Bacteroidales order have been identified in humans within the first month of life, the enormous variation in post-parturition infant environments and diets has inhibited a robust understanding of the physiological and environmental factors that govern acquisition patterns. We turned to a wild population of graminivorous nonhuman primates (geladas, Theropithecus gelada) under long-term study in the Simien Mountains National Park, Ethiopia, analysing faecal samples from infants and mothers in this population across the infancy period for richness and presence of crAssphage-like viruses (family Intestiviridae).

Female reproductive ageing persists despite high infanticide risk in chacma baboons and geladas.

Across mammals, fertility and offspring survival are often lowest at the beginning and end of females' reproductive careers. However, extrinsic drivers of reproductive success-including infanticide by males-could stochastically obscure these expected age-related trends. Here, we modelled reproductive ageing trajectories in two cercopithecine primates that experience high rates of male infanticide: the chacma baboon () and the gelada ().

High temperatures are associated with decreased immune system performance in a wild primate.

Rising temperatures due to climate change are predicted to threaten the persistence of wild animals, but there is little evidence that climate change has pushed species beyond their thermal tolerance. The immune system is an ideal avenue to assess the effects of climate change because immune performance is sensitive to changes in temperature and immune competency can affect reproductive success. We investigate the effect of rising temperatures on a biomarker of nonspecific immune performance in a wild population of capuchin monkeys and provide compelling evidence that immune performance is associated with ambient temperature.

Information Ecology: an integrative framework for studying animal behavior.

Information is simultaneously a valuable resource for animals and a tractable variable for researchers. We propose the name Information Ecology to describe research focused on how individual animals use information to enhance fitness. An explicit focus on information in animal behavior is far from novel - we simply build on these ideas and promote a unified approach to how and why animals use information.

Vascularization underlies differences in sexually selected skin coloration in a wild primate.

Male reproductive competition can select for condition-dependent, conspicuous traits that signal some aspect of fighting ability and facilitate assessment of potential rivals. However, the underlying mechanisms that link the signal to a male's current condition are difficult to investigate in wild populations, often requiring invasive experimental manipulation. Here, we use digital photographs and chest skin samples to investigate the mechanisms of a visual signal used in male competition in a wild primate, the red chest patch in geladas (Theropithecus gelada).

Urinary neopterin reflects immunological variation associated with age, helminth parasitism, and the microbiome in a wild primate.

Neopterin, a product of activated white blood cells, is a marker of nonspecific inflammation that can capture variation in immune investment or disease-related immune activity and can be collected noninvasively in urine. Mounting studies in wildlife point to lifetime patterns in neopterin related to immune development, aging, and certain diseases, but rarely are studies able to assess whether neopterin can capture multiple concurrent dimensions of health and disease in a single system. We assessed the relationship between urinary neopterin stored on filter paper and multiple metrics of health and disease in wild geladas (Theropithecus gelada), primates endemic to the Ethiopian highlands.

A novel statovirus identified in fecal samples from wild geladas in the Ethiopian highlands.

We present a novel statovirus in geladas (Theropithecus gelada), graminivorous primates endemic to the Ethiopian highlands. Using a high-throughput sequencing approach, we identified contiguous sequences in feces from two adult female geladas in the Simien Mountains National Park, Ethiopia, that share similarities to statoviruses. Our phylogenetic analysis of the whole genome, as well as the RNA-dependent RNA polymerase (RdRp) and capsid protein (CP) amino acid sequences, revealed that the gelada statoviruses cluster with those from other primates (laboratory populations of Macaca nemestrina and Macaca mulatta).

Using an on-site laboratory for fecal steroid analysis in wild white-faced capuchins.

Hormone laboratories located "on-site" where field studies are being conducted have a number of advantages. On-site laboratories allow hormone analyses to proceed in near-real-time, minimize logistics of sample permits/shipping, contribute to in-country capacity-building, and (our focus here) facilitate cross-site collaboration through shared methods and a shared laboratory. Here we provide proof-of-concept that an on-site hormone laboratory (the Taboga Field Laboratory, located in the Taboga Forest Reserve, Costa Rica) can successfully run endocrine analyses in a remote location.

Leveling with Tinbergen: Four levels simplified to causes and consequences.

In 1963, Niko Tinbergen published his foundational manuscript identifying the four questions we ask in animal behavior-how does the behavior emerge across the lifespan (development); how does it work (mechanism); how and why did it evolve (evolution); and why is it adaptive (function). Tinbergen clarified that these 'levels of analysis' are complementary, not competing, thereby avoiding many fruitless scientific debates. However, the relationships among the four levels was never established.

Bridging Captive and Wild Studies: Behavioral Plasticity and Social Complexity in .

Cognitive ethology explores the ability of animals to flexibly adapt their behavior to rapid physical and social environment fluctuations. Although there is a historical dichotomy between field and captive studies, recently, a growing interest in questions that sit at the intersection of cognitive and adaptive perspectives has helped bridge this divide. By focusing on , we discuss the three main reasons why this hybrid approach is extremely successful.

Dominance style is a key predictor of vocal use and evolution across nonhuman primates.

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from 'despotic' to 'tolerant').

The Goldilocks effect: female geladas in mid-sized groups have higher fitness.

The cost-benefit ratio of group living is thought to vary with group size: individuals in 'optimally sized' groups should have higher fitness than individuals in groups that are either too large or too small. However, the relationship between group size and individual fitness has been difficult to establish for long-lived species where the number of groups studied is typically quite low. Here, we present evidence for optimal group size that maximizes female fitness in a population of geladas ().

The structural and motivational role of the unique lip-flip movement in the gelada (Theropithecus gelada) facial display repertoire.

Objectives: Human language represents an extreme form of communicative complexity. Primate facial display complexity, which depends upon facial mobility, can be used as a model for the study of the evolution of communicative complexity. The gelada (Theropithecus gelada) is the only primate that can produce a lip-flip eversion.

Insights into the evolution of social systems and species from baboon studies.

Baboons, members of the genus comprise six closely related species distributed throughout sub-Saharan Africa and southwest Arabia. The species exhibit more ecological flexibility and a wider range of social systems than many other primates. This article summarizes our current knowledge of the natural history of baboons and highlights directions for future research.

Reduced Introgression of Sex Chromosome Markers in the Mexican Howler Monkey ( × ) Hybrid Zone.

Interspecific hybridization allows the introgression or movement of alleles from one genome to another. While some genomic regions freely exchange alleles during hybridization, loci associated with reproductive isolation do not intermix. In many model organisms, the X chromosome displays limited introgression compared to autosomes owing to the presence of multiple loci associated with hybrid sterility or inviability (the "large X-effect").