Current Research
Visit our Publications Page to view our prior work
Variation in the pace of aging in white-faced capuchins
Principal Investigator: Dr. Fernando Campos, Dr. Amanda Melin, and Dr. Katharine Jack
Co-Investigators: Dr. Michael Gurven, Dr. James Higham
Collaborators: Dr. Joe Orkin, Dr. Eva Wikberg, Dr. Yeonjoo Park
Consultant: Dr. Noah Synder-Mackler
Chronological age is a strong predictor of health and lifespan, but the pace of biological aging varies greatly between individuals. Some retain good health into advanced ages, while others experience age-related disease onset while relatively young. Much variation in the progression of human aging processes remains poorly explained, but a growing body of literature highlights the contributions of both the social and physical environment. Studies of human health and pace of aging are limited by the difficulty of collecting detailed within-subject longitudinal data on lived experience and health outcomes. Studies of humans also have numerous confounds, including individual variation in lifestyle, early-life experience, and access to health care. Studies of wild nonhuman primates can provide invaluable insights into how social and physical environmental factors influence natural aging processes and the human healthspan.
In this project, we are leveraging our established long-term study of wild, white-faced capuchins (Cebus imitator) to improve our understanding of how social and physical environmental factors contribute to heterogeneity in rates of aging and health disparities. We are developing new techniques for non-invasive, population-level sampling of wild animals to identify and study hallmarks of aging across behavioral, physiological, and molecular domains. The study of capuchin physical health in situ, when combined with our detailed dataset of lifetime social and environmental experiences, will allow us to holistically assess the impact of lived and intergenerational experiences on health outcomes and the pace of aging across individuals.
This research is funded by a grant from the National Institute on Aging at the National Institutes of Health (1R61AG078529-01).
At almost 30, Legolas was one of the oldest individuals in our study population
The Scent of an Alpha Male: The Role of Urinary Volatiles in Male Dimorphism of Capuchins
Principal Investigators: Dr. Katharine Jack and Dr. Amanda Melin (with Dr. Anja Widdig, PI, and Dr. Jacinta Beehner, Co-I). Funded by the National Science Foundation (NSF BCS-2051573).
The existence of two physically and behaviorally distinct types of males in a single species is extremely rare in mammals but has now been documented in a number of primates. In species that display these alternative male morphologies, the larger, socially dominant, alpha male morph has higher testosterone and sires more offspring than the smaller subordinate male morph. This project investigates a potential role of olfactory communication in the development and maintenance of alternative male morphologies in a species of wild primate. The study’s integrative approach will measure variation among males and advance a comprehensive understanding of this phenomenon while providing insight into the importance of olfactory communication in the biology and behavior of wild primates. Through this longitudinal and cross-sectional study, we are integrating methods from behavioral ecology with non-invasive measures of endocrinology, morphology, and chemical ecology to quantify and investigate the potential role of olfactory signaling in enforcing male rank.
This research is funded by a grant from the National Science Foundation (BCS 2051573)
Barty - Alpha male of Los Valles
Born ~2003, Barty was once a subordinate male in our Guanacaste study group. In February 2022 he fought his way to the alpha position in our Los Valles study group, though he did not last long at the top. He disappeared from the group in May 2023.
Sensory and Foraging Ecology
Principal Investigator: Dr. Amanda Melin
Through their senses, animals interface with the environment to find food, select mates, and avoid predators. The interrelationships among diet, activity pattern and the senses are central to hypotheses of primate origins and adaptive radiation and shape the ecological niches of extant species. Through the integration of observational fieldwork, genetics and genomics, and computer models of animal vision, we seek to understand the adaptive complexes of primates, including humans, using an innovative and multidisciplinary approach. Our research centers around: 1) intra- and interspecific color vision variation in primates and other mammals with functional and phylogenetic relevance to primate origins and adaptive radiation (treeshrews, fruit bats, opossums); 2) variation within and between species in diet and use of sensory behaviors (e.g. touch, sniff, lick) while foraging, with the goal of linking behavioral variation to sensory genotypes; and 3) the visual, olfactory, gustatory and mechanical cues of food quality, with the goal of identifying important cues that shape the sensory systems of consumers.
The Effects of Forest Protection, Forest Regeneration, and Climate Change on Wild Primate Populations
Principal Investigators: Dr. Katharine Jack, Dr. Amanda Melin, Dr. Fernando Campos, and Dr. Linda Fedigan
Since the project began in 1983, we have been conducting park-wide censuses of the capuchin and howler monkeys to assess the effects of forest protection, regeneration, and climate change on long-term population trends. Several interesting trends have emerged from our analyses of these long-term data, including the promising observation to conservation efforts of population rebound with forest protection and regeneration. We have documented that the population size more than doubled for both capuchin and howler monkeys between 1983 and 1999 (from <300 to > 600 individuals). However, between 1999 and 2007, the howler population experienced zero population growth, likely having reached the environmental carrying capacity of the still regenerating forest. This population plateau was followed by an abrupt crash to ~300 howlers between the 2007 and 2011 censuses, a decline that was sustained in the 2013 and 2015 censuses. We are currently exploring a variety of explanations for this dramatic decline (e.g. climate change and pesticide use).
Plasticity and Adaptation in the Gut Microbiome
Principal Investigator: Dr. Amanda Melin
Recent research on the human microbiome has demonstrated a strong effect of diet, environment and health on the gut microbiota, raising the possibility that this relationship extends to other primates. However, little is known about how changing environments, accompanied by pronounced dietary shifts, affects the microbiome and shapes digestive adaptations. Ongoing advances in massive parallel sequencing are continually increasing our ability to ask refined, detailed question of wild populations. We are conducting a fecal metagenomic study spanning the seasonal transitions in Santa Rosa, Costa Rica to identify the taxonomic composition and functional genomes of the resident intestinal microbiota of capuchin monkeys and reveal how shifts in climate and diet impact these symbiotic organisms. We are additionally assembling a genone reference for white-faced capuchin monkeys that will assist in this project and be broadly useful in comparative primate genomics. Together, this information will reveal how omnivorous primates manage the varied digestive challenges of their eclectic diet, and adapt to the profound seasonal shifts in food availability.
Making an Alpha Male: the Behavior, Endocrinology, and Genetics of Dominance in Male White-faced Capuchins
Principal Investigator: Dr. Katharine Jack
We are examining behavioral, endocrinological, and genetic correlates (including kinship, reproductive success, and the major histocompatibility complex [MHC]) of male life history and reproductive strategies. The main goal of this longitudinal project is to understand how hormonal and social factors influence the emergence, from puberty into adulthood, of dominance status in male white-faced capuchins (e.g. Jack et al., 2014). Identifying traits and processes influencing individual variability in reproductive success is fundamental to understanding evolutionary processes. In our capuchins, like many other socially living mammals including humans, there is a strong association between dominance status and reproductive success, however, we still know very little about how and why some males attain alpha status while others do not. These data, along with our ongoing studies of the role of the major histocompatibility in male dispersal and mate choice decisions (funded by the LA Board of Regents, with Jessica Lynch Alfaro), will provide us with a holistic picture for examining male dominance and reproductive biology.