Browsing by Subject "lemur"

There is a long-standing claim that humans and nonhuman primates share an evolutionarily ancient system of nonverbal number representation. By and large, the focus in the field has been on providing existence proofs of numerical competence in wide-ranging taxa or using individual species as models for comparisons with humans. Recent findings in numerical cognition have suggested that evidence for approximate numerical abilities in nonhuman species may indicate that humans and animals share a cognitive system for representing numerosities nonverbally. To date, little is known about the contextual and quantitative limits of that system, or how those limits differ between species. The studies presented here take a comparative, behavioral approach to characterizing species differences and similarities in the approximate number system, and the contexts that affect that system. Collectively, this set of studies provides evidence that the approximate number system evolved in primates as a malleable system in which numerical representations are accessed spontaneously and improved through training. Despite the sensitivity of the system to experience and context individual differences in sensitivity are greater than species differences suggesting that the selective pressures that constrained its evolution were early and general and that species variation in social group size and diet have less influence on the ANS. Finally my studies indicate that the ANS supports approximate arithmetic and is consistent with the idea that ANS representations evolved to allow animals to calculate the world around them.

The composition and function of mammalian gut microbiomes are shaped by complex endogenous and exogenous factors that present on evolutionary and proximate timescales. In the Anthropocene era, host-associated microbiota are inevitably, yet differentially, influenced by natural and anthropogenic factors that vary across individuals and populations. In this dissertation, I used descriptive and experimental approaches, largely within a single species, the ring-tailed lemur (Lemur catta), to probe the roles of host physiology, environmental conditions, anthropogenic perturbation, and microbial environment in shaping primate microbiota across scales. First, I conducted a broad investigation of ring-tailed lemur gut microbiota and soil microbiota across 13 lemur populations (n = 209 individuals) spanning this species’ natural range in Madagascar, as well as multiple captivity settings in Madagascar and the U.S. By analyzing the lemur and soil microbiota, I showed that lemur gut microbiota vary widely within and between wild and captive populations, and that lemur and soil microbiota covary, suggesting a role for environmental acquisition in shaping interpopulation variation. Second, I analyzed vaginal, labial, and axillary microbiota of female ring-tailed lemurs and Coquerel’s sifakas (Propithecus coquereli) at the Duke Lemur Center (DLC) to demonstrate the influences of stable traits (e.g., species identity and mating system) and transient traits (e.g., ovarian hormones and forest access). We found that the effects of transient traits build on underlying differences mediated by stable traits. Third, and further focusing on DLC lemurs, but with a concentration on anthropogenic influence, I worked with a team of researchers to perform an experimental manipulation in ring-tailed lemurs to determine the influence of antibiotic treatment, with or without subsequent fecal transfaunation, on lemur gut microbiomes. I applied ecological frameworks to show that different facets of lemur microbial communities, such as bacterial diversity and composition, followed different recovery trajectories following antibiotic treatment. Fourth, I expanded my focus back to multiple ring-tailed lemur populations in natural and captivity settings to investigate the links between anthropogenic disturbance and antibiotic resistance genes (ARGs). I analyzed ARGs in wild and captive lemurs and soil from their habitats to show that lemur ARGs were correlated with anthropogenic disturbance and covaried with soil ARGs; lemur resistomes reflects multiple routes of ARG enrichment, including via antibiotic treatment or environmental acquisition. Integrating across these four data chapters, my results reveal that (a) the foundations of lemur-associated microbiomes are structured according to broad environmental conditions (e.g., wild vs. captive populations), but that between and within these broad categories, lemur microbiota are sensitive to more nuanced environmental variation, (b) lemur microbiota and resistomes co-vary with environmental microbiota, demonstrating the potential role of environmental acquisition in shaping host-associated communities across varying environments, and (c) integrating host microbial data across scales (e.g., at the individual and population level) with data on multiple facets of microbial communities (e.g., diversity, composition, membership, and resistomes), was key to providing a holistic perspective on host-associated and environmental microbe interactions across different microbial landscapes.

Anthropogenic effects on ecosystems have expanded in their scope and intensity, with significant consequences for global environmental, wildlife and human health. As human encroachment into wildlife habitat grows, habitat degradation and fragmentation intensify, leading to increased contact among wildlife, humans and domestic animals. Due to this increasing frequency of interaction, and the emergence of several high-profile diseases, global concern has grown over the risk of emerging infectious disease from zoonotic origins.

Due to Madagascar's rampant rate of human population growth and deforestation, its incredible species diversity, the widespread presence of domestic and invasive species, and its evolutionary isolation, it can be viewed as a high risk region for potential disease emergence. There is a need for assessment of the zoonotic and reverse zoonotic disease potential within this country.

To contribute to this assessment, consistent baseline health monitoring provides an effective tool for evaluating wildlife health and preparing for future disease occurrences. Limited, disconnected surveys of lemur health have occurred, yet there remained a need for more extensive, country-wide evaluations that also addresses invasive species, domestic animal and human health, as well shifting patterns of environmental and climatic change.

This research has investigated the connections among human, animal (both domestic and wildlife) and ecosystem health in Madagascar. I have examined current trends in anthropogenically-driven environmental change in Madagascar--including deforestation, illegal logging of precious hardwoods, mining, hunting, and agriculture--and evaluated how this change affects patterns of lemur, domestic animal and human health by evaluating a suite of health measures and parasite prevalence and richness. I have also examined how predicted global climate changes may influence the spatial patterns of lemur parasites and human infectious disease by assessing their shifts in distributions and geographic extent.

To assess the risk of disease transmission among lemur, domestic animal and human hosts, I have modeled the areas of geographic overlap among these parasites and their hosts and identified high-risk areas for disease emergence using geospatial analysis. This information can help to develop predictive statistical and spatial tools, which can inform both environmental management and public health planning.

Through this work, I have evaluated the severe loss of distribution that rosewood species have undergone, which highly qualifies them for international trade protection. We predicted areas of high risk for future logging, many of which occurred within protected areas in the biodiverse northeast.

Secondly, I have compiled the most comprehensive record of parasites of lemurs to date. Building upon the Prosimian Biomedical Survey Project data and the published literature, we have recorded 88 parasites that have been documented in lemurs. These are composed of helminths, bacteria, ectoparasites and protozoa. Of the 23 focal parasite species studied more in depth in this study, we noted high variability in prevalence measures for unique parasites at different sites. Parasite coinfection occurred quite commonly, with up to as many as 7 parasites concurrently. On average, lemur parasites tend to be less species-, genus-, or family-specific than other parasites across all primates.

Thirdly, I documented highly significant differences in health measures from two populations of Indri that exist under differing levels of anthropogenic pressure. Of note, the parasite richness, leukocyte count and differential, and nickel and cobalt levels were significantly higher in the more exposed population, while the total protein measures were significantly lower. These data suggest that the exposed population experiencing more anthropogenic pressure suffered from elevated health and nutritional stress.

Fourthly, I have documented strong correlations among environmental drivers (temperature, precipitation and landscape-scale features) and lemur parasite distributions. Striking shifts in their distributions are predicted to occur with projected climate change in Madagascar, including an expansion of helminth, virus and ectoparasite distributions, but a contraction of bacteria distributions due to warming and drying in the south.

Fifthly, I have examined 10 human and domestic animal parasites that hold great consequence for lemur, human and domestic animal health in Madagascar. I have similarly demonstrated strong correlations among environmental drivers (temperature, precipitation and landscape-scale features) and the distributions of these human parasites. Shifts in the distributions are also predicted to occur with projected climate change, including an expansion of helminth parasites, and a contraction of viruses and bacteria due to warming and drying in the south. I have identified areas of high risk for the transmission of parasites from human hosts to lemurs, as well as conversely from lemur hosts to humans. These risk indices will serve to highlight geographic areas at particular risk, and will also help to direct limited funds and staff to those areas most in need of attention.

Sixthly, I have demonstrated a need to train a growing cadre of One Health professionals from many different disciplines. I have offered several suggestions to integrate One Health training into graduate education, and have identified several geographic regions of potential to be a Center of One Health Excellence, of which the North Carolina Triangle area is one of great promise.