Overview

Research in the Archie lab combines four areas—behavioral ecology, disease ecology, population genetics, and conservation biology—to understand the evolution of animal social behavior and its genetic and disease-related causes and consequences. These areas are linked by the critical observation that animal social behavior is shaped by, and is a major shaper of genetic structure and infectious disease dynamics in natural populations. For example, patterns of genetic relatedness (i.e. kinship) influence which animals live together, and which animals mate and produce offspring. In turn, when animals make decisions about where to live or who to mate with, they influence the genetic structure of their populations. Furthermore, these social or mating relationships can serve as roadmaps for the spread of disease and can influence susceptibility to disease, via stress, dominance and other factors. Specifically, we’re interested in answering three main questions:

1. What are the disease-related and population genetic causes and consequences of sociality?
2. How do these causes and consequences influence the evolutionary costs and benefits of social relationships?
3. How does individual genetic variation affect behavior, immunity, and fitness?

To answer these questions, we use research techniques that range from behavioral observations of wild animals to noninvasive genetic tools to genotype individuals and their parasites and pathogens.

Research systems

Research in the Archie lab involves fieldwork as well as genetics research. When we’re in the field, we observe the behavior of wild mammals and collect samples for genetic analysis—usually from noninvasive sources such as dung. In the lab, we use dung samples to characterize the parasites infecting individual animals and extract DNA to conduct genetic analyses.

We currently collaborate with three research groups, which each study well-known populations of wild mammals. First, we collaborate with Susan Alberts and Jeanne Altmann, who direct the Amboseli Baboon Research Project (ABRP), in Amboseli National Park, Kenya. ABRP began in the late 1960s, collects detailed, individual-based data on the life histories, social relationships, genetics and steroid hormones of hundreds of individual baboons. Second, we work with the Amboseli Elephant Research Project (AERP), also in Kenya, which is directed by Cynthia Moss and Joyce Poole. AERP is the longest running field study of wild elephants. Third, we collaborate with Vanessa Ezenwa at the University of Montana, in Missoula, to study the ungulates living in and around the National Bison Range in Moiese, MT—including bison, bighorn sheep, elk, pronghorn antelope, mule deer, and white-tailed deer.

Current projects

How do social organization and behavior shape nematode and bacteria transmission? The disease-related consequences of sociality are among the most important and least understood areas behavioral ecology. Knowing how animal social organization and behavior shape the transmission of infectious agents is critical to understanding the evolution of sociality, and it has applied value as infectious disease threatens several species of social animals. However, because it is challenging directly track the movements of infectious agents between animals, studies that empirically measure patterns of transmission within and between social groups of wild animals are extremely rare. This project takes a new approach to understanding how social organization and behavior influence the transmission of infectious organisms, by using noninvasive genetic tools to accomplish two tasks: (1) to sample parasitic nematodes and endosymbiotic bacteria noninvasively from the feces of wild baboons and (2) to track their movements between individual baboons and social groups. It then uses this information to address four basic questions: Are baboons more likely to be infected by nematodes or bacteria from members of their own social group? What factors predict the rate of transmission between groups? What aspects of the social network predict rates of transmission among baboons in the same group? And finally, does the rate of transmission among group members explain why some groups of baboons are more infected than others? The results will help reveal the sources of animals’ infections, and which types of infectious agents are likely to exert the greatest selection pressure on the evolution of group living. In addition, this study will illuminate predictors of transmission within and between social groups, which are critical to understanding how infection will spread to the population at large.

What are the associations between social relationships, stress, and health? Social relationships have large impacts on individual health: the strength and number of an individual’s social relationships influences their life span and susceptibility to infectious disease. Many of these health effects are presumably due to the stress response, mediated by the hypothalamic-pituitary-adrenal (HPA) axis. Evidence for this hypothesis comes from several experiments on humans and model organisms, where researchers manipulate the social environment and then measure individual changes in the HPA axis, immune response, or risk of contracting a disease after deliberate exposure to a pathogen. This approach has been extremely useful for elucidating the links between social relationships, the HPA axis and immunity, but it has been less successful in linking these predictors to disease susceptibility. In addition, this experimental approach misses the point that we live in an ecological context with natural stressors and scattered disease threats. Thus, it is as yet unclear how important social stress is in shaping susceptibility to disease in a complex ecological context. This project will investigate the relationships between social bonds, stress and disease in the wild baboon population in Amboseli National Park, Kenya. As a highly social primate, with a close evolutionary relationship to humans (94% sequence similarity genome-wide), baboons are a useful model for understanding how social behavior influences health and disease. Specifically, this project aims to understand how several factors, including social stress, genetics, physiology and environmental factors predict individual exposure and susceptibility to fecal-transmitted parasites and pathogens (e.g. E. coli, gastrointestinal microbiota, gastrointestinal worms). The results will help reveal how social relationships shape disease susceptibility in a natural, ecological context.

Understanding the relationship between MHC, disease resistance and individual behavior. One way that animals naturally resist disease is through the genes that support their immune system. Animals with the most diverse immune system genes are usually the healthiest; however, when populations are small or isolated, this genetic diversity is at risk. This is a particular conservation concern for endangered and captive species like African and Asian elephants, which face serious disease threats. For instance, herpes viruses kill Asian elephants in zoos, and wild populations of African elephants are vulnerable to several diseases, including anthrax. One first step to understanding how elephants resist disease, and to predicting which elephants are most likely to survive a given disease, is to characterize their immune system genes. One such gene family is the major histocompatibility complex (MHC), which recognizes pathogens for immune response. We are currently characterizing MHC diversity in wild and captive Asian and African elephants in collaboration with scientists and veterinarians at the Smithsonian National Zoo and researchers at the Amboseli Elephant Research Project. The results of this work will be the basis for two major research efforts: (1) testing whether MHC variation predicts mate choice in wild elephants, and (2) testing whether MHC diversity predicts pathogen resistance and reproductive success.