Click here for an overview of research in the Archie lab. Keep reading for updates on our latest research.
Strand 1: Social effects on the spread of bacteria and macroparasites.
Socially structured gut bacteria in wild baboons
This project is an ongoing collaboration with Jenny Tung, Ran Blekhman, and Luis Barriero. Social behavior is proposed to have profound effects on microbial transmission. While these effects are well known for pathogenic microbes, social effects on beneficial bacterial communities, such as the vertebrate gut microbiome, have been relatively ignored. This is in spite of the fact that variation in gut microbiome composition can affect traits linked to host fitness, such as energy acquisition, disease resistance, and immune function. We’re currently testing for social effects on gut microbiome composition via metagenomic shotgun sequencing of fecal-derived DNA from nearly all the adult baboons living in two social groups in the Amboseli ecosystem, Kenya. We hope to discover how social context, both within and between social groups, influences the taxonomic and functional genetic content in baboon gut microbiomes. The results are relevant to understanding connections between social behavior and microbiome-associated health effects, as well as the evolutionary consequences of group living.
Links between animal behavior and the microbial ecology
At first glance, understanding the bacterial communities that live in and on animals might not seem to offer much to biologists studying animal behavior. Working together with Kevin Theis, we developed conceptual frameworks for how microbial ecology might advance research on both proximate and ultimate questions in animal behavior, such as: how do animals recognize individuals, group members and kin? How do animals choose among potential mates? And what are the evolutionary costs and benefits of social relationships? Contributions to these problems from microbial ecology come from two basic ideas. First, the structure of animals’ bacterial communities are shaped by their hosts’ environments, physiologies, genotypes and social relationships. In turn, these communities can communicate this information about their animal hosts, especially through odor. Second, social relationships can mediate exposure and susceptibility to bacteria, and this socially mediated transmission can influence the evolutionary costs and benefits of social relationships. Hence, the interactions between animals and their microbes may be help solve puzzles in the evolution of behavior.
Social effects on E. coli transmission in wild elephants
Working together with Patrick Chiyo, George Wittemyer, the Amboseli Elephant Research Project, and Save the Elephants, we used population genetic tools to investigate the effects of social structure, environment, and host traits on the transmission of Escherichia coli infecting two populations of wild elephants: one in Amboseli National Park and another in Samburu National Reserve, Kenya. We found that social behavior had little affect on the transmission of E. coli in elephant populations. Instead, E. coli transmission was largely dominated by habitat and host traits. Habitat overlap between elephant social groups predicted E. coli genetic similarity, but only in the relatively drier habitat of Samburu, and not in Amboseli, where the habitat contains large, permanent swamps. We also found that elephants from similar birth cohorts were infected with genetically more similar E. coli than elephants more disparate in age. We suspect that this age-structured transmission may be driven by temporal shifts in genetic structure of E. coli in the environment and the effects of age on bacterial colonization. Together, our results support the idea that, in elephants, social structure often will not exhibit strong effects on the transmission of generalist, fecal-oral transmitted bacteria.
Strand 2: Social context affects physiology, immune responses, and life span.
Social effects on wound healing
Social status can have striking effects on health in humans and other animals, but the causes are often unknown. In male vertebrates, status-related differences in health may be influenced by correlates of male social status that suppress the immune system. For instance, low status is linked to chronic social stress, poor physical condition, and old age, while high status is linked to high energetic costs of reproduction. We tested whether these correlates could create status-related differences in immune function by measuring the incidence of illness and injury, and then examining healing rates in a 27-year data set of natural injuries and illnesses in wild baboon males. We found no evidence that the intense reproductive effort associated with high rank suppress immune responses. Instead, high-ranking males were less likely to become ill, and they recovered more quickly than low-ranking males, even controlling for differences in age. Notably, alpha males, who experience high glucocorticoids, as well as the highest reproductive effort, healed significantly faster than other males, even other high-ranking males. Hence alpha males seem to escape from the immunosuppressive costs of glucocorticoids, but low-ranking males do not, suggesting that glucocorticoids’ effects depend on an individual’s physiological and social context.
Does social connectedness predict survival?
Social integration and support can have profound effects on human survival. The extent of this phenomenon in non-human animals is largely unknown, but such knowledge is important for understanding the evolution of both lifespan and sociality. In this collaborative project with Susan Alberts, Jeanne Altmann, Michael Clark, and Jenny Tung, we’re testing whether the strength of same-sex and heterosexual social bonds predicts adult survival in wild female baboons. To date, only a handful of animal studies have found that social relationships may affect survival; we hope to extend those findings by examining bonds to both sexes in by far the largest data set yet examined for any animal. So far, our results support the idea that social effects on survival are evolutionarily conserved in social mammals.