Reciprocal feedbacks between animal sociality and infection-induced behavioral changes

Pathogens can trigger diverse changes in host social behaviors: Avoidance, enforced exclusion of infected conspecifics, proactive social distancing, active self-isolation, and passive self-isolation. Passive self-isolation (from sickness behaviors like lethargy) is perhaps the most common response; it is triggered by the animal’s immune response (e.g., pro-inflammatory cytokines) and reduces contact between the infected individual and healthy group members. Isolation of an individual from a social group, however, can pose significant fitness costs if it harms social integration, status, or relationships. To persist over evolutionary or even ecologically relevant timescales, these costs should be outweighted by benefits (e.g. physiological benefits such as conserving energy to fight an infection). My research explores this delicate balance of costs and benefits and broadly asks the question of when it is adaptive to “behave sick”. I use injections of an immunostimulant in highly social and cooperative common vampire bats (Desmodus rotundus) to investigate costs and benefits of passive self-isolation. Collaborations with Gerald „Gerry“ Carter, Rachel Page, Dan Bolnick).

Effects of pathogen exposure on social behaviors driven by susceptible or pathogen-affected individuals. Behaviors can increase (help) or decrease contact (orange squares). Figure adapted from Stockmaier et al, 2021, Science.

Foto by Gerry Carter

Co-evolution of host social behavior and infectious pathogens

Immunostimulants are widely used to evaluate social costs and physiological benefits of behavioral responses to pathogens. However, far less research has approached this question using actual pathogens that co-evolved with their hosts. The strenght and nature of infection-induced behavioral changes is a key element of host-pathogen coevolution. For instance, socially transmitted pathogens can evolve counteradaptations to a host’s behavioral response that reduces their transmission. Vampire bats are infected with a range of bacterial and viral pathogens that are spread by their many social interactions such as grooming, foodsharing or aggressive encounters. I study the behavioral effects of these naturally occuring and co-evolving pathogens using experimental infections and behavioral observations of individuals, when alone and embedded in their social networks. So far, we have collected behavioral data from rabies infected vampire bats, but we intend to explore this in other vampire bat/pathogen systems as well.

Simultaneous tracking of reservoir and host species

The ability to predict cross-species transmission is often restricted by knowledge gaps about fine-scale contact patterns that facilitate transmission across species borders. I focus on understanding the fine-scale behavior of both reservoir and host individuals that lead to inter-specific contacts and potential for transmission. Together with my collaborators, I use a recent state-of-the-art technological innovation, highly efficient and miniaturized proximity sensors that can be attached to both, large and small animals to simultaneously track encounters among many individuals. We use these loggers to map encounter networks of vampire bats and their host species (livestock such as cattle and horses) and also aim to simultaneously track pathogen transmission/sharing between species using molecular methods (collaboration with Gerald Carter, Simon Ripperger, Daniel Becker)