Alarm Communication in the Black Garden Ant (Lasius Niger)

: Characterising a Body Shake Behaviour in Response to Disease

Abstract

Social insects have evolved alarm communication systems to facilitate collective responses to incoming threats. These include chemical signals through the production of alarm pheromones, as well as mechanical signals produced through body movements and vibrational signals. This thesis examines a body shake behaviour in the black garden ant (Lasius niger), and its role as a mechanical alarm signal. While previous studies have described body shakes during aggressive encounters with non-nestmates, the behaviour is also observed between nestmates, suggesting a potential function in intra-colony communication which has not been explored. Furthermore, the body shake was observed between pathogen-exposed individuals, indicating a potential role in pathogen alarm signalling, which has not been previously documented in ants. In this thesis, I explore the general alarm function of body shakes, characterise the behavioural movement, and investigate the role of body shaking after exposing workers to the entomopathogenic fungus Metarhizium brunneum. Furthermore, the relationship between body shaking and change in activity levels, and the transmission of shakes through small groups is investigated, with the use of automated tracking software DeepLabCut along with a developed pipeline to automatically maintain individual ant identities during tracking. The findings revealed that body shakes may have a secondary role in intra-colony alarm communication in response to different threats. Additionally, the body shakes were upregulated during pathogen exposure, by both the exposed individuals and unexposed nestmates. Shakes also transmit through the social networks, to alert nestmates and cause an increase in individual activity levels. Overall, this work provides new insights to mechanical alarm communication in L. niger colonies, and highlights body shakes as a potential disease-related signal, to facilitate collective responses to disease challenge.

Date of Award	30 Sept 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Nathalie I K A Stroeymeyt (Supervisor)