Date of Award:

5-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Kezia Manlove

Committee

Kezia Manlove

Committee

Julie Young

Committee

Mary Connor

Abstract

Understanding and predicting movement is critical for conservation planning and disease risk mitigation, and important environmental drivers of animal movement have received extensive attention in the ecological literature. Social factors surrounding group fission and fusion events also directly affect movement. However, these events are infrequently measured in the wild and rarely linked to underlying mechanisms such as relatedness, agreement in reproductive status, or shared life stage. While some social factors cannot be directly observed in the field, individual animals congregating in groups and moving about a landscape can. In animal societies, groups may merge together in a fusion event, and a group may split in a fission event. These events, repeating over time within a population, constitute fission-fusion dynamics. Here, we study group structure and how individuals navigate the social environment that structure imposes, using a long-term, individual-level dataset on female bighorn sheep gathered at the Confederated Salish and Kootenai Tribal (CSKT) Bison Range in Montana, USA. In Chapter 2, we describe three dimensions of fission-fusion dynamics that clarify the context that informs an individual’s social environment: group size, composition, and spatial cohesion in this population. In Chapter 3, we relate these group attributes from the previous chapter to social processes and underlying drivers using a discrete choice model. Our analysis opens a door for understanding how social mechanisms precipitate observed space use behaviors, with implications for how we view animal societies in research. We find that general group-level attributes like group size and demographic makeup along with specific, dyadic social attributes like mother and cohort relationships each influence bighorn sheep group configurations at the Bison Range and drive fission and fusion events.

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