High society: behavioral patterns as a feedback loop to social structure in Plains bison (Bison bison bison)

Andrew J Caven,Kelsey C King,Nico Arcilla,Dustin H Ranglack,Katie G Leung

doi:10.1007/s13364-019-00416-7

Abstract

Social organization as a topic has wide application often conserved across lineages and can lead to complex cultures, yet it is still not well understood in many taxa. We observed American bison (Bison bison) to investigate the interactions of hierarchy and behavior to elucidate patterns of social organization. Bison are highly visible animals that live in relatively accessible grasslands, and most are in semi-wild conservation herds that allows for access to low-stress observation and physiological exams. We observed behaviors in a semi-wild, reintroduced herd of 53 bison in a 140-ha prairie from April to October 2015 (165 h of observation). After establishing a linear hierarchy, we categorized individuals of each sex as high, mid-, or low ranking and then evaluated behavioral trends across rank and sex. We found that high ranking males constantly defended their linear positions and focused breeding efforts on the females with the highest productivity, consistent with disruptive sex characteristics. Intra-rank conflict focused on linear positioning likely causes the volatility in male bison hierarchy and stress of domination. Female bison, however, tend to suppress the lowest class, which likely drives their hierarchy’s stability and stress of subordination. Our results show that male and female bison are impacted differently by their social rankings and show that individual aggressive actions may provide feedback loops to their social organization.

Highlights

Social structure is the foundation upon which much intraspecific competition occurs, and many species in a wide swath of taxa exhibit some social structure
We focused in interactions between bison to gather enough information to map the social hierarchy evident in the results of interactions
We mapped the social hierarchy of the bison herd, placing bison into a social ranking: high, mid, or low ranking (Fig. 1)

Summary

Introduction

Social structure is the foundation upon which much intraspecific competition occurs, and many species in a wide swath of taxa exhibit some social structure. Especially charismatic mammals, which exhibit observed social behavior, are inaccessible to extensive research. Most Plains bison (Bison bison bison) herds are in some degree of captivity, under human management, and brought into holding pens annually This allows for easy access to testing (genetic, viral, or parasite loads), and they are large and conspicuous animals, that are relatively accepting of human presence (University of Nebraska Medical Center 2016). These factors allow for humane observation and sample collection. Bison have resided in metapopulations since the late 1800s and could provide useful information on cultural and genetic differences that arise when social animals are separated by some boundary or are re-integrated (Di Fiore and Rendall 1994; Whitehead and Rendell 2014)

Methods

Results

Conclusion