Individual movement rates are sufficient to determine and maintain dynamic spatial positioning within Uca pugilator herds

Authored by Eilea R Knotts, Blaine D Griffen

Date Published: 2016

DOI: 10.1007/s00265-016-2086-2

Sponsors: United States National Science Foundation (NSF)

Platforms: NetLogo

Model Documentation: ODD

Model Code URLs: Model code not found

Abstract

Spatial location within aggregations (i.e., periphery, central) is of biological significance to gregarious animals. Because these positions are a potential consequence of consistent individual behavioral differences, or personality, a better understanding of potential mechanisms concerning personality is central to predicting an individuals' location. To determine the effects of individual personality on the dynamic spatial positioning of Uca pugilator while herding, field data collection and agent-based modeling were employed. Individuals were assayed to establish their personalities and returned to the field for observation as a means of identifying location preference within selfish herds. There was a significant difference between the extreme personalities and the proportion of time spent on the edge of the herd. The active individuals were at the periphery similar to 50 \% more of the time than less active individuals. An individual-based model qualitatively replicated these field results by applying the mechanism of activity level as an indicator of individual personality. This suggests that differences in personality-dependent movement are sufficient to explain the spatial positioning of individuals within selfish herds. This study enhances our understanding of the possible mechanisms that govern group movement, and has implications for modeling population dynamics that can be influenced by individual personality. Animal personality influences the level of exploratory activity of individual animals, with some individuals being consistently more active and others consistently less active, and may therefore be used to mechanistically predict the location of individual animals within groups or herds. Here, we investigate the relationship between individual personality and location on the edge vs. in the center of foraging herds of the sand fiddler crab Uca pugilator. We combine observational testing of activity level in lab, observations of spatial positioning within herds in the field, and agent-based computer simulation modeling to demonstrate that differences in exploratory movement can sufficiently explain the spatial positioning of individuals within herds. Thus, the spatial positioning of individual animals within herds can be explained without relying on choices by individual animals.

Tags

selfish herd Personality Group-size Trade-offs Structured populations Collective animal behavior Fiddler-crabs Fitness consequences Foraging success South-carolina