Tying animal personality to population-level trends
Given that humans display a wide range of personality types, it might not come as a great surprise to know that scientists are finding more and more evidence to support personality types in non-human species as well. In fact, individuals across a wide range of taxa have been found to consistently differ in boldness, aggressiveness, activity level, exploration tendency, sociability, and other behaviors. These differences in personality type, both within a species and among individuals within a population, can have large effects on important ecological dynamics, such as spatial distribution (e.g., more exploratory animals may disperse farther), disease dynamics (e.g., bolder animals may be at the leading edge of disease spread), or even predator-prey dynamics.
My research explores personality-dependent space-use in golden-mantled ground squirrels (Callospermophilus lateralis). Because golden-mantled ground squirrels are presumed to be territorial, and because they have only a brief summer season to reproduce and gain sufficient weight before hibernation, resources are not always accessible and this connection between personality and space-use may be particularly apparent.
I assayed individuals for personality in three main ways: 1. through repeated, standardized 'arena' trials, in which an ethogram of behaviors was quantified for a given individual during solitary (without mirror image) and 'social' (with mirror image) contexts, 2. through repeated Flight Initiation Distance trials, in which I approximated boldness by systematically approaching individuals in the field, and 3. though repeated 'behavior in trap' trials, in which I scored an animal's behavior for a given period of time after it was trapped. I then paired personality scores with known ecological parameters, such as home range size, movement speed, and resource use.
Preliminary results show that bolder individuals tend to maintain larger core home range areas, more bold and exploratory individuals move faster in the field, and more bold, exploratory, and social individuals have greater access to higher quality habitat.
Individuals undergo standardized arena trials in a solitary and 'social' context. A clip from a Mirror Image Stimulation, or social, trial is shown above. A series of variables, such as number of jumps or time spent interacting with the mirror, were quantified for each trial.
In this hotspot visualization, it's clear to see that individuals vary in activity level during arena trials. For example, the individual depicted in the top left and bottom right trials spent much of the trial in motion, while the top right and bottom left images depict the same individual, which stayed in the same place for the entirety of the trial.
In addition to manually coding behavior, I used a video software program called EthoVision to track individual movement inside of the arena and quantify more fine-grain continuous data, such as distance moved to the nearest cm, and both average and maximum velocity reached.