The effect of predator positioning and related angles on the flight-initiation distance and refuge choice of the eastern gray squirrel.

Abstract

The purpose of this study was to determine the effect that the relative positions of squirrel, predator, and refuges, as well as the predator's SPT angle (See Figure 1), had on a squirrel's choice of refuge and the length of its flight initiation distance. A running person was used to simulate an attacking predator, and the relative positions of squirrel, person, and refuges were measured using both distance and compass angle. Data were collected in September and October 2014 at several urban green spaces in Louisville, Kentucky.The SPT angle measurement was not found to be particularly useful in predicting flight initiation distance or the squirrel's refuge of choice. The distance of the person to the refuge (PTR) was found to be significantly correlated with flight initiation distance. However, the correlation was positive, the opposite relationship to what had been expected. Assessment of refuge choice by comparing the relative positions of squirrel, person, and refuges was highly successful. It was found that squirrels employ both escape trajectory and the relative distances of the squirrel and the person to a particular refuge (expressed as the PTR/STR ratio) when they select a refuge. Instead of always running to the closest tree (defined as tree 1), the squirrels select a refuge that provides them the best combination of relative squirrel/predator distances and an escape trajectory that takes them away from the predator's path.