Developing a Methodology for the Assessment of Freedom of Movement: The Influence of Spatial Parameters on Movement and Space Use in Mice (Mus musculus)

Abstract

Despite recent progress in developing housing conditions that more effectively meet the needs of managed species, there remains a lack of detailed information regarding the influence of a space on animal health and well-being. If improvements are to be made to current guidelines so that they accurately reflect the needs of the animals, this information and a reliable method for collecting it, is critical. The objective of this project was to systematically examine the effects of spatial parameters on movement and space use of mice (Mus musculus) in open-field arenas. This approach may provide researchers with a means to describe what factors are most important for maintaining an adequate welfare state, and may help address questions regarding why (and how) these factors function as they do. To accomplish this, a standardized method was used across three experiments to test the effects of floor area, arena shape and structural complexity on movement and space use of mice. In each experiment 40 female Swiss Webster mice were observed in four arenas differing in spatial characteristics. In Experiment One, mice were individually observed in four square arenas that differed in floor area (0.5, 1, 2 and 4m2). The results from this experiment demonstrated an effect of both floor area and perimeter length on movement and space use of mice, as measured by track length, area traversed and mean distance to the nearest wall. In Experiment Two, the same variables were used to describe the behavior of mice in four arenas of equal floor area (1.5m2) that differed in shape (circle, square, 2:3 rectangle or 1:3 rectangle). Observation of animals in a circular arena demonstrated the impact of corner space on continuity of movement. In the final experiment, partitions were added in pre-determined configurations to examine the influence of partition location on animals demonstrating thigmotaxis. While the addition of partitions affected the distribution of movements, the specific location of partitions had little impact on movement or space use. With some refinement, this methodology could be used across species to identify specific needs and determine how effective housing systems are at meeting them.