Use of space in the domestic fowl: separating the effects of enclosure size, group size and density

Abstract

An understanding of how confined animals move within the space available to them is essential in the design of effective captive environments that maximize animal welfare. In addition to the obvious effect of enclosure size, other factors such as the number of individuals in the group and their density per unit of area are likely to affect movement patterns. Yet determining the specific contribution of each (enclosure size, group size and density) is a challenge because confounding between two or more of these factors is experimentally difficult to avoid. The aim of our study was to isolate their unique effects by using multiple contrasts with an efficient experimental design that included combinations of groups of 10, 20 and 30 domestic fowl (Gallus gallus domesticus) housed in 1.5, 3.0 and 4.5 m2 enclosures. This treatment structure enabled us to make comparisons across increasing enclosure size at both constant group size and constant density. In this study we show that enclosure size and density are the primary factors affecting patterns of movement and use of space for groups of domestic fowl. Animals in larger enclosures maintained larger nearest-neighbour distances, travelled greater distances and had bigger home ranges as measured by minimum convex polygons. These results suggest that larger enclosures encourage more exploratory movement in groups of domestic fowl. However, the positive effects of large enclosures may be limited by the effects of density. In this study, we found that group size had few effects.