Effect of pasture size on behavioural synchronization and spacing in German Blackface ewes (Ovis aries)

This study aims to assess plot size related changes in spacing and behavioural synchronization in a herd of 14 German Blackface ewes kept on three different pasture sizes: S (126m(2)), M (1100m(2)), and L (11,200m(2)). In direct field observations, behaviour and nearest neighbour distance were recorded individually. Additionally, interindividual and nearest neighbour distances were derived from aerial photographs of the herd taken on plot sizes S and M. Nearest neighbour distances <1m accounted for more than 60% of observations, and were more frequent on plot size L than on plot sizes S (Z=3.3; p<0.01) and M (Z=3.2; p<0.01). Average interindividual distances were significantly smaller on S (4.89±2.62m) than on M plots (5.99±3.06m; t=7.3; p<0.01). Synchronization tended to increase with plot size (K(S)=0.42; K(M)=0.52; K(L)=0.66), but was not accompanied by a concomitant increase in dispersion. Aerial photography proved a valuable tool in the analysis of spacing behaviour as intraindividual repeatability of the derived distances was highly significant (Kendall's W between 0.32 and 0.58; p<0.01). The sheep kept small distances on all plot sizes, thus the high degree of behavioural synchronization might be mainly attributed to the motivation for close proximity to any conspecific.