Cattle on pastures do align along the North-South axis, but the alignment depends on herd density

Alignment is a spontaneous behavioral preference of particular body orientation that may be seen in various vertebrate or invertebrate taxa. Animals often optimize their positions according to diverse directional environmental factors such as wind, stream, slope, sun radiation, etc. Magnetic alignment represents the simplest directional response to the geomagnetic field and a growing body of evidence of animals aligning their body positions according to geomagnetic lines whether at rest or during feedings is accumulating. Recently, with the aid of Google Earth application, evidence of prevailing North-South (N-S) body orientation of cattle on pastures was published (Begall et al. PNAS 105:13451-13455, 2008; Burda et al. PNAS 106:5708-5713, 2009). Nonetheless, a subsequent study from a different laboratory did not confirm this phenomenon (Hert et al. J Comp Physiol A 197:677-682, 2011). The aim of our study was to enlarge the pool of independently gained data on this remarkable animal behavior. By satellite snapshots analysis and using blinded protocol we scored positions of 2,235 individuals in 74 herds. Our results are in line with the original findings of prevailing N-S orientation of grazing cattle. In addition, we found that mutual distances between individual animals within herds (herd density) affect their N-S preference-a new phenomenon giving some insight into biological significance of alignment.