On animal numbers and observation intervals for characterizing sheep activity.

A study was made of the effects of individual differences between sheep and of increasing the interval between observations on estimates of flock activity patterns. An interval of ten minutes or less between observations gave a precise estimate of the relatively infrequent activity states. The activity patterns of individual sheep were markedly different and indicated that an increase in the number of animals observed would lead to a considerably greater increase in the reliability of estimates than an increase in the frequency of observation.