Characterising activities of free-ranging Merino ewes before, during and after lambing from GNSS data

Abstract

Tracking the movement of grazing Merino ewes using Global Navigational Satellite Systems (GNSS) provided data which could be used to determine the behavioural characteristics exhibited during different physiological states and times-within-day. GNSS location and the resulting movement calculations from five foraging Merino ewes of known lambing date were partitioned into four different 24. h physiological states (PS): (1) seven days before lambing (L - 7), (2) day of lambing (L), (3) three days after lambing (L + 3) and (4) seven days after lambing (L + 7). Within each of these four PS the data were further partitioned into three time-within-day (TWD) intervals based on behavioural patterns: (1) 0500 to 1159. h morning foraging; (2) 1200 to 1859. h afternoon foraging and (3) 1900 to 0459. h night camping. Ewe locations were recorded at 10. min intervals over a 43 day period. Distances moved (m) and rates of travel (m/s) were analysed to characterise free-ranging ewe spatio-temporal activities within the four PS and three TWD periods. Physiological state and TWD had significant (P <. 0.001) effects on mean distance moved by ewes but there was no two-way interaction (P > 0.05). Ewe rate of travel was significantly (P <. 0.001) affected by PS and TWD and there was a significant (P <. 0.01) two-way interaction. Ewes at L spent 13.2% less time foraging than ewes in other PS (mean 53.2%), while time spent in stationary behaviour accounted for 59.5% and ewes in other PS spent a mean of 45.2% of their time stationary. Distance moved and rate of travel during foraging were significantly (P < 0.001) affected by PS and TWD. GNSS collars were satisfactory to characterise behaviour of foraging Merino ewes at different PS and TWD. However, using ewe behaviour alone to identify when lambing occurs may not be a satisfactory husbandry option.