Grazing behaviour of merinos on an undeveloped semi-arid tussock grassland block

Abstract

Flocks of merino wethers or ewes varying in size from 20 to 2200 were observed from dawn until dusk for 77 days over three summers on an 850 ha block of undeveloped, semi-arid Festuca novae-zelandiae tussock grassland with an altitudinal range of 60 m. Group location, size, and activity were recorded at half-hourly intervals together with associated weather. Sheep dispersed at dawn, grazed during the morning (about 80% at any one time), rested during the middle of the day (standing, lying, or in shade groups; total about 60%) and then grazed again in the late afternoon (about 80% grazing). Activities engaged in were determined principally by time of day and temperature. Grazing reached a maximum at 10–15°C, and numbers lying increased with temperature. Shade group formation increased rapidly above a threshold of about 15°C, particularly under sunny conditions. Sheep showed a preference for the higher terraces. Groups formed during the morning grazing period, but were irregular in composition and showed no territorial behaviour. Sheep tended to graze into the wind, more so at higher temperatures and wind speeds. Drinking was rarely observed. The proportion of the block grazed in a day depended on flock size, being about 15% per day for a flock of 20 to about 60% per day for a flock of 1600. Grazing of small areas of developed pasture appeared to be a chance occurrence.

Keywords:

• Animal behaviour
• merino sheep
• tussock grasslands
• climate interactions