Changes in sheep grazing behaviour and herbage after partial area improvement of a high country summer range

Abstract

Sheep distributions on a 590 ha part of a 6200 ha summer range were observed for 3 years before and 3 years after an unfenced 44 ha part was oversown with white clover and topdressed with fertiliser. Treatment of the unfenced area attracted sheep from unimproved parts of the study area, but not from more distant parts of the summer range. Grazing pressure (stock units/t herbage) showed a seven-fold increase on the developed area compared with the undeveloped area in the last two postoversowing and topdressing seasons. Grazing pressure was halved for the whole study area, compared with pre-oversowing and topdressing (OSTD) levels, leading to accumulation of unutilised herbage on all vegetated areas that remained undeveloped. Higher grazing pressures on developed areas were accompanied by an increase in herbage quality on offer and improvement in diet selected. Partial area improvement attracted sheep from the higher altitude areas in a similar proportion to that from all the other undeveloped land units. Sheep densities were apparently very low on the higher altitude areas in both the pre- and post-OSTD periods and there might be little benefit to such higher environments from fencing them off or from attracting sheep away from them. The improved pastoral regime might it self better justify the costs of land development.

Keywords:

• sheep behaviour
• sheep distribution
• topdressing
• oversowing
• tussock grasslands
• land conservation
• herbage mass
• herbage quality
• sheep diet
• grazing pressure