THE INFLUENCE OF VEGETATION PATTERN ON THE GRAZING OF HEATHER MOORLAND BY RED DEER AND SHEEP .1. THE LOCATION OF ANIMALS ON GRASS HEATHER MOSAICS

1. A study site comprising six 2.5 ha plots of heather (Calluna vulgar is (L.) Hull) moorland which could be viewed from afar was created in NE Scotland. Each plot contained 20% by area of Agrostis/Festuca grass land, distributed in either one large, four medium or 12 small patches . 2. The plots were grazed by groups of sheep or red deer (Cervus elap hus L.) in series of 10-day periods; in each period the activities and locations of all individuals were recorded at 30 min intervals during daylight hours on several days. In one experiment in early summer she ep and deer were compared at equivalent stocking rates, and in a secon d experiment in late summer sheep were compared at two stocking rates. 3. Sheep grazed for longer than deer (53% cf. 37% of daylight time), both species spending more time grazing in the late afternoon and even ing than earlier in the day. 4. Typical group size (groups being defin ed as animals within 30 m of others) was greater in sheep than deer. S heep were seen in smaller groups when the grass patch number increased , but in deer group size was unaffected by vegetation pattern. 5. The distribution of grass patches significantly affected the grazing time spent on heather by sheep but not by deer. In plots with one large gra ss patch sheep foraged on heather for only 9% of their grazing time (c f. 40% for deer), but in plots with 12 small grass patches the proport ions of grazing time spent on heather were 43% for sheep and 48% for d eer. 6. On the heather the densities of grazing sheep and deer were hi gher in a zone 0-5 m from the edge of grass patches than further away, and densities were higher at the edge of large patches than at the ed ge of small patches. This may damage heather at the patch edge leading to the spread of grass patches. 7. A simple ratio of grass:heather in a moorland may not be a good predictor of heather utilization because increased fragmentation of the available sass encourages grazers, and sheep in particular, to graze heather more.