THE INFLUENCES OF DEPRESSIONS MADE BY IBEX ON THE ANNUAL VEGETATION ALONG CLIFFS OF THE ZIN VALLEY IN THE NEGEV DESERT HIGHLANDS, ISRAEL

ABSTRACT

On the slopes leading to the edges of the cliffs of the Zin Valley, the Nubian ibex (Capra ibex nubiana) create thousands of depressions in the soil of slopes sheltered from strong winds, which they use as temporary beds at night. During the year the ibex groups alter in size and change their sleeping area according to the wind direction. These depressions measure from 60 to 105 × 80 to 140cm and are 6.5–10cm deep. In an area of 15 × 3m about 33 diggings were found and up to 70 diggings in an area 30 × 5m. Along 300m of the cliff about 345 diggings were counted. The depressions that the ibex abandon remain for several years and become special microhabitats for annual plants.

Runoff water, following a long and intensive rainfall, carries seeds that accumulate in these depressions, including mucilaginous seeds that may float on the runoff water. Annual plants later emerge in higher species and plant numbers than on similar sized areas upslope from the depressions. Plant species with wind- and rain-dispersed seeds were observed in greater numbers in these depressions which have similar influences on the annual plant vegetation as the porcupine diggings in the Negev highlands.