Microhabitat to landscape impacts: crested porcupine digs in the Negev Desert highlands

Indian crested porcupines (Hystrix indica) are adaptable, generalist herbiv ores with wide environmental tolerances and a large geographic range. In th e arid Negev Desert highlands of southern Israel, porcupines excavate and c onsume subterranean organs of 18 species of geophytes and hemicryptophytes in a variety of habitats. Their foraging generates a network of direct and indirect impacts on ecological processes. Porcupine digs varied in size acc ording to depth of forage and substrate, and new digs averaged about 8 cm i n depth, and 400 cm(2) and 940 cm(3) in surface area and volume, respective ly. Digging rates also differed among habitats. In hilly watersheds, highes t digging rates were in soil belts supporting the greatest cover of shrubs and geophytes. Dig densities peaked at > 1 dig m(-2), impacting up to 4% of soil surfaces. Digs are temporary soil pockets (longevities of < 2 to > 10 years) that trap soil, water, organic matter, and seeds. As highly product ive microhabitats compared to surrounding soil matrix, they promote the ger mination and growth of annual plants including some porcupine forage specie s. Loose soil excavated by porcupines enhances soil erosion and transport, and may substantially enhance ecosystem flows of water, soil, and nutrients . Porcupine digging may help to maintain bare rock outcrops in Negev waters heds, thereby promoting large runoff flows that produce mesic patches and p lant habitats. Runoff dynamics have greatly influenced past and present hum an exploitation of Negev landscapes. Recent experiments indicate that porcu pine digs have important properties as small-scale landscape disturbances, and as sources and sinks of critical environmental resources. Additional re search is needed to better define and predict porcupine digging impacts at several ecological levels, and as a basis for realistic management of Negev habitats and landscapes. (C) 1999 Academic Press.