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

Abstract

Indian crested porcupines (Hystrix indica) are adaptable, generalist herbivores with wide environmental tolerances and a large geographic range. In the arid Negev Desert highlands of southern Israel, porcupines excavate and consume 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 according to depth of forage and substrate, and new digs averaged about 8 cm in depth, and 400 cm2and 940 cm3in surface area and volume, respectively. Digging rates also differed among habitats. In hilly watersheds, highest digging rates were in soil belts supporting the greatest cover of shrubs and geophytes. Dig densities peaked at > -031 dig m−2, impacting up to 4% of soil surfaces. Digs are temporary soil pockets (longevities of < -032 to > -0310 years) that trap soil, water, organic matter, and seeds. As highly productive microhabitats compared to surrounding soil matrix, they promote the germination and growth of annual plants including some porcupine forage species. 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 watersheds, thereby promoting large runoff flows that produce mesic patches and plant habitats. Runoff dynamics have greatly influenced past and present human exploitation of Negev landscapes. Recent experiments indicate that porcupine digs have important properties as small-scale landscape disturbances, and as sources and sinks of critical environmental resources. Additional research 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.