Crested porcupine digs in the Negev desert highlands: patterns of density, size, and longevity

Abstract

Crested porcupine (Hystrix indica) feeding digs were systematically counted and measured on five 2500-m2 plots representative of several habitats in the Negev desert highlands. Densities of existing (baseline) digs varied by a > 10-fold margin, from >1 dig/m2 on a densely vegetated site on a loess plateau, to 0·1 dig/m2 on sparsely-vegetated, deep loess. Recent annual digging rates (from periodic counts during a 19-month period) averaged 0·15 ± 0·10 dig/m2, and also varied among sites but did not correspond to site differences in the number of old digs. There were large mean intersite differences in: sizes of new digs (up to 1900 cm3 volume); annual rates of surface disturbance (up to 0·8 per cent of surface area) and of soil displacement (up to 0·35 m3/1000 m2); and in total disturbed surface area at the start of study (up to 3·6 per cent). From filling-in rates, estimated mean lifespans of digs ranged from 1 year to 6·5 years, depending on site and size parameter. Distributions of old and new digs on 100-m2 sub-plots were highly correlated at three of five plots, indicating that porcupines exploited the same food patches over time at those sites. Baseline dig counts corresponded to densities of principal forage species among sites and among all 125 sub-plots combined. This pilot study suggests large site variations in porcupine foraging effort, in dig parameters, and in porcupine impacts on Negev ecosystems.