Hystrix Indica Research Articles

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

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.

Annual plant community responses to density of small-scale soil disturbances in the Negev Desert of Israel.

We investigated whether plant diversity and productivity in small-scale soil disturbances, which is known to be higher than in undisturbed soil, decreases as the density of the disturbances increases. We studied this in an experiment with soil diggings (15 cm diameter and 15 cm depth) dug at a range of densities, on a north- and a south-facing slope of a watershed in the central Negev Desert of Israel. The diggings were similar to the commonly occurring pits made by porcupines (Hystrix indica) as they forage for below-ground plant parts. We used four levels of digging density, within the naturally occurring range in the region, represented by a rectangular plot with rows of diggings dug at four distances between diggings. The plots were laid out in a blocked design with three replications on both slopes, with each block containing all four levels of digging density. In the spring of 1992, 1994 and 1995 we measured plant density, species richness and plant productivity in the diggings, and in adjacent equal-sized undisturbed control areas ("soil matrix") and on the mounds made by the removed excess soil. Plant density, species richness and productivity of annual plants were higher in the diggings than in the undisturbed matrix, while these responses were very low on the mounds. Plant density, species richness and productivity in the diggings, but not in the matrix or mounds, decreased as digging density increased. This effect varied slightly with location within a watershed and with annual rainfall. The density of seeds captured in the diggings from outside the digging during the 1995 dispersal season decreased with increasing digging density, but only on one of the slopes. At the highest digging density, plant density and species number in the diggings did not decrease down the slope, as expected if interference between diggings in runoff water capture were the cause of the digging density effect. There was a weak decrease in biomass production in 1994-1995 down the slope. We used a simple mathematical model to estimate whether the distribution of rainfall intensities that occurred during the winter of 1994-1995 could result in differences between digging densities in the amount of water captured by the diggings, and whether this could explain the observed effect of digging density. The model showed that there were four events during which less water was captured by the diggings at high digging densities, except in the topmost row of diggings. Soil moisture measurements, however, showed very little difference between diggings at different digging densities. We explain our findings as the result of the interaction between the properties of the disturbance patch with its surroundings, as the diggings capture resources in the form of runoff water, and seeds moved primarily by wind. The additional resources and seeds captured in diggings increase plant density, species richness and productivity relative to the undisturbed matrix. However, the contrast in plant responses between the disturbed patches and undisturbed soil diminishes at higher digging densities. We explain this as interference among diggings at close proximity. As we did not detect a decrease in plant responses down the slopes, we conclude that interference is due to interception of the wind-driven, non-directional flow of seeds. Interception of the down-slope flow of runoff water by upslope diggings is insufficient to affect plant density, determined at the beginning of the season. Later in the season, runoff interception may become important for biomass production.

Distribution and reproduction of the Indian Crested Porcupine Hystrix indica (Hystricidae: Rodentia) in Iraq

The distribution of the Indian Crested Porcupine Hystrtx indica in Iraq is described, with 19 additional new localities. The population has apparently has been declining during the last twenty years. Preganancy was recorded between April and September, suggesting at least two litters per year. The mean number of embryos was 2.3 per female. 98–100% of the stomach content consisted of plant material.

Evaluation of the comparative efficacy of fumigants and acute poison baits against Indian crested porcupine, Hystrix indica

Field trials were conducted to determine the efficacy of three fumigants and two acute poisons against the crested porcupine, Hystrix indica, in forest plantations and croplands. The highest mortality was obtained with the use of a two-ingredient gas cartridge, followed by sodium cyanide and aluminium phosphide. Strychnine baits were less effective than baits prepared from sodium fluoroacetate (1080). Further large-scale operational research studies are needed to develop the use of a two-ingredient gas cartridge as a single management tool against H. indica and other burrowing porcupines.

Porcupine disturbances and vegetation pattern along a resource gradient in a desert.

In the Negev Desert, Israel, the Indian crested porcupine, Hystrix indica, digs similar sized, discrete, elongated pits (257±21.3 cm3; n=144) while foraging for below-ground plant storage organs. In these digs, soil moisture content is higher than in the surrounding soil matrix. The digs disturb population and community structure due to porcupine consumption or damage of 18 species of plants, and repopulation by 55 plant species. Over the past 14 years we have studied dig dynamics on a rocky hillslope with three distinct habitats as regards soil moisture content. Midslope soil moisture is the highest, decreasing towards upper and lower slope. We have counted a total of 6,609 digs in the area: 2141 on the upper, 3211 in the middle and 1257 on the lower part of the slope. The number of digs at midslope is significantly higher than on the other parts of the slope (ANOVA; P<0.0001). There is a significant (P<0.05) correlation between the mean number of porcupine digs and the cumulative rainfall amount for the 2 years prior to dig formation. To study plant repopulation in digs, all plants in 144 digs along the slope and from equal sized plots in the undistarbed soil matrix were collected. In all, 288 samples with 20 584 plants were collected, 2042 from the matrix and 18,542 from digs. Of the 55 species, we focused on the abundance patterns of Filago desertorum, Picris cyanocarpa and Bromus rubens, which made up 69.5% of all the individuals in the digs and 68.3% in the matrix. Our results showed that all three species increased in abundance in the digs as compared to the matrix. F. desertorum density increased by a factor of 2.9, P. cyanocarpa by 9.5 and B. rubens by 12.0. There were species-specific responses in abundance to the location of the digs along the moisture gradient. The only species whose abundance responded to the moisture gradient was F. desertorum. P. cyanocarpa demonstrated peak abundance in the location with the poorest moisture regime, while B. rubens showed peak abundance at the intermediate part of the moisture gradient. We suggest a scheme for integrating the increase in density and the species-specific responses to the digs along a water gradient based on R.H. Whittaker's view of individual species abundances along an environmental gradient.

Testing values of crested porcupine habitats by experimental food patches.

We established depletable, artificial food patches in three habitats used by Indian crested porcupines (Hystrix indica) in a desert biome, and measured the number of food items remaining (i.e., "giving up density"=GUD) following nightly foraging bouts. Porcupines discriminated between resource types (peanuts vs. garbanzo beans), and exhibited clear habitat preferences in the face of uniform resource availability in time and space. Lowest GUD's (=lowest foraging costs) were in the habitat of densest cover, and during dark (little or no moon) nights. The results indicated a high sensitivity to predation risk. Crested porcupines behaved as expected of optimal foragers, and appear to be excellent subjects for further field experiments using the GUD approach.

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

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.

On the spatial behaviour of Indian crested porcupines (Hystrix indica)

Nocturnal activity of six Indian crested porcupines (Hystrix indica), inhabiting two nearby dens in the Negev desert highlands of southern Israel, was monitored for nine months by radio location telemetry. From movement simulation of 1121 relocations (187 ± 56 per animal) on a grid representation of the 20 km2 study area, mean home ranges (i.e. 90% domains) were 1–5 ± 0–4 km2 and the animals moved 2.8 ± 0.7 km per night. Spatial activity differed by main foraging habitat which, in turn, corresponded to den affiliation. Porcupines that foraged regularly on crops had narrow domains with bimodal activity centres near the den and in potato fields; and their movements were relatively stable across seasons. Animals dependent on natural forage had larger and seasonally variable domains, and more diffuse dispersions with a single activity centre near the den. Home range overlap was greater among crop foragers, and all porcupines remained closer to dens during moonlit periods. We conclude that crested porcupine dispersion patterns are flexible, and strongly linked to forage availability. The array of analytical procedures used here are recommended for future studies of animal spatial activity.

Copulation as a possible mechanism to maintain monogamy in porcupines, Hystrix indica

Copulation as a possible mechanism to maintain monogamy in porcupines, Hystrix indica

Influence of Season and Moonlight on Temporal-Activity Patterns of Indian Crested Porcupines (Hystrix indica)

During a 1-year period, onset and termination of nocturnal surface activity were monitored in as many as eight free-ranging Indian crested porcupines ( Hystrix indica ) in the Negev desert highlands of southern Israel by radio-location telemetry. Porcupines optimized winter (October–March) activity for minimal exposure to moonlight, but moonlight avoidance waned thereafter and disappeared by late summer (August–September). Rain curtailed activity, but there was no correlation between duration of activity and minimum near-ground temperatures. Individual variation in activity was large in all seasons. Duration of activity and the proportions of dark and nights hours used increased from winter to late summer. Adult-sized animals (14.1 ± 3.0 kg body mass) averaged 7.0 ± 0.4 h surface activity year-round, but this peaked at 9.2 ± 1.3 h in late summer when nearly all night hours were used. In winter, activity averaged 6.7 ± 0.8 h and porcupines were active for longer periods on dark nights than on moonlit nights. Seasonal changes in duration of activity (and moonlight exposure) may have been caused by variations in available dark hours relative to surface-activity requirements or to food-density fluctuations, but they did not clearly correspond to key stages of porcupine reproduction.

Seasonal Energy Requirements and Water Intakes of Indian Crested Porcupines (Hystrix indica) in Captivity

Four adult male Indian crested porcupines (Hystrix indica), held in covered outdoor enclosures in the Negev Desert of southern Israel, were offered ad lib. water and a dry rodent ration (16.5% protein; 9% fibre; 19.2 kJ/g dry matter) at four nutritional planes (100%, 80%, 60%, and 40% of ad lib. intake) during consecutive 10-day feeding trials in summer (July–August) and winter (January-February). Water intakes were significantly higher in summer (137 ± 61 ml kg−1 day−1X̄ ± SD) than winter (53 ± 7 ml kg−1 day−1). There were no seasonal differences in ad lib. food intake, in dry matter (DM) digestibility (annual X̄ = 76.5%), or in gross energy digestibility (80.9%). Moreover, maintenance energy requirements (estimated from body mass changes) were similar in both seasons, and averaged 220 kJ kg−1 day−1 (445 kJ kg−0.75 day−1), or 1.5 × estimated basal metabolic rate (BMR). These results, supported by limited data from free-ranging H. indica, indicate that Hystrix porcupines are capable of substantial formation and mobilization of fat reserves. This is a useful adaptation in seasonally fluctuating arid environments. Large inverse changes in the proportional composition of body water and body solids are likely such that total body mass is an inadequate index to body condition.

Patterns of crested porcupine ( Hystrix indica) damage to cultivated potatoes

Porcupine digs were counted in irrigated potato fields in the Negev desert of southern Israel. Dig rates in a sample 10-ha rectangular field increased from low levels in October to ≈30 per night beginning in mid-November and corresponded to the increasing availability of larger tubers. The temporal patterns suggest a lag in food switching, or the successive abandonment of natural food patches having low marginal value in relation to the increasing profitability of potatoes. In all three fields examined (40 ha), digs were concentrated along field peripheries and on sides furthest from artificial illumination. These patterns confirm previous findings on the predation-avoidance nature of porcupine surface activity. Total potato damage in the study area was estimated at 1.3 tons ha −1, or 0.6% of the crop. We recommend: (a) adjustments in field shape to reduce edge and (b) the use of artificial lighting as two feasible means for passive damage control.

Observations on the feeding habits of the Indian crested porcupine (Hystrix indica) and the distribution of some hemicryptophytes and geophytes in the Negev desert highlands

More than 17 geophytes and hemicryptophytes are consumed by porcupines or inhabit porcupine diggings during the year. By consuming subterranean bulbs and leaves, diggings are created, sometimes as many as 2 or 3/m2. Under desert conditions each digging accumulates organic matter, seeds and runoff water. In the flat areas covered with loess it is possible for a digging to remain for longer than 5 years. The plants which show the greatest interaction between porcupine activity and their own survival mechanisms are four species of geophytes and hemicryptophytes. Of these, porcupines consume only part of the plant—the undamaged part renews itself and develops later in conditions improved by the digging. There are four other groups: (a) Three species were totally consumed, and the porcupine digging became a suitable microhabitat for germination for at least two of them. Another 10 species of plants were: (b) either consumed, and inhabit diggings, (c) possibly not eaten by porcupines but inhabit diggings, (d) consumed from time to time, but not found in diggings.

Influences of porcupine (Hystrix indica) activity on the slopes on the northern Negev mountains - Germination and vegetation renewal in different geomorphological types and slope directions.

Preliminary results show that the number and survival of seedlings within the diggings of the Indian crested porcupine (Hystrix indica) is usually higher than in the surrounding area. Species like Erodium hirtum (Willd.) (hemicryptophyte), Helianthemum vesicarium Boiss. (perennial), and Diplotaxis harra (Forssk.) Boiss. are conspicuous by their appearance in the diggings of the porcupine more than between the diggings. In contrast there are plants like Helianthemum ledifolium (L.) Mill. (annual), that appear in high numbers outside the diggings. In the case of Erodium hirtum, it appears that the porcupines help in rejuvenating the population. The porcupines feed on the older underground plant bulbs and the pockets formed by their diggings are convenient habitats for germination and growth of the young seedlings.

Note on the Distribution of the Indian Crested Porcupine Hystrix indica

Ellerman and Morrison-Scott (checklist of palaearctic and indian mammals, 1758– 1946. 1951) list the approximate distribution of Hystrix indica as “Ceylon, Peninsular India, northwards to Rajputana, Sind, Punjab, Kashmir, Nepal, Baluchistan; Persia, Iraq, Palestine, Syria, Asia Minor, Southern Arabia, Southern and Eastern Russian Turkestan (north to Kara Kum, Tashkent …