Preferred Grazing Research Articles

Different groups’ grazing technique preferences in the Miombo woodlands of Eastern Tanzania

Grazing in Miombo woodlands is essential for the livelihoods of the pastoral and agropastoral communities that live adjacent to these fragile ecosystems. However, Miombo woodlands offer not only fodder for livestock but also fertile land for crop farming; hence, they are equally important to the farmers residing in these areas. Due to the importance of the Miombo woodlands for the livelihoods of several groups, the consumption of and competition for Miombo resources has increased over time and now threatens the overall health of the ecosystem. This study aimed to identify the grazing techniques practiced by different livelihood groups in Miombo woodlands; their preferences for different practices, as well as the factors that influence these preferences, so as to understand how sustainable grazing can be achieved for better ecosystem health. The study was conducted in Handeni, Kilombero, and Kilosa districts and covered pastoralists, agropastoralists, and farmers. We carried out focus group discussions, key informant interviews, and a survey of 246 respondents. Un-patterned rotational grazing was the most preferred grazing technique by all three groups, and the only technique the three groups shared a preference for. All the groups took a neutral stance in relation to continuous grazing. Their preferences for other grazing techniques differ. The study highlights the need to raise awareness amongst pastoralists about land ownership and management and recommends enhancing land property rights for all groups in order to harmonize livestock keeping and other land uses for achieving sustainable grazing and overall ecosystem health in the fragile Miombo woodlands of Tanzania.

GPS monitoring reveals circadian rhythmicity in free-grazing sheep

GPS collars are a technology that is used extensively to monitor livestock due to its versatility. In this study, the main objective was to confirm whether they can detect the circadian rhythmicity that modulates the behavior of free-grazing sheep. The Churra-breed flock that was monitored grazed an approx. 166-ha fenced area within a dehesa ecosystem in the northwestern Iberian Peninsula. Geolocations were recorded every 30 min for two years. Animal activities were categorized based on the speed; an animal was “moving” if the speed was > 0 m/s (the analyzed category), and “resting” if the speed was 0 m/s. Sheep grazing activity in terms of their speed, azimuth, and distance traveled, was subjected to a circadian adjustment derived from the online Cosinor tool. Results reveal that the flock activity, whether based on speed, distance traveled, or azimuth, fit a circadian rhythmicity (p < 0.05). In the summer, particularly July and August, sheep exhibited a significant advance in the acrophase (the time at which the peak of a rhythm occurs), which might have been caused by day length and temperature. In all seasons, flock activity was significantly higher in the diurnal period, while the lowest activity was found in all cases at night, although in the summer sheep activity was high at dawn. In addition, in the day, sheep activity was significantly higher in the fall than it was at other times of the year. The preferred grazing direction of the sheep was non-random, since it was modulated by the contour orientation and the limits of the grazing area. It could be concluded that GPS geolocations allow to demonstrate that free-grazing sheep activity is modulated by a circadian rhythmicity.

Evaluating Several Vegetation Indices Derived from Sentinel-2 Imagery for Quantifying Localized Overgrazing in a Semi-Arid Region of South Africa

Rangeland monitoring aims to determine whether grazing management strategies meet the goals of sustainable resource utilization. The development of sustainable grazing management strategies requires an understanding of the manner in which grazing animals utilize available vegetation. In this study, we made use of livestock tracking, in situ observations and Sentinel-2 imagery to make rangeland scale observations of vegetation conditions in a semi-arid environment, to better understand the spatial relationships between vegetation conditions and sheep movement patterns. We hypothesized that sheep graze more selectively under low stocking rates—resulting in localized overgrazing. We also assessed the importance of image spatial resolution, as it was assumed localized effects of grazing will be best explained by higher resolution imagery. The results showed that livestock tend to congregate along drainage lines where soils are deeper. The findings demonstrate how the spatial analysis of remotely sensed data can provide a landscape-scale overview of livestock movement patterns. This study illustrates that high-resolution normalized difference vegetation index (NDVI) data can be used as a grazing management tool to determine the spatial variability of productive areas across the semi-arid Upper Karoo rangelands and identify preferred grazing areas.

Feeding preferences of range-shifting and native herbivorous fishes in temperate ecosystems

Temperate reefs are being tropicalized worldwide. In temperate Western Australia, a marine heatwave led to a regime shift from kelp (Ecklonia radiata) dominated to canopy-free reefs, together with an increase in tropical herbivorous fishes that contribute to keeping low kelp abundances and even prevent kelp reestablishment in northern regions. However, whether tropical herbivorous fishes prefer kelps over other seaweeds and/or whether this preference changes with latitude remains untested. Multiple-choice experiments (young kelp vs. other seaweeds) with tropical, subtropical and temperate herbivorous fishes show shifting species-specific preferences and fish-to-fish interference shifting with latitude (assays replicated in two regions four degrees of latitude apart). Against expectations, only the temperate Kyphosus sydneyanus preferred kelp over other seaweeds, but only in the lower latitude region. Siganus fuscescens, the most abundant tropical herbivore in both regions, preferred grazing on turf, suggesting that tropical fish might reduce kelp recruitment by consuming microscopic sporophytes in turf matrix.

Response of jiggs grass to inoculation with plant growth-promoting microrganisms

Brazil is the second world producer of bovine meat, which often relies on preserved forage to decrease seasonality of forage production. Increased forage accumulation may be favored by technologies such as inoculation. Research works on this theme have been conducted with Azospirillum brasilense associated to oats, ryegrass and guinea grass. However, response of jiggs, a widely cultivated perennial grass, to plant growth-promoting microrganisms is poorly understood. Hence this study aimed to assess effects of inoculation on development of Cynodon dactylon cv. Jiggs. Four treatments were tested: T1) control, T2) Inoculation with A. brasilense, T3) Inoculation with Azospirillum, Rhizobium, Pseudomonas and Saccharomyces, T4) Inoculation + Reinoculation with Azospirillum, Rhizobium, Pseudomonas and Saccharomyces. Forage mass, percentage of leaves, stems, dead mass, reproductive structures and leaf/stem ratio were measured. Data were submitted to analysis of variance, and when significant effects were detected, means were separated by LSD Test. Positive effects of inoculation were recorded at all evaluations, mostly concerning percentage of leaves and leaf/stem ratio. A. brasilense improved leaf/stem ratio up to 56%. Also, a 64% increment on this parameter was obtained with Azospirillum, Rhizobium, Pseudomonas and Saccharomyces. Modifications of plant morphology components are important since grasses with more percentage of leaves increase nutritional value of haylage. Morphology of Cynodon dactylon cv. Jiggs is affected by Azospirillum, Rhizobium, Saccharomyces and Pseudomonas, improving aspects related to palatability and preferred grazing of livestock animals.

Grazing by microzooplankton and copepods on the microbial food web in spring in the southern Yellow Sea, China

Assessment of microzooplankton and copepods grazing pressure on picoplankton is a key requirement for resolving the microbial food web efficiency. Although microzooplankton grazing on picoplankton has been extensively studied, the impact of microzooplankton on different groups of picoplankton, i.e., heterotrophic bacteria, Synechococcus and picoeukaryotes have rarely been compared. Furthermore, in the very few existing studies there is no consistent evidence of an enhancing or restraining effect of copepods on picoplankton. More studies are needed to improve our understanding of the influence of microzooplankton and copepod on picoplankton. Dilution incubations and copepod addition incubations were performed during a cruise to the southern Yellow Sea on May 16–29, 2007. The bulk grazing of microzooplankton and the calanoid copepod Calanus sinicus on phytoplankton, flagellates and picoplankton was estimated. Stations were divided into either eutrophic or oligotrophic according to the nutrient and biological parameters. Picoplankton comprised a large part of the diet of microzooplankton in the central oligotrophic area, while phytoplankton was the main food of microzooplankton in the coastal eutrophic area. In the central oligotrophic area, microzooplankton preferred grazing on Synechococcus. After copepod addition, ciliate abundance decreased while Synechococcus abundance increased (382%, 64% and 64% at three experimental stations, respectively), indicating strong grazing pressure of microzooplankton on Synechococcus. Our results suggest that Synechococcus might be an essential carbon source the planktonic food web in the oligotrophic waters of southern Yellow Sea.

The Quest for Greener Pastures: Evaluating the Livelihoods Impacts of Providing Vegetation Condition Maps to Pastoralists in Eastern Africa

Pastoral households are faced with making migration decisions under increasing uncertainty about resource availability and limited coping strategies due to mounting socioeconomic and climatic stressors. We assess the potential of providing vegetation condition maps to support the migration decisions of pastoralists in Ethiopia and Tanzania and the impact of map usage on their herd condition and size. The maps were generated from remotely sensed data using the Normalized Difference Vegetation Index (NDVI) as a proxy for vegetation condition and overlain with pastoralists' preferred grazing areas. We surveyed pastoralists before maps were distributed (baseline), and approximately a year (midline), and two years (endline) after map distribution began. Map adopters in both countries reported an overwhelmingly positive experience and stated the maps were accurate and helpful. However, the use of maps for migration decisions was low in the follow-up periods, partly due to challenges in map distribution (26% and 2% in Ethiopia; and 35% and 29% in Tanzania at midline and endline respectively). Map usage was associated with improved animal condition in Tanzania, but we find no causal evidence that map usage affected herd size in the randomized controlled trial in Ethiopia.

Improved grazing activity of dairy heifers in shaded tropical grasslands

ABSTRACT: Trees in the production systems can effectively reduce hot weather-induced stress in the Brazilian Midwest. High temperatures cause changes in animals daily routine, and trees into pastures can promote benefits. The aim of this research was to evaluate the behavior of dairy heifers in silvopastoral systems in the state of Mato Grosso, Brazil. A herd of 24 crossbreed heifers (3/4 and 7/8 Holstein/Zebu), 350kg average weight, was evaluated over three seasons. Piatã grass was managed under three shade levels: full-sun, moderate-shade, and intensive-shade provided by 10 to 12m high Eucalyptus trees. Behavior data were collected every 15 minutes from 8:30h to 16h. Shade availability significantly impacted heifer behavior, mainly affecting grazing frequency and time during the hottest hours. Grazing behavior was affected by shade levels during the different seasons. Heifers showed preferred grazing times. Heifers in the intensive-shade system visited shady areas during the hottest hours throughout the seasons. Heifers in the full sun-system avoided grazing during the warmer times, ceasing feeding activities. Our results from the Brazilian Midwest showed that shade availability causes breed heifers to change their daily routine.

Humans: ‘Nutcracker man’ preferred grazing: Despite name, huge‐jawed human relative ate grass, sedges

Humans: ‘Nutcracker man’ preferred grazing: Despite name, huge‐jawed human relative ate grass, sedges

Effects of Prorocentrum donghaiense and Alexandrium catenella on the material transfer in a simulated marine food chain

The biochemical composition of Prorocentrum donghaiense was analyzed and the effects of P. donghaiense and Alexandrium catenella on the transport of materials through a simulated marine food chain were investigated. The results showed that the content of phenylalanine, histidine and lysine in P. donghaiense was obviously lower than that in other dietary microalgae. Fed with P. donghaiense solely, the gross conversion efficiencies (GCEs) of A. salina increased gradually when the algal densities were lower than 4 × 10 4 cells/ml, and decreased gradually at higher densities. When fed with the mixture of P. donghaiense and the diatom Nitzschia. closterium, A. salina preferred grazing on P. donghaiense to grazing on N. closterium, and the GCEs of A. salina decreased with the increasing density of P. donghaiense. Exposed to A. catenella, A. salina lost weight and no Chlorophyll a was detected in the guts, which indicated that A. salina did not ingest the algal cells. When the re-suspended cells and cell-free medium of A. catenella were mixed with N. closterium or P. donghaiense, respectively, the grazing and GCEs of A. salina were all diminished. Consequently, the large-scale blooms of P. donghaiense and A. catenella in the East China Sea could adversely affect zooplankton owing to insufficient food or nutrition, and therefore impact the material transfer efficiency through the food chain.

Site use of grazing cattle and sheep in a large-scale pasture landscape: A GPS/GIS assessment

Year-round mixed-species grazing at low densities in large-scale pasture systems has become a popular conservation concept as it is assumed to maintain the valuable biodiversity of semi-open cultural landscapes. This study aims to elucidate which vegetation types are preferentially grazed by cattle and sheep and whether the grazing animals change their preferences through the seasons so that year-round grazing leads to a utilization of all habitats. Additionally, we wanted to determine the main factors underlying the site use patterns of the animals. The study was conducted on 180 ha of a nature reserve and former military training area in northern Germany from January to October. Within this area, the positions of one cattle herd and one sheep flock were simultaneously recorded every 5 min using the global positioning system (GPS). For this purpose, we fitted one GPS collar alternately to three different cows and another to three different sheep. If the position of a collared animal had changed more than 6 m but less than 100 m within 5 min grazing was assumed based on a validation of these thresholds by direct observation. Using a geographic information system, we analysed the location data with regard to vegetation characteristics, altitude, and distance from fences, water sources, and a sheep shed. For each month, we determined Ivlev's electivity index of both herbivore species in relation to eight broad vegetation types. We used multiple linear regression to create models that describe the grazing frequencies in the grid cells of the area depending on parameters of those grid cells and their spatial position. Cattle preferred moist and productive habitats, whereas sheep preferred dry and nutrient-poor habitats. Only when feed was in extremely short supply, the animals switched to sites they had previously avoided. Differences in the spatial preferences of the two species were more marked than seasonal changes. Spatial demands of cattle and sheep were largely complementary. Grazing sites with better water availability (i.e. lower distance from the drinking trough and ponds) were significantly preferred by cattle. The sheep preferred grazing sites close to their shed. Our results show that only a combination of different herbivores guarantees that all habitats of such a large low-intensity pasture are grazed and thus are kept in a management status favourable to conservation. However, the positioning of drinking troughs, fences, and sheds should be carefully considered as these facilities seriously influence the site use of the animals.

Phosphorus Translocation by Red Deer on a Subalpine Grassland in the Central European Alps

We examined the role of red deer (Cervus elaphus L.) in translocating phosphorus (P) from their preferred grazing sites (short-grass vegetation on subalpine grasslands) to their wider home range in a subalpine grassland ecosystem in the Central European Alps. Phosphorus was used because it is the limiting nutrient in these grasslands. When we compared P removal of aboveground biomass due to grazing with P input due to the deposit of feces on a grid of 268 cells (20 m × 20 m) covering the entire grassland, we detected distinct spatial patterns: the proportion of heavily grazed short-grass vegetation increased with increasing soil-P pool, suggesting that red deer preferably grazed on grid cells with a higher soil-P pool. Biomass consumption related to increased proportion of short-grass vegetation, and therefore P removal, increased with increasing soil-P pool. However, within the two vegetation types (short-grass and tall-grass), consumption was independent from soil-P pool. In addition, P input rates from defecation increased with increasing soil-P pool, resulting in a constant mean net P loss of 0.083 kg ha−1 y−1 (0.03%–0.07% of soil-P pool) independent of both soil-P pool and vegetation type. Thus, there was no P translocation between grid cells with different soil-P pools or between short-grass and tall-grass vegetation. Based on these results, it is likely that the net rate of P loss is too small to explain the observed changes in vegetation composition from tall-herb/meadow communities to short-grass and from tall-grass to short-grass on the grassland since 1917. Instead, we suggest that the grazing patterns of red deer directly induced succession from tall-herb/meadow communities to short-grass vegetation. Yet, it is also possible that long-term net soil-P losses indirectly drive plant succession from short-grass to tall-grass vegetation, because nutrient depletion could reduce grazing pressure in short-grass vegetation and enable the characteristic tall-grass species Carex sempervirens Vill. to establish.

Behavior, preference for, and use of alfalfa, tall fescue, white clover, and buffalograss by pregnant gilts in an outdoor production system1

Sustainable outdoor pig production requires vegetation that can maintain ground cover, assimilate manure nutrients, and prevent soil erosion. Two experiments were conducted to evaluate the suitability of four forages: alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), white clover (Trifolium repens), and buffalograss (Buchloe dactyloides) for grazing or ground cover in pastures for pigs. Each forage plot covered 7.5 m2, with nine replicates in a randomized block design. In Exp. 1, eight pregnant gilts had free access to all forages during a 2-d adjustment period. Immediately thereafter, pairs of gilts were assigned randomly to one of each of four blocks of the four forages during a 2-d measurement period. The percentage of ground cover for each forage was visually estimated at 0, 24, and 48 h of study. Behavioral data, including walking, eating, grazing, rooting, drinking, standing, lying, and time spent in hut were video-monitored continuously for 48 h. Initial percentage of ground cover was 100% for all species. By 48 h, percentage of ground cover decreased (P < 0.001) for white clover (11.3 +/- 0.88%) and alfalfa (36.3 +/- 0.88%), but not for tall fescue (98.0 +/- 0.88%) or buffalograss (98.0 +/- 0.88%). Gilts spent more (P < 0.01) time grazing white clover (16.3 +/- 1.97 min/d) and alfalfa (11.2 +/- 1.97) than tall fescue (0.8 +/- 1.97) or buffalograss (0.3 +/- 1.97), and rooted more (P < 0.04) white clover than other forages. In Exp. 2, six gilts from the initial group were put on six blocks of the four forages. Each gilt was assigned randomly to three replicates of each forage, including alfalfa, tall fescue, or buffalograss (white clover was excluded because of damage by gilts during Exp. 1), and gilts grazed single forages for 2 d. After this grazing period, the percentage of ground cover was less (P < 0.01) for alfalfa than for buffalograss or tall fescue (37.5 +/- 0.38, 96.7 +/- 0.39, 96.3 +/- 0.39%, respectively). With access to a single forage, pregnant gilts spent more (P < 0.01) time grazing alfalfa (15.8 +/- 2.36 min/d) than buffalograss (1.5 +/- 2.36) or tall fescue (0.7 +/- 2.37). These gilts clearly preferred grazing white clover and alfalfa, and rooting and eating white clover compared with buffalograss or tall fescue. Rates of ground cover loss were less (P < 0.01) for tall fescue and buffalograss than for the more preferred forages. Less preferred forages could have potential as pasture for swine when the primary objective is ground cover maintenance rather than nutrient supply.

The effects of previous grazing experience and ewe presence on the response to novel grass species by weaned lambs

AbstractForty single lambs were either artificially reared indoors or were at pasture with their mothers until weaning at 3 months of age, after which one half of each group were joined by five adult, dry ewes, to examine the effects of grazing experience and presence of adult ewes on the response to the introduction of novel grass species. Lamb groups sequentially grazed paddocks with one, two, three and then four grass species in four 1-week periods, and grazing and ruminating times and pasture biting rates were recorded during daylight hours. In the first period the lambs grazed only perennial ryegrass, then timothy, cocksfoot and finally red fescue were introduced in periods 2 to 4 respectively. The total time that lambs spent grazing and ruminating were both increased (P &lt; 0·001) by grazing experience and to a lesser extent by the presence of adult ewes. Pasture biting rate was considerably increased by experience, and to a lesser extent adult presence, with a synergistic effect between these two factors (P &lt; 0·001). Timothy and to a lesser extent perennial ryegrass were the most preferred species, and lambs spent less time grazing cocksfoot than either of these two, and even less time grazing red fescue (P &lt; 0·001). Experience of grazing particularly increased the time spent grazing cocksfoot and red fescue (P &lt; 0·001), but the presence of adult ewes did not increase the time lambs spent grazing novel species (P = 0·59). The pasture biting rate was greater on species that the lambs preferred grazing (P &lt; 0·001), but neither experience nor ewe presence increased the biting rate on novel species in the period of their introduction. It is concluded that although both grazing experience and, to a lesser extent adult presence, increased the total time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.

Impact of herbivory by red deer ( Cervus elaphus L.) on patterns and processes in subalpine grasslands in the Swiss National Park

The spatial grazing patterns of red deer ( Cervus elaphus L.) in a subalpine grassland ecosystem of the Swiss National Park were analysed with reference to the phosphorus content in the topsoil and to the former agricultural management system. Changes in the composition of the vegetation and in plant species richness were studied on permanent plots set up between 1917 and 1945 in areas which today are heavily grazed by red deer, and were related to the development of the red deer population. The spatial grazing patterns of red deer are, 80 years after the Park’s foundation, still determined by former agricultural use. Red deer prefer the most phosphorus-rich, formerly irrigated parts for grazing. Grazing by red deer was found to be the driving force behind temporal changes in the vegetation observed on the subalpine grasslands. Plant succession has proceeded faster in the preferred grazing areas and the vegetation has adapted to the grazing pressure with a decrease in tall-growing plant species. At the same time, the abundance of unpalatable species has increased due to (i) morphological defences, (ii) spatial avoidance, i.e. by growing close to the ground and (iii) temporal avoidance because they have a short life-span (annuals). Changes in vegetation composition have coincided with a sharp increase in species richness. Between 1917 and 1999, the number of plant species has doubled on average. We found a highly significant correlation between the changes in the numbers of plant species and red deer, with species richness increasing with increasing deer density.

White rhinoceros range size in the south‐western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south‐western Kruger National Park. The mean annual range size of territorial males was 9.86 km2 compared to 22.83 km2 for adult females. White rhinoceros females' summer wet season range was larger (21.44 km2) than the winter dry season range (11.64 km2). It is argued that abundant field‐water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high‐lying areas. White rhinoceros range sizes in the south‐western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.

Characteristics of the herbaceous layer in preferred grazing areas of six herbivore species in the south-eastern Kruger National Park

The phytomass and species composition of the herbaceous layer in preferred grazing areas of zebra Equus burchellii, buffalo Syncerus caffer, waterbuck Kobus ellipsiprymnus, blue wildebeest Connochaetes taurinus, impala Aepyceros melampus and warthog Phacochoerusaethiopicus were investigated within the south-eastern portion of the Kruger National Park. The percentage frequency of herbaceous plants in Decreaser and Increaser categories, as determined by their reaction to different intensities of grazing, was established. The preferred grazing areas of the relevant herbivore species were compared in terms of phytomass, contribution of the Decreaser and Increaser categories, veld condition and degree of utilisation. The grazing areas of buffalo and zebra showed less utilisation than those of the other herbivore species. Warthog and impala were associated with over-utilised areas. It is clear that localised over-utilisation is an integral part of the natural grazing mosaic and should be managed as such in large African conservation areas.

Patterns of Livestock Use in Time and Space in the Summer Ranges of the Western Pyrenees: A Case Study in the Aragon Valley

Space-use patterns and rhythms of daily activity of cattle and sheep summering in the Western Pyrenees are described and the ecological factors that affect them are discussed. Differences among ruminants in relation to fiber tolerance and protein needs determine the preferred grazing areas. These and other morpho-physiological features (such as body size) lead to spatial stratification of animals along mountain slopes. Cattle need a high volume of forage intake so they graze on the lower ranges where availability is greatest and they avoid steep slopes and rocky outcrops. The pattern of space use by cattle throughout the summer season follows a concentration-expan- sion-concentration sequence determined by forage abundance and availability. The distribution of grazing cattle is affected by plant cover and the resting distribution by flatness and proximity to water. The grazing distribution of sheep is determined by shepherd strategy to allow the flock to benefit continually from optimum grass production. Bimodal distribution of daily grazing behavior occurs in both cattle and sheep activity. Two peaks of maximum grazing occur, in early morning and at evening, but that trend may vary according to environmental conditions, especially temperature.

Observations on the Feeding Ecology of Impala

The distribution, habitat preference, and diet of impala in mixed wooded savanna were studied. In the wet season impala were evenly distributed through the different vegetation types and their diet was predominantly grass, but in the dry season they concentrated in areas of Acacia savanna and changed to a mainly browsing diet. The amount of grass in the diet was related to plant moisture content and recent effective rainfall. The impala selected succulent food rich in crude protein but preferred grazing to browsing when palatable grass was available. These factors and the presence of fallen Acacia pods probably attracted impala to the Acacia areas in winter.

The influence of grazing by sheep on the structure of a saltbush (Atriplex vesicaria Hew. ex Benth.) population.

The population structure of a stand of saltbush (Atriplex vesicaria Hew. ex Benth.) was studied within one paddock by sampling the shruLq3opulationon a grid radiating from the only watering point. The pattern of both contemporary and cumulative grazing influence was found to be focussed on the watering point but it was not a simple symmetrical one. The existence and distribution of preferred grazing areas could not be explained by the data collected. There was a preferential grazing pressure of the female shrubs. The cumulative effects of this were reflected in a five-fold change in the sex ratio (males/females) of the shrub population.