Diet composition and habitat selection of eland in semi-arid shrubland

This study investigated the diet composition and habitat selection of eland in semi-arid shrubland, dominated by microphyllous and leptophyllous browse species offering low leaf: stem ratios. Browse (succulent, forb and woody species) contributed 94% to the annual diet of eland. The annual proportion of grass in eland diet was low (6%), even though palatable grass species were abundant in habitats favoured by eland. Most grass was eaten in the early wet season when grasses offered young green foliage. Woody species comprising dwarf shrubs and shrubs made up the bulk of the food eaten by eland. In each season, favoured woody species contributed substantial proportions to the diet of eland. Eland used the plateau habitats in the early wet season, but valleys and slopes in the late wet and dry seasons. Habitats favoured by eland contained high abundances of plants of woody species favoured by eland. Chemical analysis indicated that woody species favoured by eland offered lower total fibre contents than other woody species available to eland. The results of the study indicated that eland are browsers that select browse of low fibre content.     

Can methane suppression during digestion of woody and leafy browse compensate for energy costs of detoxification of plant secondary compounds? A test with muskoxen fed willows and birch

Digestion and metabolism of woody and leafy browse requires detoxification of plant secondary compounds that can incur an energy cost. Browse, however, inhibits methane (CH(4)) production and therefore could offset some costs of detoxification. We measured an index of heat increment of feeding (HIFi) and CH(4) production in muskoxen (Ovibos moschatus) given a single test meal (at 10 g/kg BM(0.75)) composed of hay mixed with one of three browse species (Willow: Salix alaxensis, S. pulchra; Birch: Betula nana). Detoxification cost was estimated as HIFi of browse diet-HIFi of hay diet and CH(4) compensation as CH(4) production of hay diet-CH(4) production of browse diet. CH(4) compensation was noted in 47% of 15 trials in which a detoxification cost was evident; six trials were with woody browse and one with leafy browse. Separate controls were responsible for the difference in CH(4) compensation for leafy browse vs. woody browse. Detoxification costs for twigs and leaves of B. nana were underestimated because of their low digestibility. In only one of six treatments was CH(4) compensation documented for B. nana. We conclude that energy saved by CH(4) suppression was small (<6%) compared with detoxification costs.     

Seasonal diet preferences of black rhinoceros in three arid South African National Parks

Black rhinoceros diet and browse availability was investigated in Augrabies Falls (AFNP), Karoo (KRNP) and Vaalbos National Parks (VNP) in South Africa. Rhino tracks were followed and 18,804 standard bite volumes recorded. Browse availability of each plant species was recorded by measuring 14,800 plants and calculating reachable browse volume. The diet comprised 51, 53 and 41 plant species in AFNP, KRNP and VNP, respectively, but three species accounted for more than 65% of the diet in each park, making diet less diverse than available browse in AFNP and KRNP. Browse availability explained 14%, 15% and 52% of diet selection in AFNP, KRNP and VNP, with consumption of most plant species significantly different from availability. A few plant species were so highly preferred that browsing intensities were unsustainable, while some common species were totally rejected. Pressure on the eaten browse averaged 4.4%, 14.5% and 1.3% annually of the volume in AFNP, KRNP and VNP. In the dry season, there was a two to sevenfold increase in browsing pressure on species with actively photosynthesizing tissues. A few key species, including Monechma and Zygophyllum species, were identified as potential early warning indicators of black rhino browsing impact.     

Recovering Riparian Plant Communities with Wolves in Northern Yellowstone,U.S.A.

Gray wolves (Canis lupus) were extirpated from Yellowstone National Park in the 1920s. The ensuing seven decades marked a period when wild ungulates, principally Elk (Cervus elaphus), extensively used woody browse species in the upper Gallatin and northern winter ranges, thus limiting the capability of establishing plants to grow more than 100 cm in height. Following the reintroduction of wolves in the mid‐1990s, we evaluated patterns of woody browse species recovery within riparian areas of these winter ranges. Measurements indicated that cottonwood (Populus spp.) recruitment (growth of seedlings/sprouts into tall saplings and trees) was occurring for the first time in several decades. A spatially patchy increase in the heights of young willow (Salix sp.) and cottonwood in the upper Gallatin and northern winter ranges, respectively, was also found within riparian transects comprising nearly 20 km in total length. Within some transects, heights of woody species have begun to exceed 200 cm (the approximate upper browse level of Elk). Results are consistent with the reestablishment of a tri‐level trophic cascade involving wolves, ungulates, and riparian vegetation. We additionally present conceptual models of vegetation recovery, illustrating differences in plant height responses to behaviorally and density‐mediated trophic cascades. Northern Yellowstone’s “experiment in time,” whereby wolves were removed and then reintroduced, provides new insights regarding how top predators can influence the structure and biodiversity of terrestrial ecosystems. Restoration ecologists and policymakers should consider the potential benefits of large predators as an option for helping restore degraded ecosystems.     

Plant Species with Potential as Food,Nesting Material,or Tools at a Chimpanzee Refuge Site in Caddo Parish,Louisiana

Surplus chimpanzees live in research laboratories where they will likely remain for the rest of their lives. An alternative to laboratory housing is an outdoor enclosure in a warm climate. Before construction, researchers should conduct a vegetation survey because chimpanzees use vegetation daily. Chimp Haven, Inc. is developing a chimpanzee sanctuary in Caddo Parish, Louisiana, and we conducted a vegetation survey at the site to 1) characterize the abundance and structure of vegetation; 2) identify plants with utility as food, nesting material, or tools; 3) determine the abundance and distribution of useful vegetation; and 4) identify any possibly hazardous vegetation. We established 48 plots, quantified the woody vegetation, and identified potentially useful and hazardous plant species from the published literature. Vegetation at the site was secondary growth from logging of loblolly pine (Pinus taeda), the most abundant tree. Other abundant trees included oak (Quercus spp.), elm (Ulmus spp.), sweetgum (Liquidambar styraciflua), and maple (Acer spp.). Small plants (1–9.9 m tall) constituted 95% of all vegetation. Forty-one of 64 plant species have edible vegetative parts, while 35 species have edible reproductive parts. We identified 55 potential nesting trees by size (dbh ≥ 25 cm) and 4 species used as tools by captive great apes. Useful vegetation was concentrated in areas with topographic relief or in a floodplain, while flat areas with fields had less. We recommend that the floodplain be cropped for fruit and browse and enclosures encompass areas with relief and fields, creating a diverse habitat.     

The savanna ecology of Kidepo Valley National Park

(1) Food habits of elephant and giraffe were recorded in short sample periods over several years using the feeding minutes technique. (2) Twelve species of common plants were collected on these occasions, separated into their main parts and analysed chemically. (3) Damage to trees was also recorded at intervals. (4) Fifty-nine species of plant were eaten by elephant. During wet months their diet was predominantly grass but during dry months woody vegetation became more important. Giraffe were observed eating from thirty-nine species of plant which were almost entirely browse throughout the year. At least eighteen of these species were also eaten by elephant. (5) Three of the browse species most important to giraffe were also important to elephant in dry seasons. In the driest month the species eaten by giraffe formed more than two-thirds of the observed diet of elephants. (6) Chemical analyses of plants show that browse leaves had a higher level of protein, fat and minerals than most other plants. (7) The trunk of an elephant and the tongue of a giraffe are highly sensitive organs which permit food selection. Elephant in particular appeared to alter their food habits seasonally and it is suggested that this may be an attempt to obtain a balanced intake of nutrients. (8) Due to the effect of elephant and other agencies there is an accelerating decline in Acacia gerrardii woodlands. Browsing and fire are independently preventing their regeneration. (9) The extensive overlap of food requirements on preferred but diminishing browse resources implies potential if not already existing competition between elephant and giraffe. (See Part III.)     

Status of the Mara Woodlands in Kenya

The woodlands of the Masai Mara National Reserve in Kenya have suffered dramatic declines over four decades as a result of elephant and fire pressure. This study examined the current status of woody resources in the Reserve and browse pressure thereon, using both classification (TWINSPAN) and ordination (DCA) techniques. From 333 widespread regular plots used to survey the vegetation, a total of 62 woody species were identified. Thirteen woody habitats were identified on the basis of species composition, varying from species‐rich closed thickets and forest to less diverse open grasslands. A NW/SE stratification of the more open habitats was observed, possibly as a result of differences in soils, rainfall and drainage. Both plant density and diversity were lower than in communal and privately managed areas outside the Reserve. Moreover, browser pressure was substantially higher than that observed previously in the ecosystem, and suggests increased competition for scarcer woody resources within the Reserve. This has implications for the management of the ecosystem as a whole. As woodland and thickets continue to decline, long‐term monitoring should expand to encompass the wider habitat diversity of the open grasslands and unprotected areas where much of the regeneration potential resides.     

Structure of the woody vegetation in disturbed and undisturbed arid savanna,Botswana

The structure of woody vegetation was studied in little disturbed arid savanna and in adjacent over-grazed vegetation. In the over-grazed areas density and cover of woody plants were higher than in the less disturbed vegetation. The difference was accounted for by one species, Acacia mellifera, which was strongly dominant in the overgrazed vegetation. In the open savanna, the woody species varied in height from small shrubs to trees, while the dense shrub vegetation was of uniformly low stature.It is suggested that, while the differences in total abundance of woody species depend on differences in the amount of soil water available for woody growth, differences in species composition and height distribution are governed by the spatial and temporal distribution of water in the soil profile.     

ELEPHANT ECOLOGY IN THE QUEEN ELIZABETH NATIONAL PARK, UGANDA

1. Aerial and ground counts in the Queen Elizabeth National Park from 1963 to 1969 indicate that the number of elephants has more than doubled. The increase appears to be the result of immigration rather than reproduction. 2. Elephant food habits were studied for 10 months in two areas of the Park. In the short-grass/thicket area, browse intake rose markedly whenever the rainfall fell below 50 mm/month. In the tall-grass area without thicket, herbs were eaten frequently during the rains and Cymbopogon grass bases in the dry season. 3. Food availability had an important influence on the diet of elephants. Sometimes, however, elephant were very selective, e.g. for Panicum maximum, Azima tetracantha, Securinega virosa, and Tribulus terrestris. Certain grass inflorescences were selected during the rains, and bases in the dry season. 4. Most browse was consumed in the thicket area during the dry season and most grass was eaten in the tall-grass area of the Park. 5. Stomach and faecal samples gave a similar result and indicated that the diet in the tall-grass area was comparable to that of elephant in Murchison Falls National Park. 6. Analyses of important plant species showed that, in general, tall-grass had a lower crude protein content than short-grass, herbs and browse. Browse leaves had a relatively high crude-protein content in the dry season. Differences were less marked in the rains. 7. Ether extract, or fat content, was high in browse leaves and in Cymbopogon, in particular its bases. These may have been selected in the dry season for this reason. 8. Grass and browse stems were very fibrous and this may have contributed to their being avoided. 9. High carbohydrate levels probably enhanced the palatability of grass bases and browse leaves. 10. Grasses were very siliceous, in particular their bases when contaminated with soil. Elephant took considerable trouble to remove soil. Browse leaves had little silica but were rich in other minerals, and this may have contributed to their greater palatability. 11. Studies of woodland dynamics show a decline in large trees which corresponds to the increase in elephants. In some cases trees have been almost eliminated. Damage to trees indicates that a most important factor in their decline is the elephant. There is some evidence that the trees are eliminated selectively. 12. In the tall-grass area there has been an increase of 46.3% in elephant numbers, but a decline of 80.3 % in buffalo, over the past 15 years. An overall decline in combined biomass of 36.9 % is calculated. Estimates of energy utilization of the annual vegetation production by elephant and buffalo indicates a decline from 6.1 % to 3.9% over this period.     

Remotely sensed vegetation phenology and productivity along a climatic gradient: on the value of incorporating the dimension of woody plant cover

Aim Woody plants affect vegetation–environment interactions by modifying microclimate, soil moisture dynamics and carbon cycling. In examining broad‐scale patterns in terrestrial vegetation dynamics, explicit consideration of variation in the amount of woody plant cover could provide additional explanatory power that might not be available when only considering landscape‐scale climate patterns or specific vegetation assemblages. Here we evaluate the interactive influence of woody plant cover on remotely sensed vegetation dynamics across a climatic gradient along a sky island. Location The Santa Rita Mountains, Arizona, USA. Methods Using a satellite‐measured normalized difference vegetation index (NDVI) from 2000 to 2008, we conducted time‐series and regression analyses to explain the variation in functional attributes of vegetation (productivity, seasonality and phenology) related to: (1) vegetation community, (2) elevation as a proxy for climate, and (3) woody plant cover, given the effects of the other environmental variables, as an additional ecological dimension that reflects potential vegetation–environment feedbacks at the local scale. Results NDVI metrics were well explained by interactions among elevation, vegetation community and woody plant cover. After accounting for elevation and vegetation community, woody plant cover explained up to 67% of variation in NDVI metrics and, notably, clarified elevation‐ and community‐specific patterns of vegetation dynamics across the gradient. Main conclusions In addition to the environmental factors usually considered – climate, reflecting resources and constraints, and vegetation community, reflecting species composition and relative dominance – woody plant cover, a broad‐scale proxy of many vegetation–environment interactions, represents an ecological dimension that provides additional process‐related understanding of landscape‐scale patterns of vegetation function.     

Use of local North Carolina browse species to supplement the diet of a captive colony of folivorous primates (Propithecus sp.)

The nutrient content and intake of locally available North Carolina browse was evaluated for use as a supplement to a herbivorous primate diet of commercial biscuit and produce. Twice weekly from May to October 1997, total dietary intakes were determined for two groups of folivorous lemurs. Group I consisted of Propithecus diadema diadema (n = 1) and P. tattersalli (n = 1) and group II consisted of P. verreauxi coquereli (n = 3). Six pooled samples of the diet and weekly samples of three browse species, Rhus copallina, Albizia julibrissin, and Liquidamber styrachiflua were analyzed for dry matter, energy, fiber, and nitrogen content. Browse species were also analyzed for nonprotein nitrogen and acid‐insoluble nitrogen. Group average dry matter intakes were 37.1 ± 2.2% (mean ± SEM) and 49.7 ± 3.0% of amount offered for groups I and II, respectively. Browse contributed 40.7 ± 2.9% and 29.6 ± 2.4% of the total daily intake for groups I and II, respectively. Browse species differed (P < 0.05) for dry matter, energy, neutral detergent fiber, acid detergent fiber, cellulose, lignin, total nitrogen, nonprotein nitrogen, available nitrogen, and available protein. R. copallina and L. styrachiflua were similar in total nitrogen, available nitrogen, and nonprotein nitrogen; A. julibrissin was higher. L. styrachiflua was highest in lignin. Dry matter, acid detergent fiber, and lignin in browse samples increased seasonally (P < 0.05), whereas available protein decreased (P < 0.01). Animals were offered and consumed R. copallina most often, followed by A. julibrisson and L. styrachiflua. With the exception of R. copallina, animals generally consumed only the immature leaves, flowers, or seeds of species offered. Daily dry matter intake varied because of both browse offered and consumed and biscuit and produce diet consumed. Thus, increased fiber density can be a major benefit of browse use only when incorporated into the total diet with respect to species use, quantity of other diet ingredients offered, and targeted nutrient intakes. Zoo Biol 20:447–461, 2001. © 2002 Wiley‐Liss, Inc.     

Effects of browse availability and quality on black rhino (Diceros bicornis michaeliGroves 1967) diet in Nairobi National Park,Kenya

Investigations were conducted to study the effects of browse availability and quality on black rhinoceros (Diceros bicornis michaeliGroves 1967) diet in Nairobi National Park, Kenya, between September 1994 and February 1995. Line intercept method was used to assess availability of browse. The ratios of browsed crowns to the total crown were applied in the estimate of browse use. Proximate analysis and extraction methods were used, respectively, to appraise browse nutritional quality and phytochemical status of twelve species. Thirty‐four plant species were identified as potential black rhino browse, whose availability differed significantly (P < 0.001). Lippia javanica (20.581 ± 3.101, n = 544) and Lannea cornuta (0.963 ± 0.529, n = 544) were the most and least available species, respectively. Only 32 species, however, were utilized, as L. cornuta and Rhynchosia hirta did not show any level of rhino feeding activity. Browse use was found to vary significantly (P < 0.001) during the study period. Grewia similis was most (20.564 ± 2.764, n = 544) and Commelina africana least (0.974 ± 0.974, n = 544) exploited, respectively. Differences in total alkaloids and phenols, crude fibre, crude protein and total ash contents among species investigated were highly significant (P < 0.001). Ether extract values were similar (P= 0.0933) across plant taxa. The study shows that the black rhino is a selective browser feeding on plants with low phenol and alkaloid contents and high fibre values. Of the nutritionally similar species, browsing was driven by availability. These findings suggest that a key habitat factor important in black rhinoceros conservation include diverse plant species with low levels of phenols and alkaloids.     

Effect of season on chemical composition and in situ degradability in cows and in adapted and unadapted goats of three Mexican browse species

Browse foliages from Lysiloma acapulcencis, Quercus laeta and Pithecellobium dulce, native to the subtropical region of southern México, were harvested during the dry season (DS) and rainy season (RS) to determine in situ degradability using ruminal inoculum from fistulated cows as well as goats previously adapted (AG) or not adapted (UG) to browse species fed in their daily diet. Browse leaf samples were incubated in the rumen of each group for 48 h. The crude protein (CP) content of browse was considerably higher in RS (P<0.001). P. dulce had the lowest neutral detergent fiber (NDFom) and acid detergent fiber (ADFom) in the two seasons; L. acapulcencis had the highest values and Q. laeta values were intermediate, with an overall increase in fiber fractions in DS browse foliage (P<0.001). The lowest in situ degradability values were in L. acapulcencis and Q. laeta had intermediate values during both seasons. Season of harvest (RS or DS), and ruminal inoculum (cows, UG, and AG) affected (P<0.001) dry matter degradability (DMD), crude protein degradability (CPD) and fiber fractions of browse. Nutrient degradabilities in all species were higher (P<0.001) in DS than RS. Goats previously exposed to these browse species (AG) had higher (P<0.001) in situ degradability of the browse species than cows or goats in UG fed diets without browse. Overall, goats had higher (P<0.001) nutrient in situ degradability than cows. Our results suggest higher potential of these browse species as forages for ruminants during the dry period in semi-arid regions, but goats previously exposed to diets supplemented with the browse species had a better ability to degrade them than cows or goats in UG. P. dulce has the highest potential as a feed protein source in small ruminants during the dry period.     

Woodland regeneration on grazed former arable land: A question of tolerance,defence or protection?

Ecological restoration of native woodlands and wooded pastures on former agricultural land is an important topic in modern conservation practice. The introduction of large herbivores is increasingly used to achieve these aims. We investigated how grazing, resistance traits of plants (concerning herbivory) and associational resistance interact and affect the establishment pattern of woody species on abandoned arable land (N-Belgium, W-Europe). In these early successional tree assemblages, we tested whether grazing increased or decreased spatial heterogeneity, which is supposed to be a crucial factor for biodiversity.With repeated measurements, 2-3 and 5-7 years after the cessation of agricultural use, we sampled 87 grazed and 56 ungrazed plots (314 m²) in 14 sampling areas (former arable land) on nutrient rich, (sandy) loam soils. We recorded established tree frequencies, related to grazing, time, resistance traits and unpalatable/spiny vegetation cover in the herb and low shrub layer. We investigated horizontal and vertical heterogeneity using variances in establishment frequencies and variances in frequencies of trees that were able to grow beyond the browse line, respectively.We found massive colonisation of grazing tolerant and resistant woody species in early successional stages. Grazing decreased frequencies and height of the most abundant tolerant species (mainly Salix caprea L.). After 5-7 years, frequencies of defensive and tolerant species were equal, but the former (mainly Betula pendula Roth) were able to grow beyond the browse line. When the cover of unpalatable/spiny vegetation was high enough (>60% of plot size), it also provided suitable nurse sites for tolerant species to grow out. In early assemblages, grazing increased horizontal and vertical heterogeneity, resulting in intermediate successional stages. In the long-term, the mechanism of associational resistance will also allow non-resistant and tolerant species to grow beyond the browse line and promote forest succession and the order of species establishment and replacement.     

巴基斯坦Pirghar 山的植被结构

Phytosociological parameters, soil and temperature conditions, importance values of species, life form, leaf size and grass biomass in vegetation of Pirghar Hills, South Waziristan Agency, Pakistan, were investigated during summer 1995. The air and soil temperatures were higher on south facing slopes which decreased with increase in altitude.The vegetation, life form and leaf size of south and north slopes differed at similaraltitudes. Leptophyllous species increased with the rise in altitude. The fresh herbage production was 500 g m-2 at 2000 m on north slope which gradually decreased to 170 g m-2 at the hill top. A similar trend was observed for the south slope which had higher productivity than comparable north slope. The original woody species are present on the hills as isolated individuals due to degradation. There is need for restoration of the habitat.     

The relative importance of conditions in wintering and passage areas on spring arrival dates: the case of long-distance Iberian migrants

Remote sensing data have been used in previous studies to assess the effects of winter ecological conditions in Africa on biological parameters recorded in bird populations during the following breeding season in Europe. Based on the results of these studies, we hypothesized that a high productivity of vegetation during the winter and, thus, high resource availability, should advance the arrival of long-distance migrants to the European breeding areas due to enhanced ecological conditions. To test this hypothesis, between 1982 and 2000 we examined the first arrival date to the Iberian Peninsula of five species (White Stork, Cuckoo, Common Swift, Barn Swallow and Nightingale) in relation to several explanatory variables: ecological conditions in their African wintering grounds and passage areas, as reflected by the normalized difference vegetation index (NDVI), temperature and precipitation in their passage areas and the winter North Atlantic Oscillation (NAO). Ecological conditions in the wintering areas were important for White Stork, Cuckoo and Barn Swallow phenology, while both NDVI in passage areas and NAO did not have an effect on any species. Migratory birds arrived earlier after winters with high vegetation productivity in Africa. Temperature in passage areas was important for the later species (i.e. Cuckoo, Common Swift and Nightingale), although in all cases the true relevance of this factor was scarce due to the poor explanatory capacity of the models. These species were recorded in the Iberian Peninsula earlier in the spring of those years with warmer temperatures in passage areas. The nexus between African NDVI and arrival phenology is hypothesized through increases in wintering survival rates and/or the faster acquisition of pre-migratory body condition and progression through sub-Saharan areas. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Selection for nutrients by red deer hinds feeding on a mixed forest edge

We studied the nutritional behaviour of hinds foraging on a mixed-forest edge by direct observation of their choices at each season and by measuring nutrient concentration in the plants. We compared nutrient concentrations in the observed diets with those in the total available vegetation, and with those of 1,000 randomly simulated diets in which we included only those plants that were actually eaten by the animal. Whether the available or the consumed feeds were used as the basis for comparisons had important consequences due to the presence of conifers and ferns, which were high in soluble sugars but were never eaten by the animals (potentially due to their toxicity). The selected diets were lower in sugars than the total available vegetation in summer, but were actually higher in sugars than the random diets generated from consumed forage species only. Hind diets contained more soluble sugars but not more protein than simulated diets in all seasons. Contrary to our prediction, anti-nutritional compounds (ADL and tannins) were avoided only in winter. Compared to simulated diets, hinds consumed more tannins in spring and summer and more ADL in summer and autumn. We suggest that this was a consequence of selection for soluble sugars, because the preferred plant species, which had high soluble sugar concentrations, also contained a large proportion of the anti-nutritional compounds eaten. In winter, the grass-dominated diets contained more fibre (NDF) and less ADL than the simulated diets, indicating that hinds orient their feeding towards digestible fibres. The switch from a browser to a grazer diet was related to a change in the availability of the nutrients, mainly soluble sugars. In our study, grasses contained more soluble sugars and proteins than deciduous browse during winter. This calls into question the dichotomy usually assumed in the literature between grass and browse in terms of nutrient content. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Sex and size related differences in the dry season feeding patterns of elephants in Chobe National Park, Botswana

Differences in feeding patterns of the African elephant were examined by sex and age during the dry season in a dystrophic savanna-woodland ecosystem in northern Botswana. Adult males had the least diverse diet in terms of woody plant species, but they consumed more plant parts than family units. The diameter of stems of food plants broken or bitten off was also greater for adult males than for females and subadult males. Adult males spent more time foraging on each woody plant than did females. The number of woody plant species and individuals present were higher at feeding sites of family units than at feeding sites of adult males, indicating that family units positioned themselves at feeding sites with higher species diversity than those of males. We argue that the most likely explanation for these differences is related to the pronounced sexual size dimorphism exhibited by elephants, resulting in sex differences in browsing patterns due to the allometric relationships that govern the tolerance of herbivores for variation in diet quality. From our results this Body Size Hypothesis is accepted rather than the alternative Scramble Competition Hypothesis, which predicts that adult male elephants consume lower quality browse because they are displaced from preferred browse as an outcome of scramble competition with adult females and their offspring. If the feeding patterns of adult male elephants were affected by intersexual scramble competition, we would expect adult males to browse at a higher level in the canopy than the smaller-bodied females and their offspring. No evidence was found for this, although adult females were found to browse at a higher level in the canopy when feeding in close proximity to subadults and juveniles than when feeding alone. Sex differences in elephant browsing patterns are, we propose, of relevance to understanding and managing elephant impacts on African woodlands.     

Water-energy dynamics, climate, and prediction of woody plant species richness: an interim general model

Predictable geographic patterns in the distribution of species richness, especially the latitudinal gradient, are intriguing because they suggest that if we knew what the controlling factors were we could predict species richness where empirical data is lacking (e.g. tropics). Based on analyses of the macro-scale distribution of woody plant species richness in Southern Africa, one controlling factor appears to be climate-based water-energy dynamics. Using the regression models of climate's relationship to species richness in Southern Africa, I was able to describe an Interim General Model (IGM) and to predict first-order macro-scale geographic variations in woody plant species richness for the continent of Africa, as well as elsewhere in the world—exemplified using South America, the United States and China.
In all cases, the geographic pattern of variation in species richness is in accord with geographic variations in vegetation (visual comparison with vegetation maps) and net primary productivity. What validation was possible (Africa and U.S.A.) suggests that the IGM provides 'reasonable' estimates for actual woody plant species richness where species richness is in relative equilibrium with climate. Areas of over- or under-prediction support the contention of earlier workers that edaphic, topographic, historical, and dispersal factors need to be considered in a more complete explanation for spatio-temporal variations in species richness.
In addition to providing a means for systematically estimating woody plant species richness where present-day empirical data is lacking, the Interim General Model may prove useful for modelling the effects of climate change (past/future) on species richness (and, by association, the vegetation).     

Encroachment of woody plants and its impact on pastoral livestock production in the Borana lowlands, southern Oromia, Ethiopia

Encroachment of woody plants has been among the major threats to the livelihoods of Borana pastoralists and their ecosystem. An approach that integrated vegetation survey and pastoralists’ perception was followed to study the impacts of encroachment of woody plants in the Borana lowlands, Ethiopia. Density of woody species was determined in 192 plots of 500 m². Canopy cover of woody plants was estimated in 123 quadrates of 400 m². Pastoralists’ perception was assessed through group discussions and a semi‐structured questionnaire. Results showed that plant density was 3014 woody plants ha^?1. Cover of woody plants was 52%, indicating an increasing trend from ≤40% cover reported in the early 1990s. It was concluded that the increase of woody plants density and cover has crossed the critical threshold and has entered into the encroached condition. Principal components analysis (PCA) and redundancy analysis (RDA) also showed that woody plants were negatively correlated with herbaceous biomass. Commiphora africana, Acacia melliphera, A. drepanolobium, A. brevispica and Lannea rivae were among the dominant encroachers. RDA revealed that soil nutrients were positively correlated with woody plants density and cover. The pastoralists perceived that encroachment of woody plants had decreased the production of their grazingland. A ban on fire was perceived as the major factor that caused encroachment of woody plants. Re‐utilization of fire and strengthening of traditional rangeland management strategies are recommended.