Renal structural flexibility in response to environmental water stress in feral hogs

Several morphological characteristics of the kidney were studied to determine the degree of acclimatization that may occur in three groups of feral hogs raised under different environmental conditions. Two groups of hogs were living in the wild, while another was raised in captivity for three generations and was directly descended from one of the wild-living groups. The two groups of wild hogs were living under two different types of water stress conditions. One group experienced periodic drought, and the other ate a high salt diet. The captive hogs were given food and water ad libitum. The captive-raised hogs had significantly lower relative medullary thickness (RMT) and relative medullary area (RMA) values (RMT of 2.35; RMA of 0.35) than either group of hogs living in the wild (RMT of 2.70 and 2.69; RMA of 0.41 and 0.44). Since the feral hogs living in the wild were exposed to a higher degree of water stress than the captive-raised hogs, it was concluded that the differences in observed kidney structure were due to acclimatization.     

Diet and distribution of elephant in the Maputo Elephant Reserve, Mozambique

The distribution and diet of the elephants of the Maputo Elephant Reserve were studied using dung counts, satellite tracking and faecal analysis. The results were compared with earlier data from before the civil war in Mozambique. The elephant population decreased during the civil war, but 180 animals still remain. Earlier studies described the elephants as preferring the grass plains. Currently, the elephants prefer the dense forest patches over the high quality forage found in the grass plains. Water salinity affected distribution; elephant dung piles were found closer to fresh water in the dry season. A total of 95 different plant species were identified in the faeces. The percentage of grass was relatively low compared with other studies, increasing at the beginning of the rainy season. At the end of the dry season, elephants concentrated on the few available browse species with young leaves, but generally preferred grass species to browse species. Diet composition was mainly affected by season and less by habitat. The elephants have changed their habitat preference in reaction to poaching, and probably increased the contribution of browse species in the diet. The presence of forest patches has been vital for the survival of the elephants.     

Estimation of food composition of Hodotermes mossambicus (Isoptera: Hodotermitidae) based on observations and stable carbon isotope ratios

Abstract The diet of the harvester termite Hodotermes mossambicus was investigated at two sites with distinct dietary components: C₄ grasses (δ¹³C isotope values, ?13.8‰ to ?14.0‰) and C₃ plants (δ¹³C isotope values, ?25.6‰ to ?27.1‰). By comparing observations of food items carried into the colony by the termites and carbon isotope ratios of whole termites (that determined assimilated carbon), the relative proportion of the C₃ and C₄ plant food components of the termite diet was estimated. There was agreement between the observational data and stable carbon isotopic data, with grass representing approximately 93% of the diet of H. mossambicus at two study sites (urban and rural) on the South African highveld. However, when correcting for mass of food items, that is, C₃ and C₄, carried by termites, the proportion of grass (C₄) in the diet may be underestimated.     

Subsistence strategies of two "savanna" chimpanzee populations: the stable isotope evidence.

Twenty-two chimpanzee hair samples collected from night nests at two different "savanna" sites were analyzed for carbon and nitrogen stable isotope ratios represented as delta13C and delta15N values. The first at Ugalla, Tanzania is a miombo woodland with grass groundcover and small patches of forest. The second at Ishasha, Democratic Republic of the Congo is a habitat composed of riverine gallery forest, semideciduous thicket forest, wooded grassland, and grassland. Based on comparative data from other primates, Ugalla hair delta13C values suggest that the chimpanzees are feeding primarily in the woodland rather than in forest patches or on grassland foods (grasses or grammivorous fauna). Similar comparisons indicate that the Ishasha chimpanzees are feeding within the forests and not in more open areas. In addition, the Ugalla chimpanzees had delta15N values that indicate extensive ingestion of leguminous flowers, seeds, and/or leaves. The Ishasha samples show a range encompassing three trophic levels. Two samples with the most positive values may indicate a nursing signal or vertebrate-feeding. Three individuals with intermediate values are similar to those in omnivorous nonhuman primate species. The four individuals with the lowest values are very similar to those in herbivorous monkeys. Stable isotope ratios permit time-averaged and habitat-specific dietary comparisons among sites, even without habituation or detailed foraging observations.     

黑斑羚粪便中碳同位素揭示的食性变化

利用稳定碳同位素数据(δ13C)分析了南非克鲁格国家公园混食性黑斑羚(Aepyceros melampus)时间和空间尺度上的食性变化,验证了两个假说,即有蹄类食性变化是由生境中木本植物与草本植物的相对配比导致;降雨控制有蹄类生态。结果表明:黑斑羚的食性涵盖了精食者-粗食者采食谱系,且食性中木本与草本比例在不同月间、季节、年度和区域间存在很大变化。栖息于开放性热带稀树草原和草原中的黑斑羚通常采食比生境中更高比例的草本,但在时间尺度上并不恒定。在克鲁格北部的一个区域(Punda Maria) ,黑斑羚采食的草本比克鲁格国家公园中其它任何区域都多。与其它生境相比,在河边的黑斑羚采食草本数量更少,尤其是在食性空间变化更为明显的旱季。因此,我们的数据不支持有蹄类食性组成变化是由生境中木本与草本比例不同造成的假说,食性与降雨量间也无明显的关系。我们的结果支持草本中蛋白含量增加引起黑斑羚采食比例的增加这一模型。粪便中氮含量在时间和空间上的变化很小,揭示在可利用食物中,无论木本还是草本,黑斑羚进行选择采食以保证最好的食物质量。基于这些结果,我们认为更具体的食物选择和可利用性最适采食理论能够更好地解释这种生态学变化。     

The isotopic ecology of East African mammals

Summary The stable carbon and nitrogen isotope ratios of bone collagen have been used to trace diet and habitat selection of the larger mammals of East Africa. 238 individuals of 43 species from montane forests and grasslands in Kenya and Tanzania have been analyzed. The results show that carbon isotopes discriminate between (1) grazers and browsers in savanna grasslands, (2) forest floor and savanna grassland herbivores and (3) forest floor and forest canopy species. Nitrogen isotopes discriminate between (4) carnivores and herbivores, (5) forest and savanna grassland herbivores, and (6) water-dependent and drought-tolerant herbivores. This technique provides a quantitative approach to assessing long-term habitat and diet selection and the role of resource partitioning in animal community structure.Also Archaeology Program     

Stable isotope evidence for impala Aepyceros melampus diets at Akagera National Park,Rwanda

Stable isotope analysis of tooth enamel was used to investigate the relative proportions of grass and browse in seasonal and overall diets of impala Aepyceros melampus at Akagera National Park, Rwanda. Bulk enamel samples suggest that on average, impala ate c. 86% C₄ grass year‐round, far more than in most previously studied impala populations across Africa. Intra‐tooth samples show that seasonal changes in the proportion of C₄ grass versus C₃ browse are minimal (c. 10%), the diet being dominated by C₄ grass year‐round in contrast to other impala populations that consume ≥50% browse during the dry season. Intra‐tooth oxygen isotope values track carbon isotope changes to a moderate degree, but are not patterned clearly enough to permit identification of wet versus dry seasons. As other studies have shown that impala select high‐protein diets, the foraging behaviour at Akagera is probably because of the availability of palatable grass for much of the year in the edaphic grasslands around the lacustrine environments of the eastern portions of Akagera National Park.     

Using carbon isotope analysis of the diet of two introduced Australian megaherbivores to understand Pleistocene megafaunal extinctions

Aim Australia lost a diverse assemblage of large marsupial herbivores in the late Pleistocene, with suggestions that the extinctions were biased towards browsers. In modern times two bovines, the Asian water buffalo (Bubalus bubalis) and banteng (Bos javanicus), have established feral populations in the Northern Territory, Australia. Buffalo have aggressively expanded throughout the savanna landscape, yet banteng remain near their point of introduction on the Cobourg Peninsula. We hypothesized that this difference is related to feeding ecology, possibly reflecting a legacy of the Pleistocene extinctions. Location Western Arnhem Land, Northern Territory, Australia. Methods Analysing a previously published dataset of body mass and feeding ecology of extinct and extant marsupial herbivores, we evaluated whether browsers were at greater risk of extinction than grazers. We compared the carbon isotope composition and nitrogen content of banteng and buffalo dung in order to evaluate the hypotheses that the differences in invasion success are related to feeding ecology, and that seasonal variation in browse consumption is linked to changing nutritional quality of grass. Results Controlling for body mass, the Pleistocene extinctions were clearly biased towards browsers. Introduced banteng appear to be primarily browsers, with their diets comprising 40% grass in the wet season and 15% in the late dry season. Buffalo have a more variable diet, with an increasing proportion of browse from the wet (30%) to the late dry season (75%), and can therefore be described as switching from grazer to browser. The decline of grass in the diet of both species appears to reflect the decline in the nutritional value of grass through the dry season, an inference supported by the negative relationship between δ¹³C values and the nitrogen content of dung. Main conclusions Banteng and buffalo are much larger than extant native herbivores, of which browsers are restricted to isolated rocky habitats. This suggests that banteng and buffalo have filled niches made vacant following the Pleistocene extinctions. The success of buffalo appears to be related to their greater dietary breadth, which enables them to graze and browse in eucalypt savannas, whilst the browsing banteng remain tethered to a mosaic of rain forest patches. The restriction of browsers may be a long‐range consequence of habitat transformations associated with Aboriginal landscape burning.     

Population ecology of the giant forest hog,Hylochoerus meinertzhageni in Chebera Churchura National Park,Ethiopia

Population, feeding habit, distribution and activity patterns of the giant forest hog (Hylochoerus meinertzhageni) were studied in Chebera Churchura National Park (CCNP), Ethiopia, using line transect sample counts. Population estimate of the hogs was 845 individuals. Among the counted individuals, 42.4% were males and 57.6% were females. Among them, 32.8% were adults, 26.9% were subadults, and 40.3% were piglets. Large sounders of up to 20 individuals were seen during the wet season. They were seen in all habitat types in CCNP with higher abundance in the riverine vegetation. Availability of food, green vegetation cover and water were factors governing distribution of forest hogs in the study area. Grass was the major food item of the hogs (90%), mainly of Panicum sp., Acalypha psilostachya, Cissapelos rigidifolia, Psilotrichum gnaphalobryum and Abutilon ceclii. Feeding was the major activity for which 49.7% of the active daytime was used. Resting (lying down, standing and wallowing) was the next major activity, for which they spent 38.8% of the daytime, followed by other activities (11.5%). Morning and late afternoon activity peaks were more intensive during the dry season. This female‐biased giant forest hog population is expected to sustain in CCNP.     

Trophic position and seasonal changes in the diet of the red wood ant Formica aquilonia as indicated by stable isotope analysis

1. Red wood ants are among the most numerous generalist predators and strongly affect the composition of arthropod communities in forest ecosystems. However, their trophic position remains poorly understood. Stable isotope analysis was applied to study the trophic position of Formica aquilonia and reveal seasonal changes in its trophic links with both myrmecophilous aphids and other invertebrates in a mixed forest of western Siberia. 2. The δ¹⁵N values of F. aquilonia exceeded those of herbivores and aphids by approximately 3.5‰. Despite obligate trophobiotic relationships with aphids, F. aquilonia occupied the trophic position of first‐order predator. The higher content of ¹³C in the worker ants, compared with members of grazing food chains, was explained by their consumption of ¹³C‐enriched aphid honeydew. 3. Myrmecophilous tree‐dwelling aphids were enriched in ¹³C and ¹⁵N relative to grass‐inhabiting species, and the honeydew of tree‐dwelling aphids had higher δ¹³C values than those of the honeydew of grass‐inhabiting aphids. 4. The decrease in δ¹³C values of the worker ants from spring and summer to autumn apparently reflected the transition from the collection of tree sap and feeding on the aphid honeydew from trees with high ¹³C content in the spring and early summer to a more diverse liquid diet in late summer, which included ¹³C‐depleted honeydew of aphids from herbs. 5. The prevalence of the ¹⁵N‐depleted aphid honeydew in the ants' diet in the second half of the summer is discussed as one possible explanation for the seasonal decline in δ¹⁵N values of the worker ants.     

Landscape-scale feeding patterns of African elephant inferred from carbon isotope analysis of feces

The African elephant (Loxodonta africana) is a large-bodied, generalist herbivore that eats both browse and grass. The proportions of browse and grass consumed are largely expected to reflect the relative availability of these resources. We investigated variations in browse (C(3) biomass) and grass (C(4)) intake of the African elephant across seasons and habitats by stable carbon isotope analysis of elephant feces collected from Kruger National Park, South Africa. The results reflect a shift in diet from higher C(4) grass intake during wet season months to more C(3) browse-dominated diets in the dry season. Seasonal trends were correlated with changes in rainfall and with nitrogen (%N) content of available grasses, supporting predictions that grass is favored when its availability and nutritional value increase. However, switches to dry season browsing were significantly smaller in woodland and grassland habitats where tree communities are dominated by mopane (Colophospermum mopane), suggesting that grasses were favored here even in the dry season. Regional differences in diet did not reflect differences in grass biomass, tree density, or canopy cover. There was a consistent relationship between %C(4) intake and tree species diversity, implying that extensive browsing is avoided in habitats characterized by low tree species diversity and strong dominance patterns, i.e., mopane-dominated habitats. Although mopane is known to be a preferred species, maintaining dietary diversity appears to be a constraint to elephants, which they can overcome by supplementing their diets with less abundant resources (dry season grass). Such variations in feeding behavior likely influence the degree of impact on plant communities and can therefore provide key information for managing elephants over large, spatially diverse, areas.     

New Zealand stream crayfish: functional omnivores but trophic predators?

1. The feeding ecology of the crayfish Paranephrops planifrons in streams draining catchments in native forest and pastoral land was investigated using analyses of both stomach contents and stable isotopes of carbon and nitrogen. We aimed to (1) identify the energy sources of crayfish, (2) determine whether these were affected by ontogeny or land use change, and (3) assess the functional and trophic roles of crayfish in New Zealand hill-country streams.
2. In native forest streams, crayfish stomach contents were dominated volumetrically by leaf detritus (>60%), but in pasture streams aquatic invertebrates constituted more than 40% of stomach volumes and leaf detritus <30%. Stable isotope analyses revealed that crayfish from both native forest and pasture streams incorporated energy from aquatic invertebrates into their body tissue but did not appear to utilize detritus for growth. Therefore, deforestation had little impact on crayfish energy sources.
3. In native forest streams, adult crayfish (≥20 mm orbit-carapace length (OCL)) consumed greater amounts of leaf detritus than juvenile crayfish, but a corresponding change in stable isotope signatures was not detected. Ontogenetic shifts in diet were not consistent between land use suggesting that change in local habitat and food resources, as a result of land use change, affect crayfish food choice more than factors related solely to age or size.
4. Crayfish appear to occupy the trophic position of a predator, but by functioning as omnivores, they have dual roles as both predators and processors of organic matter. The use of gut content analysis in conjunction with stable isotope analyses revealed that the functional and trophic roles of P. planifrons differed, with implications for the interpretation of diet studies and understanding of the role of omnivores in food webs.     

Taenia solium: immunity in hogs to the Cysticercus

Protection was induced in hogs against Taenia solium cysticercosis using an immunogenic complex obtained from its larval "bladder worm" form, Cysticercus cellulosae. Immunoelectrophoresis revealed that this complex contained at least eight antigens. In immunized hogs a total of 71 (mean 11.8) cysticerci were found, whereas in the control animals 397 (mean 74.9) were found. Histopathological studies showed that more than 40% of larvae obtained from immunized hogs were completely destroyed and the others were seen in various stages of degeneration. Eosinophils and mononuclear cells were observed infiltrating the internal structures of the larvae. Intense granulomatous reactions of eosinophils, lymphocytes, macrophages, epithelioid cells, plasma cells, and fibroblasts surrounded the larvae. Larvae from control hogs were intact and surrounded by a small inflammatory reaction. The cellular response was measured by the macrophage migration inhibition test, which was higher in immunized hogs when compared with control animals, either before the infection with T. solium eggs or before slaughter. No significant difference was found in the humoral response of immunized and control hogs.     

Use of carbon and nitrogen isotope ratios in termite research

In this paper, I review carbon and nitrogen isotopic (natural abundance levels) studies of termites. The carbon isotope ratio of CH₄ emitted from termites, together with the emission rates of CO₂, CH₄ and H₂, showed several trends corresponding to the kinds of symbiotic microbes and feeding habits. The fraction of methane oxidized in the nest structure was estimated by comparing carbon isotope ratio of CH₄ emitted from the nest with that produced by termites in the nest. Symbiotic nitrogen fixation in the gut of termites has been shown to have a significant contribution to the nitrogen economy in some wood-feeding termites. The carbon isotope ratio distinguishes between C4 from C3 plants, and the fractional contribution of grass in the diet can thereby be estimated. The carbon and nitrogen isotope ratios in termites are discernible among soil-feeders, fungus cultivators and wood-feeders. Wood/soil-interface feeders have intermediate values between wood- and soil-feeders, and thus carbon and nitrogen stable isotope ratios are assumed to characterize the degree of humification of the material consumed by termites. It is suggested that carbon and nitrogen isotope ratios are useful indicators of the functional position of termites in the decomposition process. A similar isotope pattern has been obtained in earthworms, suggesting that isotope signatures might be useful parameters in investigating detritivorous animals in general.     

黄土高原不同植被带土壤团聚体有机碳和酶活性的粒径分布特征

为探究土壤中各粒级团聚体不同形态有机碳和酶活性的分布特征,以黄土高原延河流域森林带、森林草原带、草原带土壤为对象,研究了不同粒级团聚体总有机碳、易氧化碳和腐殖质碳含量,以及纤维素酶、β-D葡糖苷酶、过氧化物酶、蔗糖酶和脲酶活性,分析了土壤团聚体有机碳及其组分与酶活性之间的相关关系.结果表明： 3种植被带土壤团聚体有机碳及其组分含量表现为森林带＞草原带＞森林草原带,3种形态有机碳含量在0.25～2 mm粒径均最高;不同植被带土壤团聚体有机碳及其组分含量和酶活性在0～10 cm土层大于10～20 cm土层;3种植被带纤维素酶、β-D葡糖苷酶、蔗糖酶和脲酶活性表现为森林带＞草原带＞森林草原带,过氧化物酶活性表现为森林带＞森林草原带＞草原带;3种植被带土壤中各种酶活性随着粒径的减小呈递增趋势.土壤纤维素酶、过氧化物酶、蔗糖酶和脲酶活性与团聚体各种形态碳含量均呈显著正相关.
     

Diet of the South African large-spotted genet<Emphasis Type="Italic">Genetta tigrina</Emphasis> (Carnivora,Viverridae) in a coastal dune forest

We studied seasonal variations in the diet of the large-spotted genetGenetta tigrina Schreber, 1776 in the coastal dune forest of the Dwesa Nature Reserve, Eastern Cape Province, South Africa. The food items with the highest relative percentage occurrence were Coleoptera, Orthoptera and Mammalia. However, by volume they ate mostly grass then followed by Coleoptera and Orthoptera. Main prey items originated from the litter layer or low lying bushes, such as arachnids, insects, myriapods, and most mammals. The latter included ten rodent (main staple:Dendromus sp.), two golden mole and two shrew species, from 10–100 g mass. They were represented dependent on species density, but switching between seasons and habitats occupied. Birds appeared under-represented in the diet for a semi-arboreal carnivore, although this correlates with data from other studies. Remains of birds in the diet, however, peaked during winter and spring probably as a result of the main nesting period in spring. There were some variation in diet between habitats (riparian, forest and beach) and seasons. Our results show the South African large-spotted genet to have an opportunistic, generalist diet.     

Effects of contrasting omnivorous fish on submerged macrophyte biomass in temperate lakes: a mesocosm experiment

1. Freshwater fish can affect aquatic vegetation directly by consuming macrophytes or indirectly by changing water quality. However, most fish in the temperate climate zone have an omnivorous diet. The impact of fish as aquatic herbivores in temperate climates therefore remains unclear and depends on their dietary flexibility. 2. We tested the effects of a flexible omnivore and an herbivore on aquatic vegetation by comparing the effects of rudd (Scardinius erythrophthalmus, the most herbivorous fish in temperate climates) with grass carp (Ctenopharyngodon idella) in a mesocosm pond study. Exclosures distinguished herbivorous effects of fish on submerged macrophytes from indirect effects through changes in water quality, whereas stable isotope food‐web analysis provided information on fish diets. 3. We hypothesised that rudd, with its flexible diet and preference for animal food items, would only indirectly affect macrophytes, whereas grass carp, with its inflexible herbivorous diet, would directly affect macrophyte biomass. 4. Only grass carp significantly reduced macrophyte biomass through consumption. Rudd had no effect. Food‐web analysis indicated that rudd predominantly consumed animal prey, whereas grass carp included more plants in their diet, although they also consumed animal prey. Grass carp significantly affected water quality, resulting in lowered pH and increased N‐NH₄ concentrations, whereas more periphyton growth was observed in the presence of rudd. However, the indirect non‐herbivorous effects of both fish species had no effect on macrophyte biomass. 5. Both fish species should be considered as omnivores. Despite the fact that rudd is the most herbivorous fish in the western European climate zone, its effect on submerged macrophyte biomass is not substantial at natural densities and current temperatures.     

石家庄西部太行山区景观格局时空变化

基于1987、2000年两期TM、ETM＋遥感数据资料,利用ArcGIS提取石家庄西部太行山区的景观类型转移矩阵,并结合重心模型,从时间和空间上对景观格局动态变化进行分析。结果表明：（1）1987～2000年,景观基质均为耕地,林地、草地、水域、建设用地和未利用土地作为斑块单元镶嵌其中;耕地、草地和水域的面积均为减少,其中草地面积减少量最大,主要向林地转化;林地、建设用地和未利用土地的面积均为增加,其中建设用地面积增加量最大,主要由未利用土地转化而来。（2）1987～2000年间,水域重心迁移距离最大;耕地、水域和建设用地的重心偏移方向为北偏西;林地和草地的重心偏移方向为北偏东;未利用土地的重心偏移方向为南偏西。     

Stable carbon isotope ratios in Asian elephant collagen: implications for dietary studies

Summary Stable carbon isotope ratios in bone collagen have been used in a variety of dietary studies in modern and fossil animals, including humans. Inherent in the stable isotope technique is the assumption that the isotopic signature is a reflection of the diet and is persistent in collagen because this is a relatively inert protein. Carbon isotope analyses of bones from a southern Indian population of Asian elephant (Elephas maximus), a long-lived mammal that alternates seasonally between a predominantly C₃ (browse) and C₄ (grass) plant diet, showed two patterns that have important implications for dietary interpretation based on isotopic studies. Relative to the quantity of the two plant types consumed on average, the δ¹³C signal in collagen indicated that more carbon was incorporated from C₃ plants, possibly due to their higher protein contribution. There was a much greater variance in δ¹³C values of collagen in sub-adult (range -10.5‰ to-22.7‰, variance=14.51) compared to adult animals (range -16.0‰ to -20.3‰, variance=1.85) pointing to high collagen turnover rates and non-persistent isotopic signatures in younger, growing animals. It thus seems important to correct for any significant relative differences in nutritive value of food types and also consider the age of an animal before drawing definite conclusions about its diet from isotope ratios.     

利用遥感信息研究西藏地区主要植被年内和年际变化规律

利用1982～2000年NOAA-AVHRR月合成NDVI遥感资料和相关气象台站数据对我国西藏地区的稀疏草地、浓密草地和Tebit森林等主要植被的变化进行了初探。利用月合成NDVI的多年平均值分析了植被指数年内季节性变化规律及其与气候因子的关系,利用多年月合成NDVI的标准差描述了NDVI年际间波动情况。结果表明,在西藏地区,浓密草地和Tebit森林的NDVI植被指数年内变化规律呈明显的季节性,而稀疏草地则不明显;在年际变化方面,浓密草地月合成NDVI值波动幅度最大,Tebit森林次之,稀疏草地最小,且波动幅度较大的月份集中在NDVI值较高的植被生长季节6～10月份。