Downward trends in Ngorongoro Crater ungulate populations 1986-2005: Conservation concerns and the need for ecological research

The concentration of over 25,000 ungulates inside Ngorongoro Crater on a 250 km² patch of the African plains was a major reason for designating the Ngorongoro Conservation Area as a World Heritage Site in 1979. As one of East Africa’s premier tourist attractions, it is also a major source of foreign exchange for Tanzania. This paper reports the decline of populations of wildebeest, Thomson’s and Grant’s gazelles since the mid-1980s and the rise to dominance of the buffalo, the results of research carried out from 1996 to 2000 on the Crater ungulates, and discusses natural and anthropogenic factors that may be linked to the population changes.Samples comparing young:adult female ratios in Ngorongoro and Serengeti populations indicated higher survival rates of Crater wildebeest and zebra young, and lower survival rates of Thomson’s gazelle. The possibility that predation by lions and spotted hyenas was responsible for reductions in the ungulate populations is belied by corresponding declines in the number of predators.Further research in the Ngorongoro Conservation Area is urgently needed to increase understanding of this complex ecosystem and promote effective stewardship, not only of Ngorongoro Crater but of the Serengeti ecosystem, of which the NCA is an integral part, comprising an International Biosphere Reserve. Our recommendations include establishment of a scientific advisory board and a research center that would attract and accommodate Tanzanian and foreign scientists.     

Patterns of spatiotemporal change in large mammal distribution and abundance in the southern Western Ghats, India

Large mammals face high risks of anthropogenic extinction owing to their larger body mass and associated life history traits. Recent worldwide mammal declines have highlighted the conservation importance of effective assessments of trends in distribution and abundance of species. Yet reliable data depicting the nature and extent of changes in population parameters is sparse, primarily due to logistical problems in covering large areas and difficulties in obtaining reliable information at large spatial scales, particularly over time. We used key informant surveys to generate detection histories for 18 species of large mammals (body mass > 2 kg) at two points in time (present and 30 years ago) in the Southern subregion of the Western Ghats global biodiversity hotspot. Multiple-season occupancy models were used to assess temporal trends in occupancy, detectability and vital rates of extinction and colonization for each species. Our results show significant declines in distribution for large carnivores, the Asian elephant and endemic ungulates and primates. There is a significant decline in detectability for 16 species, which suggests a decline in their abundance. These patterns of change in distribution and abundance repeat in our assessments of spatial variation in occupancy dynamics between the three contiguous forest complexes and two human-dominated landscapes into which the southern Western Ghats has been fragmented. Extinction rates are highest in the human-dominated landscapes. Declines in abundance for several species suggest the presence of extinction debts, which may soon be repaid with imminent range contractions and subsequent species extinctions unless immediate remedial conservation measures are taken. Detection/non-detection surveys of key informants used in an occupancy modeling framework provide potential for rapid conservation status assessments of multiple species across large spatial scales over time.     

Yellowstone’s ungulates after wolves - expectations, realizations, and predictions

We evaluated the initial implications of wolf (Canis lupus) recovery on ungulates in Yellowstone National Park and compared expectations prior to wolf restoration with observed impacts since restoration. The numerical and functional responses of colonizing wolves in Yellowstone’s prey-rich environment were higher than expected and close to the maximum rates predicted prior to wolf restoration. Counts of northern Yellowstone elk (Cervus elaphus) decreased more (50%) than predicted (5-30%), and will likely continue to decrease given the strong preference of wolves for elk and continued high kill rates despite this substantial reduction in elk abundance. Contrary to expectations, human harvests were not reduced appreciably concurrent with wolf restoration, but instead remained similar to pre-wolf restoration years. However, antler-less permits were gradually reduced by 51% during 2000-2004 and additional reductions may be necessary while wolf densities remain high. There have been no substantial effects of wolf recovery on other ungulate species (bighorn sheep (Ovis canadensis), bison (Bison bison), moose (Alces alces), mule deer (Odocoileus hemionus), pronghorn (Antilocapra americana)). However, wolf recovery may eventually contribute to increased bison and pronghorn abundance by decreasing elk and coyote abundance, respectively. Wolf recovery may also contribute to more-pronounced spatial structuring of sex/age classes of northern Yellowstone elk through changes in their distribution, migration, and age structure. The initial consequences of wolf recovery support the premise that wolves may naturally achieve densities above their threshold for ecological effectiveness and contribute to significant changes in ecosystems, including the amelioration of ungulate-caused landscape simplification.     

Large predators and trophic cascades in terrestrial ecosystems of the western United States

Large predators potentially can help shape the structure and functioning of terrestrial ecosystems, yet strong evidence of top-down herbivore limitation has not been widely reported in the scientific literature. Herein we synthesize outcomes of recent tri-trophic cascades studies involving the presence and absence of large predators for five national parks in the western United States, including Olympic, Yosemite, Yellowstone, Zion, and Wind Cave. Historical observations by park biologists regarding woody browse species and recently compiled age structure data for deciduous trees indicate major impacts to woody plant communities by ungulates following the extirpation or displacement of large predators. Declines in long-term tree recruitment indexed additional effects to plant communities and ecological processes, as well as shifts towards alternative ecosystem states. The magnitude and consistency of vegetation impacts found within these five parks, in conjunction with other recent North American studies, indicate that broad changes to ecosystem processes and the lower trophic level may have occurred in other parts of the western United States where large predators have been extirpated or displaced. Thus, where ungulates have significantly altered native plant communities in the absence of large predators, restoration of native flora is urgently needed to recover former ecosystem services. Following the reintroduction of previously extirpated gray wolves Canis lupus into Yellowstone National Park, a spatially patchy recovery of woody browse species (e.g., aspen Populus tremuloides, willow Salix spp., cottonwood Populus spp.) has begun, indicating that large predator recovery may represent an important restoration strategy for ecosystems degraded by wild ungulates.     

有蹄类营养生态学研究进展

有蹄类动物营养生态学是一门正在兴起的新学科,是现代生态学领域研究动物食物数量和质量、营养适应以及营养对种群特征作用规律的分支学科.动物种群和其环境中食物资源的相互关系及作用机理构成了这一学科的基本研究内容.本文从食性分析、营养状况评价、食物营养质量评价、消化与能量代谢、取食行为、营养容纳量和营养生态位等主要方面对这一学科进行了探讨.     

Introducing spatial grazing impacts into the prediction of moorland vegetation dynamics

Grazing by large herbivores is a major determinant of vegetation dynamics in many semi-natural ecosystems, including the replacement of heather moorland by rough grassland in the British uplands. Herbivore foraging is influenced by vegetation patterns and, in turn, their grazing drives vegetation dynamics. Although vegetation impacts are local, spatially heterogeneous local impacts can have different consequences as would the same impacts distributed uniformly. We constructed a simulation model of the spatial effects of grazing by sheep on the vegetation dynamics of heather moorland, a vegetation community of international conservation importance in the UK. The model comprised three sub-models to predict (1) annual average heather utilisation, (2) spatial variation in heather utilisation (higher near the edge of grass patches) and (3) competition between heather and grass. Here we compare the predicted heather utilisation and vegetation dynamics of the spatial model, relative to those of a non-spatial model. The spatial model resulted in a reduced loss of heather cover for a given sheep stocking rate. The model demonstrates how spatial interactions between large herbivores and their forage drive vegetation dynamics, leading to changes in community structure and composition. Indeed, omitting spatial effects in grazing models may lead to inaccurate predictions. We have shown that ecosystem modelling, based around an iterative dialogue between developers and experienced researchers, has the potential to make a substantial contribution towards the conservation and management of vulnerable landscapes. Combining modelling with experimental studies will facilitate progress towards understanding long-term vegetation/herbivore dynamics.     

基于红外相机的白水河国家级自然保护区偶蹄类活动节律调查

2017年6月—2018年9月,在四川白水河国家级自然保护区利用红外相机对保护区内偶蹄类物种活动节律进行研究.结果显示:1、保护区内共发现六种偶蹄类动物,分别为羚牛、斑羚、鬣羚、林麝、毛冠鹿、野猪.相对多度结果显示,最高的为斑羚(RAI=51.2)和毛冠鹿(RAI=32.6),明显高于其他物种.其余依次为林麝(RAI=...     

Modeling successional patterns of high-elevation forests under changing herbivore pressure – responses at the landscape level

We describe an ecological risk assessment for determining the potential long-term impacts of browsing by red deer, roe deer and chamois on the stand dynamics of mountain forests in xeric parts of Central Europe. The assessment is performed by applying a forest succession model of the FORET/JABOWA type which was supplemented with an empirically based browsing subroutine to simulate the effects of browsing by red and roe deer, and chamois. The following scenarios are assumed: (1) no browsing; (2) actual browsing intensity as determined in field trials; (3) browsing intensity twice as high as in scenario (2); and (4) browsing intensity three times as high as in scenario (2). The simulations for two different forest sites in the subalpine region of Eastern Switzerland revealed that heavy browsing can alter development and composition of the observed forests. The extent of this alteration was influenced not only by high browsing intensity, but also by the selection of tree species which were browsed on a particular site at the same time. Taking into account all the uncertainties of the model approach, we conclude from our preliminary studies that, in the regions considered, even strong herbivore pressure (2–3 times today's values) is not a major threat for the survival of the forest as a biological resource, i.e. the long-term total woody biomass is not altered significantly and the changes in the successional pathways are not dramatic. High browsing intensities, however, alter the forest structure considerably. We found that heavily browsed forests tend to be more open, mortality is higher and trees reach an intermediate and adult size quicker. This shortened development cycle of the stands may have implications for forest functions. The risk assessment yields critical values for mean browsing intensity, ‘MBI', (Pinus cembra/Pinus mugo: 30%; Picea abies: 50%; and Larix decidua: 40%), below which successional patterns and forest structures with browsing are not significantly different from forest succession without browsing.     

新疆塔什库尔干岩羊和北山羊种群密度调查

有蹄类动物为新疆塔什库尔干地区分布的雪豹、狼和猞猁等捕食动物提供了重要的食物资源。为了掌握该地区主要野生有蹄类动物的种群密度,于2009年2～3月通过车行样线和步行样线2种调查方式,采用距离取样方法,对岩羊和北山羊种群数量进行了调查分析。车行样线调查获得的岩羊密度为1.791～6.751只/km~2,北山羊密度为0～0.140只/km~2。步行样线调查获得的密度较低,岩羊和北山羊分别为0.008～0.698只/km~2和0.023～0.252只/km~2。调查结果显示该地区岩羊和北山羊种群密度较上世纪80年代中期有所下降。     

Empty forests: Large carnivore and prey abundance in Namdapha National Park, north-east India

Illegal hunting poses a dual threat to large carnivores through direct removal of individuals and by prey depletion. We conducted a camera-trapping survey in the Namdapha National Park, north-east India, conducted as part of a programme to evaluate carnivore and prey species abundance. Clouded leopard (Neofelis nebulosa) was the only large carnivore detected by camera-trapping. Indirect evidences indicated the presence of the wild dog (Cuon alpinus) and leopard (Panthera pardus), however, there was no evidence of tigers (Panthera tigris), suggesting their possible extinction from the lower elevation forests. Of the major ungulate prey species, sambar (Cervus unicolor) and wild pig (Sus scrofa) were the only large prey detected, while the Indian muntjac (Muntiacus muntjak) was the only small prey species detected. Relative abundances of all species were appreciably lower than estimates from other tropical forests in south-east Asia. We suspect that illegal hunting may be the cause for the low carnivore and prey species abundance. An ongoing community-based conservation programme presents an opportunity to reduce local people’s dependence on hunting by addressing their socio-economic needs and for using their skills and knowledge of the landscape for wildlife conservation. However, long-term wildlife monitoring is essential to assess the efficacy of the socio-economic interventions in bringing about wildlife recovery.