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Wild sheep and livestock in Nepal Trans-Himalaya: Coexistence or competition?
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Excessive grazing by livestock is claimed to displace wild ungulates in the Trans-Himalaya. This study compares the seasonal diets and habitat use of sympatric wild naur Pseudois nayaur and domestic goat Capra hircus, sheep Ovis aries and free-ranging yak Bos grunniens in north Nepal and analyses their overlap both within and across seasons. Alpine meadow and the legumes Oxytropis and Chesneya were critical resources for all animal groups. High overlap occurred cross-seasonally when smallstock (sheep and goats) in summer used the spring and autumn ranges of naur. Relatively high total ungulate biomass (3028 kg km-2) and low recruitment of naur (56 young per 100 adult females in autumn) suggested interspecific competition. The spatio-temporal heterogeneity in composition and phenology of food plants across the steep gradient of altitude, together with rotational grazing, appears to indirectly facilitate coexistence of naur and smallstock. However, owing to high cross-seasonal (inter-seasonal) overlaps, competition is likely to occur between these two groups at high stocking densities. Within seasons, naur overlapped more with free-ranging yak than with smallstock. As their habitat use and diets were most similar in winter, when both fed extensively on the same species of shrubs, naur was most likely to compete with yak during that season.
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... In Manang, forests reach up to elevations of 4400 m a.s.l. and are dominated by the East Himalayan fir (Abies spectabilis) on the southern slopes and by the Himalayan birch (Betula utilis) on the northern slopes (Chhetri et al., 2017). Shrublands, alpine grasslands, and alpine meadows adjoin the treeline, above which the highest elevations are shaped by barren lands and permanent snow fields (Shrestha and Wegge, 2008). ...
... Wherever applicable, we calculated mean densities based on prey counts in spring and autumn. This accounted for the longevity and repeated use of snow leopard scrape sites (Ahlborn and Jackson, 1988), imperfect detection of blue sheep and livestock (Suryawanshi et al., 2012), anticipated small home ranges of blue sheep (Cui 2007cited in Zhang et al., 2013, and overlap of habitats and elevation ranges used by blue sheep and livestock in both seasons (Shrestha and Wegge, 2008;Filla et al., 2021; see Table A2 for sensitivity analysis based on grids covered in both seasons). We recorded the presence/absence of Himalayan marmots based on direct sightings and observations of active burrows. ...
... In fact, snow leopard relative abundance increased in southern grid cells (i.e., in Manang), especially in the north-eastern part of this district, the Phu valley. This area, where we observed the highest blue sheep densities and snow leopard relative abundance, is indeed known to host quite high densities of both species (Shrestha and Wegge, 2008;Wegge al., 2012;McCarthy et al., 2017;Filla et al., 2021;Thapa et al., 2021). Apart from blue sheep density, snow leopard relative abundance was positively affected by terrain ruggedness. ...
Large carnivores play key roles in their ecosystems, but their protection is a major challenge in biodiversity conservation due to conflicts with human interests. The snow leopard (Panthera uncia) is the top predator of Asian high-altitude landscapes and faces various threats including wild prey depletion and illegal killings as a consequence of livestock depredation. As the interactions between snow leopards, wild prey, and livestock are still insufficiently understood, we studied the effects of 1) wild prey (blue sheep Pseudois nayaur and Himalayan marmots Marmota himalayana) and domestic prey on snow leopard relative abundance, and of 2) these ecological parameters and intervention applications on livestock depredation by snow leopards. In the Annapurna Conservation Area, Nepal, we monitored wildlife populations and livestock along transects (490.8 km) in 82 grid cells (4 ×4 km) in 2019 and 2021 and conducted questionnaire surveys to determine livestock depredation between 2018 and 2021 (n = 479 households). We applied generalized linear models (GLMs) and sample comparison testing to examine the effects of prey densities and other environmental and anthropogenic predictors on snow leopard relative abundance and livestock depredation. Blue sheep density strongly positively affected snow leopard relative abundance, which also increased with terrain ruggedness and decreased with increasing densities of livestock and the human population. The size of livestock holdings shaped depredation events of large livestock (yak, cattle and horse), whereas depredation events of sheep and goats, which accounted for most (68.6%) depredated animals, decreased with increasing human population density and marmot presence. The strong impact of blue sheep on snow leopard relative abundance supports demands for integrating this ungulate into conservation and management plans, including wild prey recovery and translocation. The rather weak evidence for effects of blue sheep on depredation events suggests that conflicts over livestock depredation by snow leopards would neither be inflicted nor solved by increasing wild prey abundance. This demonstrates the need to improve intervention strategies in the Annapurna region, such as predator-proofing corrals and optimizing daytime herding practices. We suggest further exploring the effects of marmots and other secondary prey on livestock depredation rates, and testing the suitability of additional interventions, e.g., dogs and deterrents, as conflict mitigation tools. Our results will support wildlife managers in setting conservation priorities to promote the long-term co-existence of local people and snow leopards.
... While enormous progress has been made in estimating its populations at local scales, the regional and global population estimates remain ambiguous (Suryawanshi et al. 2021). The global snow leopard population size is estimated to be between 3,920 to 7,500 (Mccarthy and Chapron 2003;Janečka et al. 2008 The declining population of snow leopard is due to threats which can be broadly categorized into three types; 1) decline in prey due to competition from livestock and habitat degradation (Shrestha and Wegge 2008;Aryal et al. 2014); 2) retaliatory killing of snow leopards as it preys on livestock (Wegge et al. 2012;Suryawanshi et al. 2013) and; 3) poaching of the animal for illegal trade in furs, bones and other body parts (McCarthy et al. 2017). Other emerging threats include climate change and land use change due to global warming and burgeoning infrastructure development (McCarthy et al. 2010;Aryal et al. 2016;Penjor et al. 2020). ...
The NSLS report 2022-2023 provides an updated status of the snow leopard in Bhutan. The report is an outcome of the camera trapping survey spanning five protected areas namely Jigme Khesar Strict Nature Reserve, Jigme Dorji National Park, Wangchuck Centennial National Park, Bumdeling Wildlife Sanctuary and Jigme Singye Wangchuck National Park and two Divisional Forest Offices of Paro and Thimphu.
A total of 310 camera stations were setup across the field sites that accumulated a survey effort of 22,636 trap nights, with over 10,000 images of snow leopards captured. A careful review of 476 images identified 96 adult individuals and 10 cubs across the landscape. Bayesian-based Spatially Explicit Capture Recapture (SECR) modelling estimated 134 snow leopards, as compared to the 2016 baseline of 96 individuals. Snow leopard density was estimated at 1.34 snow leopards per 100 km2 with possibility of higher density in western Bhutan than in central and eastern Bhutan. Habitat distribution modeling also suggests more suitable habitats in western Bhutan as compared to other regions.
... Resource sharing by livestock and wildlife in the region, especially in the Trans-Himalayas, is often seen as conflicting with conservation efforts (Ashraf et al. 2014;Bagchi et al. 2012;Berger et al. 2013;Kala 2005;Namgay et al. 2013;Sangay and Vernes 2008;Shrestha and Wegge 2008;Suryawanshi et al. 2010), with very few exceptions of coexistence (Bhatnagar 2009;Sharma et al. 2015). Only a handful of studies in the region explore the pastoral livelihoods, their knowledge systems and traditional resource use, contemporary pressures and local adaptabilities (Bhasin 2011b(Bhasin , 2012Gooch 2009;Ingty 2021;Singh et al. 2013Singh et al. , 2015Singh et al. , 2020Wu et al. 2014). ...
We discuss the main findings in the Special issue on Pastoralism in South Asia from the eight papers based on research conducted in the Himalayan region of South Asia. An overview is presented of pastoralism in the Himalayan region, including India, Pakistan, Nepal and Bhutan. Drawing parallels with the global stresses to pastoralists, papers in this special issue highlighted three sets of contemporary stresses to the pastoralists of the Himalayan region viz. (a) lack of herding labour, associated changing aspirations of youth and decline in traditional knowledge systems; (b) continued stresses from the state and between the formal and informal institutions; and (c) climatic stresses and associated impacts on the rangeland and livestock health. A synthesis of findings from all eight case studies suggests how the issues around pastoral livelihoods and rangeland management in the Himalayan region are entangled across social, political and ecological dimensions. However, instead of only being impacted by the stresses, the pastoral communities are showing adaptations to various kinds of uncertainties and variabilities. Based on these findings from across eight sites in the Himalayan region, we argue that understanding of the problems as well as proposed solutions from the policymakers should be tailored according to the particular social, political and ecological contexts. Other than the issues given prominence in this special issue, the role of markets and social security are some of the other important concerns to be addressed in the region, which can be best addressed by creating an interface between pastoralists and policymakers, practitioners and the government, while making the best use of pastoral knowledge and their way of life.
... Pastoralism (2022) 12:37 areas in search of jobs and education. Co-occurrence of wild herbivores and livestock, especially in high densities, has also been associated with negative impacts on resource availability for wild herbivores and potentially facilitates competition (Bagchi et al. 2004;Mishra et al. 2004;Shrestha and Wegge 2008;Chanchani et al. 2010). During our interviews, the Dokpas mentioned that livestock and wild herbivores maintain spatial segregation at the micro-habitat level, even for species with overlapping diets. ...
The pastoral practices of the Dokpa herders of North Sikkim have been transforming in response to the geo-political and socio-economic changes in the region. Against the backdrop of these changes, this study aims to understand the current state of pastoralism in North Sikkim with three specific objectives: (i) to understand the current rangeland management practices of the Dokpa community; (ii) to examine the social, political and ecological stresses to continuity of traditional pastoral livelihoods; and (iii) to document the baseline on human-wildlife relations. We focused on one of the two subset populations of Dokpa herders of North Sikkim and, using a mixed-methods approach, conducted 12 semi-structured interviews, four key respondent interviews and two focused group discussions. The resource use by the Dokpas is unique, and unlike the rest of the Himalayan range, they access the high-altitude pastures in winters and the lower ones in summer. Pastures in the higher altitudes experience heavier winds, which leads to lower levels of snow deposition — thus ensuring access to dried pasture forage for livestock during the lean season. The decisions pertaining to resource management are taken by the head of the local institution Dzumsa, the Pipon. Primary stresses to the continuation of traditional pastoral practices are fragmentation of pastureland postSino-Indian war of 1962 and the consequent establishment of armed forces, livestock depredation by free-ranging dogs followed by wild predators and continued socio-economic marginalisation of the pastoralists under a supposedly egalitarian institutional regime. Extreme climatic events in the recent past have also contributed to significant livestock loss. Dokpa transhumant practices are on an overall decline, with most members of the younger generation shifting to non-herding livelihoods. The availability of alternate livelihood options with the improved connectivity, access to education and development of the tourism industry has led to changing aspirations of the younger generations. In only two of the twelve households we surveyed, the younger generation continues herding, while the rest have moved to the cities and towns. In terms of human-wildlife relations, the respondents mostly hold a positive attitude towards wildlife and conservation actions despite livestock predation by wild predators, since the free-ranging dogs cause the highest livestock loss. With the inputs from the Dokpas, we provide recommendations towards a facilitative environment for the continuation of the traditional herding in the region, which is critical for the survival of pastoralism in North Sikkim, presently hinged on less than two dozen of elderly Dokpas.
... In contrast, the Manang region has polar and cold climates (Aryal et al. 2014b;Karki et al. 2015) and is covered by forest comprised of the Himalayan white pine (Pinus wallichiana), East Himalayan fir (Abies spectabilis), Himalayan birch (Betula utilis) and black juniper (Juniperus indica; Ghimire and Lekhak 2007). Vegetation above the timberline in Manang is composed of shrublands, alpine meadows, and alpine grasslands, with barren land and permanent snow fields dominating the highest elevations (Shrestha and Wegge 2008). ...
Context. Large carnivores are increasingly threatened by anthropogenic activities, and their protection is among the main goals of biodiversity conservation. The snow leopard (Panthera uncia) inhabits high-mountain landscapes where livestock depredation drives it into conflicts with local people and poses an obstacle for its conservation.
Aims. The aim of this study was to identify the livestock groups most vulnerable to depredation, target them in implementation of practical interventions, and assess the effectiveness of intervention strategies for conflict mitigation. We present a novel attempt to evaluate intervention strategies for particularly vulnerable species, age groups, time, and seasons.
Methods. In 2020, we conducted questionnaire surveys in two regions of the Annapurna Conservation Area, Nepal (Manang, n = 146 respondents and Upper Mustang, n = 183). We applied sample comparison testing, Jacobs’ selectivity index, and generalised linear models (GLMs) to assess rates and spatio-temporal heterogeneity of depredation, reveal vulnerable livestock groups, analyse potential effects of applied intervention strategies, and identify husbandry factors relevant to depredation.
Key results. Snow leopard predation was a major cause of livestock mortality in both regions (25.4–39.8%), resulting in an estimated annual loss of 3.2–3.6% of all livestock. The main intervention strategies (e.g. corrals during night-time and herding during daytime) were applied inconsistently and not associated with decreases in reported livestock losses. In contrast, we found some evidence that dogs, deterrents (light, music playing, flapping tape, and dung burning), and the use of multiple interventions were associated with a reduction in reported night-time depredation of yaks.
Conclusions and implications. We suggest conducting controlled randomised experiments for quantitative assessment of the effectiveness of dogs, deterrents, and the use of multiple interventions, and widely applying the most effective ones in local communities. This would benefit the long-term co-existence of snow leopards and humans in the Annapurna region and beyond.
... From an ecological viewpoint, 'competition between living organisms' is considered as a fundamental concept (Butt and Tumer, 2012), and, in this regard, there has been many studies on the competition between livestock and wild ungulates over resources (Mishra, 2001;Shrestha and Wegge, 2008). They have been classified as dietary competition or habitat overlap. ...
The study is devoted to the human-environmental relationships in the post-socialist period of Kyrgyzstan. It addresses the human-wildlife conflicts using the example of the Alai Valley in the south of the country. Environmental and climatic characteristics of this highland valley provide suitable conditions for pastoralism and serve as habitat for wildlife. In recent decades, the natural landscape of the region came under increasing international attention with regard to nature conservation, sustainable land management and development projects. Historically, pastoralism has played a significant role for the economy of Kyrgyzstan. Following the dissolution of the Soviet Union, the collapse of state agricultural infrastructure facilities, veterinary care, loss of markets, and privatisation of the agricultural sector of the economy and other factors have led to a major downfall in the animal husbandry industry. The number of sheep and goats decreased from ten million in 1990 to four million in 2000. Nevertheless, pastoralism has considerable importance to the national economy and remains as the crucial income source for rural livelihoods in Kyrgyzstan. The post-socialist period of Kyrgyzstan has faced rapid socio-economic and political transformation which has resulted in changes not only to local livelihoods, but also in livestock husbandry, nature protection and wildlife management. In recent decades many pastoralists often complain about the increase in livestock depredation by wild predators. It is taking place despite the presence of state sponsored predator-control activity. From another side, there are public concerns about wildlife conservation. With the engagement of many environmental NGOs and mass-media, wildlife management issues have quickly become highly politicised in Kyrgyzstan. Becoming a Party to several global environmental conventions has increased the realisation of many projects funded by external donor organisations, and the implementation of their obligations for wildlife conservation, together, have substantially raised the profile of wildlife management in Kyrgyzstan at the international level. Moreover, since the independence of Kyrgyzstan, the territory of Protected Areas has increased by three times. Protected Areas are crucial to wildlife conservation and are promoted by the nature conservation community as a beneficial measure to the mitigation of human-wildlife conflicts. Despite this fact, livestock depredation by wild predators generates conflicts and has become a serious conservation issue. The study aims to better understand human-wildlife interrelationships in connection with pastoralism, protected areas and wildlife management in Kyrgyzstan. Wildlife related conflicts are analysed to determine the status of livestock depredation and to explore its linkages with rural livelihoods and wildlife conservation concerns in the Republic. The project design emphasises different utilisation strategies for the same area of rangelands, including the provision of fodder resources, wildlife habitat area, livestock grazing, and other uses by humans. Additionally, the focus of this study is directed towards a historical aspect of the region in relation to the development processes in the Alai Valley and use of its natural resources.
... Potential for competition between livestock and native wild ungulates has generally been studied through assessment of diet similarity (Baldi et al., 2001;Odadi et al., 2007Odadi et al., , 2011, niche use (O'Connor et al., 2015) or spatial and habitat overlaps (Namgail et al., 2007;Shrestha & Wegge, 2008). However, interpretations of these patterns may confuse, rather than clarify competition: for instance, low levels of spatial overlap may indicate a lack of competition or be the end result of an adjustment to competition (Arsenault & Owen-Smith, 2002;Odadi et al., 2011). ...
Previous attempts to address the presence of interspecific competition between domestic livestock and wild ungulates have focused largely on habitat or dietary overlaps. Although overlaps in habitat or diet create opportunities for competition to occur between species, competition only results from such overlap if it affects one or both species negatively. Less attention has been afforded to possible behavioural modifications induced in wildlife by competition with domestic livestock. Here, we investigated the effects of the presence of livestock on feeding behaviour of guanaco (Lama guanicoe) in southern Patagonia, using focal sampling of individuals during foraging bouts, with instantaneous scan samples to estimate group behavioural budgets. We recorded guanaco bite and step rates, used as proxies of foraging intake and selectivity, from four different study sites over eight consecutive seasons. We also estimated sheep and guanaco densities per site, along with vegetation biomass availability. As in other ungulates, bite rates of guanaco appear to be highly flexible and generally increased with vegetation biomass availability. However, as sheep densities and thus additional grazing pressure increased, guanaco foraging strategy compensated by increasing bite rates when foraging vegetation was scarce, indicating further likelihood of competition. Additionally, scan samples indicated that the probability of guanaco feeding occurring at any one time was higher in areas shared with domestic sheep compared to national parks, suggesting guanaco have to focus more on feeding than other behaviours when sheep are present. Guanaco in southern Patagonia, Chile are increasingly dependent on sheep ranches for food resources. Here we investigated, through measures of foraging behaviour, potential competition between sheep and guanaco, and found the latter changing foraging behaviours when sheep densities are high.
Asian elephant (Elephas maximus) is one of the largest mammals classified as "Endangered" due to habitat loss and fragmentation. The main objective of this research was to evaluate the forage availability and to predict the habitat suitability and its use by Asian wild elephant in Parsa-Bagmati corridor in the Central region of Nepal.
Circular sample plots were used to collect information during vegetation survey to analyze density, frequency and abundance with Importance Value Index (IVI). Use of food plants by elephants was studied by micro-histological analysis of opportunistically collected dungs. Maximum entropy modeling of species geographic distributions (MaxEnt) was used for predicting probability of occurrence of wild elephants using MaxEnt software version 3.3.3e.
Total 119 species of vegetation were recorded with 52 trees, 39 shrubs, 11 climbers and 17 herbs. 46 species of plants belonging to 12 families were identified in the Asian wild elephant dung. Asian wild elephant is a mixed feeder consuming 21 tree, 17 grasses, 4 shrubs, 2 climbers and 2 unknown plants. The ratio of browse to grass showed strong affinity towards browse plant species. Grass contributed the highest proportion 46.05 % of diets of Asian wild elephant, followed by tree 27.28 %, climber 12.54 % and shrub 6.57 % in terms of percentage of occurrence.
The most preferred plant was Spatholobus parviflorus (11.57 %), Typha elephentia (9.82 %), Paspalum spp (7.36 %), Imperata cylindrica (5.96 %), Phoenix humilis (5.70%), Shorea robusta (5.08%), Ciricium wallichi (5%), Bridelia retusa (4.73%), Ficus nerifolia (3.68%), Lagerstroemia parvifora (3.15%), Mallotus philippensis (2.63%), Litsea monopetala (1.84%), Saccharum spontaneum (1.75%), Desmostachya bippinata (1.75%), Dryothyrium boryanum (1.66%), Ficus religiosa (1.57%), Ficus racemose (1.40%) Thysanolaena maxima (1.31%).
A total of 664.435 km 2 (59.28% of the total study area of 1120 km 2) was identified as potential suitable habitat for Asian wild elephant in the study area. Density and Shannon diversity of trees, shrubs and herbs do not pose any significant (p>0.05) difference in elephant presence in Parsa-Bagmati corridor. Food was not a limiting factor for elephant's occurrence in the central region and the study area is use as a corridor. Thus the corridor is important to maintain their traditional route for their movement.
In temperate ecosystems wild ungulates are known to switch their diets from growing season in spring and summer to lean season in winter. Such dietary shifts are crucial for wild herbivores living under temperate climatic conditions. The sympatric wild herbivores in temperate habitats may have to compete for limited food resources in winter and more diet overlap is likely to occur among them. The present study was conducted from December 2020 to February 2021 to assess winter dietary overlap between two sympatric wild caprids: markhor (Capra falconeri) and Himalayan goral (Naemorhedus goral) at Kazinag National Park (KNP) and its adjoining areas viz., Limber Wildlife Sanctuary (LiWLS), Lachipora Wildlife Sanctuary (LaWLS) and Naganari Conservation Reserve (NCR) in the Kashmir Himalaya. The two wild goats shared same habitat and limited food plants in winter at lower altitudes of KNP. We used micro-histological analysis for identifying dietary items from 120 fresh faecal samples of two wild goats (markhor, n = 60 and Himalayan goral, n = 60). The faecal samples were collected from the field after the animals left the sites. The analysis revealed 20 identified plant species from Himalayan goral diet and 17 from markhor diet shared with the former. Both wild goats maintained a higher proportion of browse (Himalayan goral = 57.58%; markhor = 70.99%) than graze (Himalayan goral = 40.43%; markhor = 25.14%) in their winter diet. Overall Shannon-diversity index values were high for Himalayan goral (2.23) and relatively low for markhor (1.95). High diversity index values were recorded in January (Himalayan goral = 2.27; markhor = 2.07) and slightly lower values for December (Himalayan goral = 2.24; markhor = 1.87) and February (Himalayan goral = 2.18; markhor = 1.90). Markhor and Himalayan goral had a higher dietary overlap (0.72 ± 0.17) for shrubs and less overlap for grasses (0.32 ± 0.09) and trees (0.22 ± 0.06) in winter. Himalayan goral had high amount of diet overlap with markhor for grasses (0.37 ± 0.14) in December and shrubs in January (0.64 ± 0.21) and February (0.49 ± 0.11). The comprehensive investigation of the winter diet overlap between two sympatric wild goats in KNP and adjoining areas would boost conservation action.
We studied the spatio-temporal overlap in resource selection by resident livestock and Asiatic ibex (Capra ibex sibirica) in Pin Valley National Park, a Trans-Himalayan protected area important for conservation of the endangered snow leopard and ibex. Approximately 350 resident livestock grazed in the 300 km 2 study area within the park between May and December every year. This relatively large livestock population could potentially compete with the estimated 250 ibex for space and food. In this paper we do not get into the debate whether livestock grazing degrades pastures, nor do we look at overlap in diets, but here, we limit to establish whether ibex and resident livestock compete at the level of habitat selection. We located seven radio-collared ibex over one year and also recorded the location of any domestic animal on a 1:50,000 topographical map. For each sighting various habitat attributes were recorded. Ibex migrated to higher elevations during summer (mean 4,400 m) while most livestock continued to use the lower valleys (<4,100 m). During spring and autumn, there was greater altitudinal overlap, however ibex primarily occurred on steeper slopes and closer to escape terrain. We suggest that ibex and resident livestock used habitat differently through out the period of overlap in the Park and thus livestock did not interfere with ibex at this scale of resource selection. We however, note that this situation was primarily due to two factors – a) nearly all resident livestock were herded back to settlements at night and were thus primarily grazed near habitations, and, b) livestock holdings were not being increased due to the limitation of collecting enough forage for winter stall feeding. Citation:
Perhaps only the English with their unwitting natural irony could have retained the name New Forest for an area that is neither new (it is one of the oldest semi-natural areas of woodland in Great Britain, as well as one of the largest) nor what most would regard as a forest. ‘New’ only when it was first created the latest in a series of ‘Royal Forests’ in the eleventh century, it is also a ‘forest’ only in the medieval sense of an area set aside as a royal hunting preserve (and thus coming under Forest rather than Common law). Set in the Hampshire Basin of southern England, between the Solent and the Avon (Figure 2.1) this ‘New Forest’ comprises a diverse mix of vegetational communities: only some 10 000 ha (of a total administrative area at the current time of approximately 37 500 ha) are actually forested in the sense of covered with trees; the remaining area is a complex mosaic of open heathland, grasslands and bog.
A statistical technique evaluating preference or avoidance of a given habitat or forage species is presented, using moose (Alces alces) distribution patterns in an area including the Little Sioux Burn of northeastern Minnesota as an example. The technique is used in conjunction with a chi-square analysis, after the chi-square has led to the rejection of the null hypothesis that a set of observations follows an "expected" occurrence pattern. The technique involves the use of a Bonferroni z statistic which may be used in estimating whether a specific observation occurs more or less frequently than expected. The technique provides a refinement of quantitative methods which heretofore have not been used to test a multinomial distribution applicable to the example.
In Rangifer tarandus a decrease in recruitment rate and adult female body size (although not in adult survival rate) develops in response to increasing population densities and is caused mainly by winter food limitation. This population response was used in modeling the maximum sustained yield (MSY) based on productivity curves in terms of annual biomass production/km2 or numerical abundance. The fit of 2nd-order polynomials was used to test for nonlinearity in the relationship between density and dynamics. The production curves peaked close to 50% of the ecological carrying capacity, suggesting a response of the type theoretically predicted for large mammals, but the biomass production peaked at a lower population density. In management terms the 1st-order derivatives from the productivity equations indicated a MSY at 1.75 animals/km2 of gross habitat, whereas numerical abundance peaked at 2.3.-from Author
On islands of the Sea of Cortez, sets of lizard species with low ecological overlaps with one another occur significantly more often than one would predict on the basis of random assortment of colonists from the Baja California mainland. This result occurs regardless of which definition of overlap one chooses among several existing in the literature and occurs on both land-bridge and oceanic islands. One generating force that might yield this result is interspecific competition. Another possibility is that the same non-overlapping sets of resources occur on the islands and lizard species simply map this non-random distribution. In this regard certain low α species sets are statistically more common in the archipelago than other equally low α sets. This may reflect non-random resource distribution or species compatibility from interference competition. /// На островах моря Кортеса группа видов ящериц с низким взаимным экологическим перекрыванием встречается значительно чаще, чем можно предпопагать на основе случайного набора колонистоб с материка в Калифорнийском заливе. Этот результат не зависит от того, какой критерий перекрывания избран среди нескольких, имеющихся в литературе и имеет место как на перешейке, так и на океанических островах. Единственный фактор, который может дать такой результат - межвидовая конкуренция. Другая возможность состоит в том, что один и те же неперекрывающиеся виды ресурсов встречаются на островах, а виды ящериц просто картируют это нерандомическое распределение. В этом отношении определенные слабые группы видов α статистически более обычны на архипелаге, чем другие такие же славые группы. Это может отражать нерандомическое распределение ресурсов или видовую совместимость при накладывакщейся конкуренции.