Search

Conservation increasingly relies on social science tools to understand human behavior. Specialized questioning techniques (SQTs) are a suite of methods designed to reduce bias in social surveys and are widely used to collect data on sensitive topics, including compliance with conservation rules. Most SQTs have been developed in Western, industrialized, educated, rich, and democratic countries, meaning their suitability in other contexts may be limited. Whether these techniques perform better than conventional direct questioning is important for those considering their use. We designed an experiment to validate the performance of four SQTs (unmatched count technique, randomized response technique, crosswise model, and bean method) against direct questions when asking about a commonly researched sensitive behavior in conservation, wildlife hunting. We developed fictional characters, and for each method asked respondents to report the answers that each fictional character should give when asked if they hunt wildlife. We collected data from 609 individuals living close to protected areas in two different cultural and socioeconomic contexts (Indonesia and Tanzania) to quantify the extent to which respondents understood and followed SQT instructions and to explore the sociodemographic factors that influenced a correct response. Data were modeled using binomial general linear mixed models. Participants were more likely to refuse to answer questions asked using SQTs compared with direct questions. Model results suggested that SQTs were harder for participants to understand. Demographic factors (e.g., age and education level) significantly influenced response accuracy. When sensitive responses to sensitive questions were required, all SQTs (excluding the bean method) outperformed direct questions, demonstrating that SQTs can successfully reduce sensitivity bias. However, when reviewing each method, most respondents (59-89%) reported they would feel uncomfortable using them to provide information on their own hunting behavior, highlighting the considerable challenge of encouraging truthful reporting on sensitive topics. Our results demonstrate the importance of assessing the suitability of social science methods prior to their implementation in conservation contexts.Validación Experimental de las Técnicas de Cuestionamiento Especializado en la Conservación Resumen La conservación depende cada vez más de herramientas de las ciencias sociales para entender el comportamiento humano. Las técnicas de cuestionamiento especializado (TCE) son un conjunto de métodos diseñados para reducir el sesgo en los censos sociales y y se usan ampliamente para recolectar datos sobre temas sensibles, incluyendo el cumplimiento de las normas de conservación. La mayoría de las TCE se desarrollaron en el hemisferio occidental, en países industrializados, educados, ricos y democráticos, lo que significa que su que su idoneidad en otros contextos puede ser limitada. Quienes piensan en usar estas técnicas consideran importante saber si tienen un mejor desempeño que el cuestionamiento directo convencional. Diseñamos un experimento para validar el desempeño de cuatro TCE (técnica de conteo sin par, técnica de respuesta aleatoria, modelo transversal, método bean) frente a las preguntas directas cuando se cuestiona sobre un comportamiento sensible de interés recurrente en la conservación: la cacería de fauna. Desarrollamos personajes ficticios y para cada método le pedimos a los respondientes que reportaran las respuestas que cada personaje ficticio debería dar al cuestionársele si cazan fauna silvestre. Recolectamos datos de 609 individuos con residencia cercana a áreas protegidas en dos contextos cultural y socioeconómicamente diferentes (Indonesia y Tanzanía) para cuantificar el grado al que los respondientes entendieron y siguieron las instrucciones de las TCE y para explorar los factores sociodemográficos que influyeron sobre las respuestas correctas. Modelamos los datos mediante modelos lineales mixtos binomiales y generales. Fue más probable que los participantes se rehusaran a responder las preguntas realizadas con las TCE en comparación con las preguntas directas. Los resultados del modelo sugirieron que las TCE eran más difíciles de entender para los participantes. Los factores demográficos (p. ej.: edad y nivel educativo) influyeron significativamente la certeza de las respuestas. Cuando se requirieron respuestas sensibles a preguntas sensibles, todas las TCE (excepto el método bean) tuvieron un mejor desempeño que las preguntas directas, lo que demuestra que las TCE pueden reducir exitosamente el sesgo por sensibilidad. Sin embargo, cuando se les preguntó sobre cada método, la mayoría de los respondientes (59-89%) reportó que se sentirían incómodos si tuvieran que usarlas para proporcionar información sobre sus propios comportamientos de cacería, lo que destaca el reto considerable que es reportar honestamente los temas sensibles. Nuestros resultados demuestran la importancia de de evaluar la idoneidad de los métodos de las ciencias sociales previo a su implementación en contextos de conservación.保护工作越来越依赖于社会科学工具来了解人类行为。专业提问技巧 (specialized questioning techniques, SQTs) 旨在减少社会调查中的偏差, 被广泛用于收集敏感话题的数据, 包括对保护规则的遵守情况。然而, 大多数 SQT 是工业化、教育水平良好、富裕且民主的西方国家开发的, 这意味着它们在其他情况下的适用性可能有限。对于考虑使用 STQ 的人来说, 这些方法是否比传统的直接提问法表现得更好是一个重要的问题。我们设计了一项实验来验证 4 种 SQT (无配对计数技术、随机回答技术、交叉模式、豆子法) 与直接提问相比, 在询问保护领域中常见的敏感行为--野生动物狩猎时的表现。我们设计了一些虚构人物, 并在每一种方法中都要求受访者报告每个虚构人物在被问及是否猎杀野生动物时应该给出的答案。我们在两种不同的文化和社会经济背景下 (印度尼西亚、坦桑尼亚) 收集了609名保护区附近居民的数据, 以量化受访者理解和遵守 SQT 指示的程度, 并探索影响正确回答的社会人口因素。我们用二项式一般线性混合模型对数据进行建模。结果显示, 与直接提问相比, 参与者更有可能拒绝回答使用 SQT 提出的问题。模型结果表明 SQT 对参与者来说更难理解。人口统计学因素 (如年龄和教育水平) 显著影响了回答的准确性。当需要对敏感问题进行敏感回答时, 除豆子法之外的所有 SQT 都优于直接提问, 表明 SQT 可以成功地减少敏感性偏差。然而, 当被问及这些方法时, 大多数受访者 (59%-89%) 都表示他们会对使用这些方法来提供有关自己狩猎行为的信息感到不舒服, 这表明鼓励对敏感话题进行真实报告仍存在巨大挑战。我们的结果表明, 在保护背景下实施社会科学方法时, 事先评估其适用性是十分重要的。【翻译: 胡怡思; 审校: 聂永刚】.

Monitoring the impacts of poaching on wildlife is crucial to the management of ecosystems and wildlife populations. Previous studies have shown that poaching can affect the demography, reproduction and behaviour of wildlife. For African elephants (Loxodonta africana), poaching has been shown to affect population numbers, structure, breeding system, behaviour and activity patterns. This study investigated whether there were significant differences in group size and composition of African elephants in Ruaha National Park, Tanzania between areas of high- and low poaching levels, based on the 2013 whole-ecosystem aerial census, which we used as a proxy for poaching pressure. Elephant group size and composition were recorded along 417.6 km of monthly transects from May to November 2016, and again from May to November 2017. Comparison of cow/calf group sizes revealed that the group sizes were larger in areas with low poaching pressure. The dependent-to-adult female ratio was higher in areas with low poaching pressure, while the proportion of adult females was higher in areas with high poaching pressure. The proportions of cow/calf and mixed group types were higher in areas with low poaching pressure. A higher proportion of bull groups were seen in areas with high poaching pressure, which could be evidence of a risk response strategy. Therefore, poaching has significantly shaped grouping patterns, composition and has caused reproductive suppression in Ruaha elephants. We recommend a genetic study of this elephant population to establish the degree of relatedness among families to understand the extent of social structure breakdown caused by social stress due to high poaching pressure in the past years.

Fast and accurate estimates of wildlife abundance are an essential component of efforts to conserve ecosystems in the face of rapid environmental change. A widely used method for estimating species abundance involves flying aerial transects, taking photographs, counting animals within the images and then inferring total population size based on a statistical estimate of species density in the region. The intermediate task of manually counting the aerial images is highly labour intensive and is often the limiting step in making a population estimate.\ud Here, we assess the use of two novel approaches to perform this task by deploying both citizen scientists and deep learning to count aerial images of the 2015 survey of wildebeest (Connochaetes taurinus) in Serengeti National Park, Tanzania.\ud Through the use of the online platform Zooniverse, we collected multiple non‐expert counts by citizen scientists and used three different aggregation methods to obtain a single count for the survey images. We also counted the images by developing a bespoke deep learning method via the use of a convolutional neural network. The results of both approaches were then compared.\ud After filtering of the citizen science counts, both approaches provided highly accurate total estimates. The deep learning method was far faster and appears to be a more reliable and predictable approach; however, we note that citizen science volunteers played an important role when creating training data for the algorithm. Notably, our results show that accurate, species‐specific, automated counting of aerial wildlife images is now possible.

In an opinion letter??to Nature (September 2010), Dobson et al. (2010) oppose the planned road through northern Tanzania that crosses Serengeti National Park (SNP). They contend that the road will jeopardize the Serengeti ecosystem by interrupting the wildebeest (Connochaetes taurinus) migratory corridor. This opinion is supported by other scientists using mathematical models (Holdo et al. 2011). However, all arguments presented against the project have been questioned (Homewood et al. 2010). As has often been the case in the conservation of African natural resources, some scientists present views that do not account for other key components of conservation: economic growth, reduction of poverty, improvement of quality of life, and social well-being. As scientists working in Serengeti, we believe that the published reports about the Serengeti road mislead the world about its potential effects on the ecosystem.

Phenological or plant age classification across a landscape allows for examination of micro-topographical effects on plant growth, improvement in the accuracy of species discrimination, and will improve our understanding of the spatial variation in plant growth. In this paper six vegetation indices used in phenological studies (including the newly proposed PhIX index) were analysed for their ability to statistically differentiate grasses of different ages in the sequence of their development. Spectra of grasses of different ages were collected from a greenhouse study. These were used to determine if NDVI, NDWI, CAI, EVI, EVI2 and the newly proposed PhIX index could sequentially discriminate grasses of different ages, and subsequently classify grasses into their respective age category. The PhIX index was defined as: ( A VNIR n + log ( A SWIR 2 n ) ) / ( A VNIR n − log ( A SWIR 2 n ) ) , where A VNIR n and A SWIR 2 n are the respective normalised areas under the continuum removed reflectance curve within the VNIR (500–800 nm) and SWIR2 (2000–2210 nm) regions. The PhIX index was found to produce the highest phenological classification accuracy (Overall Accuracy: 79%, and Kappa Accuracy: 75%) and similar to the NDVI, EVI and EVI2 indices it statistically sequentially separates out the developmental age classes. Discrimination between seedling and dormant age classes and the adult and flowering classes was problematic for most of the tested indices. Combining information from the visible near infrared (VNIR) and shortwave infrared region (SWIR) region into a single phenological index captures the phenological changes associated with plant pigments and the ligno-cellulose absorption feature, providing a robust method to discriminate the age classes of grasses. This work provides a valuable contribution into mapping spatial variation and monitoring plant growth across savanna and grassland ecosystems.

African elephants (Loxodonta africana) are imperiled by poaching and habitat loss. Despite global attention to the plight of elephants, their population sizes and trends are uncertain or unknown over much of Africa. To conserve this iconic species, conservationists need timely, accurate data on elephant populations. Here, we report the results of the Great Elephant Census (GEC), the first continent-wide, standardized survey of African savannah elephants. We also provide the first quantitative model of elephant population trends across Africa. We estimated a population of 352,271 savannah elephants on study sites in 18 countries, representing approximately 93% of all savannah elephants in those countries. Elephant populations in survey areas with historical data decreased by an estimated 144,000 from 2007 to 2014, and populations are currently shrinking by 8% per year continent-wide, primarily due to poaching. Though 84% of elephants occurred in protected areas, many protected areas had carcass ratios that indicated high levels of elephant mortality. Results of the GEC show the necessity of action to end the African elephants’ downward trajectory by preventing poaching and protecting habitat.

Elephant and impala as intermediate feeders, having a mixed diet of grass and browse, respond to seasonal fluctuations of forage quality by changing their diet composition. We tested the hypotheses that (1) the decrease in forage quality is accompanied by a change in diet from more monocots in the wet season to more dicots in the dry season and that that change is more pronounced and faster in impala than in elephant; (2) mopane (Colophospermum mopane), the most abundant dicot species, is the most important species in the elephant diet in mopane woodland, whereas impala feed relatively less on mopane due to the high condensed tannin concentration; and (3) impala on nutrient-rich soils have a diet consisting of more grass and change later to diet of more browse than impala on nutrient-poor soils. The phosphorus content and in vitro digestibility of monocots decreased and the NDF content increased significantly towards the end of the wet season, whereas in dicots no significant trend could be detected. We argue that this decreasing monocot quality caused elephant and impala to consume more dicots in the dry season. Elephant changed their diet gradually over a 16-week period from 70% to 25% monocots, whereas impala changed diets rapidly (2-4 weeks) from 95% to 70% monocots. For both elephants and impala, there was a positive correlation between percentage of monocots and dicots in the diet and the in vitro digestibility of these forage items. Mopane was the most important dicot species in the elephant diet and its contribution to the diet increased significantly in the dry season, whereas impala selected other dicot species. On nutrient-rich gabbroic soils, impala ate significantly more monocots than impala from nutrient-poor granitic soils, which was related to the higher in vitro digestibility of the monocots on gabbroic soil. Digestibility of food items appears to be an important determinant of diet change from the wet to the dry season in impala and elephants.

1. Scaling theory predicts that organisms respond to different scales of resource patchiness in relation to their own size. We tested the hypothesis that the scale of nutrient patchiness mediates resource partitioning between large trees and small grasses in a semi-arid savanna. 2. In a factorial field experiment, Colophospermum mopane trees and associated grasses were fertilized at either a fine or coarse scale of patchiness with nitrogen (N), phosphorus (P) or N + P. The growth of marked tree shoots, herbaceous biomass and leafNand P concentrations were monitored for 2 years following fertilization. 3. Responses of trees were partly scale dependent. Tree leaf N concentration and shoot length relatively increased with fertilization at a coarse scale. Tree leaf mass decreased when P was supplied at a fine scale of patchiness, suggesting intensified grass competition. 4. Phosphorus fertilization increased leaf P concentrations more in grasses than trees, whereas N fertilization increased leaf N concentration moderately in both trees and grasses. Herbaceous above-ground biomass around focal trees was negatively correlated with tree size when fertilized with N, suggesting intensified tree competition. 5. Synthesis. Our results support the hypothesis that trees benefit more from nutrients supplied at a relatively coarse scale of patchiness. No direct responses of grasses to scale were detected. In trees, the scale effect was surpassed by the effect of sample year, when rainfall varied

1. Elucidation of the mechanism determining the spatial scale of patch selection by herbivores has been complicated by the way in which resource availability at a specific scale is measured and by vigilance behaviour of the herbivores themselves. To reduce these complications, we studied patch selection by an animal with negligible predation risk, the African elephant. 2. We introduce the concept of nutrient load as the product of patch size, number of patches and local patch nutrient concentration. Nutrient load provides a novel spatially explicit expression of the total available nutrients a herbivore can select from. 3. We hypothesized that elephant would select nutrient-rich patches, based on the nutrient load per 2500 m(2) down to the individual plant scale, and that this selection will depend on the nitrogen and phosphorous contents of plants. 4. We predicted that elephant would cause more adverse impact to trees of lower value to them in order to reach plant parts with higher nutrient concentrations such as bark and root. However, elephant should maintain nutrient-rich trees by inducing coppicing of trees through re-utilization of leaves. 5. Elephant patch selection was measured in a homogenous tree species stand by manipulating the spatial distribution of soil nutrients in a large field experiment using NPK fertilizer. 6. Elephant were able to select nutrient-rich patches and utilized Colophospermum mopane trees inside these patches more than outside, at scales ranging from 2500 down to 100 m(2) . 7. Although both nitrogen and phosphorus contents of leaves from C. mopane trees were higher in fertilized and selected patches, patch choice correlated most strongly with nitrogen content. As predicted, stripping of leaves occurred more in nutrient-rich patches, while adverse impact such as uprooting of trees occurred more in nutrient-poor areas. 8. Our results emphasize the necessity of including scale-dependent selectivity in foraging studies and how elephant foraging behaviour can be used as indicators of change in the availability of nutrients.

There is a growing concern that the feeding habits of the African elephant, which include pushing over, uprooting and snapping trees, may have a negative impact on other herbivores. Browsed trees are known to respond by either increasing production (shoots and leaves) or defence (secondary compounds). It is not clear, however, what proportion of the browsed biomass can be made available at lower feeding heights after a tree is pushed over or snapped; thus, it is also unclear how the forage quality is affected. In a field survey in Kruger National Park, South Africa, 708 Mopane trees were measured over four elephant utilization categories: snapped trees, pushed-over trees, uprooted trees and control trees. The elephants’ impact on the leaf biomass distribution was quantified, and the forage quality (Ca, P, K and Mg, N, digestibility and condensed tannin [CT] concentrations) were analyzed. Pushed-over and uprooted trees had the maximum leaf biomass at lower height s( o1m), snapped trees at medium heights (1‐2m) and control trees at higher heights (42m). In all three utilization categories, the minimum leaf biomass was seven times higher than it was for control trees at a height of below 1m. Leaf nitrogen content increased in all three categories and was significantly higher in snapped trees. CT concentrations increased slightly in all trees that were utilized by elephants, especially on granitic soils in the dry season. The results provide the insight that elephants facilitate the redistribution and availability of browse and improve the quality, which may positively affect small browsing herbivores.

In savannas, the tree-grass balance is governed by water, nutrients, fire and herbivory, and their interactions. We studied the hypothesis that herbivores indirectly affect vegetation structure by changing the availability of soil nutrients, which, in turn, alters the competition between trees and grasses. Nine abandoned livestock holding-pen areas (kraals), enriched by dung and urine, were contrasted with nearby control sites in a semi-arid savanna. About 40 years after abandonment, kraal sites still showed high soil concentrations of inorganic N, extractable P, K, Ca and Mg compared to controls. Kraals also had a high plant production potential and offered high quality forage. The intense grazing and high herbivore dung and urine deposition rates in kraals fit the accelerated nutrient cycling model described for fertile systems elsewhere. Data of a concurrent experiment also showed that bush-cleared patches resulted in an increase in impala dung deposition, probably because impala preferred open sites to avoid predation. Kraal sites had very low tree densities compared to control sites, thus the high impala dung deposition rates here may be in part driven by the open structure of kraal sites, which may explain the persistence of nutrients in kraals. Experiments indicated that tree seedlings were increasingly constrained when competing with grasses under fertile conditions, which might explain the low tree recruitment observed in kraals. In conclusion, large herbivores may indirectly keep existing nutrient hotspots such as abandoned kraals structurally open by maintaining a high local soil fertility, which, in turn, constrains woody recruitment in a negative feedback loop. The maintenance of nutrient hotspots such as abandoned kraals by herbivores contributes to the structural heterogeneity of nutrient-poor savanna vegetation.

1. Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. 2. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. 3. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. 4. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. 5. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. 6. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena.

Browsing intensity influences a plant’s response to herbivory. Plants face a trade-off between investment in the production of secondary compounds and investment in growth. To elucidate this trade-off, we simulated four browsing intensities (0%, 50%, 75% and 100%) on mopane saplings, Colophospermum mopane (J.Kirk ex Benth.) J.Leonard, in a greenhouse experiment. This showed that, with increasing defoliation intensity, plants change their investment strategy. At intermediate levels of defoliation (50%), mopane saplings increased the synthesis of condensed tannins, so that tannin concentrations followed a hump-shaped relation with defoliation intensity, with significantly higher tannin concentration at intermediate defoliation levels. When defoliated heavily (75% and 100%), tannin concentrations dropped, and plants were carbon stressed as indicated by a reduced growth rate of the stem diameter, and leaf production and mean individual leaf mass were reduced. This suggests that, at intermediate defoliation intensity, the strategy of the plants is towards induced chemical defences. With increasing defoliation, the relative costs of the secondary metabolite synthesis become too high, and therefore, the plants change their growing strategy. Hence, browsers should be able to benefit from earlier browsing by either adopting a low or a relatively high browsing pressure.

We investigated whether mass and morphological spatial patterns in plants possibly induced the development of enlarged soft mouth parts in especially megaherbivores. We used power functions and geometric principles to explore allometric relationships of both morphological and foraging characteristics of mammalian herbivores in the South African savannah, covering a body size range of more than three orders magnitude. Our results show that, although intradental mouth volume scaled to a power slightly less than one to body mass, actual bite volume, as measured in the field, scaled to body mass with a factor closer to 1.75. However, when including the volume added to intradental mouth volume by soft mouth parts, such as tongue and lips (or trunks in elephant), mouth volume scaled linearly with actual bite volume and in a similar fashion as actual bite volume to body size. Bite mass and bite leaf mass scaled linearly with body size.We conclude that these scaling relationships indicate that large herbivores use their enlarged soft mouth parts to not only increase bite volume and thereby bite mass, but also select soft plant parts and thereby increase the leaf mass fraction per bite.

Aerial surveys are vital to assessing animal populations as part of an effort to understand ecosystem health, a primary component of social and economic development in rural regions of Africa. This paper describes the design, deployment and preliminary performance results of a mobile application that provides visual real-time feedback to assist cockpit crews conducting aerial surveys.

Conservation management is strongly shaped by the interpretation of population trends. In the Serengeti ecosystem, Tanzania, aerial total counts indicate a striking increase in elephant abundance compared to all previous censuses. We developed a simple age-structured population model to guide interpretation of this reported increase, focusing on three possible causes: (1) in situ population growth, (2) immigration from Kenya, and (3) differences in counting methodologies over time. No single cause, nor the combination of two causes, adequately explained the observed population growth. Under the assumptions of maximum in situ growth and detection bias of 12.7% in previous censuses, conservative estimates of immigration from Kenya were between 250 and 1,450 individuals. Our results highlight the value of considering demography when drawing conclusions about the causes of population trends. The issues we illustrate apply to other species that have undergone dramatic changes in abundance, as well as many elephant populations.

Understanding the behavior of species threatened with extinction is important for conservation planning and for solving problems facing species in captivity and the wild. We examined diurnal activity budgets and habitat use of the extinct in the wild Kihansi spray toad to provide insights into ongoing conservation initiatives for this species. Observations on eight target behaviors were made each morning and evening for 14 days, in two subpopulations at Kihansi and University of Dar es Salaam captive breeding centers. There were significantly more bouts of resting than calling, amplexing, hunting, walking, climbing, or feeding. There was no difference in mean time spent in each activity between the two subpopulations. The use of habitat was variable between age classes, subpopulations and sampling time. Young toads spent significantly more time resting at the top of vegetation and on walls while adults rested more on logs. Further, adults foraged more on the walls and vegetation in the morning and on the ground in the evening. Contrastingly, young toads foraged more on the ground in the morning and switched to elevated patches during evening. The similarity of the toads' behavior suggests that important biological traits are still maintained in captivity and retained across toad generations. Furthermore, temporal and spatial variations in the use of habitat structures between age groups suggest fine-scale resource partitioning to reduce competition in this gregarious species. These results highlight the importance of maintaining diverse habitat structures in captivity and are useful for planning species reintroduction and future restocking programs. Zoo Biol. 33:411–418, 2014. © 2014 Wiley Periodicals Inc.

Understanding the behavior of species threatened with extinction is important for conservation planning and for solving problems facing species in captivity and the wild. We examined diurnal activity budgets and habitat use of the extinct in the wild Kihansi spray toad to provide insights into ongoing conservation initiatives for this species. Observations on eight target behaviors were made each morning and evening for 14 days, in two subpopulations at Kihansi and University of Dar es Salaam captive breeding centers. There were significantly more bouts of resting than calling, amplexing, hunting, walking, climbing, or feeding. There was no difference in mean time spent in each activity between the two subpopulations. The use of habitat was variable between age classes, subpopulations and sampling time. Young toads spent significantly more time resting at the top of vegetation and on walls while adults rested more on logs. Further, adults foraged more on the walls and vegetation in the morning and on the ground in the evening. Contrastingly, young toads foraged more on the ground in the morning and switched to elevated patches during evening. The similarity of the toads' behavior suggests that important biological traits are still maintained in captivity and retained across toad generations. Furthermore, temporal and spatial variations in the use of habitat structures between age groups suggest fine-scale resource partitioning to reduce competition in this gregarious species. These results highlight the importance of maintaining diverse habitat structures in captivity and are useful for planning species reintroduction and future restocking programs.

Multiple factors determine diet selection of herbivores. However, in many diet studies selection of single nutrients is studied or optimization models are developed using only one currency. In this paper, we use linear programming to explain diet selection by African elephant based on plant availability and nutrient and deterrent content over time. Our results indicate that elephant at our study area maximized intake of phosphorus throughout the year, possibly in response to the deficiency of this nutrient in the region. After adjusting the model to incorporate the effects of this deficiency, elephant were found to maximize nitrogen intake during the wet season and energy during the dry season. We reason that the increased energy requirements during the dry season can be explained by seasonal changes in water availability and forage abundance. As forage abundance decrease into the dry season, elephant struggle to satisfy their large absolute food requirements. Adding to this restriction is the simultaneous decrease in plant and surface water availability, which force the elephant to seek out scarce surface water sources at high energy costs. During the wet season when food becomes more abundant and energy requirements are satisfied easier, elephant aim to maximize nitrogen intake for growth and reproduction. Our study contributes to the emerging theory on understanding foraging for multiple resources

Surface water is one of the constraining resources for herbivore populations in semi-arid regions. Artificial waterpoints are constructed by wildlife managers to supplement natural water supplies, to support herbivore populations. The aim of this paper is to analyse how a landowner may realize his ecological and economic goals by manipulating waterpoints for the management of an elephant population, a water-dependent species in the presence of water-independent species. We develop a theoretical bio-economic framework to analyse the optimization of wildlife management objectives (in this case revenue generation from both consumptive and non-consumptive use and biodiversity conservation), using waterpoint construction as a control variable. The model provides a bio-economic framework for analysing optimization problems where a control has direct effects on one herbivore species but indirect effects on the other. A landowner may be interested only in maximization of profits either from elephant offtake and/or tourism revenue, ignoring the negative effects that could be brought about by elephants to biodiversity. If the landowner does not take the indirect effects of waterpoints into consideration, then the game reserve management, as the authority entrusted with the sustainable management of the game reserve, might use economic instruments such as subsidies or taxes to the landowners to enforce sound waterpoint management.

1. Elucidation of the mechanism determining the spatial scale of patch selection by herbivores has been complicated by the way in which resource availability at a specific scale is measured and by vigilance behaviour of the herbivores themselves. To reduce these complications, we studied patch selection by an animal with negligible predation risk, the African elephant. 2. We introduce the concept of nutrient load as the product of patch size, number of patches and local patch nutrient concentration. Nutrient load provides a novel spatially explicit expression of the total available nutrients a herbivore can select from. 3. We hypothesized that elephant would select nutrient-rich patches, based on the nutrient load per 2500 m(2) down to the individual plant scale, and that this selection will depend on the nitrogen and phosphorous contents of plants. 4. We predicted that elephant would cause more adverse impact to trees of lower value to them in order to reach plant parts with higher nutrient concentrations such as bark and root. However, elephant should maintain nutrient-rich trees by inducing coppicing of trees through re-utilization of leaves. 5. Elephant patch selection was measured in a homogenous tree species stand by manipulating the spatial distribution of soil nutrients in a large field experiment using NPK fertilizer. 6. Elephant were able to select nutrient-rich patches and utilized Colophospermum mopane trees inside these patches more than outside, at scales ranging from 2500 down to 100 m(2) . 7. Although both nitrogen and phosphorus contents of leaves from C. mopane trees were higher in fertilized and selected patches, patch choice correlated most strongly with nitrogen content. As predicted, stripping of leaves occurred more in nutrient-rich patches, while adverse impact such as uprooting of trees occurred more in nutrient-poor areas. 8. Our results emphasize the necessity of including scale-dependent selectivity in foraging studies and how elephant foraging behaviour can be used as indicators of change in the availability of nutrients.

Forage quality within an African savanna depends upon limiting nutrients (nitrogen and phosphorus) and nutrients that constrain the intake rates (non-digestible fibre) of herbivores. These forage quality nutrients are particularly crucial in the dry season when concentrations of limiting nutrients decline and non-digestible fibres increase. Using artificial neural networks we test the ability of a new imaging spectrometer (CAO Alpha sensor), both alone and in combination with ancillary data, to map quantities of grass forage nutrients in the early dry season within an African savanna. Respectively 65%, 57% and 41%, of the variance in fibre, phosphorus and nitrogen concentrations were explained. We found that all grass forage nutrients show response to fire and soil. Principal component analysis, not only reduced image dimensionality, but was a useful method for removing cross-track illumination effects in the CAO imagery. To further improve the mapping of forage nutrients in the dry season we suggest that spectra within the shortwave infrared (SWIR) region, or additional relevant ancillary data, are required.

1. Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. 2. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. 3. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. 4. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. 5. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. 6. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena.

Predation risk from lions (Panthera leo) has been linked to habitat characteristics and availability and traits of prey. We separated the effects of vegetation density and the presence of drinking water by analyzing locations of lion kills in relation to rivers with dense vegetation, which offer good lion stalking opportunities, and artificial water points with low vegetation density. The spatial distribution of lion kills was studied at the Klaserie Private Nature Reserve, South Africa. The distance between 215 lion kills and the nearest water source was analyzed using generalized linear models. Lions selected medium-sized prey species. Lion kills were closer to rivers and to artificial water points than expected by random distribution of the kills. Water that attracted prey, and not the vegetation density in riverine areas, increased predation risk, with kills of buffalo (Syncerus caffer), kudu (Tragelaphus strepsiceros), and wildebeest (Connochaetes taurinus) as water-dependent prey species. Traits of prey species, including feeding type (food habits), digestion type (ruminant or nonruminant), or body size, did not explain locations of lion kills, and no seasonal patterns in lion kills were apparent. We argue that the cascading impact of lions on local mammal assemblages is spatially heterogeneous.

1. Globally, both climatic patterns and nitrogen deposition rates show directional changes over time. It is uncertain how woody seedlings, which coexist with herbaceous plants in savannas, respond to concurrent changes in water and nutrient availability. 2. We investigated competition effects between herbaceous vegetation and tree seedlings (Colophospermum mopane) under changed water and nutrient (fertilized) conditions in a garden experiment situated in a semi-arid savanna. 3. Herbaceous competition significantly suppressed woody seedling growth. The effect of herbaceous competition on woody seedling growth remained constant with both increasing water and nutrient availability. However, during a wet-season drought, herbaceous competition apparently caused premature leaf senescence in non-irrigated treatments. Fertilization exacerbated negative competition effects during the drought, while irrigation prevented leaf loss of tree seedlings in spite of herbaceous competition and fertilization. 4. Based on a conceptual model, we propose that the vigorous response of herbaceous plants to increased nutrient availability leads to faster depletion of soil water, which increasingly causes water stress in woody seedlings if the interval between watering events is prolonged, e.g. during wet-season droughts. 5. Synthesis. Our data support the notion that changes in drought frequency are of greater importance to woody recruitment success than changes in annual rainfall amount. Based on the water and nutrient interactions observed in our experiment, we suggest that the effect of increased nitrogen deposition on woody seedling recruitment is contingent on water availability.