Elephant Density Research Articles

Elephant (Loxodonta africana) Demography and Behaviour in the Tarangire-Manyara Ecosystem, Tanzania

The increasing prevalence of humans in areas used by elephants is a major challenge to elephant conservation. To investigate anthropogenic impacts on elephants, data on population structure, sex ratios, social structure and behaviour of elephants were examined along vehicle road transects in areas with different protection status. These included: Lake Manyara National Park (protected), Manyara Ranch (partially protected), and the adjacent communal area (non-protected). The maximum number of elephants seen in one day (with similar search effort per day) was 117 in the park and 25 on the ranch, suggesting a higher elephant density inside the park. No elephants were seen in the community area during the survey. In the park, the adult sex ratio was skewed towards females, while on the ranch the adult sex ratio was skewed towards males. The mean group size of elephants was significantly larger in the park compared to the ranch. Tusk sizes of male elephants were significantly larger in the park than on the ranch and elephants on the ranch were significantly more responsive to human approach than elephants in the park. Considering elevated rates of poaching for ivory in the ecosystem and the apparently poor safety for elephants in Manyara Ranch, we strongly suggest improving law enforcement on the ranch.

Delayed physiological acclimatization by African elephants following reintroduction

Managers of reintroduced wildlife commonly encounter behavioral problems post-release that have been linked to physiological condition and elevated stress hormone concentrations. However, there is uncertainty about the generality of a stress response among populations, factors influencing the intensity of the response and the amount of time needed to physiologically acclimatize. We evaluated the relationship of temporal, climatic and social factors to stress hormone concentrations in five African elephant (Loxodonta africana) populations following reintroduction. We determined fecal glucocorticoid metabolite concentrations (FGMs) in 1567 fecal samples collected from elephants reintroduced to five fenced reserves with differing reintroduction histories in South Africa during 2000‐2006. Variation in FGMs across the five reserves was best explained by the number of years that elapsed since initial release. Compared with FGMs 1 year after release, FGMs were 10% lower 10 years after release and 40% lower 24 years after release. Across all reserves, FGMs were consistently highest in the dry season, although daily and monthly temperature and rainfall were not as important as other factors. FGMs did not vary solely in relationship to reserve size or elephant density. Our findings suggest that regardless of reintroduction site conditions, elephants and likely other species subject to reintroduction require an extended period of time to physiologically acclimatize to their new surroundings. Managers should prepare for prolonged behavioral and physiological consequences of long-term elevated stress responses following reintroduction, such as restricted space use and aggressive behavior.

Unmanned Aerial Survey of Elephants

The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to test animal reaction as the UAS passed, and visibility on the images. No reaction was recorded as the UAS passed at a height of 100 m. Observations, made on a set of more than 7000 images, revealed that only elephants (Loxodonta africana) were easily visible while medium and small sized mammals were not. The easy observation of elephants allows experts to enumerate them on images acquired at a height of 100 m. We, therefore, implemented an aerial strip sample count along transects used for the annual wildlife foot count. A total of 34 elephants were recorded on 4 transects, each overflown twice. The elephant density was estimated at 2.47 elephants/km2 with a coefficient of variation (CV%) of 36.10%. The main drawback of our UAS was its low autonomy (45 min). Increased endurance of small UAS is required to replace manned aircraft survey of large areas (about 1000 km of transect per day vs 40 km for our UAS). The monitoring strategy should be adapted according to the sampling plan. Also, the UAS is as expensive as a second-hand light aircraft. However the logistic and flight implementation are easier, the running costs are lower and its use is safer. Technological evolution will make civil UAS more efficient, allowing them to compete with light aircraft for aerial wildlife surveys.

Understanding spatial differences in African elephant densities and occurrence, a continent-wide analysis

The densities and survival of many wild animals are presently at risk. Crucial for improving conservation actions is an understanding on a large scale of the relative importance of human and ecological factors in determining the distribution and densities of species. However, even for such charismatic species as the African elephant (Loxodonta africana), spatially explicit, large-scale analyses are lacking, although various local-scale studies are available. Here we show through continent-scale analysis that ecological factors, such as food availability, are correlated with the presence of elephants, but human factors are better predictors of elephant population densities where elephants are present. These densities strongly correlate with conservation policy, literacy rate, corruption and economic welfare, and associate less with the availability of food or water for these animals. Our results suggest that conservation strategies should be organized in a socioeconomic context. The successful conservation of large animal species could depend more on good human education, greater literacy, good governance, and less corruption, than merely setting aside areas for conservation.

Accuracy, precision, and cost-effectiveness of conventional dung density and fecal DNA based survey methods to estimate Asian elephant (Elephas maximus) population size and structure

Non-invasive DNA-based capture–mark–recapture (CMR) methods have been developed to estimate population size and other parameters and have the advantage that samples can be collected without the need to see or disturb the animals. There are, however, few comparisons of DNA-based CMR estimates of animal population size with estimates from non-genetic methods. We compared the results of a dung-density based survey of an Asian elephant (Elephas maximus) population with a simultaneous fecal DNA-based CMR survey of the same population. We found 545 dung-piles along 116 line transects, converted dung-pile density to elephant density using rates of defecation and dung disappearance, and derived a population estimate of 141 (95% CI=[95, 208]) elephants. We collected 267 fecal samples during three CMR sampling sessions: 215 (81%) yielded sufficient genotypic information for analysis and gave an estimated population size of 132 (95% CI=[120,149]) elephants, closely matching the estimate produced by the dung-density method but with greater precision. The DNA-based method also provided information on population structure. We conclude that DNA-based CMR methods provide more precise abundance estimates, and more data about population structure and dynamics, than dung density-based methods. Fecal DNA-based CMR methods also require less time in the field and can be used when dung density methods are impracticable. Finally, fecal DNA based CMR methods are now cheaper than dung density based methods when line transect survey costs are approximately equal to CMR survey costs and dung decay rate monitoring costs are greater than laboratory costs (which will usually be the case).

Zero Tolerance: Evolving Wildlife Management in Kenya

This study investigates the impact of contrasting wildlife management regimes on the probability of elephant presence in the Tsavo ecosystem base on the New York “zero tolerance policing”. Point data for the location of elephant, elephant carcasses, cattle, buffalo, giraffe, occupied bomas, charcoal kilns, settlements and farms, and water points were collected through aerial survey from 7-12 February 2011. Secondary data layers included main rivers, 30m resolution digital elevation model, and moderate resolution imaging spectro-radiometer (MODIS) 250m spatial resolution normalized difference vegetation index (NDVI) data for January 2011. Information on the three management regimes (none, passive, and active) adopted by protected areas and ranches in Tsavo ecosystem was identified through interviews. The Maxent algorithm was used for modeling the probability of elephant presence in the ecosystem. Multicollinearity of the fourteen explanatory variables was tested using Eigen values and Condition Index (CI). We used Maxent with elephant location points as the presence only data and the twelve explanatory variables as environmental variables. Bootstrapping of ten replications was included in the model. The accuracy of the model was determined using the area under the curve (AUC) of the Receiver Operating Characteristic (ROC) function. The results indicated that elephants were significantly more likely to be found in the protected areas than the non-protected areas. The northern sector of Tsavo West and the Voi sector of Tsavo East were the most likely areas to record elephants. Sectors with protected areas and ranches that practiced active management were more likely to show elephant than those with passive or no management. The areas with high probability of elephant occurrence coincided with actual high elephant density. Elephant carcasses, buffalo, giraffe, and settlements were the main variables that predicted the probability of elephant presence. Elephants are more likely to be in protected areas and ranches that were managed actively than those passively or not managed. In order to capitalize on the notion of protection and active management, we propose a wildlife management model based on the New York ‘zero tolerance’ policing. Any misdemeanor is not tolerated, especially illegal charcoal burning and livestock grazing in the ranches.

The interactions of the flow regime and the terrestrial ecology of the Mana floodplains in the middle Zambezi river basin

ABSTRACTThe flow regime of a river is the main driver of the processes that make up a floodplain ecosystem. Changes in a flow regime will therefore result in changes in the floodplain. The Mana floodplains in the middle Zambezi river basin have been impacted by the construction of the Kariba dam as indicated by the decline in the population of mature, Faidherbia albida (F. albida) trees and the absence young trees. However, the relationship between the effects of the river impoundment, some 50 years ago, and the current ecological state of the floodplain is not well understood. Hence, this study is aimed at describing the historic (pre‐Kariba and post‐Kariba dam) and the current terrestrial ecological state of the Mana floodplains. Data was gathered through review of literature, archival records and hydrological records. Furthermore, vegetation plots were set up to measure diameter at breast height (dbh) of F. albida trees and hence describe the current F. albida stand structure. Results from this study show that the Kariba dam altered the peak mean monthly flows by about 60%. The frequency distribution of the dbh sizes of the current F. albida trees depicted an even‐aged stand structure (mean dbh of 103 cm). There was no evidence of growth of young F. albida trees as there were no trees with smaller (less than 40 cm) dbh sizes. The dry season densities of elephants, (Loxodonta africana) on the Mana floodplains have been increasing since the 1990s, and these also seem to have impacted on the F. albida stand structure. This perhaps partially has to do with the increased length of the dry season as a result of the changed river flows. Therefore, the influence of the altered flow regime and the impact of wildlife have acted interdependently in influencing the noted detectable changes to the ecology of the Mana floodplains. Copyright © 2012 John Wiley & Sons, Ltd.

Does large herbivore removal affect secondary metabolites, nutrients and shoot length in woody species in semi-arid savannas?

We hypothesised that exclusion of long-term browsing leads to decreased nutrient concentrations, increased carbon-based secondary metabolites (CBSMs) and decreased shoot length in woody plants in semi-arid savannas. To test this, we sampled four deciduous woody species in a large-scale, long-term exclusion experiment. We found a tendency for large herbivore exclusion to either decrease nitrogen or increase tannin in two tree species. Phosphorus and total polyphenol responses indicated complex interactions with herbivore assemblage. Shoot length decreased under exclusion in two species, while a similar tendency existed in the remaining species. Therefore, we found limited support for our predictions that exclusion of browsing results in reduced nitrogen or increased CBSMs, but moderate support for decreased shoot length in semi-arid savannas. Dichrostachys cinerea, a fast-growing, aggressive invader in savannas, displayed C-limitation with removal of large herbivores because both shoot length and CBSMs decreased. In conclusion, effects of long-term browsing on deciduous trees in semi-arid savannas depend on the plant species, specific nutrients or CBSMs measured and the composition of the herbivore assemblages. Because elephant densities in the study area were high and most responses were associated with their exclusion, we conclude that elephants are important drivers of browse quality in the study area.

Quantity and Configuration of Available Elephant Habitat and Related Conservation Concerns in the Lower Kinabatangan Floodplain of Sabah, Malaysia

The approximately 300 (298, 95% CI: 152–581) elephants in the Lower Kinabatangan Managed Elephant Range in Sabah, Malaysian Borneo are a priority sub-population for Borneo's total elephant population (2,040, 95% CI: 1,184–3,652). Habitat loss and human-elephant conflict are recognized as the major threats to Bornean elephant survival. In the Kinabatangan region, human settlements and agricultural development for oil palm drive an intense fragmentation process. Electric fences guard against elephant crop raiding but also remove access to suitable habitat patches. We conducted expert opinion-based least-cost analyses, to model the quantity and configuration of available suitable elephant habitat in the Lower Kinabatangan, and called this the Elephant Habitat Linkage. At 184 km2, our estimate of available habitat is 54% smaller than the estimate used in the State's Elephant Action Plan for the Lower Kinabatangan Managed Elephant Range (400 km2). During high flood levels, available habitat is reduced to only 61 km2. As a consequence, short-term elephant densities are likely to surge during floods to 4.83 km−2 (95% CI: 2.46–9.41), among the highest estimated for forest-dwelling elephants in Asia or Africa. During severe floods, the configuration of remaining elephant habitat and the surge in elephant density may put two villages at elevated risk of human-elephant conflict. Lower Kinabatangan elephants are vulnerable to the natural disturbance regime of the river due to their limited dispersal options. Twenty bottlenecks less than one km wide throughout the Elephant Habitat Linkage, have the potential to further reduce access to suitable habitat. Rebuilding landscape connectivity to isolated habitat patches and to the North Kinabatangan Managed Elephant Range (less than 35 km inland) are conservation priorities that would increase the quantity of available habitat, and may work as a mechanism to allow population release, lower elephant density, reduce human-elephant conflict, and enable genetic mixing.

Combining multi‐scale socio‐ecological approaches to understand the susceptibility of subsistence farmers to elephant crop raiding on the edge of a protected area

Summary Coexistence between subsistence farmers and elephants leads to problems for conservation and food security, especially on the edge of protected areas. Crop‐raiding patterns have been investigated for decades, but understanding both social and ecological determinants remains a key challenge to defining realistic management options in a context of increasing human and elephant densities. Hwange National Park, Zimbabwe, and its periphery, hosts one of the highest densities of free‐ranging elephants. As scale is a critical element of ecological systems, we analysed the determinants of crop raiding at three spatial scales: the study area (217 households in 200 km²), the village (30 fields in 14 km²) and the edge of the refuge area (30 fields in less than 3 km²). We combined foraging ecology with sociological approaches, including a participatory experiment, to understand the processes behind the susceptibility of subsistence farmers to crop raiding. Distance to refuge area was the most influential determinant in decreasing crop‐raiding risk, with no damage occurring further than 4·4 km. We obtained consistent models between the three scales with high explanatory power for field damage at village and edge scales (94% and 68% respectively). Household density acted as an obstacle to elephants. Millet patches seemed to provide refuges, and thus promoted damage. The participatory experiment allowed rigorous testing of the efficiency of traditional guarding practices. The presence of people was crucial for guarding efficiency. More innovatively, we demonstrated the role of neighbours and the importance of cohesive guarding as a promising strategy of reducing crop loss at the edge, primarily in areas with a high density of elephant paths. Synthesis and applications. This paper provides evidence that multi‐scale multidisciplinary approaches can unravel endogenous processes shaping human–elephant coexistence on the edge of protected areas. We believe that manipulating perceived risks for elephants, through mitigation methods based on the ‘ecology of fear’, and spatial organization of households, could create a ‘soft fence’ which, when combined with adequate incentives to farmers, promotes a better integration of the protected area in its territory.

Estimating Asian Elephant, Elephas Maximus, Density Through Distance Sampling in the Tropical Forests of Biligiri Rangaswamy Temple Tiger Reserve, India

To determine abundance, density and distribution of wild animals, it is crucial to estimate populations using reliable sampling techniques. In most earlier studies, elephant populations were estimated employing block counts or dung counts, which provide biased estimates due to limitations of the methods. We estimated an Asian elephant population using distance sampling, a quantitatively robust technique, in Biligiri Rangaswamy Temple Tiger Reserve, a critical elephant conservation area in the Nilgiri Biosphere Reserve in south India. We laid 33 transects with a total length of 93 km. We walked these transects five to 11 times amounting to a total of 795.5 km of walks. We collected data on location, number and age-sex classes through direct elephant sightings, using rangefinders, global positioning systems and compass. We used DISTANCE software for analysis. We estimated per km2 cluster density as 0.69 elephant herds, mean cluster size as 2.44, and elephant density as 1.7 animals. This amounts to a total of 713 elephants in 610 km2 of the sanctuary. A high percentage of males less than 30 years old and a low immature:adult female ratio indicated the severity of poaching in the recent past in the study region.

Exploring the relationship betweenNDVIand African elephant population density in protected areas

AbstractAssessing the extent to which populations are limited by bottom‐up processes driven by food limitation is crucial to our understanding of how ecosystems should be managed. Using satellite‐derived Normalised Difference Vegetation Index (NDVI) as an index of resource availability, we investigated the relationships between greenness levels and African elephant (Loxodonta africana) population densities. Our results unveiled a positive relationship betweenNDVIand elephant densities in nonforest populations, but failed to capture any significant effects of survey area and type, number of years after the continental poaching ban and theIUCNcategory of the protected area in which the survey was undertaken. The number of forest elephant populations for which density estimates were available was very low, and no significant relationship betweenNDVIand forest elephant density could be established. Altogether, our study suggests thatNDVIcan successfully be linked to megaherbivore abundance across Africa and further highlights that a continental approach to energy–abundance relationships can be conducted in a relatively low‐cost manner and short timescale, supporting managers' efforts to identify future suitable areas for elephant populations.

Spatiotemporal patterns of elephant poaching in south-eastern Kenya

Context Poaching of the African elephant for ivory had been on the increase since 1997 when the Convention on International Trade in Endangered Species (CITES) allowed a one-off legal sale of ivory by several southern Africa countries. In Kenya, reports indicate continuous year-to-year increase in elephant poaching since 2003. Aims The goals of the study were to describe the temporal and spatial patterns of elephant poaching in south-eastern Kenya between 1990 and 2009, and examine relationships between observed patterns of poaching, and human and biophysical variables. The study aimed to answer the following questions: (1) how has elephant poaching varied seasonally and annually; (2) what are the spatial patterns of elephant poaching in the Tsavo Conservation Area (TCA); and (3) what are the relationships between observed patterns of poaching and human and biophysical variables? Methods The study used elephant-poaching data and various GIS-data layers representing human and environmental variables to describe the spatial and temporal patterns of elephant poaching. The observed patterns were then related to environmental and anthropogenic variables using correlation and regression analyses. Key results Elephant poaching was clustered, with a majority of the poaching occurring in the dry season. Hotspots of poaching were identified in areas with higher densities of roads, waterholes, rivers and streams. The Tsavo East National Park and the Tsavo National Park accounted for 53.7% and 44.8% of all poached elephants, respectively. The best predictors for elephant poaching were density of elephants, condition of vegetation, proximity to ranger bases and outposts, and densities of roads and rivers. Conclusions Predictor variables used in the study explained 61.5–78% of the total variability observed in elephant poaching. The location of the hotspots suggests that human–wildlife conflicts in the area may be contributing to poaching and that factors that quantify community attitudes towards elephant conservation may provide additional explanation for observed poaching patterns. Implications The poaching hotpots identified can be a used as starting point by the Kenya Wildlife Service (KWS) to begin implementing measures that ensure local-community support for conservation, whereas on other hotspots, it will be necessary to beef-up anti-poaching activities. There is a need for Kenya to legislate new anti-poaching laws that are a much more effective deterrence to poaching than currently exist.

Resource Wars and Conflict Ivory: The Impact of Civil Conflict on Elephants in the Democratic Republic of Congo - The Case of the Okapi Reserve

Human conflict generally has substantial negative impacts on wildlife and conservation. The recent civil war (1995-2006) in the Democratic Republic of Congo (DRC) resulted in a significant loss of wildlife, including elephants, due to institutional collapse, lawlessness and unbridled exploitation of natural resources such as minerals, wood, ivory and bushmeat. We used data from distance sampling surveys conducted before and after the war in a protected forest, the Okapi Faunal Reserve, to document changes in elephant abundance and distribution. We employed Generalized Additive Models to relate changes in elephant distribution to human and environmental factors. Populations declined by nearly fifty percent coinciding with a major increase in elephant poaching as indicated by reports of ivory trade during the war. Our results suggest that humans influenced elephant distribution far more than habitat, both before and after the war, but post-war models explained more of the variation. Elephant abundance declined more, closer to the park boundary and to areas of intense human activity. After the war, elephant densities were relatively higher in the centre of the park where they were better protected, suggesting that this area may have acted as a refuge. In other sites in Eastern DRC, where no protection was provided, elephants were even more decimated. Post-war dynamics, such as weakened institutions, human movements and availability of weapons, continue to affect elephants. Survival of remaining populations and recovery will be determined by these persistent factors and by new threats associated with growing human populations and exploitation of natural resources. Prioritizing wildlife protection, curbing illegal trade in ivory and bushmeat, and strengthening national institutions and organizations in charge of conservation will be crucial to counter these threats.

Characterising wide spatial variation in population size structure of a keystone African savanna tree

Elephant impact on trees is of conservation concern in African savannas, but it’s effect on population size structure of heavily utilised species has received little attention. Although studies have shown that the population structure and density of Sclerocarya birrea subsp. caffra (marula), a heavily utilised savanna tree species, varies widely across its range, the causes of this variation are poorly understood. This study aimed to describe and compare these divergent structures and develop an understanding of the relationship between population structure and site characteristics, specifically disturbance. Four distinct groups of population structure were identified: (1) adult dominated populations consisting of only adults and no juveniles or seedlings. The size class distributions (SCDs) of this group were bell-shaped, indicating an unstable population which may have come about through circumstances that no longer occur in these areas, for example human settlement or a massive episodic recruitment event. High impala utilisation of seedlings or rodent seed predation are proposed to be the main cause of the lack of recruitment; (2) rotated sigmoid (or negative J shaped) curves, representing stable population structures, when protected from elephants, as well as at high rainfall sites with elephants, indicating that without elephants and in suitable habitats with elephants, marulas are able to attain a relatively stable size structure and instability is not inherent; (3) juvenile dominated populations with almost no adults. Adults are relegated to a few refugia, where elephants are unable to reach them; (4) juvenile dominated populations consisting of mostly juveniles and few adults. These populations, all exposed to fire and elephants, have “missing size classes” varying between 5 and 40 cm in stem diameter and 2–8 m in height. This unstable structure was most likely caused by fire suppression of juveniles combined with elephant utilisation of individuals in the “missing size classes”. Consistent application of this pressure is postulated to result in the progression from stable to “missing size class” structure, to juvenile or adult dominated populations, and finally to local extirpation, with increasing elephant densities and concomitant utilisation, interacting with fire, rainfall and soil type.

Erratum to: Elephants Also Like Coffee: Trends and Drivers of Human–Elephant Conflicts in Coffee Agroforestry Landscapes of Kodagu, Western Ghats, India

Kodagu district produces 2% of the world's coffee, in complex, multistoried agroforestry systems. The forests of the district harbour a large population of the Asian elephant (Elephas maximus). The combined effects of high elephant density and major landscape changes due to the expansion of coffee cultivation are the cause of human-elephant conflicts (HEC). Mitigation strategies, including electric fences and compensation schemes implemented by the Forest Department have met with limited success. Building on previous studies in the area, we assessed current spatial and temporal trends of conflict, analysed local stakeholders' perceptions and identified factors driving elephants into the estates. Our study, initiated in May 2007, shows that the intensity of HEC has increased over the last 10years, exhibiting new seasonal patterns. Conflict maps and the lack of correlation between physical features of the coffee plantations and elephant visits suggest elephants move along corridors between the eastern and western forests of the district, opportunistically foraging when crossing the plantations. Dung analyses indicate elephants have selectively included ripe coffee berries in their diet. This is, to our knowledge, the first report of wild elephants feeding on coffee berries. If this new behaviour spreads through the population, it will compound an already severe conflict situation. The behavioural plasticity, the multiplicity of stakeholders involved, the difficulty in defining the problem and the limits of technical solutions already proposed suggest that HEC in Kodagu has the ingredients of a "wicked" problem whose resolution will require more shared understanding and problem solving work amongst the stakeholders.

Elephants Also Like Coffee: Trends and Drivers of Human–Elephant Conflicts in Coffee Agroforestry Landscapes of Kodagu, Western Ghats, India

Kodagu district produces 2% of the world's coffee, in complex, multistoried agroforestry systems. The forests of the district harbour a large population of the Asian elephant (Elephas maximus). The combined effects of high elephant density and major landscape changes due to the expansion of coffee cultivation are the cause of human-elephant conflicts (HEC). Mitigation strategies, including electric fences and compensation schemes implemented by the Forest Department have met with limited success. Building on previous studies in the area, we assessed current spatial and temporal trends of conflict, analysed local stakeholders' perceptions and identified factors driving elephants into the estates. Our study, initiated in May 2007, shows that the intensity of HEC has increased over the last 10years, exhibiting new seasonal patterns. Conflict maps and the lack of correlation between physical features of the coffee plantations and elephant visits suggest elephants move along corridors between the eastern and western forests of the district, opportunistically foraging when crossing the plantations. Dung analyses indicate elephants have selectively included ripe coffee berries in their diet. This is, to our knowledge, the first report of wild elephants feeding on coffee berries. If this new behaviour spreads through the population, it will compound an already severe conflict situation. The behavioural plasticity, the multiplicity of stakeholders involved, the difficulty in defining the problem and the limits of technical solutions already proposed suggest that HEC in Kodagu has the ingredients of a "wicked" problem whose resolution will require more shared understanding and problem solving work amongst the stakeholders.

Water-Body Use by Asian elephants in Southern Sri Lanka

We assessed water-body use by elephants through monitoring elephant signs around them. Elephant footprints and dung piles were recorded at 25 water bodies fortnightly for one year. Elephants preferred perennial water bodies and avoided those with temporary human dwellings. Human activities did not significantly affect elephant use of water bodies, suggesting low incidence of activities and behavioral adaptation to them by elephants. Elephant signs at perennial water bodies increased in the dry season. The monitoring technique was able to detect differences in elephant densities in two areas and establish the presence of herds even at low densities. We conclude that outside protected areas, large perennial water bodies represent a preferred resource for elephants, and that assessing elephant signs around water bodies is a useful technique for monitoring elephant presence for management and research purposes.

Increasing elephantLoxodonta africanadensity is a more important driver of change in vegetation condition than rainfall

The impact of African elephantsLoxodonta africana Blumenbuch, 1797 on biodiversity is hotly debated in wildlife management circles with scientists polarised in their views. This polarisation is largely due to the individual experiences of researchers. We aimed to determine whether elephants or rainfall patterns drove changes in vegetation condition (Normalised Difference Vegetation Index; NDVI) by avoiding a site-specific approach and looking at the issue at a broader scale. We used published estimates of elephant population density from 30 sites and recorded the change in density from 1995–1999, from 1999–2002 and from 2002–2006. We also recorded the deviation of annual rainfall from the long-term mean for those periods. We modelled these variables against the change in NDVI between periods using mixed effects models. We found that elephants were more influential in driving change in vegetation condition than rainfall, and this also occurred at one of our individual test sites where long-term data were available (Kruger). Elephants and rainfall combined to drive change in vegetation condition at our other long-term test site (Amboseli). Management activities (fencing, water provision) may cause the differences between the two long-term study sites. Change in productivity driven by rainfall has ramifications for biodiversity, suggesting that elephant derived changes in vegetation productivity (NDVI) also impacts on biodiversity. Thus, this study supports previous findings from individual sites that elephants impact vegetation, however there is also a suggestion that these impacts may vary according to management actions.

Requisite simplicities to help negotiate complex problems.

Decision makers responsible for natural resource management often complain that science delivers fragmented information that is not useful at the scale of implementation. We offer a way of negotiating complex problems by putting forward a requisite simplicity. A requisite simplicity attempts to discard some detail, while retaining conceptual clarity and scientific rigor, and helps us move to a new position where we can benefit from new knowledge. We illustrate the above using three case studies: elephant densities and vegetation change in a national park, the use of rules of thumb to support decision making in agriculture, and the management of salt in irrigation. We identify potential requisite simplicities that can allow us to generate new understanding, lead to action and provide opportunities for structured learning.