Estimating forest elephant density in Sapo National Park (Liberia) with a rainfall model

The number of elephant dung‐piles lying on the forest floor is a function of the number of elephants present and the rainfall in the 2 preceding months. We present the results of a stochastic model that describes this relationship and we show how it can be used to estimate elephant numbers. The data from a survey in Sapo NP (Liberia) in 1989 are used as an example. The dung‐pile density was estimated at 152 km^?2 with confidence interval from 72 to 322, and the number of elephants was estimated to be 313 with confidence interval from 172 to 617.     

Seed dispersal of Acacia erioloba by African bush elephants in Hwange National Park, Zimbabwe

Approximately two-thirds (64%) of all dry season samples of elephant dung analysed during a 3-year study in the Main Camp subregion of Hwange National Park, Zimbabwe, contained seed and/or pod materials from Acacia erioloba . Most seeds were recovered intact and actively germinating seeds were not uncommon. Very little pod mass relative to seed mass was recovered in most instances, with pod fragments recorded from only 56% of all exhaustively sampled elephant dung piles containing A. erioloba fruit materials. Nonetheless, large pod fragments and even entire intact pods were recovered occasionally from elephant dung. Seeds and pods of A. erioloba may comprise 12% or more of total wet-weight dung mass; individual dung piles were found which contained > 5000 A. erioloba seeds. Birds and smaller mammals search out and consume A. erioloba seeds present within elephant dung piles. The findings of this study indicate that potential digestibility of A. erioloba seeds for bush elephants ( Loxodonta africana africana ) may be much higher than expected from previous studies. In controlled feeding trials with captive bush elephants (age 11–15 years old) maintained on predominantly free-range dry season diets, the estimated efficiency of digestion for A. erioloba seeds consumed in pods was 81% to 96%, with a gut-transit time of between 24.5 and 36.0 h. On the basis of throughput times determined in experimental feeding trials, potential elephant-dispersal distances of 20–50 km are predicted for A. erioloba in the Kalahari Sands landscapes of southern central Africa.     

Seasonality in elephant dung decay and implications for censusing and population monitoring in south-western Cameroon

Dung decay rates have been used in the past to correct elephant dung counts to estimates of population numbers. These assume that the dung is in a ‘steady state’ where production rates are equal to disappearance rates. The inter‐seasonal variation in decay rates, however, has never been fully investigated for elephant dung. This study, in the Banyang‐Mbo Wildlife Sanctuary in SW Cameroon, investigated whether a single dung decay rate is really appropriate when converting dung counts to population density estimates. A total of 870 fresh elephant dung‐piles were monitored until they had completely decayed, with at least 60 fresh dung piles located each month of the year between July 1994 to June 1995. The elephant dung decay rate obtained was 55.6% to 66.7% lower than those obtained for the rainforests of Gabon. This has implications for using decay rates obtained elsewhere to compute elephant densities from dung counts. Statistically significant differences were found in the mean duration of dung‐piles between different months and different seasons. Environmental variables, with the exception of rainfall, did not aid in predicting the duration of elephant dung‐piles. The model of Plumptre & Harris was used to estimate the standing crop of dung at any particular time of the year. The results show that, if there was no emigration of elephants from the population, then there was only a three‐month period when the dung was in a ‘steady state’. If emigration occurred during the wet season as is thought to occur then there was no period of ‘steady state’.     

Dung survey bias and elephant population estimates in southern Mozambique

We used dung surveys to estimate population size and extracted an age structure from boli diameters for the elephants living in the Maputo Elephant Reserve. Our estimate was based on published defecation rates, dung decay rates, distance-sampling techniques and 1,672 dung piles encountered on 204 line-transects. The reserve had at least 311 (95% CI: 198–490) elephants at a density of 0.60 (95% CI: 0.38–0.94) per km². However, observer bias reduced effective strip widths and inflated estimates and their confidence limits. The age structure extrapolated from dung measurements indicated few newborn calves compared with other populations. To detect population changes of 2–5% at 80% power, dung surveys should be carried out every second year for the next 20 years using 100 transects of at least 500 m each. Comparison with a 1995 dung survey suggests that the population is stable and that previous fears of a major population decline during the civil war have no foundation.     

Relatedness and demography of African forest elephants: inferences from noninvasive fecal DNA analyses

African forest elephants (Loxodonta cyclotis) are genetically and morphologically distinct from their savannah counterparts, but their biology remains poorly understood. In this study, I use noninvasive fecal DNA analyses to examine the relatedness structure and historical demography of forest elephants at 2 sites in SW Gabon, central Africa. Pairwise relatedness values calculated between 162 elephant individuals genotyped at 8 microsatellite loci were significantly higher within spatially associated dung piles than between random pairings for one site. First- and second-order relatives were most commonly detected among dung piles from adult female pairs and adult females and juveniles. Pairwise relatedness estimates suggested that, like savannah elephants, forest groups are largely composed of adult females, their sisters, and juvenile offspring. Associations between males, and groups containing juveniles from multiple related females, were detected but at much lower frequency. Analysis of mitochondrial d-loop sequences from 70 elephant individuals identified 2 haplogroups in SW Gabon.     

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

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

How reliable are dung counts for estimating elephant numbers?

Dung counts are the most commonly used techniques for estimating elephant numbers in forests, yet there is considerable scepticism concerning their accuracy. Published accounts of dung counts show that they give estimates similar to those from other methods for vertebrates ranging in size from lizards to elephants. For ungulates, macropods and elephants there are strong correlations between estimates from dung counts and other methods. Thus, dung counts are as accurate or inaccurate as other methods for estimating vertebrate numbers, including elephants. Dung counts for elephants give estimates that are as precise as, and sometimes more precise than, those from aerial surveys of elephants. This is because the variance in dung density is usually low and results in a lower than expected variance for the final elephant estimate when combined with the variances of defecation and decay rates. Dung counts may be more appropriate than aerial surveys for monitoring small or declining elephant populations.     

Physiological indicators of stress in African forest elephants (Loxodonta africana cyclotis) in relation to petroleum operations in Gabon,Central Africa

Aim Human activities are major determinants of forest elephant (Loxodonta africana cyclotis) distribution in Gabon, but the types and intensity of disturbance that elephants can tolerate are not known. We conducted dung surveys within the Gamba Complex of Protected Areas in SW Gabon to examine (1) the feasibility of noninvasive faecal analyses for monitoring stress physiology, and (2) the influence of petroleum operations on stress levels in forest elephants. Location Gabon, Central Africa. Methods We identified multiple dung piles from the same individual by matching their eight‐locus microsatellite genotypes, and measured faecal concentrations of glucocorticoid metabolites as an indicator of stress in areas subject to different levels of disturbance: (1) Loango National Park (2) an ‘industrial corridor’ dominated by oil fields, and (3) a nearby area of human settlements. Results We obtained unique microsatellite genotypes and faecal glucocorticoid metabolite (FGM) concentrations for 150 forest elephant individuals, which is the largest hormonal data set for wild African forest elephants to date. Adults exhibited higher mean FGM concentrations than juveniles, and in contradiction of our expectations of chronic stress around oil fields, elephants in Loango National Park exhibited significantly higher FGM concentrations than elephants in the industrial corridor. Main conclusions We argue that forest elephants in the industrial corridor of the Gamba Complex have become acclimated to oil fields, resulting in part from oil company regulations that minimize stressful interactions between elephants and petroleum operations. Our findings for a flagship species with substantial ecological requirements bode well for other taxa, but additional studies are needed to determine whether oil operations are compatible over their life span with rain forest ecosystems in Central Africa.     

Rainfall and the population dynamics of elephant dung‐piles in the forests of southern Ghana

Decaying dung‐piles were observed at three sites in the lowland forests of southern Ghana. Time to disappearance was inversely related to rainfall in the month of deposition. The monthly survival of each age‐class decreased with age and was inversely proportional to rainfall in the month of deposition. A simulation revealed that if elephant numbers and defaecation rates are constant, then dung density in a given month will be governed by rainfall in the two preceding months. Changes in annual rainfall and its monthly distribution in southern Ghana mean that dung‐pile densities will vary from one month to the next, and between the same months in different years, even if elephant numbers are constant. Thus dung counters must take rainfall into account. A new method of censusing elephants in Ghana is presented, and suggestions are made for improving elephant counts in central African forests.     

Population structure and behaviour of crop-raiding elephants in Kibale National Park, Uganda

We examined patterns of crop raiding by elephants across gender and age classes in relation to elephant life history and sociobiology and estimated the quantitative contribution of crops to elephant diet in Kibale National Park (KNP). Elephant dung‐boli sizes were used to estimate age and sex, while the presence of crop remains in the dung of crop‐raiding elephants was used as evidence of repeated raiding. To estimate the expected proportion of elephants raiding per age class, the age distribution of raiders was compared with the age distribution of all KNP elephants. Elephants raiding crops were predominantly males. They began raiding in expected proportions at 10–14 years while a higher than expected proportion raided crops at 20–24 years. These results suggest that crop raiding is initiated at an age when male elephants leave their families and a large proportion of elephants raid when they are approaching reproductive competition. Evidence from dung of crop raiders, suggests that repeated raiding increases with age. Crop raiders derived 38% of their daily forage from the short time spent raiding, consistent with expectations of foraging theory. Males may be more likely to learn crop raiding because they are socially more independent and experience intense mating competition than females.     

Distribution of savannah elephants (Loxodonta africana africana Blumenbach 1797) within Nazinga game ranch,Southern Burkina Faso

We tested the hypothesis that elephant distribution inside the Nazinga Game Ranch (Southern Burkina Faso) during the wet season is influenced by villages outside, while in the dry season elephants are restricted only by water. Occupancy was evaluated by recording elephant dung‐piles on 54 line transects in each of three seasons: wet 2006, dry 2007 and dry 2008. We measured the distance of each transect from nearest villages, nearest permanent water sources, nearest guard posts and tourist camps. The results were unexpected: elephant occupancy in the wet season was independent of villages but influenced by poaching, while their occupancy in both dry seasons was determined by the proximity of villages as well as water. In the dry season, elephants were attracted to villages by grain stores and fruiting trees. There has been a dramatic shift in the dry season distribution of elephants, and consequently in browsing pressure, over the last two decades. We suggest that this change is a consequence of the expansion of human activities outside the ranch. This study shows that the effects of growing human disturbance on elephant populations in small protected areas are not predictable. Correcting for spatial autocorrelation had a negligible effect upon the models.     

Forest Elephants: Tree Planters of the Congo

The abundance of large vertebrates is rapidly declining, particularly in the tropics where over-hunting has left many forests structurally intact but devoid of large animals. An urgent question then, is whether these 'empty' forests can sustain their biodiversity without large vertebrates. Here we examine the role of forest elephant ( Loxodonta africana cyclotis ) seed dispersal in maintaining the community structure of trees in the Ndoki Forest, northern Congo. Analysis of 855 elephant dung piles suggested that forest elephants disperse more intact seeds than any other species or genus of large vertebrate in African forests, while GPS telemetry data showed that forest elephants regularly disperse seeds over unprecedented distances compared to other dispersers. Our analysis of the spatial distribution of trees from a sample of 5667 individuals showed that dispersal mechanism was tightly correlated with the scale of spatial aggregation. Increasing amounts of elephant seed dispersal was associated with decreasing aggregation. At distances of<200 m, trees whose seeds are dispersed only by elephants were less aggregated than the random expectation, suggesting Janzen–Connell effects on seed/seedling mortality. At the landscape scale, seed dispersal mode predicted the rate at which local tree community similarity decayed in space. Our results suggest that the loss of forest elephants (and other large-bodied dispersers) may lead to a wave of recruitment failure among animal-dispersed tree species, and favor regeneration of the species-poor abiotically dispersed guild of trees.     

Feeding patterns of elephants at the Atherstone Collaborative Nature Reserve

The African savannah elephant (Loxodonta africana Blumenbach) is a generalist herbivore that relies on widely distributed resources. Vegetation decline, aggravated by these elephants, can compromise local conservation efforts. Thus it imperative to understand the factors that drive them to consume specific plant species and plant parts. The objective of our study was to investigate the feeding patterns of African savannah elephants in the enclosed bushveld savannah at the Atherstone Collaborative Nature Reserve in South Africa. For 1 year, we examined elephant selection of woody versus herbaceous vegetation, and identified which plant species and parts were preferentially consumed. We accomplished this by directly observing feeding elephants, and by utilizing data collected on elephant footprints, dung piles, stripped bark and broken branches. We further conducted vegetation surveys to determine selection frequency relative to species abundance. Elephants showed a preference for different plant parts consumption in the feeding plots. In total, leaves, branches and bark contributed mostly to their diet. Seasonal selection patterns showed an increasing proportion of bark and branch consumption during the dry season.     

Synchronization of defaecation in the African elephant (Loxodonta africana)

The ecological significance of defaecation in African elephants ( Loxodonta africana ) has been discussed from a number of points of view. Dropping counts have been used to investigate population size and movements (Wing & Buss, 1970; Laws, Parker & Johnstone, 1975); the chemical composition of dung has been examined (Dougall, 1963; Weir, 1972); and dung decomposition and its role in nutrient cycles have been described (Anderson & Coe, 1974). Defaecation in captive African elephants has been examined (Coe, 1972) and food consumption of wild elephant herds has been calculated from data on gross assimilation efficiency and dung production (Coe, 1972; Rees, 1982). This paper presents evidence of a synchronization of defaecation in elephants and discusses its possible ecological significance.     

Feral horses dung piles as potential invasion windows for alien plant species in natural grasslands

Small scale disturbances could act as patches that provide sites for the colonization of competitively inferior species, promoting the establishment of non-native species in some cases. We analyzed the vegetation associated with feral horse dung piles in montane pampas grasslands in Mid-East Argentina and described the changes following their abandonment, evaluating whether dung piles act as invasion windows, allowing the entrance of alien plant species. We estimated the portion of the study area directly covered by horse manure and dung height was used to estimate the time elapsed after the abandonment of each pile. Vegetation replacement on dung piles of different ages was assessed and compared with grassland controls using discriminant analysis. We used regression analysis to look for changes in vegetation cover, species richness, species diversity and evenness in response to height (age) of the dung piles, and principal component analyses (PCA) to identify groups of plants associated with different successional stages. We compared cover of alien plant species on dung piles with grassland controls using one-way ANOVA. On average, 2.5% of the study area was covered by horse dung. Total vegetation cover, species richness, diversity and evenness increased after the piles were abandoned. Characteristic plant groups were associated with initial, middle and last phases of the studied succession. Vegetation on the dung piles significantly differed from that in grassland controls and two species were consistently associated with dung piles: the invasive Red Star Thistle, Centaurea calcitrapa, and a native grazing-intolerant grass, Nassella clarazii. Non-native species cover was also higher in dung piles than in control plots. Dung piles cover a significant portion of grassland area in our study site, produce significant changes in the vegetation and are associated with some invasive alien plants that could eventually colonize more pristine areas in the vicinity. On the other hand, they might represent refuges for palatable species, since horses seem to avoid them for grazing.     

Dung as a potential medium for inter-sexual chemical signaling in Asian elephants (Elephas maximus)

Chemical signaling is a prominent mode of male-female communication among elephants, especially during their sexually active periods. Studies on the Asian elephant in zoos have shown the significance of a urinary pheromone (Z7-12:Ac) in conveying the reproductive status of a female toward the opposite sex. We investigated the additional possibility of an inter-sexual chemical signal being conveyed through dung. Sixteen semi-captive adult male elephants were presented with dung samples of three female elephants in different reproductive phases. Each male was tested in 3 separate trials, within an interval of 1-3 days. The trials followed a double-blind pattern as the male and female elephants used in the trials were strangers, and the observer was not aware of the reproductive status of females during the period of bioassays. Males responded preferentially (P<0.005), in terms of higher frequency of sniff, check and place behavior toward the dung of females close to pre-ovulatory period (follicular-phase) as compared to those in post-ovulatory period (luteal-phase). The response toward the follicular phase samples declined over repeated trials though was still significantly higher than the corresponding response toward the non-ovulatory phase in each of the trials performed. This is the first study to show that male Asian elephants were able to distinguish the reproductive phase of the female by possibly detecting a pre-ovulatory pheromone released in dung.     

Estimating the defaecation rate of the African forest elephant (Loxodonta cyclotis) in Banyang-Mbo Wildlife Sanctuary, south-western Cameroon

Defaecation rate is an important parameter in the conversion of dung counts to elephant numbers, yet estimates of elephant defaecation rates are available for a few sites, especially rainforest sites. The Banyang‐Mbo Wildlife Sanctuary in south‐western Cameroon is no exception in this regard. We tracked a radio‐collared herd of four forest elephants, counted their fresh droppings in two 24‐h periods each month in 36 consecutive months. Our results show a mean defaecation rate of 15.9 [95% CI (12.2–19.7)] dung piles per elephant per day. We found significant monthly and inter‐annual variation in defaecation rates with implications for their predictability and forest elephant surveys. In particular, our results show that mean defaecation rates are higher for the wettest period of the year than the relatively dry months.     

A population survey of forest elephants (Loxodonta africana cyclotis) in northern Congo

From February to April of 1989 transects were run in four forested areas of northern Congo (Brazzaville) to census elephant populations using dung counts. A total of 401.0 km of line transects was completed during the survey. An overall extrapolated density of 0.7 elephants/km² was obtained with a variation from 0.3 to 0.9 elephants/km². This study shows for the first time that elephants occur in high densities in a number of sites in northern Congo. When elephant dung density is plotted against distance from the nearest village for each transect a significant positive linear correlation results. Based on this correlation we hypothesize that the population of elephants in much of northern Congo is high. Local reports and our own observations indicate that elephant poaching is heavy in northern Congo and that the CITES ban on trade in African elephant ivory has had a limited effect on the level of poaching.     

Counting elephants in Montane forests: some sources of error

The dung count method is widely used to estimate elephant numbers in forests. It was developed in the lowland forests of Central Africa but it is also used in Montane forests in eastern Africa. Using data collected on Mount Kenya and computer simulations, this paper explores the following issues associated with dung surveys in Montane forests:

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  High rainfall at 3000 m altitude on Mount Kenya was expected to accelerate dung pile decay but no significant difference was found between 3000 and 2500 m where less rain falls, possibly because high rainfall at 3000 m is counteracted by lower temperatures;
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  Physical obstacles make it difficult to walk long, straight transects in Montane forests. Deviating from a straight line pushes the distribution of distance measurements from dung piles to the transect centre line (pdist) towards a negative exponential (NE), which complicates data analysis and may give inaccurate estimates. Using short transects largely alleviate this problem;
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  Analysis of dung count simulations shows that the expected sightability curve of pdist pushes towards a NE with increasing numbers of obstacles blocking the view, even along perfectly straight transects;
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  Extrapolating measured dung density to map area on Mount Kenya resulted in an underestimate of c. 13%. An unstratified correction of map area to ground area for Montane areas would be biased because of the strong tendency for elephants to avoid steeply sloping areas.