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.     

Foraging site recursion by forest elephants Elephas maximus borneensis

Recursion by herbivores is the repeated use of the same site or plants. Recursion by wild animals is rarely investigated but may be ubiquitous. Optimal foraging theory predicts site recursion as a function of the quality of the site, extent of its last use, and time since its last use because these influence site resource status and recovery. We used GPS collars, behaviour and site sampling to investigate recursion to foraging sites for two elephant Elephas maximus borneensis herds in the Lower Kinabatangan Wildlife Sanctuary, Borneo, over a 12 month period. Recursion occurred to 48 out of 87 foraging sites and was most common within 48 hours or between 151-250 days, indicating two different types ofrecursion. Recursion was more likely to occur if the site had previously been occupied for longer. Moreover, the time spent at a site at recursion was the same as the time spent at the site on the first occasion. The number of days that had passed between the first visit and recursion was also positively correlated with how much time was spent at the site at recursion. Habitat type also influenced the intensity of site-use, with more time spent at recursion within riverine/open grass areas along forest margins compared to other habitat types. Recursion is a common behaviour used by the elephants and its pattern suggests it may be a foraging strategy for revisiting areas of greater value. The qualities of recursion sites might usefully be incorporated into landscape management strategies for elephant conservation in the area [Current Zoology 60 （4）： 551-559, 2014].     

New evidence for hybrid zones of forest and savanna elephants in Central and West Africa

The African elephant consists of forest and savanna subspecies. Both subspecies are highly endangered due to severe poaching and habitat loss, and knowledge of their population structure is vital to their conservation. Previous studies have demonstrated marked genetic and morphological differences between forest and savanna elephants, and despite extensive sampling, genetic evidence of hybridization between them has been restricted largely to a few hybrids in the Garamba region of northeastern Democratic Republic of Congo (DRC). Here, we present new genetic data on hybridization from previously unsampled areas of Africa. Novel statistical methods applied to these data identify 46 hybrid samples – many more than have been previously identified – only two of which are from the Garamba region. The remaining 44 are from three other geographically distinct locations: a major hybrid zone along the border of the DRC and Uganda, a second potential hybrid zone in Central African Republic and a smaller fraction of hybrids in the Pendjari–Arli complex of West Africa. Most of the hybrids show evidence of interbreeding over more than one generation, demonstrating that hybrids are fertile. Mitochondrial and Y chromosome data demonstrate that the hybridization is bidirectional, involving males and females from both subspecies. We hypothesize that the hybrid zones may have been facilitated by poaching and habitat modification. The localized geography and rarity of hybrid zones, their possible facilitation from human pressures, and the high divergence and genetic distinctness of forest and savanna elephants throughout their ranges, are consistent with calls for separate species classification.     

Levels of aloe mortality with and without elephants in the Thicket Biome of South Africa

Studies concerning the influence of African elephants ( Loxodonta africana ) on vegetation have produced contradictory results; some show minimal or no effect while others report significant elephant-induced effects. Elephants are generalist megaherbivores but will selectively feed from preferred plant species. We investigated the mortality of aloe plants (highly preferred food items for elephants) at five sites with elephants (treatment) and five paired sites without elephants (control) in the Eastern Cape Province of South Africa. A significantly higher proportion of aloes were dead at treatment sites and significantly more aloes that had lost their crown (headless) were found at treatment sites compared with controls. We conclude that although the proportions of dead aloes at treatment sites were significantly higher, it remains unclear whether there is a need to be concerned with the potential small-scale extinction of aloes from parts of the Eastern Cape Province. The observed mortality may merely be an artefact of the loss of large herbivores through disease (e.g. rinderpest) and hunting in the past.     

Differences in woody vegetation are unrelated to use by African elephants (Loxodonta africana) in Mkhuze Game Reserve, South Africa

The reintroduction of African elephants into fenced game reserves throughout South Africa has presented managers with several challenges. Although elephants are a natural part of southern African ecosystems, their confinement to fenced protected areas in South Africa has exacerbated their potential to impact their habitats negatively. However, many studies investigating the impact of elephants have failed to control for the effects of other browsers on the vegetative community. In this study, we used location data on an elephant herd to delineate high-use and low-use areas. This paired design allowed us to minimize confounding factors that could explain differences in the structure, diversity and utilization of woody species. We found little evidence to suggest elephant-mediated change in, or selection for, the structure or diversity of woody species; however, our results suggest that elephants may be altering the composition of species by preferentially using areas with higher canopy diversity and by enhancing sapling recruitment. Although stripping of bark was higher in high-use areas, there was no evidence of differential mortality of tree species. Therefore, in our study area, and over the current time scale, elephants are having a negligible impact on the vegetative community.     

Sexual segregation in habitat use by elephants in Chobe National Park, Botswana

We report on a study conducted on free‐ranging African elephants in the woodlands of northern Botswana. We compared bull groups and family units with regard to (1) their patterns of habitat use and (2) their ranging distances from perennial water sources. During the dry season, adult males frequented more habitat types than family units, whereas family units used a wider diversity of habitats than bulls during the wet season. Bulls roamed widely (>10 km) from perennial drinking water in the dry season, when family units congregated within 3.5 km of the rivers. During the wet season, when ephemeral pans were abundant, all elephant groups were found at intermediate distances (5 km) from the rivers. The spacing of elephants in the dry season is consistent with sexual segregation but we reject the hypothesis that this is an outcome of indirect competition for food, because our concurrent studies on elephant feeding ecology found no evidence for intraspecific competition. Instead, we propose that most adult male elephants space themselves to avoid conflict with musth bulls and roam widely in the dry season between discretely distributed feeding ‘hotspots’. The small proportion of males that are in musth remain close to family units to maximize mating opportunities, and family units are unable to range far from water in the dry season. This is due to (1) comparatively high rates of water turn‐over among juveniles and lactating cows and (2) the reduced mobility of neonates.     

Water distribution at local and landscape scales affects tree utilization by elephants in Chobe National Park,Botswana

African elephant distribution and impacts are influenced by water availability. This study investigates the formation of piospheres – gradients of vegetation degradation with increasing proximity to water – at local and landscape scales in Chobe National Park, Botswana. Thirty‐four plots record elephant impact on trees in a transect extending over 60 km from the Chobe River, differentiating between debarking and browsing on branches. Elephant utilization exhibits local patterns nested within a landscape‐level context. At a local scale, branch herbivory decreases with distance from water, while debarking first decreases and then increases again. At a landscape scale, regression and canonical correlation analyses show decreasing debarking with distance from the river. Surprisingly, branch herbivory increases with distance from river, except within the first 10 km where previous studies have focused. Elephant impact on vegetation is both more complex and extensive than previously assumed. Piosphere predictions are upheld at the local scale, with utilization decreasing with distance from water. This does not hold at the landscape scale, however, likely due to seasonal shifts in elephant distribution, diet and the presence of water in ephemeral pans. These findings have important implications for elephant management and emphasize the importance of looking across scales when assessing elephant impact.     

Epigenetic clock and methylation studies in elephants

Age‐associated DNA‐methylation profiles have been used successfully to develop highly accurate biomarkers of age ("epigenetic clocks") in humans, mice, dogs, and other species. Here we present epigenetic clocks for African and Asian elephants. These clocks were developed using novel DNA methylation profiles of 140 elephant blood samples of known age, at loci that are highly conserved between mammalian species, using a custom Infinium array (HorvathMammalMethylChip40). We present epigenetic clocks for Asian elephants (Elephas maximus), African elephants (Loxodonta africana), and both elephant species combined. Two additional human‐elephant clocks were constructed by combining human and elephant samples. Epigenome‐wide association studies identified elephant age‐related CpGs and their proximal genes. The products of these genes play important roles in cellular differentiation, organismal development, metabolism, and circadian rhythms. Intracellular events observed to change with age included the methylation of bivalent chromatin domains, and targets of polycomb repressive complexes. These readily available epigenetic clocks can be used for elephant conservation efforts where accurate estimates of age are needed to predict demographic trends.     

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.     

The movement of African elephants in a human-dominated land-use mosaic

Land outside of gazetted protected areas is increasingly seen as important to the future of elephant persistence in Africa. However, other than inferential studies on crop raiding, very little is understood about how elephants Loxodonta africana use and are affected by human-occupied landscapes. This is largely a result of restrictions in technology, which made detailed assessments of elephant movement outside of protected areas challenging. Recent advances in radio telemetry have changed this, enabling researchers to establish over a 24-h period where tagged animals spend their time. We assessed the movement of 13 elephants outside of gazetted protected areas across a range of land-use types on the Laikipia plateau in north-central Kenya. The elephants monitored spent more time at night than during the day in areas under land use that presented a risk of mortality associated with human occupants. The opposite pattern was found on large-scale ranches where elephants were tolerated. Furthermore, speed of movement was found to be higher where elephants were at risk. These results demonstrate that elephants facultatively alter their behaviour to avoid risk in human-dominated landscapes. This helps them to maintain connectivity between habitat refugia in fragmented land-use mosaics, possibly alleviating some of the potential negative impacts of fragmentation. At the same time, however, it allows elephants to penetrate smallholder farmland to raid crops. The greater the amount of smallholder land within an elephant's range, the more it was utilized, with consequent implications for conflict. These findings underscore the importance of (1) land-use planning to maintain refugia; (2) incentives to prevent further habitat fragmentation; (3) the testing and application of conflict mitigation measures where fragmentation has already taken place.     

Food utilization by insects: Interpretation of observed differences between dry weight and energy efficiencies

Over 80% of the values of approximate digestibility (AD), efficiency of conversion of assimilated food to biomass (ECD) and efficiency of conversion of ingested food (ECI) calculated using energy terms are greater than the corresponding dry weight (DW) values, based on data for over 65 species (38 studies; number of comparative values: AD=139, ECD=128 and ECI=169). Largest positive differences (energy > DW values) are 30 (AD, ECD) and 24 (ECI) percentage points and largest negative differences (energy < DW values) are 9 (AD), 11 (ECD) and 8 (ECI) percentage points. These differences generally are least for ECI (71% of the differences fall between 0 and +5 percentage points), and AD (68%), followed by ECD (only 47% fall between 0 and +5), and they may vary with temperature, food and other factors. The differences tend to increase (esp. for ECD and ECI) when comparing later with earlier instars. Energy > DW efficiency values are commonly expected for AD because of the generally greater energy content of food than feces, and for ECD and ECI because of the generally greater energy content of insect biomass than ingested and assimilated food. Deviations from predicted differences in surveyed literature data are discussed in terms of possible methodological sources of error.

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Résumé Plus de 80% des valeurs de la digestibilité approchée (AD), de l'efficacité de la conversion de la nourriture assimilée en biomasse (ECD) et de l'efficacité de la conversion de l'aliment ingéré (ECI), calculées en termes énergétiques, et obtenus à partir de données sur 65 espèces, sont supérieures aux valeurs des poids secs correspondants (DW): 38 études; valeurs comparatives: AD=139, ECD=128, ECI=169. Les plus importantes différences positive (énergie>valuers DW) sont de 30 (AD, ECD) et de 24 (ECI) centièmes (les différences négatives les plus fortes = 9 (AD), 11 (ECD) et 8 (ECI); ces différences sont moindres pour ECI (71% des différences tombent à 0 et +5 centièmes), et AD (68%), suivi de ECD (seulement 47% tombent entre 0 et +5). Ces différences peuvent varier avec la température, l'alimentation et d'autres facteurs; les différences tendent à croître (particulièrement pour ECD et ECI) quant on les compare plus tard avec des stades plus précoces. Energie > aux valeurs d'efficacité DW sont généralement attendues pour AD par suite du contenu énergétique supérieur de l'aliment à celui des excréments, et pour ECD et ECI par suite du contenu énergétique généralement plus élevé pour la biomasse de l'insecte que pour l'aliment ingéré et assimilé. Les écarts par rapport aux différences prédites dans les données de la littérature examinée sont analysées en considérant les sources possibles d'erreurs méthodologiques.

     

Behavioural inbreeding avoidance in wild African elephants

The costs of inbreeding depression, as well as the opportunity costs of inbreeding avoidance, determine whether and which mechanisms of inbreeding avoidance evolve. In African elephants, sex-biased dispersal does not lead to the complete separation of male and female relatives, and so individuals may experience selection to recognize kin and avoid inbreeding. However, because estrous females are rare and male-male competition for mates is intense, the opportunity costs of inbreeding avoidance may be high, particularly for males. Here we combine 28 years of behavioural and demographic data on wild elephants with genotypes from 545 adult females, adult males, and calves in Amboseli National Park, Kenya, to test the hypothesis that elephants engage in sexual behaviour and reproduction with relatives less often than expected by chance. We found support for this hypothesis: males engaged in proportionally fewer sexual behaviours and sired proportionally fewer offspring with females that were natal family members or close genetic relatives (both maternal and paternal) than they did with nonkin. We discuss the relevance of these results for understanding the evolution of inbreeding avoidance and for elephant conservation.     

Social factors influence ovarian acyclicity in captive African elephants (Loxodonta africana)

Nearly one-third of reproductive age African elephants in North America that are hormonally monitored fail to exhibit estrous cycle activity, which exacerbates the nonsustainability of the captive population. Three surveys were distributed to facilities housing female African elephants to determine how social and environmental variables contribute to cyclicity problems. Forty-six facilities returned all three surveys providing information on 90% of the SSP population and 106 elephants (64 cycling, 27 noncycling and 15 undetermined). Logistic analyses found that some physiological and social history variables were related to ovarian acyclicity. Females more likely to be acyclic had a larger body mass index and had resided longer at a facility with the same herdmates. Results suggest that controlling the weight of an elephant might be a first step to helping mitigate estrous cycle problems. Data further show that transferring females among facilities has no major impact on ovarian activity. Last, social status appears to impact cyclicity status; at 19 of 21 facilities that housed both cycling and noncycling elephants, the dominant female was acyclic. Further studies on how social and environmental dynamics affect hormone levels in free-living, cycling elephants are needed to determine whether acyclicity is strictly a captivity-related phenomenon. Zoo Biol 28:1–15, 2009. © 2008 Wiley-Liss, Inc.     

Drought mortality of bush elephants in Hwange National Park, Zimbabwe

African bush elephants inhabiting the undeveloped Kalahari Sands region of Hwange National Park, Zimbabwe are subject to episodic mortality during droughts. We monitored the drought‐related mortality of elephants in Hwange National Park over the course of an extended drought between 1993 and 1995. The drought‐related mortality of elephants was higher during 1994 than 1995, despite significantly higher rainfall in 1994 than 1995. We found significant differences in the age‐specific mortality of elephants during 1994 and 1995. The cumulative mortality profile from this study differed significantly from previous die‐offs at this site, with a higher mortality among adult age classes than that reported from earlier studies in Hwange National Park. The effective duration of the rainy season, not total annual precipitation, appears to be the best predictor for the potential severity of drought mortality among elephants in the Kalahari Sands habitats of Hwange National Park.     

Seasonal variation in forages utilized by the African buffalo (Syncerus caffer) in the succulent thicket of South Africa

The succulent thicket of the Eastern Cape, South Africa, is characterized by densely wooded vegetation that is dominated by succulents with little understory of ephemeral and weakly perennial grasses and forbs. Studies have developed around the question: how do bulk grazers such as the African buffalo (Syncerus caffer) survive in the succulent thicket? In this study, the diet of the African buffalo at the Great Fish River Reserve (GFRR) was studied in two seasons (wet and dry). The diet profile was assessed from faecal matter, using the micro‐histological analysis method. During the wet season, grass species contributed 72% to the diet while 28% was contributed by browse species. In the dry season there was a significant increase in the intake of browse by 5% (χ² = 19.94, df = 11, P < 0.05). There were species that were neglected in the wet season but became principal dietary items in the dry season, these included Setaria neglecta, Cymbopogon plurinodis, Capparis sepiaria and Portulacaria afra. Diet quality, as estimated from faecal samples, suggested that the buffalo were nutritionally stable; however, the presence of sarcoptic mange in the buffalo suggests nutritional stress.