African Elephant Populations Research Articles

Modelling the effectiveness of contraception for controlling introduced populations of elephant in South Africa

AbstractRe‐introduced African elephant (Loxodonta africana Blumenbach) populations are growing at very high rates in many of southern Africa’s reserves, have attained densities higher than previously thought possible and may be exhibiting irruptive growth. Active management of such populations is necessary to prevent the potentially negative effects on habitat and biodiversity that are associated with elephant overpopulation. One potentially feasible method of elephant management is immunocontraception, but very little is known about the long‐term effectiveness of this method. Using demographic data from three South African elephant populations, we made model projections of the effects of contraception on population growth rates to determine whether contraception may be a feasible management tool for elephant. In comparison with noncontracepted populations, realistic reductions in population growth rate after 20 years of contraception were projected to be up to c. 64%, with 50% being a very feasible target. Through its ability to reduce population growth rates, immunocontraception should be an effective tool for preventing or minimizing irruption in elephants and, perhaps, other introduced ungulate species.

Aerial Survey Intensity as a Determinant of Estimates of African Elephant Population Sizes and Trends

Population estimates based on strip transect aerial surveys of large herbivores can aid management decisions if estimates are accurate and precise. Because sampling intensities may influence precision, we simulated survey intensities to determine which could yield accurate and precise population estimates and detect population changes for several African elephant (Loxodonta africana) populations. Simulated surveys of hypothetical elephant populations had to cover 5-20% of a study area to yield accurate estimates, but this depended on how density and distribution varied. Precise estimates, however, needed survey intensities greater than 50%. In addition, the detection of typical rates of population change needed greater sampling intensities than those currently used for most elephant surveys. Survey intensity plays an important role in estimating the accuracy and precision of population estimates and the detection of population trends. Population managers should consider existing information on population density, distribution, and survey intensity to design aerial surveys that will yield both accurate and precise estimates.

Behavioural correlates of low relatedness in African elephant core groups of a poached population

Poaching removed adult female elephants, Loxodonta africana , from a social system centred on kin support and female philopatry, creating a natural experiment in many matrifocal African elephant populations. We hypothesized that core groups lacking kin display less cohesion and cooperate and compete with elephants outside of their core group more frequently compared to more discriminating genetically intact core groups. We collected behavioural data on 77 known elephant core groups in Mikumi National Park, Tanzania, across three dry seasons (2003–2005) via focal group and scan sampling during transect and waterhole surveys. Pairwise relatedness was derived by genotyping females at 10 microsatellite loci. We categorized core groups as having low relatedness if their relatedness fell 1 SD below a simulation-generated threshold value; otherwise, they were considered to be highly related. We analysed indexes of cohesion, tolerance, affiliation and agonism to determine the influence of core group composition on the frequency of these behaviours. Cohesion, measured by a proximity index, was primarily driven by the actions of young adult females and was greater in core groups with an old matriarch. Between core groups, tolerance was the most frequent response. Core groups of low-related individuals displayed a higher frequency of affiliation and agonism with other unrelated core groups than did highly related core groups. Thus, less discriminating social behaviour may enable individuals that lack kin to avoid the risks of solitary foraging. However, this comes with the cost of increased agonism, potentially leading to negative consequences for these elephants.

The affects of artificial water availability on large herbivore ranging patterns in savanna habitats: a new approach based on modelling elephant path distributions

AbstractAim Artificial water points are often used in protected savanna ecosystems to maintain populations of large herbivores. However, these interventions lead to increased ranging and foraging pressure and can negatively impact important habitats and species. This study investigated the influence of artificial water provision on the foraging and movement paths of an African elephant population and modelled the impact of changing water availability on sensitive habitat types.Location Tembe Elephant Park (TEP), KwaZulu‐Natal, South Africa.Methods We mapped and classified 414 km of elephant movement and foraging paths in a 300‐km2 fenced protected area. The data were analysed to determine the relationship between path size, distribution and distance to water. We also used a logistic modelling approach to explore the predicted effects of removing artificial water points on path distribution.Results Elephant paths were unevenly distributed throughout the habitats of TEP and the most established and heavily used paths were found closest to water. We also discovered a number of elephant ‘rest areas’ along the paths, which were distinct clearings that tended to be close to water and in sand forest habitat. Our model predicted that the removal of artificial water points would reduce the area crossed by elephant paths by 79%, leading to an 89% reduction in the presence of elephant paths in sand forest.Main conclusions Our study provides further evidence that manipulating surface water availability can be a useful tool for managing large herbivore impacts on vegetation and acts as the basis for further research on the trade‐offs between conservation objectives.

The International Ban on Ivory Sales and its Effects on Elephant Poaching in Africa

The Convention on International Trade in Endangered Species (CITES) secured an agreement in 1989 among its member states to ban the international trade in ivory. This disruption of the international ivory market was intended to reverse a sharp decline in the African elephant population, which resulted from widespread poaching for ivory in the previous decade. The continent's overall population of elephants increased after the ban, but an analysis of elephant population data from 1979 to 2007 found that some of the 37 countries in Africa with elephants continued to lose substantial numbers of them. This pattern is largely explained by the presence of unregulated domestic ivory markets in and near countries with declines in elephant populations.

Activities for Students: Estimating African Elephant Populations (Part 2)

The March 2009 “Activities for Students” presented the first installment of a two-part activity on counting African elephant populations. Part 1 offered two scenarios and asked students to estimate populations by using data given in each one. In part 2, we present the final scenario, noting that the mathematics involved is somewhat more sophisticated than that required for last month's activities. For readers' ease, we re-present the history portion of last month's installment.

Activities for Students: Estimating African Elephant Populations (Part 1)

How many elephants remain in Africa? For a variety of environmental reasons, monitoring the population of elephants in Africa is extremely important. When attempting to estimate the size of an elephant population in a certain area, a researcher must make several decisions. Should the count be conducted from the air or from the ground? Should the elephants in the entire area be counted or only those in a representative area? Should only the elephants themselves be counted, or should signs of their presence—such as dung, tracks, and feeding evidence—be considered as well? Over the past four decades, the approaches used to count elephants have become more statistically refined. This twopart article, to be continued in next month's issue, will explore the mathematics of some of the methods used to count elephants and will present related activities for the mathematics classroom. In this part, we will provide a brief but pertinent history of the African elephant and then present two different methods of counting elephants. This activity may be used as an entire unit or as an application of a particular concept and may be incorporated into several courses. Algebra and geometry students will be able to handle the necessary mathematics. Although this activity informally exposes students to several statistical concepts, a sophisticated understanding of statistics is not required to complete the first two scenarios. The mathematics for the third scenario is more advanced, however; thus, it could be used in higher-level classes such as statistics and calculus. The tasks involved in all three scenarios encourage students to make connections between mathematics and other disciplines and touch on the various implications of mathematical decisions.

Genetic relatedness and disrupted social structure in a poached population of African elephants

We use genetic measures of relatedness and observations of female bonding to examine the demographic signature of historically heavy poaching of a population of free-ranging African elephants. We collected dung samples to obtain DNA and observed behaviour from 102 elephant families over a 25-month period in 2003-2005 in Mikumi National Park, Tanzania. Poaching reduced the population by 75% in the decade prior to the 1989 ivory trade ban; park records indicate that poaching dropped significantly in Mikumi following the ban. Using 10 microsatellite loci, DNA was genotyped in 203 elephants and pair-wise relatedness was calculated among adult females within and between groups. The Mikumi population is characterized by small group size, considerable variation in group relatedness, females with no first-order adult relatives and females that form only weak social bonds. We used gene-drop analysis and a model of a genetically intact pedigree to compare our observed Mikumi group relatedness to a simulated genetically intact unpoached expectation. The majority of groups in Mikumi contain 2 to 3 adults; of these, 45% were classified as genetically disrupted. Bonding, quantified with a pair-wise association index, was significantly correlated with relatedness; however only half of the females formed strong bonds with other females, and relatedness was substantially lower for a given bond strength as compared to an unpoached population. Female African elephants without kin demonstrated considerable behavioural plasticity in this disturbed environment, grouping with other females lacking kin, with established groups, or remaining alone, unable to form any stable adult female-bonds. We interpret these findings as the remaining effect of poaching disturbance in Mikumi, despite a drop in the level of poaching since the commercial trade in ivory was banned 15 years ago.

Long‐Term Impacts of Poaching on Relatedness, Stress Physiology, and Reproductive Output of Adult Female African Elephants

Widespread poaching prior to the 1989 ivory ban greatly altered the demographic structure of matrilineal African elephant (Loxodonta africana) family groups in many populations by decreasing the number of old, adult females. We assessed the long-term impacts of poaching by investigating genetic, physiological, and reproductive correlates of a disturbed social structure resulting from heavy poaching of an African elephant population in Mikumi National Park, Tanzania, prior to 1989. We examined fecal glucocorticoid levels and reproductive output among 218 adult female elephants from 109 groups differing in size, age structure, and average genetic relatedness over 25 months from 2003 to 2005. The distribution in group size has changed little since 1989, but the number of families with tusked old matriarchs has increased by 14.2%. Females from groups that lacked an old matriarch, first-order adult relatives, and strong social bonds had significantly higher fecal glucocorticoid values than those from groups with these features (all females R(2)= 0.31; females in multiadult groups R(2)= 0.46). Females that frequented isolated areas with historically high poaching risk had higher fecal glucocorticoid values than those in low poaching risk areas. Females with weak bonds and low group relatedness had significantly lower reproductive output (R(2)[U]=0.21). Females from disrupted groups, defined as having observed average group relatedness 1 SD below the expected mean for a simulated unpoached family, had significantly lower reproductive output than females from intact groups, despite many being in their reproductive prime. These results suggest that long-term negative impacts from poaching of old, related matriarchs have persisted among adult female elephants 1.5 decades after the 1989 ivory ban was implemented.

Translocation stress and faecal glucocorticoid metabolite levels in free-ranging African savanna elephants

Abstract There are local populations of African elephants (Loxodonta africana) which have increased to levels where they are implicated in altering vegetation types. The local reduction of elephant numbers for wildlife management objectives can involve contraception, killing excess animals, or translocation to alternative habitats. The effects these management decisions can have on the physiological stress response of free-ranging African savanna elephants are still not fully understood. We examined the effect of translocation on faecal glucocorticoid metabolite levels of an African elephant family group,which was translocated within the Kruger National Park, South Africa. We found that translocation resulted in a significant increase in faecal glucocorticoid metabolite levels (up to 646 ng/g wet weight) compared to (1) pre-translocation levels in this group, (2) post-translocation levels in this group, and (3) levels measured in undisturbed ‘control’ groups in the area. However, the faecal glucocorticoid...

Activity Budgets and Sexual Segregation in African Elephants (Loxodonta africana)

Abstract The activity budget hypothesis is 1 of 4 main hypotheses proposed to explain sexual segregation by large herbivores. Because of their smaller body size, females are predicted to have higher mass-specific energy requirements and lower digestive efficiency than males. As a result, females are expected to forage longer to satisfy their nutritional demands. Maintaining the cohesion of a mixed-sex group with differing activity budgets and asynchronous behavioral patterns is increasingly difficult, ultimately leading to spatial segregation of males and females. We tested this hypothesis using data (2002–2005) from 3 distinct populations of African elephants (Loxodonta africana), a species that exhibits marked sexual segregation. Group and individual behaviors were assessed at discrete points in time throughout the day, with a minimum of 10 min between consecutive records. Focal samples of individual male and female elephants also were recorded, with behavioral data logged every minute for 15 min. Data ...

Resource variability, aggregation and direct density dependence in an open context: the local regulation of an African elephant population

1. An emerging perspective in the study of density dependence is the importance of the spatial and temporal heterogeneity of resources. Although this is well understood in temperate ungulates, few studies have been conducted in tropical environments where both food and water are limiting resources. 2. We studied the regulation of one of the world's largest elephant populations in Hwange National Park, Zimbabwe. The study period started in 1986 when the population was released from culling. Using census data we investigated changes in elephant abundance with respect to rainfall and density across the entire park and across waterholes. 3. The population more than doubled since culling stopped. The population increased continuously during the first 6 years, and then fluctuated widely at about 30,000 individuals. Immigration processes must have been involved in the increase of the population size. 4. Population growth rates were negatively related to previous population density by a convex relationship, and negatively related to the ratio of previous population density on annual rainfall by a linear relationship. However, only this latter model (i.e. assuming a fluctuating carrying capacity related to annual rainfall) produced realistic dynamics. Overall, population decreased during dry years when the elephant density was high. 5. During dry years there were fewer waterholes retaining water during the dry season and consequently elephant numbers at waterholes increased, while their aggregation level across waterholes decreased. On the long-run elephant numbers increased only at the less crowded waterholes. 6. We suggest that the interaction between population size and the available foraging range determined by the number of active waterholes during the dry season controls the park population. 7. Our results emphasize the need to understand how key-resource areas cause resource-based aggregation, which ultimately influences the strength of density dependence. More specifically, this study suggests that climate variability strongly affects local elephant population dynamics through changes in surface-water availability. Finally, as dispersal is likely to be an important driver of the dynamics of this population, our results support views that a metapopulation framework should be endorsed for elephant management in open contexts.

Assisted Reproduction in Female Rhinoceros and Elephants – Current Status and Future Perspective

Over the last few decades, rhinoceroses and elephants became important icons in the saga of wildlife conservation. Recent surveys estimate the wild Asian (Elephas maximus) and African (Loxodonta africana) elephant populations to be, at most, 50 250 and 637 600 respectively. For the five rhinoceros species, black (Diceros bicornis), white (Ceratotherium simum), Indian (Rhinoceros unicornis), Javan (Rhinoceros sondaicus) and Sumatran rhinoceros (Dicerorhinus Sumatrensis), the population estimates of 3610, 11 330, 2400, 60 and 300, respectively, are of even greater concern. Protected against habitat loss, poaching and left undisturbed, rhinoceros and elephants reproduce well in the wild. But small and decreasing populations make successful captive management of these taxa increasingly important. In captivity, however, most populations face possible 'extinction' because of historically poor reproductive performance. From the first descriptions of the reproductive anatomy and the oestrous cycle (Laws 1969; Kassam and Lasley 1981; Balke et al. 1988a,b; Plotka et al. 1988; Godfrey et al. 1991) to the present use of advanced assisted reproduction technologies, researchers have strive to understand the function and dysfunction of the reproductive biology of these charismatic species. This paper reviewed the current knowledge on rhinoceros and elephant reproduction biology, reproductive cycle, gestation, dystocia, reproductive pathology, oestrous induction and artificial insemination, sperm sexing, IVF and contraception, and how this knowledge is or might be used to aid species conservation for maximal reproductive efficiency and enhancement of genetic management.

Age, musth and paternity success in wild male African elephants, Loxodonta africana

Male African elephants experience intense intrasexual selection in gaining access to oestrous females, who represent a very scarce and highly mobile resource. An unusual combination of behavioural and physiological traits in males probably reflects this intense selection pressure. Males show prolonged growth, growing throughout much or perhaps all of their long life span (ca. 60e65 years), and they show musth, a physiological and behavioural condition exclusive to elephants, which is manifested by bouts of elevated testosterone and aggression and heightened sexual activity. Most observed matings are by males over 35 years of age and in musth, suggesting that age and musth are both important factors contributing to male reproductive success. Here we report the results of a genetic paternity analysis of a well-studied population of wild African elephants. Patterns of paternity for 119 calves born over a 22-year period showed significant effects of both age and musth on paternity success. Among males in musth, paternity success increased significantly with age until the very oldest age classes, when it modestly declined. When not in musth, males experienced relatively constant, low levels of paternity success at all ages. Thus, despite the importance of both musth and age in determining male paternity success, adult males both in and out of musth, and of all ages, produced calves. In general, however, older males had markedly elevated paternity success compared with younger males, suggesting the possibility of sexual selection for longevity in this species.

Prospects for managing African elephant population growth by immunocontraception: a review

Immunocontraception has been proposed as a tool for managing African elephant populations threatening to ʻoutgrowʼ a wildlife reserve. To date, however, the only immunocontraceptive technique tested on elephant cows is porcine zona pellucida (pZP) vaccination, in which solubilized pZP is injected together with an adjuvant to induce formation of circulating anti-zona pellucida antibodies, which block fertilization. A review of the literature on the use of pZP vaccination in free-ranging mammals reveals that the contraceptive efficacy ranges between 22% and 100% (15 trials, 2 in elephants). A pZP vaccine can be delivered by dart, but at present more than one inoculation is needed to ensure contraceptive antibody titres. Initial studies in elephants suggest that pZP vaccination is safe, even in pregnant animals, does not pass through the food chain and is reversible, at least in the short term. However, little is known about possible long-term side effects. Elephants are social animals that live in matriarchal herds, and inhibiting individual fertility and herd growth may have unforeseen longer-term consequences on behaviour and social structure. There is also a fear that immunization may favour weaker animals by preferentially sterilizing individuals capable of mounting a vigorous immune response, or that animals may become resistant to vaccination. In short, while pZP vaccination appears to be a promising tool for controlling elephant population growth, questions about the long-term side effects need to be answered before use on a large scale can be recommended. Lʼimmuno-contraception est un des moyens proposés pour la gestion des populations dʼéléphants qui menacent de dépasser les capacités dʼune réserve de faune. A ce jour pourtant, la seule technique dʼimmuno-contraception testée sur des femelles éléphants est le vaccin porcin contre la zone pellucide (pZP), une injection de pZP soluble et dʼun adjuvant pour induire la formation dʼanticorps contre la zone pellucide, qui bloque la fertilisation. Une révision de la littérature traitant de lʼutilisation de la vaccination pZP chez des mammifères en liberté révèle que lʼeffet contraceptif a une efficacité qui va de 22% à 100% (15 essais, deux chez lʼéléphant). Un vaccin pZP peut être administré par fléchette, mais pour le moment, il faut plus dʼune inoculation pour garantir le taux dʼanticorps contraceptifs. Les premières études montrent que la vaccination pZP est sans danger pour les éléphants, même pour les femelles enceintes, quʼelle ne passe pas par la chaîne alimentaire et quʼelle est réversible, en tout cas à court terme. Cependant, on sait peu de choses de ses effets secondaires à long terme. Les éléphants sont des animaux sociables qui vivent en groupes matriarcaux, et le fait dʼempêcher la fertilité individuelle et la croissance du groupe peut avoir à long terme des conséquences imprévues sur le comportement et la structure sociale. On peut aussi craindre que lʼimmunisation puisse favoriser des animaux plus faibles en stérilisant de préférence les individus capables de manifester une réponse immunitaire vigoureuse, ou que les animaux deviennent résistants au vaccin. En brèf, si le vaccin pZP semble un outil prometteur pour contrôler la croissance des populations dʼéléphants, il faut dʼabord répondre aux questions sur les effets secondaires à long terme avant de pouvoir en recommander lʼusage à grande échelle.

Tusklessness and tusk fractures in free-ranging African savanna elephants (Loxodonta africana)

The incidence of tusklessness varies between free-ranging African elephant populations. Sex-linked genetic drift predicts 2 outcomes--the condition becomes fixed and sex-specific incidences diverge when populations are small and/or heavily poached. By contrast, for large and intact populations, tusklessness diminishes and there is no variation between sexes. We tested these predictions by comparing sex-specific incidences between 15 populations: a small one with a skewed founder effect towards tusklessness; 5 that had experienced intense levels of poaching; 2 that had been subjected to non-selective culling and 7 that are relatively pristine. Patterns of rainfall were studied of tusk fractures amongst these populations to correct for any effect that acquired tusklessness may have on our predictions. The incidence of tusk fractures was related to annual rainfall, but the mechanism that leads to an increase of the condition in drier areas was not clear Incidences of tusk fractures in free-ranging populations implied that the frequency of acquired bilateral tusklessness is low and should not affect our results. All males had tusks. Tusklessness in females was high in the small skewed founder population and some of those where there was a history of poaching. The incidence is expected to decline if the residual population is large.

Effects of poaching on bull mating success in a free ranging African elephant (Loxodonta africana) population in Tarangire National Park, Tanzania

Poaching and habitat encroachment for human settlement are the two major factors that caused contraction of elephant populations in Africa. While the effects of poaching on many aspects of elephant social systems have been studied, the impacts on mating patterns are not yet understood and such information is still lacking in most African countries. In this study, we used elephant specific-microsatellite DNA to generate genotypes from 86 elephant samples (84 fresh faeces and two tissue samples) from Tarangire National Park (TNP), Tanzania to assess the mating success of individual males. We also tested whether the oldest bulls are more likely to sire most of the offspring in a severely poached population. Genetic paternity analysis was compared to behavioural observations of matings collected over a 3-year period (1998–2001) to determine the success of bull mating strategy. The genotypes of 26 infants, their known mothers and 10 out of 43 potential breeding bulls in TNP were used to assign 31% of the offspring at 80% confidence level to their potential fathers with simulation assuming that 23% (10/43) of the breeding males were sampled. Mating success of individual bull based on both behavioural and genetic data showed that the oldest remaining bulls performed most of the matings and fathered the majority of infants. We speculate that the lifetime fitness of bulls that have survived poaching may be elevated because their period of dominance increases.

Forest Elephant Crisis in the Congo Basin

Debate over repealing the ivory trade ban dominates conferences of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Resolving this controversy requires accurate estimates of elephant population trends and rates of illegal killing. Most African savannah elephant populations are well known; however, the status of forest elephants, perhaps a distinct species, in the vast Congo Basin is unclear. We assessed population status and incidence of poaching from line-transect and reconnaissance surveys conducted on foot in sites throughout the Congo Basin. Results indicate that the abundance and range of forest elephants are threatened from poaching that is most intense close to roads. The probability of elephant presence increased with distance to roads, whereas that of human signs declined. At all distances from roads, the probability of elephant occurrence was always higher inside, compared to outside, protected areas, whereas that of humans was always lower. Inside protected areas, forest elephant density was correlated with the size of remote forest core, but not with size of protected area. Forest elephants must be prioritised in elephant management planning at the continental scale.

Complex phylogeographic history of central African forest elephants and its implications for taxonomy.

BackgroundPrevious phylogenetic analyses of African elephants have included limited numbers of forest elephant samples. A large-scale assessment of mitochondrial DNA diversity in forest elephant populations here reveals a more complex evolutionary history in African elephants as a whole than two-taxon models assume.ResultsWe analysed hypervariable region 1 of the mitochondrial control region for 71 new central African forest elephants and the mitochondrial cytochrome b gene from 28 new samples and compare these sequences to other African elephant data. We find that central African forest elephant populations fall into at least two lineages and that west African elephants (both forest and savannah) share their mitochondrial history almost exclusively with central African forest elephants. We also find that central African forest populations show lower genetic diversity than those in savannahs, and infer a recent population expansion.ConclusionOur data do not support the separation of African elephants into two evolutionary lineages. The demographic history of African elephants seems more complex, with a combination of multiple refugial mitochondrial lineages and recurrent hybridization among them rendering a simple forest/savannah elephant split inapplicable to modern African elephant populations.

Cyto-nuclear genomic dissociation and the African elephant species question

Studies of skull morphology and of nuclear DNA have strongly concluded that African elephants comprise two species. Nonetheless, a recent article [Debruyne (2005). A case study of apparent conflict between molecular phylogenies: the interrelationships of African elephants. Cladistics 21, 31–50] has suggested a single-species model for Loxodonta based on the polyphyly of a single genetic locus, mitochondrial DNA (mtDNA). Discordant patterns between mitochondrial and nuclear DNA markers were subsequently reported in some African savanna elephant populations, further supporting a two-species model, and prompting us to re-examine here the geographic distribution of different elephant morphotypes and their relationship to nuclear and mtDNA phylogeographic patterns. We used exact tests to compare the distribution of forest elephant-typical and savanna elephant-typical characteristics across eight published datasets containing morphological, mtDNA or nuclear DNA data for African elephants. Among the elephants examined by Debruyne (2005), we found that patterns of forest vs. savanna characteristics were significantly different ( p<10 −5) between mtDNA and morphology, suggesting the presence of cyto-nuclear genomic dissociation. We show that the eight African elephant continent-wide datasets compared, including that of Debruyne (2005), together support a two-species model with cyto-nuclear genomic dissociation rather than a one-species model, and together indicate that Africa harbors two species of elephant.