Rudi J. van Aarde

A Meta-Analysis of the Impact of African Elephants on Savanna Vegetation

Abstract Large herbivores such as elephants (Loxodonta africana) apparently have a negative impact on woody vegetation at moderate to high population densities. The confounding effects that fire, drought, and management history have may complicate assignment of such impacts to herbivory. We reviewed 238 studies published over 45 years and conducted a meta-analysis based on 21 studies that provided sufficient information on response of woody vegetation to elephants. We considered size and duration of studies, elephant densities, rainfall, fences, and study outcomes in our analysis. We detected a disproportionate citation of 20 published studies in our database, 15 of which concluded that woody vegetation responded negatively to elephants. Our analysis showed that high elephant densities had a negative effect on woody vegetation but that rainfall and presence of fences influenced these effects. In arid savannas, woody vegetation always responded negatively to elephants. In transitional savannas, an increase in elephant densities did not influence woody vegetation response. In mesic savannas, negative responses of woody vegetation increased when elephants occurred at higher densities, whereas elephants confined by fences also had more negative effects on woody plants than elephants that were not confined. Our analysis suggested that rainfall and fences influenced elephant density related impact and that research results were often site-specific. Local environmental conditions and site-specific objectives should be considered when developing management actions to curb elephant impacts on woody vegetation.

Solutions for elephant Loxodonta africana crop raiding in northern Botswana: moving away from symptomatic approaches

Conflict between people and elephants in Africa is widespread yet many solutions target the symptoms, rather than the underlying causes, of this conflict. To manage this conflict better the underlying causes of the problem need to be examined. Here we examine factors underlying spatial use by elephants and people along the Okavango Panhandle in Ngamiland, northern Botswana, to provide ways to address the causes of the conflict between elephants and people. We found that (1) elephant spatial use was a function of season, (2) spatial use did not differ between breeding herds and bull groups, (3) spatial use by elephants and people only overlapped significantly at night, during the dry season, (4) crop raiding by elephants was a function of season and social grouping, and (5) crop raiding by elephants had social and economic implications. Based on these results we suggest measures to manipulate elephant spatial use to reduce the causes of this conflict. We also reflect on present compensation measures for elephant crop damage and advocate that a more direct performance payment approach may benefit both the Botswana Government and local farmers.

Species Inequality in Scientific Study

Some conservationists argue for a focused effort to protect the most critically endangered species, and others suggest a large-scale endeavor to safeguard common species across large areas. Similar arguments are applicable to the distribution of scientific effort among species. Should conservation scientists focus research efforts on threatened species, common species, or do all species deserve equal attention? We assessed the scientific equity among 1909 mammals, birds, reptiles, and amphibians of southern Africa by relating the number of papers written about each species to their status on the International Union for Conservation of Nature Red List. Threatened large mammals and reptiles had more papers written about them than their nonthreatened counterparts, whereas threatened small mammals and amphibians received less attention than nonthreatened species. Threatened birds received an intermediate amount of attention in the scientific literature. Thus, threat status appears to drive scientific effort among some animal groups, whereas other factors (e.g., pest management and commercial interest) appear to dictate scientific investment in particular species of other groups. Furthermore, the scientific investment per species differed greatly between groups-the mean number of papers per threatened large mammal eclipsed that of threatened reptiles, birds, small mammals, and amphibians by 2.6-, 15-, 216-, and more than 500-fold, respectively. Thus, in the eyes of science, all species are not created equal. A few species commanded a great proportion of scientific attention, whereas for many species information that might inform conservation is virtually nonexistent.

Population control: African elephants and contraception

Protected from hunting and provided with access to water-holes during droughts, elephant numbers can double in a decade, severely damaging natural vegetation and the many species dependent upon it. Culling is an effective but controversial control strategy, so Fayrer-Hosken et al. have assessed the efficacy of using immunocontraception through vaccination, concluding that this could be a practical way of controlling elephant numbers. However, an intervention feasible in reproductive physiology may not be a practical way to control a population. Fayrer-Hosken et al. have not considered calculations that undermine the practicality of their method, nor alternative management strategies.

Geographical and taxonomic biases in research on biodiversity in human-modified landscapes

Biodiversity persistence in human-modified landscapes is crucial for conservation and maintaining ecosystem services. Studies of biodiversity in landscapes where humans live, work, and extract resources could support defensible policy-making to manage land-use. Yet, research should cover relevant regions, and biases in study topics should not lead to gaps in the evidence base. We systematically reviewed the literature of biogeography in human-modified landscapes published in eight eminent biogeography, conservation, and ecology journals to assess geographical bias among biomes and geopolitical regions and taxonomic bias among species groups. We compared research output per biome to area, biome type, species richness, proportion of transformed land, and the ratio of transformed to protected land. We also compared research output per geopolitical region to area, proportion of transformed land, the ratio of transformed to protected land, and human population density. Research output was distributed unequally among biomes, geopolitical regions, and species groups. Biome type was a clear factor in research bias, and forest biomes were the subject of 87% of papers, while species richness was not generally associated with bias. Conservation in human-modified landscapes is most important in regions with low protected area coverage, high land conversion, and high pressure from human populations, yet the distribution of published papers did not generally reflect these threats. Seventy-five percent of studies focused on the Americas and Europe, while Africa and Asia were critically understudied. Taxonomically, plants and invertebrates were the most studied groups; however, research output was not correlated with species richness per group. Protected areas alone will not conserve biodiversity in the long term. Thus, a strong biogeographical evidence base is required to support policies for biodiversity maintenance on human-modified land. Under-studied regions and species groups deserve further research to elucidate what, where, and how biodiversity persists in human-modified landscapes to inform conservation policy and enhance efficacy.

Elephant survival, rainfall and the confounding effects of water provision and fences

Elephant are increasing across some areas of Africa leading to concerns that they may reduce woodlands through their feeding. Droughts may help limit elephant numbers, but they are generally both episodic and local. To explore more general impacts of rainfall, we examine how its annual variation influences elephant survival across ten sites. These sites span an almost coast-to-coast transect of southern Africa that holds the majority of the ~500,000 remaining savanna elephants. Elephants born in high rainfall years survive better than elephants born in low rainfall years. The relationship is generally weak, except at the two fenced sites, where rainfall greatly influenced juvenile survival. In these two sites, there are also extensive networks of artificial water. Rainfall likely affects elephant survival through its influence on food. The provision of artificial water opens new areas for elephants in the dry season, while fencing restricts their movements in the wet season. We conclude that the combination of these factors makes elephant survival more susceptible to reductions in rainfall. As a result, elephants living in enclosed reserves may be the first populations to feel the impacts of global warming which will decrease average rainfall and increase the frequency of droughts. A way to prevent these elephants from damaging the vegetation within these enclosed parks is for managers to reduce artificial water sources or, whenever practical, to remove fences.

Histo- and cytophysiology of the lactating mammary gland of the African elephant (Loxodonta africana)

Abstract The lactating mammary gland of the African elephant (Loxodonta africana) has been studied with a panel of morphological techniques focusing on (1) the functional changes during the secretory process, (2) proliferative process [by application of proliferating cell nuclear antigen (PCNA) immunohistochemistry] and apoptotic phenomena [by use of the TUNEL technique] in the individual lobules, and (3) components of milk and milk-fat-globule membrane. In the lactating gland, the lobules are variably differentiated; within a lobule, however, the alveoli are usually similarly differentiated. The morphology of their alveoli suggests a classification of the lobules into types 1–3. Lobules of type 1 are composed of immature tubular alveoli with mitotic figures and numerous PCNA-positive nuclei; advanced type 1 alveoli contain abundant glycogen and specific secretory granules. Lobules of type 2 are further subdivided. In type 2a lobules, the epithelial cells of the alveoli form tall apical protrusions, which in part are occupied by small lipid droplets and which are pinched off in an apocrine fashion. The number of lysosomes varies considerably. Type 2b is the most common type, with striking basal membrane foldings, abundant rough endoplasmic reticulum cisterns, large Golgi apparatus, numerous mitochondria, lipid droplets, and protein vesicles with 30- to 90-nm-wide casein micelles. The lipid droplets are pinched off with minimal amounts of cytoplasm. Type 2c is composed of alveoli with a cuboidal epithelium and few signs of secretory activity. Increasing expression of peanut-agglutinin-binding sites parallels the maturation and differentiation of the glandular cells. Type 3 lobules are marked by numerous TUNEL-positive nuclei and large lipid droplets and are apparently degenerating structures. Cytokeratin (CK) 14 is usually present in the myoepithelial cells; CK 19 and CK 7 mark ductal and immature alveolar epithelia. Milk protein content varies between 2.6% and 6.3%, and casein micelles range from 35 to 90 nm in diameter. The diameter of intra-alveolar milk fat globules ranges from 5 to 25 µm and the membranes bear a filamentous surface coat composed of membrane-anchored mucins; gel-electrophoretic analysis of these mucins from different individuals demonstrates the presence of mucin MUC 1, which is expressed with considerable genetic heterogeneity.

Food, reproduction and survival in mice on sub-Antarctic Marion Island

The house mouse Mus musculus is the most widespread introduced mammal on sub-Antarctic islands, where it may alter ecosystem function. Ambient temperature and food availability affect reproduction and survival for mice. It is unclear how these factors influence mouse demography in the sub-Antarctic, and we tested the influence of food experimentally on Marion Island. Using food supplementation trials, we did not alter reproduction or overwinter survival. Alternatively, we argue ongoing climatic change on Marion could increase mouse densities through summer, while increased winter survival may reduce population growth rates the following summer through density dependence. The overall influence of these apposing forces depends on their relative strengths but may limit changes in mouse numbers with ongoing changes in climate in the sub-Antarctic.

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 afrlcana) 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.

Elephant populations and CITES trade resolutions

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) relies on the Elephant Trade Information System (ETIS) and Monitoring the Illegal Killing of Elephants Programme (MIKE) monitoring systems and trends in elephant numbers and the illegal killing of elephants to put resolutions forward to the Conference of Parties. Imprecision in elephant estimates and trends, as well as the spatial reality of elephant dynamics constrain CITES resolutions. Clusters of populations should instead serve as management units and demographic profiling predicting future population trends may complement existing approaches to inform CITES decisions.