Published Research

Contrasting evolutionary history, anthropogenic declines and genetic contact in the northern and southern white rhinoceros (Ceratotherium simum)

The white rhinoceros (Ceratotherium simum) has a discontinuous African distribution, which is limited by the extent of sub-Saharan grasslands. The southern population (SWR) declined to its lowest number around the turn of the nineteenth century, but recovered to become the world's most numerous rhinoceros. In contrast, the northern population (NWR) was common during much of the twentieth century, declining rapidly since the 1970s, and now only two post-reproductive individuals remain. Despite this species's conservation status, it lacks a genetic assessment of its demographic history. We therefore sampled 232 individuals from extant and museum sources and analysed ten microsatellite loci and the mtDNA control region. Both marker types reliably partitioned the species into SWR and NWR, with moderate nuclear genetic diversity and only three mtDNA haplotypes for the species, including historical samples. We detected ancient interglacial demographic declines in both populations. Both populations may also have been affected by recent declines associated with the colonial expansion for the SWR, and with the much earlier Bantu migrations for the NWR. Finally, we detected post-divergence secondary contact between NWR and SWR, possibly occurring as recently as the last glacial maximum. These results suggest the species was subjected to regular periods of fragmentation and low genetic diversity, which may have been replenished upon secondary contact during glacial periods. The species's current situation thus reflects prehistoric declines that were exacerbated by anthropogenic pressure associated with the rise of late Holocene technological advancement in Africa. Importantly, secondary contact suggests a potentially positive outcome for a hybrid rescue conservation strategy, although further genome-wide data are desirable to corroborate these results.

Matrilineal population structure and distribution of the Angolan giraffe in the Namib desert and beyond

The distribution maps of giraffe (Giraffa) subspecies in southern Africa are based on historical assumptions, yet some populations have likely been misidentified, hindering effective conservation efforts. Particularly, the populations in Zimbabwe are poorly studied, and translocations, such as the 1991 movement of giraffe from Namibia's Etosha National Park to mitigate the human-induced decline of Namibia's desert-dwelling giraffe in the lower Hoanib and Hoarusib Rivers, was concluded without consideration of genotype. Mitochondrial DNA sequence analyses from cytochrome b and control region revealed that instead of the South African giraffe subspecies (G. giraffa giraffa), the Angolan giraffe (G. g. angolensis) occurs in southern Zimbabwe's Bubye Valley Conservancy. Furthermore, Namibia's desert-dwelling giraffe and those from Etosha National Park form distinct matrilineal lineages within the Angolan giraffe subspecies clade. Thus, despite the translocation and proximity of the Etosha National Park, the Etosha giraffe genotype has not spread amongst the desert-dwelling giraffe. Use of mutation rate estimates indicates that there has been no matrilineal exchange between Etosha and the desert-dwelling giraffe for ca. 40,000 years. While philopatry could produce distinct mitochondrial lineages, the short geographical distance and long time involved, makes it more likely that the Etosha giraffe cannot successfully compete with a putatively better adapted desert-dwelling giraffe. The analyses also show that the distribution of the Angolan giraffe extends further eastwards than expected. These findings provide important implications for giraffe conservation, and translocation in particular, which may not always be an effective means of improving genetic diversity.

Water for African elephants (Loxodonta africana): faecal microbial loads affect use of artificial waterholes

In semi-arid protected areas, artificial waterholes ensure that water is locally available to animals for extended periods. However, artificial waterholes may limit animal movement, which contributes towards habitat deterioration. Challenges of artificial water provisioning worsen in the presence of ecosystem engineers like African elephants Loxodonta africana, capable of transforming environments. Camera traps were used to monitor elephant visitation at 21 artificial waterholes in the Kruger National Park, South Africa. We also assessed if water quality parameters influenced elephant preference for certain waterholes. There were no significant correlations between elephant abundance and water physicochemical properties. However, there was a strong negative correlation between elephant abundance and levels of Escherichia coli in water. Our findings suggest that elephants avoid drinking water with high levels of faecal microbial loads. Whereas most studies addressing animal management in protected areas consider waterholes as homogeneous units, we posit that water quality could also determine local landscape use and movement patterns of key species like elephants, a finding with relevant implications in reserve management practices.

Birdcall lures improve passerine mist-net captures at a sub-tropical African savanna

Field research techniques are constantly evolving to meet the needs of the scientific community. There is a growing need for field biology studies to shift towards increasing efficiency and quality of results while simultaneously decreasing cost in both the researcher’s time and resources. I tested the efficacy of using multiple recorded birdcall lures (n = 172 species) to improve mist-net captures at a subtropical African savanna setting. Capture success was compared between passive and birdcall enhanced mist-nets during winter and summer seasons. Results suggest that the use of birdcalls does significantly increase the total number of birds caught in both seasons and also increases the diversity of passerine species. Conventional passive mist-nets without an audio lure were initially productive but their capture rate subsequently decreased as sampling days progressed. Birdcall lure enhanced mist-nets had a constant capture output during the summer season. The most responsive birds to audio lures were gregarious species (e.g. Pycnonotus barbatus, Dryoscopus cubla, Prionops plumatus, Phoeniculus purpureus, Turdoides jardineii and Lamprotornis chalybaeus) and the aggressive Dicrurus adsimilis and Acridotheres tristis. I conclude that birdcall lures can be used in summer and winter seasons to improve mist-net captures especially for studies focusing on gregarious and aggressive passerine species in a sub-tropical African savanna setting.

Temperature fluctuations inside savanna termite mounds: do size and plant shade matter?

Mound building termites are key ecosystem engineers of subtropical savanna regions. Mounds allow termites to maintain suitable conditions for termite reproduction and food cultivation ('fungus gardens'). We studied how the internal mound temperature of Macrotermes natalensis, a dominant mound-building termite of the subtropical savanna of southern Africa, responds to a number of environmental variables. We used general additive mixed models (GAMM) to determine how external temperature, mound size (volume) and the amount of vegetation shade affects mound internal temperature over a 24-h period. Internal mound temperature varied daily following changes of the external temperature, although the range of variation was much smaller. Active termite mounds maintained a higher internal temperature than inactive ones, and mound activity reinforced the positive effect of mound size and moderated the negative effect of vegetation shade on internal temperatures. In turn, external temperature fluctuations equally affected active and inactive mounds. Large mounds maintained near optimal internal temperatures compared to smaller sized mounds. We therefore conclude that termite mound size is a stronger determinant of internal mound temperature stability compared to plant shade cover.

Estimating lion’s prey species profile in an arid environment. Journal of Zoology

Information on large carnivore diet composition is important when conservationists seek to address stressors such as habitat encroachment, bush meat trade and retribution killing on the persistence of populations. Detailed diet sampling approaches can contribute to effective conservation management. We compare different approaches including GPS cluster analysis, scat analysis and opportunistic observations and describe lion diet profiles in the Kgalagadi Transfrontier Park (KTP). We determined that a sample size of between 65–69 lion feeding events out of 278 found by GPS cluster analysis and 55–59 lion scats out of 189 samples can provide a representative description of lion diet in the KTP. Our opportunistic observations (n = 52) were found to be too few for robust deductions. Scat analysis yielded the highest prey diversity (n = 11) and best representation of prey <50 kg, but required 160 scats at ~ 263 km driven per scat collected. GPS cluster analysis provided good information for large prey, but underrepresented prey <50 kg. Kill remains were found at only 37% of the investigated GPS cluster points (n = 823). Even so, GPS cluster analysis yielded diet descriptions quicker than scat analyses. The use of GPS cluster and scat analysis in tandem is recommended for the estimation of lion diet in this arid environment.

The distribution and numbers of cheetah (Acinonyx jubatus) in southern Africa. (In press)

Assessing the numbers and distribution of threatened species is a central challenge in conservation, often made difficult because the species of concern are rare and elusive. For some predators, this may be compounded by their being sparsely distributed over large areas. Such is the case with the cheetah Acinonyx jubatus. The IUCN Red List process solicits comments, is democratic, transparent, widely-used, and has recently assessed the species. Here, we present additional methods to that process and provide quantitative approaches that may afford greater detail and a benchmark against which to compare future assessments. The cheetah poses challenges, but also affords unique opportunities. It is photogenic, allowing the compilation of thousands of crowd-sourced data. It is also persecuted for killing livestock, enabling estimation of local population densities from the numbers persecuted. Documented instances of persecution in areas with known human and livestock density mean that these data can provide an estimate of where the species may or may not occur in areas without observational data. Compilations of extensive telemetry data coupled with nearly 20,000 additional observations from 39 sources show that free-ranging cheetahs were present across approximately 789,700 km2 of Namibia, Botswana, South Africa, and Zimbabwe (56%, 22%, 12% and 10% respectively) from 2010 to 2016, with an estimated adult population of 3,577 animals. We identified a further 742,800 km2 of potential cheetah habitat within the study region with low human and livestock densities, where another ∼3,250 cheetahs may occur. Unlike many previous estimates, we make the data available and provide explicit information on exactly where cheetahs occur, or are unlikely to occur. We stress the value of gathering data from public sources though these data were mostly from well-visited protected areas. There is a contiguous, transboundary population of cheetah in southern Africa, known to be the largest in the world. We suggest that this population is more threatened than believed due to the concentration of about 55% of free-ranging individuals in two ecoregions. This area overlaps with commercial farmland with high persecution risk; adult cheetahs were removed at the rate of 0.3 individuals per 100 km2 per year. Our population estimate for confirmed cheetah presence areas is 11% lower than the IUCN’s current assessment for the same region, lending additional support to the recent call for the up-listing of this species from vulnerable to endangered status.

The legal challenges of transboundary wildlife management at the population level: The case of a trilateral elephant population in southern Africa.

What do geese (Anser spp., Branta spp.) and wolves (Canis lupus) in Europe have in common with elephants (Loxodonta africana) in southern Africa? In fact, quite a lot. All three enjoy protected status under multiple international legal instruments. At the same time, all three have a high potential for so-called human–wildlife conflict and are subject to smaller or larger degrees of lethal control. These traits, in turn, are linked to the fact that the life histories of geese, wolves, and elephants require populations of these animals to range beyond designated protected areas (PAs) into the wider landscape. Last but not least, many populations of geese, wolves, and elephants—and many other species besides—are transboundary, overlapping the territories of several countries. These traits, however, can lead to a potential mismanagement of transboundary populations because of a mismatch between the scales at which these animal populations operate and the scale at which administrations operate.

Large mammal distribution in a transfrontier landscape: Trade-offs between resource availability and human disturbance.

Understanding factors that affect the persistence of charismatic megafauna in human‐dominated landscapes is crucial to inform conservation decision‐making and reduce human‐wildlife conflict. We assessed the effect of environmental and anthropogenic factors at different landscape and management scales in predicting the distribution of African elephant (Loxodonta africana) within the Greater Mapungubwe Transfrontier Conservation Area in Southern Africa. We combined aerial distribution counts over a 12‐yr period with 14 variables, representing food availability, landscape, and anthropogenic effects, into generalized linear models. Generalized linear models were run for the broader landscape, as well as three separate management units within the broader landscape, namely ecotourism, trophy hunting, and a combination of hunting and ecotourism. Human activities within different management units forced elephant to trade‐off between disturbance avoidance, and good food and water availability. In addition, the important predictors of elephant distribution within each of the management units differed from the predictors at the broader landscape. Overall, our results suggest that at the fine scale, elephant are constraint by factors that may be masked at the broader landscape scale. We suggest that accounting for anthropogenic disturbance is important in determining the distribution of large, wide‐ranging, mammal species in increasingly human‐dominated landscapes, and that modeling needs to be done at the spatial scales at which conservation decisions are made.

Continent-wide survey reveals massive decline in African savanna elephants.

African elephants (Loxodonta africana) are imperiled by poaching and habitat loss. Despite global attention to the plight of elephants, their population sizes and trends are uncertain or unknown over much of Africa. To conserve this iconic species, conservationists need timely, accurate data on elephant populations. Here, we report the results of the Great Elephant Census (GEC), the first continent-wide, standardized survey of African savannah elephants. We also provide the first quantitative model of elephant population trends across Africa. We estimated a population of 352,271 savannah elephants on study sites in 18 countries, representing approximately 93% of all savannah elephants in those countries. Elephant populations in survey areas with historical data decreased by an estimated 144,000 from 2007 to 2014, and populations are currently shrinking by 8% per year continent-wide, primarily due to poaching. Though 84% of elephants occurred in protected areas, many protected areas had carcass ratios that indicated high levels of elephant mortality. Results of the GEC show the necessity of action to end the African elephants’ downward trajectory by preventing poaching and protecting habitat.

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