African Journal of Ecology最新文献

At the time of the recent description of Beytell's bullfrog (Pyxicephalus beytelli), no information about the breeding biology of this frog was known to science. The intensive publicity in the social media that followed this description caught the eye of a USA-based film maker who incidentally recently filmed the breeding biology of this frog in the Okavango Delta in northern Botswana. This paper is based on these observations.

Poplar is an invasive alien plant (IAP) that encroaches on fragile landscapes in South Africa, but the environmental factors that contribute to its spread are not well understood. To address this gap, we conducted a study using generalised linear models (GLM) to identify the most significant local environmental factors that drive poplar establishment and dispersion in Golden Gate Highlands National Park (GGHNP). We then ranked these variables according to their contribution to poplar occurrence using a random forests regression approach. Our GLM analysis revealed that soil properties such as soil organic carbon, sand and silt, topographical variables such as aspect and slope, normalised difference moisture index (NDMI) and poplar distance from rivers are significant factors affecting poplar survival. After ranking the variables, we found that the three most important factors influencing poplar occurrence were aspect, slope and poplar distance to rivers, followed by the sand, silt, NDMI, and soil organic carbon. Our results are consistent with previous studies, indicating that topographical variables and the availability of sufficient water supply are the primary drivers of the spread of IAPs. This study provides useful insights in managing and monitoring poplars in delicate landscapes.

Surface water assumes a pivotal role in sustaining a wide range of wildlife species in semi-arid protected areas. However, differences in surface water body typology, underlying soil type, wildlife activity, the presence of phytoplankton amongst other factors, result in high variability of surface water spectral reflectance and detection accuracy. In this study, the performance of radar and optical methods was evaluated in detecting surface water of variable spectral reflectance in Hwange National Park, Zimbabwe using Sentinel-1 radar and Sentinel-2 optical images for the period 2016–2023. Results demonstrated that radar methods had low surface water detection accuracy which was highly variable as shown by overall accuracy and kappa statistic measures which continuously changed over time compared with optical methods. The overall best-performing method was the optical AWEI_nsh (sharpened) which showed high surface water detection accuracy and consistency (OA: 94%–100%) and (κ: 0.88–1.00) from 2016 to 2023. Therefore, optical methods present a stable and robust way for surface water monitoring in heterogeneous semi-arid protected areas. However, radar-based methods should be continually explored where optical-based technologies are impeded as a result of vegetation cover and cloud conditions.

Understanding the composition and distribution of dung beetle species across various habitat types is crucial for elucidating their ecosystem functions. Dung beetles play pivotal roles in ecological processes such as nutrient cycling, seed dispersal and parasite suppression. Despite numerous studies on the influence of habitat types on dung beetle communities, knowledge gaps persist, particularly on how these beetles respond to different vegetation types in protected areas. In this study, we surveyed dung beetle species in Nyerere National Park, Tanzania, using baited pitfall traps across four habitat types: closed miombo woodland, open miombo woodland, marshland and riverine. We identified a total of 5534 individuals representing 63 species, 29 genera and nine tribes. Significant variations in species diversity were observed among the habitats, with the closed miombo woodland exhibiting the highest diversity and the open miombo woodland the lowest. Notably, certain species, such as Euoniticellus intermedius, Euonthophagus carbonarius, Gymnopleurus ignites, Onitis alexis, Onthophagus, Onthophagus vinctus, Onthophagus plebejus and Sisyphus goryi displayed a generalist distribution across all habitat types. Our findings underscore the critical importance of maintaining and conserving the quality of diverse habitat types to ensure the long-term preservation of dung beetle biodiversity and the ecosystem services they provide. This study contributes valuable insights into dung beetle ecology and offers practical implications for ecosystem management and conservation strategies.

Current theory predicts that plains zebra (Equus quagga) populations should be resource-limited. Long-term, detailed work in the Hwange ecosystem (Zimbabwe) on zebras and all their major predators provides empirical data to test this on a population that has been at a low density for at least 2 decades and is largely naturally regulated. Information on body condition is used as an indicator of resource use, and offtakes by the three major predators are estimated from a synthesis of data on densities and diets. This information leads to rejection of the expectations for resource limitation. Zebras provide a significant part of the diets of all the main predators and are important (11%) for the most abundant of these, spotted hyaenas (Crocuta crocuta). Using conservative values, we calculate that the three main predators, hyaenas, lions (Panthera leo), and leopards (Panthera pardus), kill some 17.5% of the zebra population. Given that this estimated offtake is of the same order of magnitude as maximum population growth (22.3% per year), we conclude that this population is likely to be limited by predation. Further work is needed to better understand the mechanisms by which the greater susceptibility of juveniles to predation in ungulates contributes to population limitation.

A great challenge for African conservationists is human–wildlife conflict outside the boundaries of protected areas (PAs). This is particularly true when considering large mobile species, such as elephants, that often disperse from PAs into community land. In Zimbabwe's Hwange National Park, studies on elephant dispersal have focused on breeding herds. Here, we analyse the movements of five older, large males fitted with GPS collars. We found some dispersal outside Hwange, but large males were largely restricted to the Park, especially during the late dry season when water was scarce. Our findings may be useful to regional conservation decision makers.

Hyaena faeces and mineral licks represent highly concentrated nutrient resources for leopard tortoises (Stigmochelys pardalis) living in nutrient-poor environments. Here, we provide direct evidence for the consumption of hyaena faeces and artificial mineral licks by leopard tortoises in the Kalahari Desert. Tortoises aggregated at hyaena latrines and lick sites during the wet season between 10 AM and 6 PM in groups of 1–5 individuals. Where both salt and mineral licks were available, tortoises displayed a preference for salt. We suggest that calcium, phosphorus and sodium deficits are likely driving coprophagy and geophagy behaviours by tortoises in the Kalahari.

Plant traits and connectivity influence habitat usage, but fine-scale ecological characteristics that determine fossorial animal movement patterns remain unclear. To understand the influence of landscape connectivity on movement behaviour, we examined vegetation characteristics relative to tracks between vegetation hummocks left by the short blind dart skink, Typhlacontias brevipes, a fossorial lizard inhabiting dunes of the Namib Desert. We measured characteristics of >700 plant hummocks and 293 T. brevipes tracks. Tracks were relatively direct from hummock to hummock (median straightness = 0.94). Vegetation hummocks with tracks were significantly larger than hummocks without tracks, indicating that vegetation size was the most important factor we measured in predicting track occurrence and was more important to skinks than the distances between hummocks, with only 24% of tracks occurring between nearest neighbouring vegetation hummocks. Network clusters consisting of as many as 15 vegetation hummocks were connected by tracks. Skink tracks had a median length of 815 cm and were oriented primarily from 0° to 30°. Our study highlights the importance of vegetation size to fossorial skinks and raises questions regarding other vegetation features that might influence the movement and ecology of fossorial lizards.

The hypothesis that certain woody species may be prone to local extirpation under chronic elephant utilisation was examined for Colophospermum mopane open woodland, for an area within the foraging range of elephants from permanent water. Elephant density increased from nearly absent in the 1970s to >3 elephants km⁻², with 0.62 adult bulls km⁻², by 2022. Study components of vegetation impact included a long-term elephant exclosure, a fence-line contrast with an adjacent communal area, comparison with an adjacent wildlife reserve carrying a fifth of the elephant density and the use of historical studies of the vegetation. A history of elephant utilisation resulted in woodland becoming hedged through pollarding of tree stems by elephants. Impacted woodland was characterised by a slightly lower tree density, reduced average height of trees, altered shrub composition and lower species richness. The dominant C. mopane and sub-dominant species had persisted. However, about 14 species were potentially trending towards local extirpation on account of very high levels of adult mortality, but had persisted because of a low level of seedling recruitment. Fleshy fruits were a shared attribute among most extirpation-trending species, which, together with a reduction in woody species richness that affects browsers, has ramifications for trophic flows.

This field study in a semi-arid savannah at Senkelle Swayne's Hartebeest Sanctuary, Ethiopia, examined livestock grazing effects on rangeland condition, plant species composition and richness, and population of the endangered Swayne's hartebeest (Alcelaphus buselaphus swaynei). Rangeland condition was analysed using a common protocol for the assessment of semi-arid rangelands. A total count method was used to estimate ungulate numbers. Grazing reduced all measures of range condition and productivity and affected the composition and richness of the herbaceous species. Grazing also induced an increase in the density and number of encroaching woody species Vachellia seyal and Senegalia senegal. The population of the Swayne's hartebeest significantly affected by livestock grazing (mean number of hartebeests observed under moderately and lightly grazed sites were 10.00 ± 2.49 and 6.75 ± 2.06, respectively). No individual hartebeest was observed roaming in the heavily grazed zone, which implies an effective reduction in the extent of habitat available for the hartebeest. The overall condition of the rangeland was poor. Measures to reduce livestock presence in areas from which the hartebeest has been displaced and controlled seasonal livestock grazing within non-sensitive parts of the Sanctuary may benefit the hartebeest. Coupled with these, livestock exclusions for up to a year and interseeding may help improve rangeland condition and hartebeest's habitat.