2016-2020

Termites and mammalian herbivores might derive mutual benefit from each other through positive feedback loops, but empirical evidence is lacking. One suggested positive feedback loop is between termites and elephant, both ecosystem engineers. Termites, as decomposer organisms, contribute to nutrient cycling and soil enrichment, creating hotspots with increased forage quality. Elephant are known to select these high quality vegetation patches, depositing woody debris when foraging, but it is unknown whether elephant presence might affect termites, and if a feedback loop between these two taxa exists. We tested this hypothesis by measuring termite diversity and activity over three months in the summer wet season, inside and outside a long-term (eight years) elephant exclosure experiment in Sand Forest at Phinda Private Game Reserve, South Africa. Termites were sampled using cellulose baits and woody debris was quantified using line transects. Termite activity was not affected by eight years of elephant absence, despite a greater volume of woody debris where elephant were present. Termite assemblages were similarly unaffected by elephant absence. Apart from Schedorhinotermes, all other termite genera were sampled in both treatments. Therefore, the postulated positive feedback loop between termites and elephant is not supported in Sand Forest. However, this does not contradict findings that areas with high termite activity positively influence herbivore foraging, only that elephant foraging does not affect termite activity. This suggests that elephant disturbance (and elephant management policies) has little to no effect on termites and the fundamental roles they play in ecosystems over at least the short-term.

Habitat quality is often assumed to be directly related to increased consumer density, but such assumptions cannot be made without supporting demographic data that indicate improved fitness. Habitat selection might be especially important for denning species, where vulnerable offspring are confined to a single location for extended periods, but the effect of den choice on the reproductive success of denning species is poorly understood. By combining airborne high-resolution Light Detection and Ranging (LiDAR) measurements with data on pack composition, we investigated den site selection by endangered African wild dogs in Hluhluwe-iMfolozi Park, South Africa, examining whether habitat selection based on ecological factors resulted in increased litter sizes and thus reproductive success compared with social factors known to be important. Although there was selection for den sites in areas of increased terrain ruggedness and vegetation density, only vegetation density was associated with larger litter sizes and translated into increased reproductive success. Moreover, pack size was only influential when a minimum vegetation density around den sites was achieved, indicating that although social variables have a powerful effect on reproductive success, they are mediated by ecological factors defining habitat quality. Our results demonstrate the importance of distinguishing between density- and fitness-based indicators of habitat quality, and how this can affect management actions, particularly for endangered species conservation.

Herbivores do not forage uniformly across landscapes, but select for patches of higher nutrition and lower predation risk. Macrotermes mounds contain higher concentrations of soil nutrients and support grasses of higher nutritional value than the surrounding savanna matrix, attracting mammalian grazers that preferentially forage on termite mound vegetation. However, little is known about the spatial extent of such termite influence on grazing patterns and how it might differ in time and space. We measured grazing intensity in three African savanna types differing in rainfall and foliar nutrients and predicted that the functional importance of mounds for grazing herbivores would increase as the difference in foliar nutrient levels between mound and savanna matrix grasses increases and the mounds become more attractive. We expected this to occur in nutrient‐poor areas and during the dry season when savanna matrix grass nutrient levels are lower. Tuft use and grass N and P content were measured along transects away from termite mounds, enabling calculation of the spatial extent of termite influence on mammalian grazing. Using termite mound densities estimated from airborne light detection and ranging (LiDAR), we further upscaled field‐based results to determine the percentage of the landscape influenced by termite activity. Grasses in close proximity to termite mounds were preferentially grazed at all sites and in both seasons, but the strength of mound influence varied between savanna types and seasons. In the wet season, mounds had a relatively larger effect on grazers at the landscape scale in the nutrient‐poor, wetter savanna, whereas in the dry season the pattern was reversed with more of the landscape influenced at the nutrient‐rich, driest site. Our results reveal that termite mounds enhance the value of savanna landscapes for herbivores, but that their functional importance varies across savanna types and seasons.

Predators affect ecosystems not only through direct mortality of prey, but also through risk effects on prey behavior, which can exert strong influences on ecosystem function and prey fitness. However, how functionally different prey species respond to predation risk and how prey strategies vary across ecosystems and in response to predator reintroduction are poorly understood. We investigated the spatial distributions of six African herbivores varying in foraging strategy and body size in response to environmental factors and direct predation risk by recently reintroduced lions in the thicket biome of the Addo Elephant National Park, South Africa, using camera trap surveys, GPS telemetry, kill site locations and Light Detection and Ranging. Spatial distributions of all species, apart from buffalo, were driven primarily by environmental factors, with limited responses to direct predation risk. Responses to predation risk were instead indirect, with species distributions driven by environmental factors, and diel patterns being particularly pronounced. Grazers were more responsive to the measured variables than browsers, with more observations in open areas. Terrain ruggedness was a stronger predictor of browser distributions than was vegetation density. Buffalo was the only species to respond to predator encounter risk, avoiding areas with higher lion utilization. Buffalo therefore behaved in similar ways to when lions were absent from the study area. Our results suggest that direct predation risk effects are relatively weak when predator densities are low and the time since reintroduction is short and emphasize the need for robust, long-term monitoring of predator reintroductions to place such events in the broader context of predation risk effects.

Soils are integral to agricultural productivity, biodiversity, and the maintenance of ecosystem services. However, soil ecosystem research depends on foundational biological knowledge that is often missing. In this review, we present a comprehensive, cross-taxa overview of the soil biota of South Africa. We discuss the literature and sampling methods used to assess soil biota, the available taxonomic expertise and main collections within South Africa, the availability of identification guides and online resources, and the status and distribution of described species. We include species lists for all South African soil biota and, for groups with sufficient distribution records, species richness maps. Despite South Africa being only 0.8% of the earth’s terrestrial area, it contains nearly 1.8% of the world’s described soil species (mean per taxon 3.64%, range 0.17–15%; n = 36 groups), with nematodes and earthworms showing a remarkable (6.4 and 7.7%) proportion of globally described diversity. Endemism is high for most groups, ranging from 33–92%. However, major knowledge gaps exist for most soil biota groups. While sampling has been relatively comprehensive in some areas for a few groups (particularly those with direct socioeconomic impacts), the Nama-Karoo, Northern Cape and Eastern Cape are poorly sampled. Natural soils in biodiversity hotspots, such as the Fynbos Biome, are also understudied. We argue that a more integrative approach to acquiring foundational knowledge in soil biodiversity is needed if applied soil research is to be effective in ensuring sustainable soil health. Considerable investment will be required to bring our understanding of the soil biodiversity in this megadiverse region to a level where the Millennium Development Goals can be reached.

 

Aim

Termite mounds form small islands of enhanced water and soil nutrient availability on otherwise dry and nutrient‐poor hill crests, which can have important impacts on the plant community. However, the way in which termite mounds alter the spatial distribution of particular tree species across broad savanna landscapes is poorly understood. We aimed to understand the nature and extent of the relationship between termite mounds and key woody savanna species at landscape scales through the use of airborne remote sensing.

Location

Kruger National Park, South Africa.

Methods

We mapped 9894 termite mounds and 666,679 savanna trees from 15 species across two landscapes with contrasting rainfall regimes using airborne imaging spectroscopy and LiDAR data. We then examined changes in tree species densities and community composition with respect to distance from termite mounds.

Results

In both landscapes, termite mounds reduced overall tree densities over distances up to 10 m from mound centres. However, the effect of termite mounds on tree density differed among species, with some species, typically associated with lowland and riparian habitats, showing increased density near termite mounds. Indeed, changes in overall tree community composition revealed that termite mounds harbour tree communities similar to lowland communities, with this similarity decreasing with increased distance from the nearest mound. Termite effects were more pronounced in the savanna landscape receiving higher annual rainfall, whereas a greater percentage of the landscape was affected in the drier landscape due to higher mound densities.

Main conclusions

Termite mounds mediate the spatial distribution of tree species in savanna landscapes, increasing the abundance of tree species typically associated with lowland habitats. This contributes to the spatial heterogeneity of savanna vegetation within landscapes and the maintenance of savanna biodiversity.

 

African savannas are highly seasonal with a diverse array of both mammalian and invertebrate herbivores, yet herbivory studies have focused almost exclusively on mammals. We conducted a 2-yr exclosure experiment in South Africa’s Kruger National Park to measure the relative impact of these two groups of herbivores on grass removal at both highly productive patches (termite mounds) and in the less productive savanna matrix. Invertebrate and mammalian herbivory was greater on termite mounds, but the relative importance of each group changed over time. Mammalian offtake was higher than invertebrates in the dry season, but can be eclipsed by invertebrates during the wet season when this group is more active. Our results demonstrate that invertebrates play a substantial role in savanna herbivory and should not be disregarded in attempts to understand the impacts of herbivory on ecosystems.

In almost every ecosystem, ants (Hymenoptera: Formicidae) are the dominant terrestrial invertebrate group. Their functional value was highlighted by Wilson (1987) who famously declared that invertebrates are the “little things that run the world.” However, while it is generally accepted that ants fulfil important functions, few studies have tested these assumptions and demonstrated what happens in their absence. We report on a novel large‐scale field experiment in undisturbed savanna habitat where we examined how ants influence the abundance of other invertebrate taxa in the system, and affect the key processes of decomposition and herbivory. Our experiment demonstrated that ants suppressed the abundance and activity of beetles, millipedes, and termites, and also influenced decomposition rates and levels of herbivory. Our study is the first to show that top‐down control of termites by ants can have important ecosystem consequences. Further studies are needed to elucidate the effects ant communities have on other aspects of the ecosystem (e.g., soils, nutrient cycling, the microbial community) and how their relative importance for ecosystem function varies among ecosystem types (e.g., savanna vs. forest).

Predator-prey relationships are integral to ecosystem stability and functioning. These relationships are, however, difficult to maintain in protected areas where large predators are increasingly being reintroduced and confined. Where predators make kills has a profound influence on their role in ecosystems, but the relative importance of environmental variables in determining kill sites, and how these might vary across ecosystems is poorly known. We investigated kill sites for lions in South Africa’s thicket biome, testing the importance of vegetation structure for kill site locations compared to other environmental variables. Kill sites were located over four years using GPS telemetry and compared to non-kill sites that had been occupied by lions, as well as to random sites within lion ranges. Measurements of 3D vegetation structure obtained from Light Detection and Ranging (LiDAR) were used to calculate the visible area (viewshed) around each site and, along with wind and moonlight data, used to compare kill sites between lion sexes, prey species and prey sexes. Viewshed area was the most important predictor of kill sites (sites in dense vegetation were twice as likely to be kill sites compared to open areas), followed by wind speed and, less so, moonlight. Kill sites for different prey species varied with vegetation structure, and male prey were killed when wind speeds were higher compared to female prey of the same species. Our results demonstrate that vegetation structure is an important component of predator-prey interactions, with varying effects across ecosystems. Such differences require consideration in terms of the ecological roles performed by predators, and in predator and prey conservation.

Integration of multiple technologies greatly increases the spatial and temporal scales over which ecological patterns and processes can be studied, and threats to protected ecosystems can be identified and mitigated. A range of technology options relevant to ecologists and conservation practitioners are described, including ways they can be linked to increase the dimensionality of data collection efforts. Remote sensing, ground-based, and data fusion technologies are broadly discussed in the context of ecological research and conservation efforts. Examples of technology integration across all of these domains are provided for large-scale protected area management and investigation of ecological dynamics. Most technologies are low-cost or open-source, and when deployed can reach economies of scale that reduce per-area costs dramatically. The large-scale, long-term data collection efforts presented here can generate new spatio-temporal understanding of threats faced by natural ecosystems and endangered species, leading to more effective conservation strategies.