Albert S. van Jaarsveld

ENERGY, SPECIES RICHNESS, AND HUMAN POPULATION SIZE: CONSERVATION IMPLICATIONS AT A NATIONAL SCALE

The maintenance of biodiversity rests on understanding and resolving conflict between patterns of species occurrence and human activity. Recent debate has centered on the relationship between species richness and human population density. However, conclusions have been limited by the lack of investigations of these relationships for individual countries, at which level most practical conservation actions are determined, and for a spatial resolution at which practical conservation planning takes place. Here, we report the results of the first such analysis, for birds in South Africa. Species richness and human density are positively correlated, apparently because both respond positively to increasing levels of primary productivity. High species richness is maintained by currently designated reserves, but the areas surrounding these have higher human population densities than expected by chance, placing the reserves under increasing external pressure. Not all species lie within protected areas, but the options are limited for building on the present network to generate a more comprehensive one, which protects all species and significantly reduces the conflict with human activities by designating new reserves in areas with lower human populations. Ultimately, the only solution to the conflict between biodiversity and people is likely to be individual-based regulation of human population size.

Conservation of heterogeneity among dung beetles in the Maputaland Centre of Endemism, South Africa

Abstract In southern Africa the Maputaland Centre is one of the most significant, though less well-known, centres of biotic endemism. Here we examine variation in dung beetle assemblages between habitats and between reserves on two Maputaland reserves (Tembe Elephant Park and Sileza Nature Reserve). Dung beetle assemblages were found to be homogeneous within habitat types and within reserves, but assemblages differed between habitat types (Sand Forest and Mixed Woodland). There was, however, significant between-reserve heterogeneity in dung beetle assemblages for each particular habitat type. Given that there are significant differences in both dung beetles and plants, it is clear that these forests must be conserved in both Tembe and Sileza, especially because of increasing damage by elephants to Sand Forests in Tembe. We identify dung beetle indicator species that are specific to each habitat type in each reserve, and detector species that can be used to monitor changes in Sand Forests in those reserves. ©

Species and environment representation: selecting reserves for the retention of avian diversity in KwaZulu-Natal, South Africa

Abstract Multivariate analyses and complementarity-based reserve selection algorithms were used as tools for delimiting representative conservation areas in KwaZulu-Natal, South Africa, based on environmental variables and records for 566 breeding and non-breeding birds. The relationships between species assemblages and 20 environmental variables were investigated; including climate, topography, vegetation, landscape attributes, and land-use. Detrended correspondence analysis, canonical correspondence analysis, and hierarchical classification suggested that the major gradients of bird species variation are primarily related to climatic variables such as growing season temperature and seasonality of precipitation, reflecting the strong east–west gradient in oceanicity in KwaZulu-Natal, and water balance, reflecting a strong north–south gradient in aridity. Hierarchical classification was applied to the ordination data and revealed five representative types of bird communities. Four of the five bird communities and 37 species are under-represented in the existing reserve system, and the environmental processes required for long-term maintenance of birds have not been adequately sampled, showing that additional reserves are needed to ensure a more functional representative system. As an alternative, the inclusion of species spatial turnover structure together with associated environmental gradients were employed in both rarity and richness-based complementary reserve selection algorithms to provide a better representation of birds and environmental processes. Improvements on the current generation of reserve selection techniques derived by including ordination analysis and spatial structure are discussed.

Patterns of coalition formation and spatial association in a social carnivore, the African wild dog ( Lycaon pictus )

In many social species, relationships within groups seem to be non-random but related to variables such as rank, kinship or sexual attractiveness. The endangered African wild dog Lycaon pictus is a social carnivore that lives in large, stable packs, and intra-pack associations might be expected to display similar patterns. We investigated patterns of coalition formation (support during dominance interactions, and partnership interactions) and resting associations between members of a captive pack of 19 wild dogs. The social organization of the captive pack was similar to that of free-ranging packs in many respects. Polyadic (group) incidents of coalition support were also observed in a free-ranging pack. Patterns of coalition formation in the captive pack were related to rank. Most aggressive interactions involved high-ranking individuals (particularly the alpha, beta and third-ranking males) and coalitionary support tended to reinforce the existing hierarchy. However, there was at least one example of support influencing a successful rank challenge. Support was affected by potential risks and benefits, the latter including dominance through association and revolutionary alliances. An even stronger pattern overlaid associations between pack members: coalitions and resting associations were strongest between members of the same age–sex cohort, and may have enabled the eventual dominance of younger pack members over adults. Among adults, coalitionary associations were sometimes overridden by intersexual relationships. The results from this captive pack suggest that wild dogs are sensitive to differences in competitive ability. This information, in conjunction with strong affiliative bonds between littermates, is used to manoeuvre for position in the social hierarchy. It may also be important during dispersal, in encounters with other dispersing groups of the same sex. Although most features of the social structure of the captive pack were comparable to those of free-ranging packs, aspects such as the influence of relatedness on coalition formation still need to be explored.

Reduced dispersal and opportunistic territory acquisition in male lions (Panthera leo)

Life-history patterns in lions Panthera leo living in savanna woodlands of the Kruger National Park, South Africa, were investigated and compared with those of the Tanzanian ‘plains-like’ ecosystems (e.g. Serengeti Plains and Ngorongoro Crater). First, lower levels of mortality in the juvenile age classes were found in Kruger lions, which in turn, extend the inter-birth period. A further difference was a prolonged period of association of sub-adult males with their natal pride, either directly or in a land tenure system that has not been described previously. Most (80%) of young male coalitions rather than becoming nomadic, remained close to their natal territory after leaving the pride, either as non-territorial sub-adults or adults and even as territorial adults. Only 20% of coalitions did not stay close to their natal range, one of which acquired a territory 20 km away from its natal pride. The pattern of territory acquisition, in fact, was one in which the majority of holders acquired territories close to their natal ranges. These behaviour patterns contrast markedly with those from ‘plains-like’ ecosystems where dispersing males usually move far away from their natal prides range (>200) km and often remain nomadic for extended periods of time. Dense bush and access to sufficient prey resources in the form of resident buffalo Syncerus caffer herds may be important factors allowing extended residence near the natal prides territory. Buffalo were more available in our study area habitat than in neighbouring habitats, and comprised the majority of male lion kills. Extended male residence contrasts markedly with current theory on dispersal in polygynous mammals, which holds that only one sex (females for lions) gain an advantage by staying close to the territory of their natal pride. In Kruger it seems that both sexes gain an advantage by not dispersing far, and use currently undocumented mechanisms to avoid inbreeding.

Identification of potential conflict areas between land transformation and biodiversity conservation in north-eastern South Africa

Abstract Transformation of natural vegetation to other land-uses, such as crop cultivation and urban development, presents the most important threat to biodiversity. Plant and animal species distribution data were employed to identify areas of high biodiversity value in the major summer crop production region in north-eastern South Africa. These areas of biodiversity conservation importance were then evaluated in terms of their (1) potential overlap with areas currently transformed by land-uses in the region and (2) potential co-occurrence with areas of natural vegetation cover likely to become cultivated. Integrating species distribution, land-cover and land capability data allowed for potential conflict areas, i.e. areas with a high biodiversity value facing large current or future land transformation threats to be identified. Areas of potential conflict appear to be central Gauteng, the KwaZulu-Natal coastline, Maputuland and the escarpment of Mpumalanga. Most of the arable areas, that are not currently under some form of land-use, are marginal lands where the physical land characteristics demand high input costs, give rise to low yields and are thus not suitable for full scale commercial cultivation. As the results indicate some of these areas have a high biodiversity value, land reform programs should therefore refrain from promoting cultivation on marginal lands in these conflict areas, as they provide the last safe havens for many species. The proportion of bird, butterfly, mammal and plant species’ ranges remaining in an untransformed state was quantified. Animal species with less than 60% of their natural range remaining, referred to as impacted species, comprised 63 bird, 207 butterfly and 15 mammal species. The grid cells containing these impacted species were identified as additional potential conflict areas. This study presents evidence that there is significant overlap between areas of biodiversity conservation interest and transformed or arable land in this region of South Africa and that there is an urgent need for the formulation of appropriate policies to promote biodiversity conservation on private farmland.

Ranking priority biodiversity areas: An iterative conservation value-based approach

Abstract We present (1) a composite rarity-based iterative reserve selection (CRIRS) algorithm and apply it to three regional mammal databases in north-eastern South Africa. Two types of ‘rarity’ are used to resolve ties between 25×25-km grid cells in the region, species-specific conservation priority scores and conventional database rarity. As expected, grid cell pre-selection (the forced inclusion of grid cells with a specified percentage of their areas dedicated to conservation) and grid cell filtering (the removal of unsuitable grid cells from consideration by the ‘near minimum set’ (NMS) algorithm) results in decreased efficiency of species representation. Grid cell post-selection, to add the top 5% of richest sites to the selected NMS sites, indicates minimal overlap between rarity- and richness-based procedures. (2) A comparison with the Nicholls and Margules (1993) algorithm ( Biol. Con. , 64 , 165–169) reveals minor differences in efficiency, whereas different input data sets influence the relative efficiencies and extent of grid cell sharing by these algorithms. (3) A further ‘greedy’ algorithm, which assigns ‘relative biodiversity scores’ (RBS) to sites by combining grid cell richness and summed rarity scores, is presented. This enables biodiversity assessments to be incorporated into development planning. These three approaches (CRIRS, Nicholls & Margules (1993) and RBS) and single-criterion variations of the CRIRS algorithm are compared using mammal data from north-eastern South Africa and their respective strengths are emphasized.

Testing generalities in the shape of patch occupancy frequency distributions.

Bimodal patch occupancy frequency distributions regularly appear in studies of a variety of taxa at a variety of spatial scales. Metapopulation models associated with the core-satellite hypothesis and a strong rescue effect predict the occurrence of this bi- modality. However, there have been numerous other explanations, both artifactual and biological, of bimodality in patch occupancy frequency distributions. One approach to a better understanding of the phenomenon is to conduct studies on a variety of taxa and spatial scales. Here we examine patterns of patch occupancy frequency distributions for plants, dung beetles, and birds at four spatial scales in sand forest and mixed woodland in Tembe Elephant Park and Sileza Nature Reserve in South Africa. We then examine the predictions of each alternative mechanism proposed to explain bimodality with respect to the patterns found in this study. The incidence of bimodality was high. Little evidence was found for any of the artifactual or nonmetapopulation-based explanations of bimodality. Although there were no between-taxon differences in the shape of occupancy distributions, there was a clear trend of decreasing frequency of bimodality with an increase in the size of the area examined. The general shape of range-size frequency distributions in combi- nation with an area effect is suggested as a mechanism underlying this pattern. Metapopula- tion dynamics associated with a strong rescue effect could also not be excluded as a possible mechanism playing a role in generating the bimodality found at the patch scale.

Modelling the spatial distribution of two important South African plantation forestry pathogens

Pathogens, pests and diseases impact heavily on commercial plantation forestry in South Africa, and must thus be considered in any diversified and adaptive management approach. Two important fungal pathogens of Pinus and Eucalyptus species, respectively, are Sphaeropsis sapinea and Cryphonectria cubensis. The aim of this study was to explore the use of bioclimatic modelling to predict the habitat distribution for these pathogens, and to consider potential distribution patterns under conditions of climate change. High-risk areas identified for Sphaeropsis dieback coincide with the summer rainfall hail belt, emphasising the need for planting resistant Pinus spp. in these regions. A much smaller area of South Africa is predicted to be suitable for the occurrence of C. cubensis than for S. sapinea, but a range shift westward in suitable habitat for C. cubensis is predicted under a climate change scenario. Of concern is that many of these areas are currently being planted with disease susceptible Eucalyptus clones. These preliminary results, and further refinement of the model, will lay a valuable foundation for future risk assessment and strategic management planning in the South African forestry industry.

Social Dynamics and the Cortisol Response to Immobilization Stress of the African Wild Dog, Lycaon pictus

The aims of the study were to characterize the cortisol response to immobilization stress in African wild dogs (Lycaon pictus) and to investigate the relationship between stress and sociality in these pack-living canids. Ad lib. observations were made on a captive pack of 19 wild dogs. Individuals were classified as either dominant or subordinate. Cardinal and ordinal dominance indices were also calculated for pack members, as were three other behavioral indices. Active and passive dominance styles were distinguished. Serial blood samples were drawn from animals after chemical immobilization and again after ACTH challenge. The relationship among rank, plasma cortisol concentration, and behavioral style was investigated. When data were combined over the entire study period, there was no obvious relationship between rank and cortisol concentrations or cortisol responsiveness to immobilization stress. Instead, younger animals had higher cortisol concentrations than older ones. Age cohorts were also clearly separated on the basis of behavioral profiles. For males, these distinctions among age classes were especially apparent during the second part of the study period, when subadults occupied dominant positions in the hierarchy. Adult males maintained relatively low cortisol concentrations, despite being involved in and losing a high proportion of dominance interactions. Age-related differences in cortisol profiles of dominant individuals may be explained by differences in the style of dominance employed, with younger males using proportionately more active dominance (threats used to elicit submission). The separation of age classes according to rank, behavioral styles, and cortisol concentrations may reflect improved social skillfulness with age.