OpenUCT :: Browsing by Author "Cumming, Graeme S"

Browsing by Author "Cumming, Graeme S"

Now showing 1 - 20 of 20

Restricted
Assessing the broad-scale impact of agriculturally transformed and protected area landscapes on avian taxonomic and functional richness
(2009) Child, Matthew F; Cumming, Graeme S; Amano, Tatsuya
Anthropogenic modification of natural habitat is resulting in a widespread loss of biodiversity. One of the primary responses of human societies to biodiversity loss has been the creation of protected areas. Two of the most important questions in conservation biology are: (1) whether protected areas are playing their intended role as reservoirs of biodiversity; and (2) whether habitat outside protected areas, particularly in agricultural landscapes, plays a significant role in maintaining biodiversity and the ecosystem services that it provides. Even though empirical evidence is still lacking on the exact mapping from functional group richness to specific ecosystem services, functional groups are good indicators of ecosystem functioning and thus service provision. We classified the South African avifauna into nine functional groups and tested at a coarse grain for differences in functional group composition between landscapes containing predominantly agricultural vs. protected areas. We used a matched pair sampling design to control for confounding variance. We found that avian functional groups respond in quantitatively and qualitatively distinct ways to agriculturally dominated landscapes. Raptors and scavengers displayed the most consistent losses, while nutrient dispersers and grazers tended to increase. Spatial detrending and randomisation tests suggested that only raptors and scavengers are negatively affected by agricultural landscapes independently of spatial autocorrelation. Thus, protected area landscapes are serving as important reservoirs of functionally important upper trophic populations while agricultural landscapes facilitate the presence of species that link aquatic and terrestrial systems. These results demonstrate the potential for complementary facets of functional diversity to exist on landscapes containing vastly different land-uses.
Open Access
Environmental influences on moult and movement strategies in southern African waterfowl
(2012) Ndlovu, Mduduzi; Cumming, Graeme S; Hockey, Phil A R
Waterfowl annual life history events in north-temperate regions are driven primarily by predictable seasonal variations in temperature. In contrast, the spatio-temporal availability of adequate resources to waterfowl in the semi-arid regions of southern Africa is determined by rainfall which is extremely variable in timing and intensity. I studied the environmental influences on flight-feather moult and movement strategies of southern African waterfowl. Six duck species that are fairly common in most parts of South Africa were selected for the study, namely; Egyptian Geese, Alopochen aegyptiaca, Spur-winged Geese, Plectropterus gambensis, South African Shelducks, Tadorna cana, Yellow-billed Ducks, Anas undulata, Red-billed Teals, A. erythrorhyncha and Southern Pochards, Netta erythrophthalma. I chose two study sites to represent the extremes of environmental conditions in southern African, namely Barberspan (summer-rainfall region) and Strandfontein (temperate winter-rainfall region). I investigated the underlying responses of Afrotropical waterfowl to stochastic varying environmental conditions in southern Africa and the life-history strategies they have evolved to cope with this variability. The study also compares and contrasts the life-history strategies of southern hemisphere waterfowl with those of the northern hemisphere.
Open Access
Host specificity and co-speciation in avian haemosporidia in the Western Cape, South Africa
(Public Library of Science, 2014) Okanga, Sharon; Cumming, Graeme S; Hockey, Philip A R; Nupen, Lisa; Peters, Jeffrey L
Host and pathogen ecology are often closely linked, with evolutionary processes often leading to the development of host specificity traits in some pathogens. Host specificity may range from ‘generalist’, where pathogens infect any available competent host; to ‘specialist’, where pathogens repeatedly infect specific host species or families. Avian malaria ecology in the region remains largely unexplored, despite the presence of vulnerable endemic avian species. We analysed the expression of host specificity in avian haemosporidia, by applying a previously developed host specificity index to lineages isolated from wetland passerines in the Western Cape, South Africa. Parasite lineages were isolated using PCR and identified when possible using matching lineages deposited in GenBank and in MalAvi. Parasitic clades were constructed from phylogenetic trees consisting of Plasmodium and Haemoproteus lineages. Isolated lineages matched some strains of Plasmodium relictum , P. elongatum , Haemoproteus sylvae and H. lanii . Plasmodium lineages infected a wide range of hosts from several avian families in a generalist pattern of infection. Plasmodium spp. also exhibited an infection trend according to host abundance rather than host species. By contrast, Haemoproteus lineages were typically restricted to one or two host species or families, and displayed higher host fidelity than Plasmodium spp. The findings confirm that a range of host specificity traits are exhibited by avian haemosporidia in the region. The traits show the potential to not only impact infection prevalence within specific host species, but also to affect patterns of infection at the community level.
Open Access
Human networks of tetrapod translocations in the Western Cape, South Africa: trends and potential impacts on biodiversity
(2012) Goss, Jeremy R; Cumming, Graeme S
Global trends show an increase in wildlife trade associated with the process of globalisation and increased international trade. In addition, biodiversity managers are increasingly turning to species translocations to achieve conservation goals. These human induced movements of wildlife have a number of potential impacts, one being the introduction of non-native species that may establish and become invasive. Although the underlying mechanisms are debated, it is accepted that invasive species are having detrimental effects on biodiversity worldwide.
Open Access
The influence of location on the structure and functioning of private land conservation networks in the Western Cape province of South Africa
(2016) Baum, Julia; Cumming, Graeme S
Protected areas are an important tool for biodiversity conservation. Statutory protected areas are, however, perceived to currently be insufficient in extent and functioning for achieving conservation goals. Conservation action on privately owned land plays an increasingly vital role in expanding the global conservation estate. Private Land Conservation Areas (PLCAs) exist with internal properties and external contexts and do not occur isolated in space and time. They can thus best be described as linked social-ecological systems. Little comprehensive work has yet been done concerning the structure and functioning of PLCAs. However, an understanding of their emergence, long-term persistence and contribution to conservation is highly relevant. How can PLCAs maintain their identity against disturbances in order to be resilient into the future? Spatial patterns and relationships determine the answer to this question. Geographical location influences the private conservation estate through different drivers, namely biophysical conditions, network connections and membership, as well as socio-economic conditions. I thus used a comparative, spatially explicit and holistic approach to better understand spatial resilience of PLCAs in the Western Cape Province of South Africa as case study region. The approach was based on assessing representative measures for four elements of system identity (being components, relationships, sources of continuity, and sources of innovation). I expected that geographical location and spatial variation in social-ecological factors strongly influence PLCA types, socio-economic interaction networks among protected areas and other stakeholders, contribution to conservation by PLCAs and their ecotourism performance. Information and data for this research were obtained from personal interviews conducted with owners and managers of 70 PLCAs across the province. Additional data were derived via conservation authorities and online tools. My findings show that the identity and resilience of PLCAs are strongly dominated by the influence of spatial location and heterogeneity in factors such as ecological features or socioeconomic context. I was able to verify existing PLCA types, namely game and habitat reserves, which strongly depended on the biophysical context. Visitation rates were influenced by location which determined the adopted corporate model of PLCAs. Clear neighbourhood effects emerged in socioeconomic interaction networks, which further highlighted great potential to enhance collaboration across scales. PLCAs provided a substantial contribution to conservation targets in terms of importance (covering critical biodiversity areas) and urgency (protecting ecosystems of threatened status). My findings will be valuable to highlight opportunities for more effective conservation in the study region, and to advance insights into the spatial resilience of social-ecological systems.
Open Access
Investigating avian influenza infection hotspots in old-world shorebirds
(Public Library of Science, 2012) Gaidet, Nicolas; Mamy, Ahmed B Ould El; Cappelle, Julien; Caron, Alexandre; Cumming, Graeme S; Grosbois, Vladimir; Gil, Patricia; Hammoumi, Saliha; de Almeida, Renata Servan; Fereidouni, Sasan R
Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered.
Open Access
Landscape heterogeneity by termitaria and its effect on ant community composition in the miombo woodlands of Chizarira Naitonal Park, Zimbabwe
(2010) Skidmore, Allison Mae; Cumming, Graeme S; Cumming, David HM
Open Access
Large vegetated termitaria and fire impacts on reptilitan community assemblage in a miombo woodland system heavily impacted by elephants
(2010) Heermans, Ben Cooper; Cumming, Graeme S; Cumming, David HM; Seymour, Colleen
Open Access
Linking avian communities and avian influenza ecology in southern Africa using epidemiological functional groups
(BioMed Central, 2012-10-26) Caron, Alexandre; de Garine-Wichatitsky, Michel; Ndlovu, Mduduzi; Cumming, Graeme S
The ecology of pathogens, and particularly their emergence in multi-host systems, is complex. New approaches are needed to reduce superficial complexities to a level that still allows scientists to analyse underlying and more fundamental processes. One promising approach for simplification is to use an epidemiological-function classification to describe ecological diversity in a way that relates directly to pathogen dynamics. In this article, we develop and apply the epidemiological functional group (EFG) concept to explore the relationships between wild bird communities and avian influenza virus (AIV) in three ecosystems in southern Africa. Using a two year dataset that combined bird counts and bimonthly sampling for AIV, we allocated each bird species to a set of EFGs that captured two overarching epidemiological functions: the capacity of species to maintain AIV in the system, and their potential to introduce the virus. Comparing AIV prevalence between EFGs suggested that the hypothesis that anseriforms (ducks) and charadriiforms (waders) drive AIV epidemiology cannot entirely explain the high prevalence observed in some EFGs. If anseriforms do play an important role in AIV dynamics in each of the three ecosystems, the role of other species in the local maintenance of AIV cannot be ruled out. The EFG concept thus helped us to identify gaps in knowledge and to highlight understudied bird groups that might play a role in AIV epidemiology. In general, the use of EFGs has potential for generating a range of valuable insights in epidemiology, just as functional group approaches have done in ecology.
Open Access
Movement patterns of African elephants (Loxodont africana, Blumenbach) in a seasonally variable ecosystem in south-eastern Chad
(2014) Labuschagne, Zanne Claire; Cumming, David HM; Cumming, Graeme S
African elephant (Loxodonta africana) range and numbers have declined over the past century as a result of increasing human populations, agricultural development, and illegal hunting for ivory. Understanding the dynamics of wide-ranging animal migrations is important for the conservation of these species and their habitats in a rapidly changing world. The study of movement has greatly advanced in the past few decades and novel approaches for characterizing and interpreting complex movement data, predominantly collected through telemetry, have emerged. The Zakouma National Park elephant population has declined dramatically over the past ten years due to rampant ivory poaching. Several elephants in this population were fitted with satellite collars between 2011 and 2012. The telemetry data collected from these animals, in combination with data collected from the same population ten years earlier, provides spatiotemporal movement data from before and after a period of severe poaching. Broad scale shifts in seasonal movement patterns between these two time frames were explored. Movement behaviour was analysed at a finer spatial and temporal scale by comparing the rate of movement within different areas, during the day and night. A spatially-explicit approach for characterizing movement behaviour within discrete grid squares was used to identify seasonal patterns in the distribution of movement behaviour indicative of stress. After ten years of highly stressful poaching conditions, extensive seasonal migrations to the north and west of Zakouma National Park persist. At a finer spatial scale movement behaviour indicative of human-induced stress has emerged, especially in the areas utilized to the north of the park. Elephant behaviour to the north of Zakouma, particularly in response to the main road intersecting this area, suggests that barriers to dispersal may soon arise. Furthermore, the absence of migration in the wet season of 2013, after the data cut-off point for this study, suggests that the migration behaviour of this elephant population may be changing. In light of these findings, land-use planning in this area should be carried out in order to realign the boundaries of protected areas to include important elephant dispersal areas.
Open Access
A multi-scale study on the movement ecology of Afrotropical waterbirds
(2016) Henry, Dominic A W; Cumming, Graeme S
Understanding the processes and mechanisms governing animal movement is a fundamental goal in ecology. Processes driving movement can occur across multiple spatiotemporal scales and have important consequences for the structure and dynamics of populations, communities and ecosystems. The study of movement provides insights into the ecological resources and habitats necessary for persistence of species and communities. It also provides a theoretical and applied basis from which to formulate informed conservation plans. Waterbirds in semiarid southern Africa are an ideal study group for understanding interactions between movement and environmental factors because they exhibit a wide range of movement strategies and are located within a landscape in which resources are characterised by high levels of spatiotemporal variability. Emphasis has been placed on understanding movement phenomena from individually-tracked animals, but cases which consider this approach in conjunction with traditional community ecology perspectives are rare. In this thesis I explored questions of movement in both individuals and communities, and argue that an integrated multi-scale approach is necessary to advance our broader understanding of movement in waterbirds. In the first part of the study I addressed an individual-level movement perspective. I used fine-scale telemetry data from 35 individually tracked Egyptian Geese Alopochenaegyptiaca and Red-billed Teal Anas erythrorhyncha with novel analytical techniques to explore questions of trade-offs in habitat selection, functional responses and whether movement responses to landscape resources are reactive or prescient. My findings suggested that, at the home-range scale, both forage optimisation and predation risk were limiting factors of movement and habitat selection of Egyptian Geese. I also showed for the first time that waterbirds exhibit functional responses in relation to changes in the availability of habitat types. I subsequently showed that the proximate drivers of waterfowl movement are the dynamics of rainfall and primary productivity. Egyptian Geese and Red-billed Teal were able to perceive and respond to temporal shifts in resource conditions prior to habitat patch occupation. This in turn suggested that their movements in semi-arid landscapes are underpinned by an intimate knowledge of the local environment and that waterfowl exhibit a complex behavioural movement strategy. In the second part of the study I used waterbird count data collected from wetlands in KwaZulu-Natal, South Africa, to address the community-level movement perspective.
Open Access
Multi-scale, social-ecological influences on private land conservation in South Africa
(2016) Clements, Hayley S; Cumming, Graeme S; Hoffman, Timm
In understanding the behaviour of social-ecological systems, much focus has been placed on the role of institutions that govern how natural resources should be managed, and the biophysical processes affected by this management. Somewhat less attention has been given to the role played by the natural resource managers themselves. Novel insight into social-ecological systems can be gained from understanding why managers act as they do and how management actions become reinforced into (un)sustainable management regimes. In this thesis I applied a social-ecological systems perspective to the phenomenon of private land conservation. With increasing interest in the role that the private sector can play in global conservation efforts, a pertinent but largely unexplored question is whether private land conservation areas (PLCAs) can conserve biodiversity over sufficiently long time scales. This thesis contributes to social-ecological systems theory through an in-depth analysis of the multi-scale interactions among natural resources, managers and socioeconomic processes, which affect PLCA management practices and their sustainability. The potential ability for commercially operated PLCAs to generate the funds necessary for their maintenance makes them an attractive conservation strategy in an economically-orientated world. There are concerns, however, that (a) their long-term sustainability may be dependent on their ability to become and remain financially viable; and (b) they may be tempted to prioritize profit over biodiversity protection in their management practices, thereby jeopardizing their ecological sustainability. The objectives of this thesis were to investigate if, how and why commercial PLCA managers (a) meet their financial objectives and (b) adopt unsustainable ecological management practices. During 2014 and 2015 I interviewed the managers of 72 commercial PLCAs in the Western and Eastern Cape Provinces of South Africa, a region that supports a rapidly growing yet poorly understood PLCA industry. I applied theories from organizational ecology to understand patterns in the income-generating strategies adopted by PLCA managers. Distinct business models were evident, differentiated by incompatibilities in the biophysical (size, fauna) and socioeconomic (activities, affordability) characteristics of these conservation areas. PLCAs characterized by financial objectives but unprofitable business models suggest that these incompatibilities constrain the ability of managers to effectively adapt to their economic environment, a concept known as "structural inertia" in organizational ecology. Profitability was highest on PLCAs that supported megaherbivores and large predators, reflecting international tourist preferences for charismatic game. Managers' financial objectives influenced the strategies that they employed to manage these mammals. When managers used revenue-generation to inform their management decisions, they undertook management actions that enabled them to maximize and stabilize game populations. While this intensive management resulted in higher revenues, it corresponded in many cases with a lack of ecological monitoring and an increased risk of overstocking game. Regional policy guidelines for large predator management both mitigated and exacerbated the mismatch between financially-desirable and ecologically-sustainable management, depending on whether species-specific guidelines were ecologically appropriate or not. Simulations of a mechanistic PLCA model were used to test whether adopted management strategies influenced the observed constraints on business model adaptation. If the income-generating potential of an adopted business model was low, managers were unable to accumulate the capital necessary to overcome the biophysical and socioeconomic incompatibilities that separated business models, constraining their adaptive capacity. Intensively managed PLCAs were able to generate a more stable annual income, accumulate more capital and overcome constraints on adaptation faster than PLCAs managed according to ecological monitoring. This unique, large-sample assessment of the social-ecological mechanisms underlying PLCA sustainability emphasizes the significant role that managers can play in promoting resilient social-ecological systems. When financial viability is an important consideration, broad-scale socioeconomic factors can influence fine-scale management decisions. Through constraints on adaptation, and the presence or absence of corrective feedbacks between management actions and ecological monitoring, these management decisions can become reinforced into management regimes on a trajectory towards, or away from, sustainability. This study therefore provides a novel contribution to our understanding of how the interactions between managers and ecosystems influence the behaviour of social-ecological systems.
Open Access
The role of waterbirds in the dispersal of aquatic organisms in southern Africa
(2016) Reynolds, Chevonne; Cumming, Graeme S
Dispersal is a fundamental process with far-reaching ecological and evolutionary consequences. Not all organisms are capable of dispersing on their own and instead produce propagules that must be transported to new habitat by a vector. Propagule dispersal by frugivorous bird species is well researched, but only very recently has the capacity of highly mobile waterbirds to disperse aquatic organisms received similar attention in the dispersal literature. Dispersal is important for the organisation of communities, and therefore understanding the frequency and scale of waterbird-mediated dispersal provides insight into the structure of wetland communities. Additionally, the study of waterbird-mediated dispersal in arid southern Africa provides an opportunity to expand our knowledge on the persistence of populations of aquatic organisms in heterogeneous environments. Recently, field and laboratory studies have demonstrated the remarkable ability of waterbirds to disperse the propagules of both plants and aquatic invertebrates. However, these studies have largely been based in the northern hemisphere and many have focussed on long-distance dispersal by migratory waterbirds. Therefore, it is difficult to generalise how waterbird-mediated dispersal plays out in different landscapes and throughout the annual cycle. Furthermore, there is still little knowledge of the spatial patterns of propagule dispersal and the mechanisms that cause these patterns to vary in space and over time. This thesis aims to addresses several of these knowledge gaps in waterbird-mediated dispersal and presents the first detailed study of propagule dispersal by waterbirds anywhere in Africa. In Chapters 2 - 5, I adopt a field- and experimental-based approach to develop a general understanding of waterbird-mediated dispersal in southern Africa. Firstly, making use of faecal samples and feather brushings collected from several waterfowl (duck) species at three locations in South Africa, I determine the quantity and viability of propagules transported via endozoochory and ectozoochory. I then assess the relative contributions of each dispersal mode to the dispersal of plants and aquatic invertebrates in the field. I show that endozoochory is the dominant dispersal mechanism, but it may be complementary to ectozoochory as different propagules are transported via this mode. Secondly, by making use of an experimental feeding trial with two captive waterfowl species, Egyptian Goose and Red-billed Teal, I explore how seed traits mediate a trade-off in recoverability and germinability against gut retention times. I show that small, hard-seeded species are retained for longer and therefore may be dispersed further. Thirdly, I incorporate gut retention time data and Egyptian Goose and Red-billed Teal movement data, acquired from GPS satellite transmitters across five study populations in southern Africa, into a mechanistic model to explore spatial patterns of seed dispersal. The model demonstrates that waterfowl generally facilitate dispersal on the local scale of below 5 km, but on occasion can transport seeds as far as 500 km from a seed source. There was variation in dispersal distances between the vectors and across the study populations and the results indicate that dispersal is affected by both intrinsic and extrinsic drivers of animal movement. In Chapters 6 and 7, I apply the concept of waterbird-mediated dispersal more broadly to address (1) the role of waterbirds in the dispersal of aquatic invaders; and (2) the determination of seed dispersal functional groups amongst a waterfowl community. I conducted a literature review to objectively describe the role of waterbirds in the dispersal of aquatic weeds. Waterbirds are important vectors of aquatic invasive species and consideration of the spatially explicit manner in which birds move is imperative to our understanding of invasive spread. In the second case, I used diet data from the 16 waterfowl species indigenous to southern Africa to explore whether finer level seed dispersal functional groups were evident. I found support for several functional groups of seed disperser based on unique plant families in the diet and suggest that important functional differences do occur between groups of waterfowl species.
Open Access
Tracking socioeconomic vulnerability using network analysis: insights from an avian influenza outbreak in an ostrich production network
(Public Library of Science, 2014) Moore, Christine; Cumming, Graeme S; Slingsby, Jasper; Grewar, John
BACKGROUND: The focus of management in many complex systems is shifting towards facilitation, adaptation, building resilience, and reducing vulnerability. Resilience management requires the development and application of general heuristics and methods for tracking changes in both resilience and vulnerability. We explored the emergence of vulnerability in the South African domestic ostrich industry, an animal production system which typically involves 3-4 movements of each bird during its lifetime. This system has experienced several disease outbreaks, and the aim of this study was to investigate whether these movements have contributed to the vulnerability of this system to large disease outbreaks. METHODOLOGY/PRINCIPAL FINDINGS: The ostrich production system requires numerous movements of birds between different farm types associated with growth (i.e. Hatchery to juvenile rearing farm to adult rearing farm). We used 5 years of movement records between 2005 and 2011 prior to an outbreak of Highly Pathogenic Avian Influenza (H5N2). These data were analyzed using a network analysis in which the farms were represented as nodes and the movements of birds as links. We tested the hypothesis that increasing economic efficiency in the domestic ostrich industry in South Africa made the system more vulnerable to outbreak of Highly Pathogenic Avian Influenza (H5N2). Our results indicated that as time progressed, the network became increasingly vulnerable to pathogen outbreaks. The farms that became infected during the outbreak displayed network qualities, such as significantly higher connectivity and centrality, which predisposed them to be more vulnerable to disease outbreak. Conclusions/Significance Taken in the context of previous research, our results provide strong support for the application of network analysis to track vulnerability, while also providing useful practical implications for system monitoring and management.
Open Access
Understanding Highly Pathogenic Avian Influenza outbreaks in Western Cape Ostrich industry: did network dynamics enhance vulnerability? Christine Moore.
(2012) Moore, Christine; Cumming, Graeme S; Slingsby, Jasper
Disease outbreaks in both domestic and wild systems in recent years indicate the increasing potential for disease spill-over of generalist pathogens between domestic and wild species. Events of this nature are of considerable threat to rare or endangered species, while also being of significant economic concern for the farming industry. Understanding how disease moves within and between these contrasting systems is vital to prevent large-scale, multi-system epidemics in the future. This study utilized network analysis to understand how the movement of ostrich stock between farm locations in the Western Cape, South Africa may have contributed an epidemic outbreak of Highly Pathogenic Avian Influenza (HPAI) within the ostrich industry in 2011.
Open Access
Understanding pathogen transmission dynamics in waterbird communities: At what scale should interactions be studied?
(Academy of Science of South Africa, 2011) MacGregor, Lindy H; Cumming, Graeme S; Hockey, Philip A
Pathogen transmission in animal populations is contingent on interactions between and within species. Often standard ornithological data (e.g. total counts at a wetland) are the only data available for assessing the risks of avian pathogen transmission. In this paper we ask whether these data can be used to infer fine-scale transmission patterns. We tested for non-randomness in waterbird assemblages and explored waterbird interactions using social network analysis. Certain network parameter values were then compared to a data set on avian influenza prevalence in southern Africa. Our results showed that species associations were strongly non-random, implying that most standard ornithological data sets would not provide adequate information on which to base models of pathogen spread. In both aquatic and terrestrial networks, all species regularly associated closely with other network members. The spread of pathogens through the community could thus be rapid. Network analysis together with detailed, fine-scale observations offers a promising avenue for further research and management-oriented applications.
Open Access
Understanding pattern-process relationships in a heterogeneous landscape effects of large termitaria on diversity and disturbance regimes in Miombo woodlands of Northern Zimbabwe
(2012) Joseph, Grant Stuart; Cumming, Graeme S; Cumming, David HM
Spatial heterogeneity has been shown to influence ecosystem processes and important ecosystem properties like resilience and biodiversity, allowing species with specific habitat needs or weaker competitive abilities to persist in disturbed systems that might otherwise have excluded them. Miombo covers 2.7 million km² and is Africa’s largest savanna woodland. Much of this is characterized by Macrotermes termitaria, which can be hotspots of both plant (primary) productivity and animal abundance (secondary and tertiary productivity). To investigate the modulating influence of spatial heterogeneity in the form of large Macrotermes termitaria on woody plant and avian diversity in the face of herbivore impacts and fire (the two disturbances most amenable to management), research progressed in stages.
Open Access
Using real-time forest loss alerts and global deforestation maps to assess the effectiveness of Africa's tropical protected areas
(2015) Bowker, Jenna; Cumming, Graeme S
Tropical rainforests harbor a significant portion of the world's remaining biodiversity. Having undergone rapid changes in forest cover over the last two decades, a large amount of irreplaceable biodiversity has been lost. The establishment of protected areas has been a key strategy to hinder the loss of tropical forests and biodiversity. However, the effectiveness of designating protected areas has been called into question, particularly in regions such as tropical Africa where widespread conditions of poverty, rapid population growth and political instability are evident. Quantitative measurements of park effectiveness for forest conservation are urgently needed, however accurate inferences concerning park effectiveness across broad regions is difficult. Whilst remote sensing techniques have been proposed as a practical solution, the intensity of data processing has made it untenable until recently. Here, I use remote-sensing methods to analyze high-resolution satellite imagery of tropical forest loss (as a proxy for tropical deforestation) within and outside 224 parks across 23 countries in Africa. I compare the extent of tropical forest loss inside parks to outside of them to show that the majority of African parks in the Subtropical and Tropical Moist Broadleaf forest biome are effective in curbing forest loss within park boundaries. However, certain parks were more effective in forest conservation than others. Whilst smaller parks were less effective at preventing forest loss inside park boundaries than larger parks, older parks were less effective than younger parks. Furthermore, parks of varying IUCN management categories exhibited negligible differences in forest loss between one another. Lastly, significant geographical variations in park effectiveness existed: West African parks exhibited the most forest loss within park boundaries and Central African parks exhibited the least. My results demonstrate the complexity of factors which influence a park's ability to curb forest loss within its boundaries. Furthermore, this study is the first bioregional-wide assessment of park effectiveness using remote sensing. These results supplement scarce literature on tropical deforestation in Africa and demonstrate the potential of using remote satellite imagery for measuring the relative impact of park establishment on forest conservation in this region.
Open Access
Using stable isotopes to trace the movements of ducks in southern Africa
(2010) Mutumi, Gregory Lilgee; Cumming, Graeme S
Despite the importance of movement ecology studies, the field faces a prevailing challenge of methodological limitations in tracking individual organisms. This research investigated the utility of the stable isotope technique to trace movements of ducks in southern Africa. I sampled and analysed feathers of ten duck species for stable isotope proportions of Carbon (δ13C), Nitrogen (δ15N) and Hydrogen (δD), from five wetlands (Strandfontein and Barberspan in South Africa, the Manyame catchment in Zimbabwe, Lake Chuali in Mozambique, and Lake Ngami in Botswana) as test cases.Sampling was carried out at different seasons to account for seasonal isotope signature variations. Isotope signatures of feathers grown at different moulting locations were compared to test whether southern Africa shows stable isotope spatial patterns (distinct isotopic regions). Feathers grown at different life-phases were compared to test whether different sites had been used and if more mobile species showed more and stronger isotope distinctions. Finally, growing flight feathers grown at moulting locations were compared across species to query how much information on diet and foraging behaviour can be inferred from southern African duck feather stable isotopes.Feather isotope signatures were distinct by site in at least one of the tested isotopes, for the majority of ducks tested. Strandfontein had more and stronger distinctions of isotope signatures between feathers grown at different life phases. This site is the closest to the sea and most likely to have marine-influenced isotope signatures especially in δ15N, it falls within the Mediterranean climatic conditions experiencing winter rainfall unlike all the other sites. Vegetation compositions (C3 and C4 plant distributions) therefore vary across sites influencing δ13C patterns. More mobile species (only Egyptian Goose Alopochen aegyptiacus from Strandfontein, and Cape Shoveler Anas smithii from Barberspan; determined by mobility scores from other studies) had more and stronger distinctions between flight and body feathers. All the other species did not comply with mobility scores. They showed weaker and fewer tissue signature distinctions than their mobility scores suggested. There were high isotopic signature overlaps in δ13C and δ15N across and within feeding guilds at each moulting site implying dietary overlaps during moulting. More overlaps occurred during the dry seasons (summer in Strandfontein and winter in Lake Chuali, Manyame catchment site, and Lake Ngami). Higher isotopic variances (higher dietary flexibility) were associated with isotope signature divergence to mobility scores especially in Cape Teals and Yellow-billed Ducks.The isotope technique is flawed with uncontrollable sources of variation which potentially confound movement inferences. It is best used when accompanied by conventional methods to detect and counter against species specific biology and dietary behaviour imposed biases in tissue isotope signatures. Further research on how species specific biological processes affect the reflection of spatial patterns of isotopes in feathers is recommended. Multi-isotope time explicit approaches and trace element analysis were also recommended. Scientists should be wary about basing management strategies or building theory about movement patterns of species based on the technique at least in stochastic environments such as southern Africa. My results provide empirical evidence that the technique is unreliable at this scale of analysis. In particular, the majority of ducks in this region are not good candidates for use of isotopic signatures in distinguishing movement patterns of southern African ducks.4983
Open Access
Weaving through the matrix: investigating the influence of urban land use on weaver bird movements into and out of Cape Town wetlands
(2014) Calder, Jordan-Laine; Cumming, Graeme S; Oschadleus, Hans-Dieter
Urbanization, a fast growing and destructive human land use, causes local extinctions, biotic homogenization and fragmentation of natural habitats. Understanding how the nature of the urban matrix affects the species residing within a city’s fragmented habitats is an important founding component of urban conservation. This study investigated the influence that the urban matrix, as well as patch isolation, size and quality, had on weaver bird movement into and out of wetland sites in Cape Town, a growing city within a global biodiversity hotspot. Weaver bird movement data from 42 wetland sites were obtained through a long term mark - release - recapture project. Distance - based linear models revealed that site proximity was important as a predictor of weaver movement into and out of sites, while the site variables ( wetland size, bird abundance and weaver colony size) had limited and inconclusive influence. Once the variation explained by the proximity and site variables had been accounted for, the composition of the urban matrix and the presence of rivers as potential movement corridors (measured at three spatial scales) had little influence on weaver movement. The finding that proximity (or site isolation) influences weaver movement has important implications for maintaining current landscape connectivity. Habitat isolation, resulting from further habitat removal or destruction, could be expected to reduce movements of weavers, and potentially other species, among patches of favourable habitat. Weavers are robust, vagile birds that do well in the presence of humans and may not be highly sensitive to the nature of the urban matrix. Research into how other, less resilient and vagile species respond to the degree of urbanization in the matrix between wetlands would contribute further to our knowledge of urban biodiversity in this global biodiversity hotspot.