Friday, September 13, 2013

Effective conservation of large herbivore biodiversity in Africa: the need for a general framework of functional seasonal resources.”

Dr Richard Fynn a Senior Researcher in Rangeland and grazing ecosystem ecology at Okavango Research Institute, Maun, presented a paper entitled “ Effective conservation of large herbivore biodiversity in Africa: the need for a general framework of functional seasonal resources”on Thursday 12th Sept 2013. The same presentation will be given at the South African Wildlife Management Association conference (SAWMA conference 15-19th September 2013) in Kruger National Park. What follows is the summary of the presentation: functional heterogeneity/diversity of seasonal habitats and resources needed to enable various large herbivore species to adapt spatially to large temporal variation in resource availability (energy, nutrients and water), and to variation in their own resource demands, while minimizing the risk of predation. Adaptation to high demands for energy and nutrients during the period of pregnancy and lactation requires acquisition of high-quality resources. High-quality resources consist of easily digestible forage with high concentrations of energy, protein and minerals such as Ca, Na and P. For grazers with wide mouths relative to their body size, short grasses with high leaf to stem ratios and high leaf density, which facilitate high bite size of digestible green leaf, are typical high-quality resources, whereas for grazers with relatively narrow mouths individual green leaves on taller grasses are typical high-quality resources. For browsers certain leafy leguminous forb species often provide the highest quality forage. Owing to their preferred nature and location in less productive habitats, high-quality resources are quickly depleted and maintenance of a consistent intake of energy and nutrients over most of the annual cycle is generally achieved by access to appropriate staple resources, while adaptation to reduced resource quantity and quality over the dry season is achieved by access to reserve and bridging resources. During drought years the lowest quality components of the forage base, generally left uneaten in most years, provides a buffer or key resource that stabilizes population dynamics. In general, reserve, bridging and buffer resources occur in more productive habitats and are, therefore, coarser in nature but more reliable in forage production than high-quality resources with staple resources being intermediate between these classes. For grazers, bridging resources are created by dry-season fires in various wetland types and floodplains, which stimulate a bridge of green regrowth over the dry season, while less preferred deciduous trees that sprout new leaves (only palatable when newly emerged) over the dry season provide a bridge of green forage for browsers. These resource types are generic in that they are functionally relevant to all grazing and browsing herbivores and, therefore, provide a general framework for organizing our understanding and modeling of herbivore adaptive foraging strategies over the annual cycle. For a specific application of this generic resource framework to the conservation of a wide variety of African herbivore species, the framework must be linked to our understanding of how mouth part, digestive anatomy and body size influence herbivore perceptions of these generic resources and of predation risk. This knowledge can then be used to assess and conserve appropriate functional heterogeneity of habitats in conservation areas. Moreover, this framework enables us to understand how to apply ecosystem engineering inputs (e.g. through livestock management) that manipulates and enhances functional heterogeneity, especially in regions where wildlife numbers and their associated impacts have declined or where certain rare species are being specifically targeted by management.

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