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Dissertation zugänglich unter
Communities of small mammals in Kafue National Park and their response to fire, vegetation and land use
Kleinsäugergemeinschaften im Kafue-Nationalpark und ihreReaktion auf Feuer, Vegetation und Landnutzung
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Freie Schlagwörter (Englisch):
Small mammals , Kafue National Park , Miombo woodland , termitaria , grassland , fire , land use
43.31 , 42.91 , 42.65 , 42.84
Ganzhorn, Jörg U. (Prof. Dr.)
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
Small mammals assume multiple and cardinal roles in ecosystem functionality. They are known to influence the composition and structure of plant communities through their herbivorous and seed predation activities, as agents of soil aeration through their burrowing activities, pest controllers as the consume large amounts of insects and plant material, and as food for a variety of prey. Yet, the understanding of small mammal ecology is overshadowed by studies of large mammals as small mammals have very little tourism appeal and are often viewed as vermin benefiting from human disturbances. Even so, many small mammals are known to be highly sensitive to anthropogenic factors.
This lack of information on small mammals also applies to the Kafue National Park (KNP), Zambia, including the Busanga Flood Plain as one of KNP’s critical habitats and a wetland of international importance (RAMSAR site number 1659). Not much is known about small mammals in the KNP, much less the influence of anthropogenic and non-antropogenic factors on their communities. Given that KNP is a protected area where the human foot print is minimized, anthropogenic factors that act upon the communities of small mammals include bush fires, that occur repeatedly (annually) on wildlands. These are ignited by various stakeholders including park authorities that set fires in the early dry season (May to mid-July) in order to reduce incidences of fires in the late dry season, and to clear vegetation for photographic tourism. The other anthropogenic factor is habitat modification arising from infrastructure developments in the natural habitats of small mammals as given by the park’s management zones. In order to come to a better understanding of the relationships between small mammals and some of the ecosystem components of KNP, the aims of the study were to (i) provide checklists of small mammals in KNP together with an assessment of their functional characteristics, (ii) investigate the interaction of small mammal communities with three major vegetation formations, land use and fire, and (iii) assess dietary resource-use and partitioning among small mammal species.
In a first step, a literature review provided a species list on which future studies could be based upon. This review identified termitaria, grassland and woodland as the three most important habitats for small mammals in the park. These habitats were then used to assess relationships between small mammals, vegetation, land use and fire. Thus, during the dry season of 2014 and 2015, 6,273 trap nights were employed to trap 105 individuals of 16 species of small mammals in Miombo woodland, termitaria and grassland vegetation. In each of these vegetation types replicate sites were set in areas of low and high fire recurrence. Sites that experienced less than eight years of fire between the years 2000 and 2013 were classified as low fire recurrence sites and those that experienced eight or more, were classified as high fire recurrence sites. For each site, fire age was assigned based on the last time a site experienced fire. For dietary resource-use and partitioning, stable isotope biochemistry techniques were employed. These techniques provide quantitative records of an animal’s feeding ecology based on the signatures of stable isotopes of nitrogen (δ15N) and carbon (δ13C) found in an animal’s tissues. Values of δ13C in animals reflect the carbon source of food whilst δ15N reflects the trophic position in a community. Linear models and multivariate analysis were used to asses the effect of vegetation, land use and fire on the community measures.
More than 50% of the small mammal species described in Zambia occur in KNP, which makes it an important conservation area for this group of mammals. These belong to the orders Rodentia, Soricomorpha and Macroscelidea. Of these, only one species, Fukomys kafuensis bears a high conservation status and is listed as vulnerable by the International Union for Conservation. Important habitats for small mammals include termitaria, woodland and grassland, with the former two being the habitats for Fukomys kafuensis.
Land use as prescribed by the management zones has no influence on the community structure and composition of small mammals. However, vegetation does and thus, conservation actions aimed at preserving vegetation formations would be more beneficial to small mammals than the large tracts of land assigned as management zones in the park. Termitarias proved to be important for small mammals particularly in areas prone to disturbance. In the Busanga Flood Plain, termitarias act as refugia for species during periods of disturbance as they provide shelter against fire, as it may be easier to dig in the mounds as compared to the hard-compacted soils in the grasslands after floods. Further in the wet season, in times of floods, they offer dry ground as they are elevated. This role, was corroborated by the large dietary space small mammal communities in termitarias occupied, that encompassed almost all the dietary spaces of other communities in miombo and grasslands.
Although fire recurrence as a single factor had no significant impact on species richness its effect became significant when combined with the time elapsed since the last fire. This suggested adaptation of small mammal communities to the fire regimes in their environments, as areas that were burnt frequently, had fewer species irrespective of the time elapsed since the last fire had occurred. Further, the smaller sized species seemed to be more affected by recent burns than larger species that may have fewer problems escaping fire and recolonizing burnt areas. This response to fire by small mammals was also reflected in the difference in the dietary niche widths particularly for rodents. Rodents had broader dietary niches under high fire recurrence and may indicate relaxed competition under this regime because their populations do not reach the carrying capacity of the habitat, or reduced species numbers under high-versus-low fire frequency regimes. This is an important finding as it provides an understanding on the boundary conditions under which small mammals reach their carrying capacity in this ecosystem. For shrews, the opposite persists as they appear to have narrower dietary niches in areas under high fire frequencies and their dietary niche differentiation remains unresolved. Another important finding was that rodent communities appeared to be structured by size (differences in body mass between species of the same guild by a factor of two), dietary guilds (based on carbon isotopes) or trophic levels (based on nitrogen isotopes), suggesting mechanisms of coexistence to avoid competition.
In conclusion, small mammals are important components of the KNP, and their responses to the various environmental factors acting upon them, needs to be incorporated into the management plans of the park. Further, as competition appears to be an important component structuring rodent communities in the park, it signifies limiting resources. Since the limitations of dietary resources are likely to affect large and small mammals alike, studies of African savannas should use a broad approach to come to a comprehensive understanding of African ecosystems.