Dots show individual data, labeled by species, as indicated in the legend, while lines indicate 95% confidence ellipses for each species. Points indicate individual data, labeled according to the fragment size class from which they were collected, as indicated in the legend, while lines indicate 95% confidence ellipses for each fragment size class.
Introduction
General Introduction
Their potential use as an indicator, although time-consuming and resource-intensive, could provide conservationists with a method to select renosterveld fragments for restoration. This potential has been explored for other taxa in the region, with black oil being a potential indicator to assess the suitability of a renosterveld fragment for restoration (Jenkins et al., 2013).
Background
External pressures such as grazing and predation also play a role in determining small mammal community composition (Bovendorp et al., 2019). Investigating the diversity and abundance of small mammals in fragments of the eastern Rûens Renosterveld is hoped to shed more light on the environmental conditions in fragments of the Renosterveld scattered in an agricultural landscape.
Description of project and layout of thesis
Literature Review
- Global context of land use change
- Agriculture and land use change
- Habitat fragmentation
- Effects of habitat fragmentation
- South African context: The Cape Floristic Region
- Renosterveld
- Small mammals
- Stable Isotopes: further insight into landscape use
Some species become restricted to the core of the fragment due to edge effects (Bierregaard et al., 1992). High rainfall has been shown to have a positive effect on the abundance and diversity of small mammals (Yarnell et al., 2007).
Aims and Objectives
Small mammal species play an important role in the maintenance of ecosystem services, thereby playing an important role in the restoration of native vegetation in fragmented habitats. No hypothesis is stated, as this study serves as a preliminary survey of small mammal communities in the region, contributing to a greater understanding of the small mammal communities in Rûens Renosterveld.
Small Mammal diversity and abundance in Eastern Rûens Shale Renosterveld
Introduction
- Eastern Rûens Shale Renosterveld
According to this theory, diversity would increase with increasing habitat area within a landscape and would be independent of fragment size (Presley, et al., 2019). Changes in small mammal communities based on these feeding patterns can have important implications for ecosystem processes (Hurst et al., 2014). The South Coast Renosterveld is largely confined to the semi-arid and sub-humid coastal foreland areas of the southern Cape coast (Rebelo et al., 2006).
Less than 1% of the original area of this vegetation type is formally protected (Rouget et al., 2006). They have been shown to act as pollinators (Wiens et al., 1983) and seed dispersers (Midgley & Anderson, 2005) for some fynbos species.
Rationale
55 Fragmentation in the East Ruens area has occurred on a regional scale, with an extensive transformation in agriculture occurring in the early 1900s. From an ecological perspective, this extensive transformation has resulted in a rapid and relatively recent loss of habitat and fragmentation in the region. The resulting spatial heterogeneity in environmental conditions has likely altered the outcome of species interactions and community dynamics, as has been shown elsewhere (Holt, 1984; Pickett & Cadenasso, 1995).
Small mammals have been shown to be important components of natural ecosystems as consumers, predators and dispersers of seeds, diggers and as prey for carnivores and predators within the CFR (Hoffmann & Zeller, 2005). Various other studies have shown them to be an important factor in the functional ecology of fynbos vegetation (Bond, 1984; Bond. & Breytenbach, 1985), although very little has been studied within reindeer veld.
Research Questions
56 owned Eastern Ruens Shale Renosterveld, and the effects that fragmentation has had on diversity and abundance, and to reflect on these findings in relation to wider restoration and conservation considerations for this type of vegetation. It is part of a multi-disciplinary study with the Table Mountain Fund, with the broad aim of using this information to improve ecological understanding of patterns and processes in this fragmented system. The data obtained will contribute to the work being done by the Overberg Lowlands Conservation Trust and will provide baseline data on small mammals in this type of vegetation, which can be relied upon in future studies.
Study Site
- Location
- Vegetation Patterns
- Geology and Soils
- Climate
This study focuses specifically on the Eastern Rûens, or Eastern Overberg region, which is exclusively characterized by the Eastern Rûens Skalierenosterveld. The distribution of Oos-Rûens Skalierenosterveld extends from Bredasdorp to the Breede River, near Swellendam. In the Eastern Rûens region, vegetation is dominated by small-leaved, low to moderately tall grass-rich shrublands that are restricted to fine-grained, clay-rich soils (Rebelo et al., 2006).
Recent research has highlighted the prevalence of siliceous silcrete outcrops scattered across remnant fragments of the eastern Rûens Renosterveld, showing a similar community structure to that of the Karoo Succulent Biome (Curtis, Stirton & Muasya, 2013). The area where the renosterveld of the eastern Rûens shale renosterveld is found is predominantly composed of fine-grained shales of the Bokkeveld Group Shales, which give rise to clayey and loamy soils, with a minor contribution of Mesozoic sediments of the Uitenhage Group in the northeast.
Methodology
- Small mammal data collection
- Habitat data collection
- Abiotic measures
- Data Analysis
- Species richness, abundance and diversity
- Statistical analysis
Small mammals captured in traps were transferred to a mesh bag, measured and marked with a xylene-free pen near the base of the tail to mark recaptures, and then released. Isolation distance was taken as the distance from the center of a fragment to the perimeter of the nearest continental area of regenerated vegetation. The percentage of each of these types of matrix bordering the fragment, i.e., constituting the edge of the fragment, was calculated.
Species richness, abundance and diversity of small mammal communities were calculated for each of the sites. The disadvantages of the Shannon index are that it is sensitive to sample size and relies on the assumption that all species are equally represented in the sample.
Results
- Trapping
- Species richness and diversity
- Statistical analyses
Species trapped in each fragment size class, number of unique individuals captured, recaptures shown in parentheses. Additionally, functional group abundance was compared across all fragment size classes, with no significant differences between groups. One-way Analysis of Variance test results of species abundance, by fragment size (small, medium and large), at p<0.05.
Results of the Kruskal-Wallis test of species diversity, functional diversity, by fragment size (small, medium and large), at p<0.05. Results of one-tailed Kruskal-Wallis test of functional group abundance based on fragment size (small, medium and large), at p<0.05.
Discussion
This result has been found in other studies, where fragment size was not found to be a strong factor controlling small mammal diversity (Ehlers Smith et al., 2020; Mattos et al., 2021). Results of a similar study of small mammals in the Brazilian savanna found similar results, where no relationship was found between patch size and small mammal diversity (Mattos et al., 2021). Bösing et al., (2014) found that habitat type had the strongest influence on the abundance and diversity of small mammals in the Knersvlakte, a region typified by quartz fields similar to the quartz patches found in the Eastern Rûens ( Curtis, Stirton and Muasya suggest that ecological studies focus on fragmentation and small mammal communities.
Statistical analysis of the relationship between a number of habitat variables and small mammal diversity was attempted, but none were found to be significant. This may be an underlying reason for differences in small mammal species richness observed in the study.
Conclusion
Renosterveld found in transformed agricultural landscapes typically has very low structural heterogeneity (O'Farrell et al., 2008), and although it appears that habitat attributes are more important than fragment size in determining small mammal species, it is possible that the region is already so severely altered and homogenized that any refined signal in small mammal community structure is lost in the region. 2019) highlights the scenario where researchers have shown that species richness is lower in small fragments compared to large fragments, where conservation agencies interpret the result to mean that smaller fragments of habitat have much lower conservation value. 88 more important than isolation or habitat abundance in the landscape in determining the structure of small mammal communities. Like previous studies (see Bond, Ferguson & Forsyth, 1980; . Kerley, 1992), this study found that small mammal populations are negatively correlated with land conversion through agricultural practices, with larger fragments of greater habitat complexity supporting a greater diversity and abundance of small mammal.
Farmer owners' decisions about the management of natural fragments of the Renosterveld can therefore have important implications for small mammal populations. From the context of landowners within an agricultural area, preserving fragments of the rhinoster field for greater density and diversity of small mammals may limit livestock loss to predation by providing alternative prey sources to predators (O'Farrell et al., 2008) .
Isotopic analysis of small mammal faecal samples
- Introduction
- Methodology
- Small mammal data collection
- Sample preparation and isotopic analysis
- Interpretation of isotopic results
- Statistical analysis
- Results
- Mean isotopic values
- MANOVA
- ANOVA
- Species specifics
- Discussion
- Conclusion
There are very few studies examining dietary differences between small mammalian communities in the Cape Floristic Region. Fecal samples from six small mammal species were collected from 15 different fragments of renosterveld vegetation in the Overberg. MANOVA and ANOVA results, testing differences in the values of the stable isotopes δ13C and δ15N of small mammals sampled at 15 sites, classified by size, in East Rûens Renosterveld.
The δ15N and δ13C results for all captured individuals do not show any distinct species separation, as suggested in the literature (Codron et al., 2015). Differences in the range of δ13C between individuals captured in small, medium and large fragments were evident.
Conclusion
Small mammal community characteristics as indicators of ecological disturbance in the Willem Pretorius Nature Reserve, Free State, South Africa. The use of small mammal community characteristics as an indicator of ecological disturbance in the Korannaberg Conservancy. Effects of livestock grazing and habitat characteristics on small mammal communities in the Knersvlakte, South Africa.
Biotic and abiotic correlates of small mammal community structure in the Groendal Wilderness Area, Eastern Cape, South Africa. Influence of variations in land use intensity on species diversity and abundance of small mammals in the Nama Karoo, Namibia. Conservation options for large and medium-sized mammals in the hotspot of the Cape Floristic Region, South Africa.
Formulating conservation goals for biodiversity pattern and process in the Cape Floristic Region, South Africa.
