Understanding resource use of an invasive species: Diet of the common warthog in Eastern Cape succulent thicket
- Authors: Mgqatsa, Nokubonga , Jama, Kanyisa , Landman, Marietjie , Kerley, Graham I H
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462746 , vital:76331 , xlink:href="https://doi.org/10.1016/j.jaridenv.2024.105155"
- Description: Understanding resource use of invasive species provides insights for predicting and mitigating their impacts on biodiversity. We explored the predictability of diet of the invasive common warthog by describing and comparing the diet of warthog populations from two semi-arid, invaded sites, Addo Elephant National Park (AMC), and Great Fish River Nature Reserve (GFRNR), Eastern Cape, South Africa. These sites are both dominated by the Subtropical Thicket biome, but differ in vegetation type. We used forage availability to estimate diet preferences at AMC. We predicted that warthog would consume grass in invaded landscapes. Additionally, we predicted that the diet at one invaded site would predict this at another invaded site. As predicted, warthog mainly consumed grass at both sites (AMC – 87.4%, GFRNR – 88.5%), eating few woody plants, succulents, and forbs. Cynodon dactylon was the most consumed species in AMC, in GFRNR this was Eragrostis curvula and Cymbopogon pospichilii. Our ability to predict the diet between sites was constrained by variation in the plant species consumed. We found strong relationships between the consumption of preferred plant species at AMC and their consumption at GFRNR. We show that warthogs are specialised grazers outside their native range and thus can be expected to impact grass communities in invaded areas, especially preferred grass species. Thus, conservation managers need to monitor grasses in areas invaded by warthog to better detect and manage their impacts.
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- Date Issued: 2024
Using photo by-catch data to reliably estimate spotted hyaena densities over time
- Authors: Mgqatsa, Nokubonga , Jama, Kanyisa , Landman, Marietjie , Kerley, Graham I H
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462757 , vital:76332 , xlink:href="https://doi.org/10.1016/j.jaridenv.2024.105155"
- Description: Protected areas are becoming increasingly isolated refugia for large carnivores but remain critical for their survival. Spotted hyaenas (Crocuta crocuta) are important members of the African large carnivore guild but, like other members of the guild, routinely come into conflict with people because of their large home ranges that are not always confined to protected areas. To effectively conserve spotted hyaena populations, it is paramount to monitor their abundance through reliable and cost-effective techniques. We estimated the density of spotted hyaenas in Hluhluwe–iMfolozi Park (HiP), South Africa using camera trap images and a spatially explicit capture-recapture (SECR) framework between 2013 and 2018. We estimated an average of 18.29 ± 3.27 spotted hyaenas per 100 km2 between 2013 and 2018, with an annual estimated high of 20.83/100 km2 in 2014 and a low of 11.98/100 km2 in 2015. Our results demonstrate that camera trap by-catch data can be used for estimating spotted hyaena densities over time. We believe that given the widespread use and deployment of camera traps across Africa, collaborative efforts to use existing data to improve regional and continental estimates and population trends for spotted hyaenas should be a priority.
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- Date Issued: 2024
Elephant effects on treefall and logfall highlight the absence of megaherbivores in coarse woody debris conceptual frameworks
- Authors: Landman, Marietjie , Mgqatsa, Nokubonga , Cromsigt, Joris P , Kerley, Graham I H
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/462614 , vital:76319 , xlink:href="https://doi.org/10.1016/j.foreco.2019.02.015"
- Description: Despite the importance of coarse woody debris (CWD) in woody ecosystems, conceptual frameworks of its dynamics currently exclude the role of the megaherbivores, focusing instead on the role of insects, disease, fire, wind and droughts. However, recognizing the ecological roles of the megaherbivores is one of the most urgent contemporary issues, particularly as their decline will likely have unanticipated outcomes at the ecosystem-level. Here we used sites with and without elephants in a semi-arid woodland ecosystem in South Africa to test whether elephants changed the quantitative and qualitative features of the CWD profile in relation to other wood producers. We show that elephants increased the abundance of CWD, influenced its quality by toppling mostly maturing trees, and changed the distribution of large woody items along gentle hillslopes. Surprisingly, and despite the recognized importance of both CWD and elephants for biodiversity, there is almost no published data on the role of elephants in shaping wood-living communities by changing fallen woody debris dynamics. Our study contributes towards developing a broader conceptual framework of CWD dynamics that includes the role of megaherbivores and provides a novel view of the ecological consequences of the loss of the Pleistocene megaherbivores. Our findings have important implications for CWD restoration efforts in transformed systems that previously supported megaherbivores.
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- Date Issued: 2019
The Aardvark as an ecological engineer in the Eastern Karoo: dig patterns and emergent processes
- Authors: Martin, Stephanie Ann , Landman, Marietjie
- Date: 2017
- Subjects: Ecosystem services -- South Africa -- Eastern Cape Environmental engineering -- South Africa -- Eastern Cape Soil dynamics -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11952 , vital:27010
- Description: Species which play particularly important roles in ecosystem patterns and processes are recognised as keystone species or ecosystem engineers. The conservation of these species is critical for the maintenance of the ecological role they play in ecosystem function. The aardvark, Orycteropus afer, is known to play a role in biopedturbation through digging for refuges and for prey, and as a consequence of these digging activities is expected to serve the role of an ecosystem engineer and keystone species. This study aimed to describe and quantify the ecological patterns and processes driven by the aardvark through their digging activities, within the eastern Karoo, and thereby evaluate the significance of aardvarks as ecosystem engineers and keystone species in a semi-arid environment. The landscape pattern (dig abundance and distribution) and soil displacement of aardvark forage and refuge digs in a semi-arid Karoo landscape, as well as the ecological processes (generating fertile, seed retention hotspots) driven by aardvark forage digs was measured. Refuge digs occurred in the highest densities in areas characterised by a specific suite of soil, vegetation and elevation features, while forage digs occurred in high abundance in most habitats measured, and were likely driven by prey availability. Forage digs served as litter and seed retention hotspots, with accelerated decomposition rates of litter as a function of increased soil moisture in digs. The functional processes (i.e. resource capture, shelter for plants and animals, germination sites, soil aeration, organic turnover, mineralization rates, fertile soil displacement and transport) driven by aardvark digs are not restricted to refuge digs. Forage digs occurred in most habitats measured and their functional role is unique and perhaps greater across the landscape in comparison to refuge digs. The aardvark has a disproportionate effect in ecosystems, in terms of its refuge and forage digs relative to its abundance and therefore its role as a keystone species and ecosystem engineer is confirmed. Conservation and protection of this species is therefore essential to maintain its important role in ecosystem function.
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- Date Issued: 2017
Megaherbivores in succulent thicket: resource use and implications
- Authors: Landman, Marietjie
- Date: 2012
- Subjects: Elephants , African elephant , Black rhinoceros , Succulent plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10689 , http://hdl.handle.net/10948/d1007956 , Elephants , African elephant , Black rhinoceros , Succulent plants
- Description: This study aims to develop a predictive understanding of the resource use, impacts and interactions of elephant Loxodonta africana and black rhinoceros Diceros bicornis in the succulent thickets of the Eastern Cape, South Africa. While these megaherbivores typically dominate the biomass, elephant are more abundant, such that their impacts off-set that of all other herbivores. Consequently, this thesis has three main foci: first, developing a mechanistic understanding of the influences of elephant; second, developing predictive insights into elephant impacts on plant communities; finally, an understanding of the knockon-effects of the impacts for coexisting rhinoceros. Thus, by documenting the diet and dietary preferences of elephant, I firstly show that only about 18 percent of the species previously thought vulnerable to herbivory, occur in the diet. This refutes the generally held belief that elephant herbivory is the primary driver of decline among plants, and emphasizes the likely contribution of other mechanisms (e.g. trampling, knock-on-effects, etc.). Thus, the accurate prediction of the impacts caused by elephant requires an understanding of previously marginalized mechanisms. From here, I quantify >50 years of impacts on the thicket shrub community and test their spatial and temporal extent near water. I confirm the vulnerability of thicket to transformation (particularly near water) as the accumulated influences of elephant reduce community composition and structure, and predict that these impacts will eventually bring about landscape-level degradation and a significant loss of biodiversity. Importantly, results show an uneven distribution of effects between elements of this community: from community composition and structure, to the structure of individual canopy species and ecological functioning. While these findings confound our interpretation of the extent of the impacts, it demonstrates the importance of explicitly recognizing biodiversity and heterogeneity for the conservation management of elephant. Finally, I test the consequences of the impacts for coexisting rhinoceros. While I show that this causes rhinoceros to change their foraging strategies in the presence of elephant at high densities, I also show that elephant may facilitate access to food for rhinoceros at reduced densities. These findings indicate the importance of elephant in driving the structure and composition of the thicket shrub community and the consequences of this for coexisting large herbivores. Thus, developing a predictive understanding of the spatial and temporal variations of elephant impacts between elements of biodiversity and the mechanisms driving these changes are key to their management. This implies that the effective conservation management of elephant can only be achieved through the careful, scientific design of monitoring programmes.
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- Date Issued: 2012