Browsing by Subject "Zoology and Entomology"

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    Caracals as sentinels for metal exposure in a human-transformed landscape
    (2023) Parker, Kim; Bishop, Jacqueline; Leighton, Gabriella
    Urbanisation and associated anthropogenic activity release large quantities of metallic elements and metalloids into the environment. Due to their toxicity, environmental persistence and bioaccumulative nature, these chemical pollutants threaten wildlife and human health. As urbanisation increases and top predators are forced to utilise more urban spaces, they will likely be exposed to more toxic heavy metals and metalloids. As secondary and tertiary consumers, terrestrial carnivores may be at increased risk of metal exposure through biomagnification effects. Relatively little is known about this emerging threat to terrestrial carnivores persisting in human-transformed landscapes, especially in the Global South. To better understand the extent of this issue, I quantified the level of metallic element and metalloid exposure in a sentinel top predator, the caracal (Caracal caracal), inhabiting the rapidly-urbanising, primarily coastal metropole of the Greater City of Cape Town, South Africa. Whole blood samples (n = 67) from GPS-collared (n = 25) and opportunistically sampled (n = 31) individuals were collected. Using Redundancy Analysis (RDA) and mixed-effect models, I explored the relative influence of caracal demography, landscape use, and diet on levels of individual exposure to 11 metallic elements and metalloids: Aluminium (Al), Arsenic (As), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Mercury (Hg), Manganese (Mn), Lead (Pb), Selenium (Se), and Zinc (Zn). Mean metal concentrations (including Al, Cd, Co, Cu, Hg, Mn, Pb, Se and Zn) were generally found to be below toxic thresholds, however, As and Cr are present at potentially sublethal levels in certain individuals. The results suggest that increased use of human-transformed landscapes in home ranges (particularly urban areas, roads, and vineyards) was significantly associated with increased caracal exposure to Al (P < 0.05), Co (P = 0.05) and Pb (P = 0.07). Home ranges closer to the coast (RDA, P < 0.05) and feeding within aquatic food webs (marine and wetland-adapted prey) were associated with higher blood levels of Hg (P < 0.05), Se (P < 0.01) and As (P < 0.05). Further, increased predation on seabirds and aquatic birds likely facilitates the transfer of metals from aquatic to terrestrial food webs. Overall, these findings highlight the importance of urbanisation and anthropogenic activity as major environmental sources of metal exposure in terrestrial wildlife, including more natural areas through long-distance transport of pollutants. Further, they contribute towards a growing global evidence base suggesting cities act as ecological traps for wildlife, threatening their long-term health and persistence in these landscapes. Therefore, it is crucial that cities work to reduce the large quantities of chemical pollutants released into their surrounding environment. In Cape Town, this effort could be focused on the urban edge, waste management, water treatments, roads and agricultural areas. Future research into a possible ecological trap for urban-adapted carnivores should focus on assessing metal exposure at different trophic levels and investigating the potential physiological responses of exposure in species. I argue that the caracal is a valuable sentinel for assessing metal exposure and should be used in tandem with other small and mediumsized carnivores and aquatic bird species in local and national pollutant monitoring programmes to mitigate further exposure and promote carnivore conservation in human landscapes. A charismatic species, with a well-established local platform of research and science communication, the caracal is centrally positioned to help promote greater public awareness and engagement in issues concerning environmental pollutant contamination and monitoring.
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    Wasps (Hymenoptera: Chalcidoidea) associated with galls in seed-capsules of Eucalyptus camaldulensis (Myrtaceae) in South Africa : species composition, trophic relationships and effects
    (2009) Klein, Hildegard; Hoffmann, John
    The Australian river red gum (Eucalyptus camaldulensis Denhardt) (Myrtaceae) is regarded in South Africa as a valuable general-purpose utility and ornamental tree, as well as an essential source of nectar and pollen to sustain the honeybees which are crucial for pollinating the economically important fruit crops in mainly the Western Cape Province. Despite its utility value, it is regarded as invasive in South Africa, the major concern being the large amounts of water it consumes when growing along watercourses. River red gum is therefore the subject of conflicts in interests between government agencies that target it for control actions, and farmers and beekeepers who utilize it. As a contribution towards resolving this conflict in interests, a research project was initiated to investigate the potential use of host-specific insects that might reduce the number of viable seeds produced by E camaldulensis. The aim was to reduce its invasive potential while retaining its general utilizability for all concerned. From the start, the need for introduced agents from Australia was weighed against the presence of two species of chalcidoid wasps, both regarded as gall inducers, in the seed capsules of E camaldulensis in South Africa. The current study was motivated by the need for information on the biology of these two species and the effect they were having on seed production in their host plant. As it progressed, three more chalcidoid species, all undescribed at that time and probably of Australian origin, were found to be emerging from the seed capsules of E camaldulensis collected in several parts of South Africa, and these became part of the investigation.