Browsing by Author "Baxter-Gilbert, James"

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    The cost and complexity of assessing impact
    (Pensoft, 2020-10-15) Measey, John; Wagener, Carla; Mohanty, Nitya Prakash; Baxter-Gilbert, James; Pienaar, Elizabeth F.
    ENGLISH ABSTRACT: The environmental and socio-economic impacts of invasive species have long been recognised to be unequal, with some species being benign while others are disastrous. Until recently there was no recognised standard impact scoring framework with which to compare impacts of species from very different taxa. The advent of the Environmental Impact Classification for Alien Taxa (EICAT) and Socio‐Economic Impact Classification of Alien Taxa (SEICAT) schemes allows for the possibility of assessing impact through a standard approach. However, both these schemes are still in their infancy and the associated costs of the research that informs them is unknown. We aimed to determine the study costs and complexity associated with assessing invasive species’ socio-economic and environmental impacts. We used amphibians as a model group to investigate papers from which EICAT and SEICAT scores could be drawn up to 2019. Our analysis shows that studies that resulted in higher impact scores were more costly. Furthermore, the costs of studies were best predicted by their complexity and the time taken to complete them. If impact scores from EICAT and SEICAT are allowed to inform policy, then we need to carefully consider whether species with low scores represent true impact, or require more research investment and time. Policy makers needing accurate assessments will need to finance larger, more complex, and rigorous studies. Assessing impacts in low and middle income countries may need investment using international research collaborations and capacity building with scientists from high income areas.
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    Hamerkop (Scopus umbretta) predation on an Augrabies flat lizard (Platysaurus broadleyi)
    (2019) Baxter-Gilbert, James; Parsons, Julian; Bostock, Charlotte; Riley, Julia L.
    On 27 August 2018 at Augrabies Falls National Park (28.5942° S, 20.3381° E) we observed an adult Hamerkop (Scopus umbretta) foraging adjacent to the main waterfall along a rock shelf midway down the cliff-side. At 15:37 h we saw the bird capturing and swallowing an Augrabies flat lizard (Platysaurus broadleyi; Fig. 1). This observation is noteworthy as to date the primary predators of Augrabies flat lizards are known to be raptors (e.g. Rock Kestrel, Falco rupicolus, and Booted Eagles, Aquila pennatus) and sand snakes (Psammophis sp.), with other potential predators being mongooses and large arthropods, such as spiders and centipedes (Whiting, 2002; A. Jenkins pers. comm.). Hamerkop, to the best of our knowledge, have not been documented previously to consume reptiles, and as such there have been no previous observations of them eating this specific lizard species. The known diet of Hamerkop consists of frogs, particularly of the genus Xenopus, insects, and fish (Skead, 1953; Liversidge, 1963; Dean & MacDonald, 1981; Kahl, 1987; Yohannes, et al., 2014).