I have had the great pleasure of being involved in a study on invertebrates in Gcwihaba cave in Botswana (sadly remotely so far, although I hope to visit the cave one day). The cave is the largest one in Botswana, and relatively well visited by tourists, but surprisingly no proper studies on their invertebrate diversity have been conducted. The project was led by Dr Richard Mazebedi from the Botswana International University of Science & Technology as part of his field project under my supervision for the Postgraduate Certificate of Ecological Survey Techniques at the University of Oxford.
In the paper, we describe our preliminary findings of the macroinvertebrates within the first 50 m of the cave surveyed through visual searches on cave walls and shifting through guano on the cave floor. We found 12 species in 10 families and 8 invertebrate orders with the cave cockroaches (Gyna sp.) and cave crickets (Spelaeiacris sp.) being by far the most abundant, although I was happy that three species of spiders were also found (violin spiders – Loxosceles sp., cellar spiders – Smeringopus sp. and flat spiders – Selenops sp.). I hope to be involved in future more in depth studies on the invertebrate fauna of this and neighbouring caves.
Mazebedi, R. and Hesselberg, T. (2020). A preliminary survey of the abundance, diversity and distribution of terrestrial macroinvertebrates of Gcwihaba cave, northwest Botswana. Subterranean Biology 35, 49-63.
doi: 10.3897/subtbiol.35.51445
Abstract
Inventories of cave species and in-depth understanding of cave ecosystems are essential for informing conservation approaches for the unique and vulnerable cave fauna. Gcwihaba cave is the largest cave in Botswana but its ecology is poorly understood. This study set out to provide the first quantitative survey of the cave’s terrestrial macroinvertebrates. Macroinvertebrates were collected from sample sites at 10 m intervals into the cave from the cave entrance. At each site, macroinvertebrates on the cave floor were collected by quadrat sampling while macroinvertebrate from cave walls were collected by visual opportunistic searches. Moisture content, pH and electrical conductivity of the cave floor substrate were measured at each site to examine the influence of the floor properties on the distribution of macroinvertebrates on the cave floor. Twelve species in 10 families and 8 orders of terrestrial macroinvertebrates were collected. The occurrence of taxa varied across the sites, with most taxa occurring in the light and twilight sectors of the cave (within 30 m), whereas the dark sector (beyond 30 m) was dominated by cave cockroaches (Gyna sp.). The abundance of the cave cockroaches, darkling beetles (Tenebrionidae, Tenebrio sp.) and cave wasps (Sphecidae) positively correlated with floor substrate of high moisture content and high electrical conductivity, which became increasingly common with distance into the cave. The abundance of other taxa from the cave floor positively correlated with a floor substrate of high pH and low moisture, which was common near the cave entrance.
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