Year: 2009
Type: dissertation
Abstract: From 2005-2007, I studied the ecology of Bitis gabonica, a terrestrial forest viperid that occurs in \nsubtropical northeast extremes of South Africa. I monitored ten individuals (six males and four \nfemales) using radiotelemetry inside the iSimangaliso Wetland Park in KwaZulu-Natal. I used two \ndifferent home range estimators to analyze space use among individuals; minimum convex polygons \n(MCPs) and kernel density contours (KDs). MCPs averaged 28.58 ha (42.48 ha for males, 7.72 ha \nfor females) and ninety-five percent kernel density contours (KDs) averaged 28.92 ha (42.65 ha for \nmales, 8.32 for females). Fifty percent KDs (core areas of activity) averaged 6.74 ha, with the mean \nmale core activity centre almost five times greater than that of females. Telemetered B. gabonica \nwere highly sedentary, especially during winter when individuals remained at single localities for \nextended periods (max. 87 days). Activity peaked for both sexes at the onset of the breeding season, \nwith individuals averaging a movement distance of 598 m during March. \nAt sites where telemetered B. gabonica were observed, I measured a suite of sixteen critical habitat \nvariables and then used MANOVA to test for differences among habitat characteristics for several \ndifferent categories (season, sex and habitat selection). Bitis gabonica habitat preferences were \nstrongly influenced by season, with individuals selecting open-canopied areas during cooler months, \npresumably because the forested habitat individuals utilize the rest of the year is not adequate for the \nspecies’ thermoregulatory requirements during winter. Female B. gabonica used slightly less \nshrubby microhabitats than males. The variability found between B. gabonica sites and random sites was primarily explained by features that constitute the understory, with snake sites having denser \nunderstory structures and being located closer to woody vegetation. This type of “thicket” \nmicrohabitat is important for the protection, thermoregulation and food acquisition requirements of \nGaboon Adders. \nAmong telemetered B. gabonica, feeding activity varied between seasons, with individuals spending \nlong periods of time at single localities in an ambush position, especially during summer. Snakes \nexhibited strong ambush site fidelity, often remaining immobile for weeks at a time. Sites where \nambush behaviour was observed were frequently in close proximity (< 1 m) to game trails created by \nantelope, and new B. gabonica feeding records from my field work (e.g., Red Duiker; Cephalophus natalensis) indicate individuals may target large prey (close to their own body mass) when available. \nThe unique morphological adaptations of B. gabonica are discussed in the context of foraging \necology. \nEcological research from this study, coupled with new molecular data that shows South African and \ncentral African B. gabonica are genetically similar, suggests the South African B. gabonica \npopulation’s conservation status is better than what was previously assumed. However, long-term \nprotection and management of the coastal dune forest corridor (found primarily inside the \niSimangaliso Wetland Park) is needed for a viable, local B. gabonica population. A handbook is \nprovided specifically for Park staff which summarizes the ecology and threats to B. gabonica, and \nprovides up-to-date management decisions on controversial protective measures (e.g. translsocation).
Author: Jonathan K. Warner
Language: English
Domain: Life Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W84675904