My main research interests are in dispersal ecology and landscape connectivity modelling. Dispersal and landscape connectivity play a pivotal role in ecology, linking demographic to spatial patterns. Understanding the causes and consequences of the redistribution of individuals within or among populations also has profound implications for conservation and wildlife management in today’s increasingly fragmented landscapes.
My current research at the Swiss Ornithological Institute - Vogelwarte focuses on the dispersal ecology of the little owl Athene noctua, an endangered species in Switzerland. I am interested in understanding patterns and mechanisms of juvenile dispersal in response to habitat structure and individual characteristics using a large telemetry data set collected in Southern Germany. We then use this knowledge of dispersal movement to empirically parameterize an individual-based model (IBM) to quantify the potential for little owls to recolonize suitable areas in Switzerland which are seemingly isolated from other populations. Our approach differs from classical connectivity models in that we do not set a priori destinations needed by least-cost path or circuit theory algorithms. In our view IBM are more realistic in the context of natal dispersal, when individuals unlikely have pre-conceived knowledge of their destination, and imperfect knowledge of the broader landscape. It also accounts for time, eg. the number of generations it would take to effectively link two populations.
This work is in line with the core of my PhD research on the spatial, dispersal and landscape ecology of leopard Panthera pardus, and subsequent post-doc research on landscape connectivity for leopard and other felids. During my PhD at UKZN, in collaboration with Panthera under the co-supervision of Rob Slotow, Luke Hunter, Guy Balme and Hugh Robinson, I demonstrated that functional connectivity corresponds to structural connectivity; that is suitable breeding adult habitats was a good predictor of dispersal movement through the landscape. Marginal habitat may therefore not be sufficient to provide functional landscape connectivity to leopards. I recorded the longest dispersal event in leopards to date - c. 350 km through three countries. Such long-distance dispersal events can have tremendous implications for population linkage if they are successful. This also calls for transfrontier landscape conservation approach to leopard conservation as current management units are likely interconnected. Even more so since male dispersal rates and distances increased following the population recovery after unsustainable hunting in our study area. Contrastingly, subadult females remained philopatric, which limits somewhat the potential demographic and gene flow among population in the region.
After my PhD, I visited Mark Hebblewhite's lab at the University of Montana, USA for six months to work on landscape connectivity modelling in several large felid species in tight collaboration with Hugh Robinson of the Panthera's GIS lab. I also collaborated with Ross Pitman during his PhD at UKZN on modelling landscape connectivity for leopards in the Limpopo Province, South Africa as part of another Panthera project. The results have practical implications to the design of sustainable legal trophy hunting quotas. Harvest pressure in the least connected management units should be lower than in better connected units, as the local population could take longer to recover through limited immigration rates.