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Associate professor | Staff scientist at the Smithsonian Tropical Research Institute (www.stri.si.edu/jansen) | Coordinator of the Vertebrate Program of ForestGEO, a global network of >60 large-scale Forest Dynamics Plots (www.forestgeo.si.edu) | Coordinator of the Tropical Ecology Assessment and Monitoring (TEAM) program - the World's largest camera-trapping program - for the Smithsonian (www.teamnetwork.org) | Involved in eMammal (emammal.si.edu) en Agouti (agouti.eu), two platforms for collecting, processing, archiving and sharing wildlife images and data.
My research focuses on interactions of wildlife with plants, with each other, and with parasites and pathogens. I am particularly interested in the consequences of wildlife extirpation, for example due to bushmeat poaching, as well as wildlife return, such as through rewilding and colonization of novel habitats such as cities.
I work in regions where forest is the natural vegetation, both in the tropics and in the temperate zone. My principal experimental sites are the Barro Colorado Nature Monument in Panama, and National Park De Hoge Veluwe in the Netherlands.
Much of my work involves the use of camera traps, for example to assess the abundance of terrestrial wildlife, and to quantify interactions. We develop new methods for doing these measurements. We also built a platform, called Agouti, to manage, process and store images for camera-trapping studies: http://agouti.eu.
My vertebrate-plant interactions research aims to understand how vertebrates affect the species composition, diversity and functioning of forest ecosystems, for example through species-specific seed dispersal, seed predation and herbivory. What specific roles vertebrates play in forests? How do vertebrate species they interact with different plant species? How do they contribute to the maintenance of high plant species diversity? And, ultimately, how does degradation of vertebrate communities – due to bushmeat hunting and forest fragmentation – or the wildlife restoration – such as through rewilding – affect the species composition and diversity of forests?
In Panama, studies focus on the Central American agouti and the two large-seeded palm species that this scatter-hoarding rodent disperses and depredates. In Europe, studies focus on how ungulates influence forest dynamics by feeding on young trees.
The vertebrate interactions research considers interactions between vertebrates, particularly competition for food and space, and predator-prey interactions. Here, we seek to understand how vertebrates partition resources, how predation risk and food availability affect animal behavior, when and why animals are active, amongst others. This work yields basic knowledge that we apply in the plant-vertebrate interaction research. Here, too, agoutis and ungulates are important objects of research.
The parasites and disease ecology research aimed at understanding how the community composition of vertebrates affects that of parasites such as ticks and fleas, and ultimately agents of infectious disease, including diseases that are harmful to people. We seek to determine how host-specific parasites are to vertebrates, how host-specific disease agents are to their parasite hosts, and how suitable different vertebrates are as reservoirs for diseases. The key hypothesis that we are testing is that vertebrate diversity reduces the prevalence of diseases through a dilution effect.