Research Overview

How do anthropogenic changes affect forest wildlife?

Forests are experiencing increasingly high anthropogenic disturbance worldwide, including habitat destruction, habitat fragmentation, poaching and climate change. How are these changes affecting the composition wildlife communities? Are protected areas effective in conserving healthy populations of wildlife?

How does wildlife loss affect tree communities?

Many forests that seem ‘intact’ in fact lack important components of their original fauna. The consequences of wildlife loss for forest ecosystems are potentially massive, because species affect plant species in multiple ways, such as by seed dispersal, seed predation and seedling herbivory. How does wildlife loss affect the composition of the vegetation and the ecosystem services that forests provide?

Does loss of wildlife cause disease outbreaks?

All animals are hosts to pathogens that travel between individuals and species via vectors, such as ticks and mosquitos. Some of these pathogens cause diseases in wildlife, livestock and people. How does anthropogenic change of wildlife communities affect the prevalence of such pathogens? Does a healthy wildlife community control diseases? And could wildlife loss promote disease outbreaks?

Does El Niño cause die-off of vertebrates?

The El Niño Southern Oscillation causes large fluctuations in weather patterns globally. Scientists predict that the frequency of extreme El Niño events is increasing. We study how such extreme events affect wildlife in tropical forests, such as Barro Colorado Island. Do El Niño events cause die-off of mammal populations via periodic food shortage?

Do animals contribute to the coexistence of plant species?

Animals affect the vital rates of their food plants in many ways, such as by seed dispersal and seed predation. We ask the question whether and how such processes vary with the relative abundance of food plants. Do animals produce density dependence of tree performance, and may they thus contribute to tree species coexistence? What are the consequences of their loss?

Can camera traps be used to measure population levels of wildlife?

Mammals in forest ecosystems are difficult to survey due to the dense vegetation, and to the low densities and secretive behaviors of mots species. A possible solution comes from motion-sensitive camera traps that photograph passing animals, and record the use of small plots of forest by wildlife. Can we translate these capture rates into estimates of abundance and habitat use? How can sampling be optimized and standardized?

Education

Ph.D., Wageningen University, Wageningen, 2003

M.S., Wageningen Agricultural University, Wageningen, 1993

Selected Publications

Peguero, G., H. Muller-Landau, P.A. Jansen & S.J. Wright (2017). Cascading effects of defaunation on the coexistence of two specialized insect seed parasitoids. Journal of Animal Ecology 86: 136-146. doi: 10.1111/1365-2656.12590

Wright, S.J., O. Calderón, A. Hernandéz, M. Detto & P.A. Jansen (2016) Interspecific associations in seed arrival and seedling recruitment in a Neotropical forest. Ecology 97: 2780–2790. doi: 10.1002/ecy.1519

Garzon-Lopez, C.X., L. Ballesteros-Mejia, A. Ordoñez, S.A. Bohlman, H. Olff & P.A. Jansen (2015). Indirect interactions among tropical tree species through shared rodent seed predators: a novel mechanism of tree species coexistence. Ecology Letters 18:752–760. doi: 10.1111/ele.12452.

Jansen, P.A., M.D. Visser, S.J. Wright, G. Rutten & H.C. Muller-Landau (2014). Negative density-dependence of seed dispersal and seedling recruitment in a Neotropical palm. Ecology Letters 17: 1111–1120. doi: 10.1111/ele.12317

Jansen, P.A., J. Ahumada, E. Fegraus & Tim O’Brien (2014). TEAM: a standardised camera-trap survey to monitor terrestrial vertebrate communities in tropical forests. Pp 263-270 in Meek, P. D., Ballard, A. G., Banks, P. B., Claridge, A. W., Fleming, P. J. S., Sanderson, J. G., and Swann, D. E. (Eds). Camera Trapping: Wildlife Research and Management. CSIRO Publishing, Melbourne, Australia.

Hirsch, B.T., R. Kays, V.E. Pereira, P.A. Jansen (2012). Directed seed dispersal towards areas with low conspecific tree density by a scatter-hoarding rodent. Ecology Letters 15: 1423–1429. doi: 10.1111/ele.12000. Editor’s choice in Science.

Jansen, P.A., B.T. Hirsch, W.J. Emsens, V. Zamora-Gutierrez, M. Wikelski & R. Kays (2012). Thieving rodents as substitute dispersers of megafaunal seeds. Proc. Natl. Acad. Sci. USA. 31: 12610–12615. doi: 10.1073/pnas.1205184109

Visser, M.D., H. C. Muller-Landau, S.J. Wright, G. Rutten & P.A. Jansen (2011). Tri-trophic interactions affect density dependence of seed fate in a tropical forest palm. Ecology Letters 14: 1093-1100. doi: 10.1111/j.1461-0248.2011.01677.x. Editor’s choice in Science.

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