Drawing on a rich two-year ethnographic study that followed evolutionary biologists in their everyday work, this paper explores the making of scientific knowledge through the spatial conceptual imagery developed by Deleuze and Guattari. In particular, this paper focuses on a field expedition to the South Pacific and investigates how different rhythms, forces and intensities are harmonized and assembled in the production of scientific knowledge. Within this setting, maintaining a balance between striating and smoothing forces is an important yet difficult task. On many occasions, alternative rhythms and ‘tropical forces’ jeopardized the success of the expedition, despite the scientists’ best efforts to formalize the research process and bring the striations of the laboratory into the forest. Paradoxically, these challenges also played a key role in the inquiry as they opened new possibilities and ultimately led to more intense engagements with the tropical forest and its rhythms and spatiality.