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Collaboration, avoidance and conflict between disciplines around a shared field. This article addresses collaborations, conflicts and avoidances that develop between disciplines over a shared field of study. In this perspective and using the notion of border zone (Kohler, 2001 and 2011), I analyzed the Sénart forest on the outskirts of Paris, the study area of researchers working on Lyme disease and its primary vector, ticks of the Ixodes genus. For sciences such as ecology, geography or epidemiology that base their assumptions on field observation and the interpretation of indices, Sénart is an exceptional site. It combines all the risk factors currently identified as favoring the persistence and development of Lyme disease cases. However, these various factors and their combinations exceed the scope of a single scientific community or a single researcher. To investigate the risk factors. interdisciplinary work developed on the Sénart case through common research projects. However, instead of remaining mere collaborative work, the project turned out to be a source of conflicts, competition and critics within the research teams involved. These issues still need addressing. In this paper I discuss the kinds of relationships and the various learning processes enabled by this shared space. I show in particular that researchers view study representativeness differently depending on their field practice. To conclude I show that the relations between these various actors seem to be determined in fine by three types of nested conditions : institutional, cognitive, and ethical.