The twentieth century witnessed the rise of a conservation movement that presented itself as 'international' and 'science-based'. This article analyses the changing transnational networks of experts mobilised by this movement. It does so by studying the participant lists of 21 influential international conservation conferences held between 1913 and 1990. On the basis of a database we were able to trace changes in the national background, disciplinary allegiance and gender balance of conference attendants. Furthermore, we singled out a so-called 'congress elite' of often returning participants, whose background we analyse more in depth. The overall composition of the congress network as well as that of its elite, we show, changed only through a slow and laborious process. This process accounts for both the continuity in the sensibilities of international conservation experts and the gradual changes in their approach.