When studying hybrid systems, like ecosystems or interspecific cohabitation, it is frequent to consider them as hybrid semiosphere (in the acceptance of Hoffmeyer, 1997), compounded of a variety of separated Umwelt (Kull, 2010). But could we go further and talk about shared Umwelt? By definition, an Umwelt is specific to an individual (Kull, 1998), but individuals are connected to each other. Could it be possible to consider that their Umwelten are sometimes so deeply connected that they might be, even partially, shared? In this presentation, I will use three composite cases (i.e. study cases that are a gathering of different real cases for the purpose of the presentation) to introduce suggestions and questioning regarding three major aspects of the Umwelt: the shared physiology, the shared perception and the shared meaning-making. The aim is to analyse borderline cases, in order to see how these situations can be addressed with our current tools or if some hybridity situations require the implementation of shared Umwelt in the strict meaning of the term. Hoffmeyer, Jesper. (1997). Signs of Meaning in the Universe. Indiana University Press.Kull, Kalevi. (2010). ‘Ecosystems Are Made of Semiosic Bonds: Consortia, Umwelten, Biophony and Ecological Codes’. Biosemiotics, 3 (December): 347–57.Kull, Kalevi. 1998. ‘On Semiosis, Umwelt, and Semiosphere’. Semiotica 120 (3–4): 299–310.