Slip markings produced on the surfaces of Ni-3(Al, Ta) single crystals, plastically deformed at various temperatures in the flow stress anomaly domain, were examined by atomic force microscopy (AFM). A dominant feature is that for all investigated temperatures, the slip traces are rectilinear and correspond to the primary octahedral glide plane. In addition, their lengths drastically decrease when the temperature is raised. This latter result is interpreted as a strong increase of the exhaustion rate of mobile dislocations with increasing temperatures. The consequences of these results in the understanding of Ni3Al flow stress anomaly are discussed.