Vocal signatures and individual recognition are documented in a wide range of avian and mammalian species, but little is known about cervids. However, the existence of individual characteristics in cervid vocalizations is highly probable, as the individual morphology of their vocal organ determines the spectral structure of the uttered signal. Here, we report the presence of individual characteristics in the spectral structure of fallow deer groans recorded during the rutting period. We digitized 147 vocalizations from four adult males and transformed each of them into a power spectrum of 32 values in order to represent the frequency distribution of the sound power. A neural network discrimination with cross validation performed on the resulting variables allowed us correctly to identify 87.9 % of the tested vocalizations. The spectrum characteristics of an individual remained stable over the rutting period, and probably over several consecutive ruts (the vocalizations of one male recorded during a previous rutting period were also correctly classified). We therefore conclude that the groan may constitute a vocal signature. The individually structured groan may provide a valuable basis for individual recognition during the breeding season and therefore may play an important role in the social interactions observed during this period.