Seismic signals occur in at least two distinct lineages of subterranean rodents (Bathyergidae and Spalacinae), indicating that this mode of communication cannot be explained solely in terms of phylogenetic history. Understanding the evolutionary context in which each signal type has developed remains a significant challenge to biologists studying communication in subterranean rodents. The importance of social behaviour for the type of vibrational signals used has been emphasised, implying that solitary taxa are more likely to exhibit seismic signals than social taxa because of their greater need for communication between burrows. Because seismic signals propagate better through the soil than vocal signals, the former should be favoured in solitary species in which communication occurs primarily between burrows. The majority of Ctenomys species are solitary and territorial, living in individual burrows that never approach other burrows nearer than 40 cm outside of the reproductive season, thus long distance inter-burrow communication is a candidate for the use of seismic signals. Nevertheless, no Ctenomys is known to produce seismic signals but almost all of them vocalise loud enough to be heard at a considerable distance outside the burrows. Data from six Ctenomys species show that these vocalisations are low frequency, repetitive, rhythmic signals which present structural similarities with the seismic signals emitted by other subterranean rodents. These facts suggest that the use of low-frequency rhythmic signals could be a result of the constraints imposed by the underground environment and that the propagation conditions may determine that rhythm is more reliable than frequency modulation. Then, solitary subterranean rodents may use low frequency, rhythmic, repetitive signals for long distance communication, either vocal or seismic, to overcome the environmental constraints. A possible explanation for the use of one of both channels by different species has been discussed elsewhere.