Demographic and reproductive attributes of dispersers in two populations of the subterranean rodent Ctenomys talarum (tuco-tuco)

The demographic and reproductive characteristics of dispersers in the fossorial rodent Ctenomys talarum, the tuco-tuco, were studied by removing animals from two experimental plots. Data on dispersers' attributes were compared with those of resident and transient individuals from previous capture–mark–release and removal studies performed in the same localities. Average weekly dispersal by tuco-tucos was 2.38% (range 0–5.75%) at Necochea and 5.75% (range 0–15.75%) at Mar de Cobo. The low proportion of dispersers reflects their fossorial habit. At Mar de Cobo, the sex ratios of dispersers and transients showed a 1:1 relationship, whereas residents showed an excess of females. All groups did not differ from a sex ratio of 1:1 at Necochea. At both localities, dispersers did not differ qualitatively from residents in age composition, litter size, or body mass. Transients and dispersers of both populations were characterized by a higher proportion of immature individuals than residents. We conclude that dispersal may be an important factor regulating the C. talarum population and may counteract the restrictions imposed by its subterranean habitat.