CONICET | Buscador de Institutos y Recursos Humanos

South American subterranean rodents known as tuco-tucos (Ctenomys aff. knighti) emerge daily to the surface during daylight, in brief episodes. Seasonal variation on daily activity patterns was observed in populations of desert epigeous rodents and was attributed to daily variations of environmental temperature. This feature was also observed in the individual surface activity pattern of tuco-tucos, using distinct recording methods in semi-natural enclosures: direct observations, light exposure (surface activity) and body temperature (Tb). Here we present the first activity data of tuco-tucos in both field and laboratory conditions, obtained with accelerometers (0.7g; 460 days, 1Hz samples). Our aim is to verify the contribution of endogenous and exogenous factors in the seasonal variation observed on daily rhythms of surface activity in tuco-tucos. During summer and winter, accelerometers and light-loggers were tied to 9 freshly caught animals (5 males, 4 females; 178±39g). Animals were kept inside enclosures (12m×6m×1.5m) for one month. Environmental temperature was recorded simultaneously. Recaptured animals were transferred to laboratory and kept in constant conditions for 10 days. In summer, general activity inside enclosures was observed throughout the day and presented peaks coincident with crepuscular surface activity. In winter, both activity components became diurnal. Independently of season, transition from enclosures to laboratory caused general activity to become concentrated at night. Daily surface activity of tuco-tucos was better predicted by time of day than by environmental temperature. During winter season, however, environmental temperature has a stronger contribution on the temporal pattern of emergence in tuco-tucos.

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