Characterization of day-time above-ground activity of a South American subterranean rodent (Ctenomys cf. knighti), the tuco-tuco

- TOMOTANI BM; FLORES DANILO EFL; TACHINARDI P; ODA GA; VALENTINUZZI VS

Ein Gedi

Workshop; International workshop: The diversity, evolution and mechanisms controlling activity patterns; 2012

Ctenomys cf. knighti is a subterranean rodent from a semi-arid region in Northwest  Argentina. These animals have a clear day-time activity component in the field, while in the laboratory, under LD 12:12 (L: 200 lux), they display nocturnal running-wheel rhythms. Comparison between the activity phases of animals transferred directly from the field, and from the lab LD12:12, to constant conditions showed that the circadian oscillator is equally entrained in both field and laboratory conditions, with the clock-controlled activity expressed during the night. The total disappearance of day-time activity of the former group upon transference to constant conditions indicates that this component is not clock-controlled. Then, what are these animals doing above-ground during the day in the field? Our continuous observations during the light phase (12 to 14 hours each day per 10 days) of 3 animals individually kept in a field-enclosure, showed that during above-ground emergences tuco-tucos engaged in foraging and soil removal activities. Foraging consisted of emergences, lasting few minutes, when the animals quickly collected dry leaves, entire plants or other vegetal material. Soil removal consisted of much longer episodes, in which animals vigorously kicked out the sand accumulated in their burrows. This accumulated sand was probably the result of previous underground excavations during tunnel expansions, which are thought to increase proportionally to the necessity of finding more food sources. Our observations also suggested that environmental factors such as wind and rain can directly mask the expression of aboveground day-time activity. The diurnal components that disappeared upon  transference from field-enclosures to constant conditions were related to food gathering. In contrast, animals received ad libitum food in the laboratory and consequently did not spend energy in foraging or excavation. Finally, we present tentative correlations between food availability levels - which greatly differed in the three series of observations - and the amount of day-time activity.  Support: CONICET, FAPESP, CNPq, CAPES.