Temporal Dissociation Between Activity and Body Temperature Rhythms of a Subterranean Rodent () in Field Enclosures.

Several wild rodents, such as the subterranean tuco-tucos (), switch their time of activity from diurnal to nocturnal when they are transferred from field to the laboratory. Nevertheless, in most studies, different methods to measure activity in each of these conditions were used, which raised the question of whether the detected change in activity timing could be an artifact. Because locomotor activity and body temperature (Tb) rhythms in rodents are tightly synchronized and because abdominal Tb loggers can provide continuous measurements across field and laboratory, we monitored Tb as a proxy of activity in tuco-tucos transferred from a semi-field enclosure to constant lab conditions.

Telling the Seasons Underground: The Circadian Clock and Ambient Temperature Shape Light Exposure and Photoperiodism in a Subterranean Rodent.

Living organisms anticipate the seasons by tracking the proportion of light and darkness hours within a day-photoperiod. The limits of photoperiod measurement can be investigated in the subterranean rodents tuco-tucos ( aff. ), which inhabit dark underground tunnels.

Maximising survival by shifting the daily timing of activity.

Maximising survival requires animals to balance the competing demands of maintaining energy balance and avoiding predation. Here, quantitative modelling shows that optimising the daily timing of activity and rest based on the encountered environmental conditions enables small mammals to maximise survival. Our model shows that nocturnality is typically beneficial when predation risk is higher during the day than during the night, but this is reversed by the energetic benefit of diurnality when food becomes scarce.

Acute effects of light and darkness on the activity and temperature rhythms of a subterranean rodent, the Anillaco tuco-tuco.

Tuco-tucos from Anillaco (Ctenomys aff. knighti), are subterranean rodents that run vigorously on laboratory wheels during the night but are active during the day in semi-natural enclosures, where they surface for foraging and burrow maintenance, under intense sunlight. Several studies have shown that light causes opposite, inhibitory and stimulatory, "masking" effects on the activity levels between nocturnal and diurnal species, respectively.

The Interplay of Energy Balance and Daily Timing of Activity in a Subterranean Rodent: A Laboratory and Field Approach.

The tuco-tuco (Ctenomys aff. knighti) is among the rodent species known to be nocturnal under standard laboratory conditions and diurnal under natural conditions. The circadian thermoenergetics (CTE) hypothesis postulates that switches in activity timing are a response to energetic challenges; daytime activity reduces thermoregulatory costs by consolidating activity to the warmest part of the day.

Nocturnal to Diurnal Switches with Spontaneous Suppression of Wheel-Running Behavior in a Subterranean Rodent.

Several rodent species that are diurnal in the field become nocturnal in the lab. It has been suggested that the use of running-wheels in the lab might contribute to this timing switch. This proposition is based on studies that indicate feed-back of vigorous wheel-running on the period and phase of circadian clocks that time daily activity rhythms.

Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions.

Modeling natural photic entrainment in a subterranean rodent (Ctenomys aff. knighti), the Tuco-Tuco.

Subterranean rodents spend most of the day inside underground tunnels, where there is little daily change in environmental variables. Our observations of tuco-tucos (Ctenomys aff. knighti) in a field enclosure indicated that these animals perceive the aboveground light-dark cycle by several bouts of light-exposure at irregular times during the light hours of the day.

Field and laboratory studies provide insights into the meaning of day-time activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

South American subterranean rodents (Ctenomys aff. knighti), commonly known as tuco-tucos, display nocturnal, wheel-running behavior under light-dark (LD) conditions, and free-running periods >24 h in constant darkness (DD). However, several reports in the field suggested that a substantial amount of activity occurs during daylight hours, leading us to question whether circadian entrainment in the laboratory accurately reflects behavior in natural conditions.