In the depths of winter, when the days are short and the nights are long, many animals enter a state of torpor, or deep sleep. This is a way to conserve energy when food is scarce and the weather is harsh. But how do animals know when to enter torpor?

The answer lies in their circadian clocks. These internal clocks are found in all animals, and they help us to regulate our sleep-wake cycles, as well as other bodily functions. In hamsters, the circadian clock is controlled by a group of genes called the clock genes. These genes produce proteins that build up and break down over the course of a day, creating a cycle of activity and rest.

In Siberian hamsters, the clock genes are also responsible for regulating torpor. When the days get shorter in the winter, the levels of clock proteins in the hamsters' brains increase. This signals the hamsters to enter torpor. When the days get longer in the spring, the levels of clock proteins decrease, and the hamsters come out of torpor.

This study provides new insights into how the circadian clock regulates torpor in hamsters. It also suggests that the clock genes may be involved in regulating torpor in other animals, including humans.