The snooze that saves energy

Life has evolved many remarkable ways to survive despite hostile conditions. One of them is for organisms to go into a near-death-like state, called daily torpor. During this phase, the body’s temperature drops significantly, body functions slow down, and the organism is motionless and unresponsive. Warm-blooded animals, which regulate their body temperatures, spend large amounts of energy maintaining it. Any dip or rise may turn out fatal in most cases. However, during frigid temperatures, food shortages or drought, some animals and birds choose to shut down their body functions and slip into torpor for a few hours in the day.

Daily torpor saves about 50% to 90% of the energy depending on the size and activity levels of the organism. In some hummingbirds that live in cold climates, body temperature drops to a low of 3 degrees celsius from the average 38. Their heart rate drops to about 50 beats per minute from a whopping 1200. Recent studies have shown that hummingbirds have two states of torpor—a shallow state and a deep state. Daily torpor is seen in some animals that live in warmer regions. For example, the nectar-eating blossom bats enter torpor during summer when nectar becomes hard to find.

Animals and birds that enter daily torpor synced it with their 24-hour body clock. They are woken up when it’s time to eat or when sunlight warms them up. Scientists believe some hormones, like leptin, thyroid hormones, corticosterone and testosterone, may be playing a role in the beginning and end of the torpor phase. Some animals, like Siberian hamsters, sync their torpor cycles with each other and go into a group snooze.

Scientists believe this state could help humans in planetary missions. If astronauts could slip into the torpid state, they could carry up to 75% less water and food in spacecraft. Perhaps, the day when humans are packed off in their near-deathly-snooze to some faraway planet may not be far away!

Spoorthy Raman