Penguins have unusual sleeping patterns. Instead of sleeping for an extended period of time, they take short naps throughout the day and night, either lying down or standing.
How Do Penguins Sleep?
As mentioned above, penguins don’t have a regular sleep pattern. With humans and most predatory mammals, a steady sleep cycle is maintained. Either sleeping at night with the day being our active hours (diurnal) or sleeping in the day and being active at night (nocturnal).
Penguins, however, not only sleep during the day and night, but instead of falling into a prolonged deep sleep, they take periodic naps. The length of these naps varies, depending on species, location, time of year, and safety factors.
Do Penguins Sleep Standing or Lying Down?
As with most of the sleeping habits of penguins, their sleeping position also differs according to species and location. Most species of penguins can be found sleeping standing up, but this doesn’t mean it is their sole sleeping position.
Penguins found in icy environments tend to sleep the majority of the time standing up. This is believed to be because it limits their exposure to the icy floor, thus preventing heat loss.
Species such as the king penguin favor lying on their bellies when they sleep, while African penguins tend to sleep lying down in burrows. Penguins, like all birds, need to feel safe before they fall asleep. Ultimately, penguins will sleep in a position that is comfortable, warm, and safe.
Why Do Penguins Sleep in Groups?
There is no conclusive evidence as to exactly why penguins huddle and sleep in groups, however, there are two common theories that are followed. The first is the one briefly mentioned above, for safety. As with many hunted animals, safety is found in numbers, and penguins are no different.
With large colonies, individuals are difficult to spot and single out, especially when tightly huddled together. The second theory, which is more robustly supported by research, is warmth.
Even with their array of fluffy feathers, birds still get cold, especially those that live on the ice. Although birds are warm–blooded, when exposed to extreme conditions, penguins need assistance to not freeze to death.
One paper found that when tightly huddled, the ambient temperature around the birds rose from -17 C to above 0 C. In extremely tight huddles, the temperature rose to almost 37.5 °C, which is close to the penguin’s body temperature.
Do Penguins Sleep With Their Eyes Open?
If penguins fascinate you, it’s likely that you’ve heard someone talk about them sleeping with their eyes open. We know that birds such as owls sleep with their eyes open, but is this the case for penguins, and can they sleep with their eyes open?
Yes, some species of penguins, such as the emperor penguin and Humboldt penguin, sleep with one eye open. Surprisingly, unilateral eye closure is common among many animals, such as birds, aquatic mammals, and reptiles.