Chinstrap penguins only sleep around four seconds on average, but they sleep more than 10,000 times per day. In addition, they sometimes use both brain hemispheres, sometimes only one, like an international team of researchers in a scientific journal Science reported. This means they get an average of around 15 hours of sleep every day. According to the study, the microphases consist of long-wave sleep (slow wave sleep), which people often call deep sleep.
A chinstrap penguin usually has to guard the nest alone from birds of prey because its partner often travels for days to fetch food. Females and males take turns. Extended periods of sleep at the nest would endanger eggs and chicks. On King George Island off the tip of West Antarctica, a brown-feathered skua, the Subantarctic skua, is particularly targeting them. It prefers to attack nests at the edges of the colony. The penguins also have to deal with their peers in the colony.
The research team equipped 14 chinstrap penguins (Pygoscelis antarctica) on King George Island with GPS and small devices that recorded certain brain waves and muscle movements. The researchers led by Paul-Antoine Libourel from the Center de recherche en neurosciences de Lyon in Bron also filmed the animals.
Surprising result: penguins that bred at the edge of the colony were less stressed than those in the center. They slept more, more deeply and with fewer interruptions. According to the researchers, the results indicate that the penguins in the center of the colony are more disturbed by conspecifics. The causes are probably aggression between each other and the associated stress, but also the noise in the middle of the colony.
The breeding penguins’ partners spent between 3 and 43 hours walking to the coast, diving for fish and returning. They traveled 6 to 130 kilometers away from the colony and dived an average of up to 53 meters deep for food. They usually eat krill, but also small fish.
Like many birds, chinstrap penguins can sleep with their right and left hemispheres individually, but also with both at the same time. Overall, they slept an average of 8.55 hours per day with both hemispheres of the brain, an additional 2.98 hours with only the left and 3.38 hours with only the right. That’s about 11.5 to 12 hours of sleep per hemisphere of the brain and around 15 in total.
Sleeping at short intervals has already been discovered in other penguin species, the authors write. However, they had significantly longer sleep periods. Other birds have also developed special sleeping techniques. Mallard ducks (Anas platyrhynchos) sleep with both hemispheres of their brains and both eyes closed when they are in a group. At the edge of the group they sleep with one eye open and one half of their brain awake. In contrast to chinstrap penguins, they obviously feel safer in the center of the group than at the edge.