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Half-Slumber Design in Animals We have a clock in our brain that is based on circadian rhythms. The clock is connected to Earth’s rotation, and it provides daily periods of rest and recovery called sleep. Animals have it too, and for many animals, sleep is a dangerous time if there are predators around. Scientists have discovered that many animals, especially marine mammals, have a half-slumber system designed to keep them safe and yet allow them to sleep.

The half-slumber system allows half of the brain to sleep while the other half is awake and able to respond to danger or navigational needs. Studies in dolphins have shown that there are different regions of the brain that work together to allow one side of the brain to function while the other side sleeps. The hypothalamus contains ventrolateral preoptic nuclei that exchange messages between the left and the right sides of the brain. They determine which side sleeps and which side remains alert to danger. This also allows movement of the dolphin’s fins and tails to generate body heat in the coolness of the marine environment. It also allows the animal to surface, to breath, and to swim with its companions.

Northern fur seals have a similar system but highly modified. The fur seals come out on land and assume a posture that allows them to put one flipper in the water which they paddle with while keeping the other three flippers in the air to avoid heat loss. Their nostrils are out of the water, allowing breathing and one eye is open and looking for predators. The part of the seal’s brain that provides vision is not connected to the other functions of breathing or movement.

Birds also use the half-slumber design. Mallard ducks have a unique system where the ducks form a group. Ducks on the outside of the group have one eye open, and their brains function differently than ducks at the center of the group. Migrating birds that fly for very long times also use the half-slumber design with one eye and one side of the brain watching where the bird is going while the other side of the brain slumbers. Great frigate birds fly for ten days at a time using this system. Swainson’s thrush gets its sleep by taking micro naps when it is perched.

It seems that every creature using the half-slumber design to get its required sleep uses it differently. The changes are not small and are highly complex involving many organs. Intricate design differences in the brain primarily direct them. Studies of animal sleep are in an early stage, but the complexity of the system is undeniable. The Bible tells us that we can “know there is a God through the things He has made” (Romans 1:18-20). It is a very difficult challenge to understand just how complicated God’s design is. Even in our sleep, we demonstrate God’s plans and engineering.
— John N. Clayton © 2019

Have you ever asked why birds stand on one leg? We live on a river that has a massive number of ducks in it. When the ducks are resting on the edge of the river, they generally stand on one leg. When guests visit us, they want to know why. Ducks are not the only birds that stand and even sleep on one leg. Geese and Flamingos do the same thing.

The answer to why birds stand on one leg seems to be a simple matter of the application of basic physics. For an object to be stable, its center of gravity has to be directly above the point of support. In my basic physics classes, we have some demonstrations of that principle. A spinning bicycle wheel will do strange things if its pivot point is not under the center of gravity. A top that is not symmetrical will invert when spun with its round side in touch with the table. There are toys that appear to be suspended in space, but in reality, their center of gravity is located at one end which makes it look odd when it is on the edge of a table.

When you stand on two legs, your center of gravity is somewhere between the legs. That may sound stable, but in reality, it isn’t. When you stand, you waver as your body senses that any movement you make throws you off balance. There is a constant muscular effort that counteracts this movement. Just standing for a long time can be fatiguing because a lot of energy is expended to counteract this wavering.

Recent studies with flamingos show that when they stand on one leg, the center of gravity falls directly over the point that touches the ground. Standing on one leg, the bird’s body is quiescent. When the bird is on two legs, there is more muscle movement and the center of pressure on the foot touching the ground changes. If you look carefully at a duck standing on one leg, you will see that it stands a little lopsided, so the mass is completely above the point of support. In addition to energy conservation, standing on one leg allows birds to withstand cold temperatures by keeping one leg close to the body. So thermoregulation is also involved in this odd-looking design.

So if you have ever asked why birds stand on one leg, remember this. Anytime we see something in nature that we don’t understand; it is almost 100% sure that there is a design feature involved. What the animal is doing may look strange, but it has at least one significant function. Truly we can “Know there is a God through the things He has made” (Romans 1:18-20).
Data from Science News, June 24, 2017, page 15.
–John N. Clayton © 2017

Tag: duck

Half-Slumber Design in Animals

Why Birds Stand on One Leg