Fluffy EngineersDo prairie dogs become engineers when they build their burrows? Do sea anemones use scientific principles to help them catch food? A team of students and professors at the Comparative Biomechanics Laboratory of Tufts University is exploring these very questions. What answers are these researchers finding?
The projects at Tufts University's Comparative Biomechanics Laboratory examine the ways in which animals use science and engineering principles. The teams conducting these studies include middle school, high school, and college students, as well as Tufts professors. What they have found about the animal kingdom may surprise you.
For instance, prairie dogs — squirrel-like rodents — are fascinating little builders. Their underground tunnels contain many rooms, including bedrooms, nurseries, and bathrooms. These tunnels, or burrows, even include a listening room close to the entrance, where the prairie dog listens for danger before going outside. The burrows go down about 3 meters and can be 15 meters long.
What is even more interesting is the way prairie dogs build the entrances of their burrows. They surround the holes they have dug with piles of soil to form a conical shape. These mounds serve as lookouts and protect the burrows against floods.
A close look at the two entrances of a burrow shows that one is taller than the other. This difference is not coincidental. Prairie dogs have figured out that they can ventilate their burrows by building the entrances this way. They actually create a natural air conditioning system! And while prairie dogs might not realize it, they are using Bernoulli's principle to create a natural flow of air in their burrow.
Imagine that the entrances of a prairie dog burrow are hills and that you are a runner. Your goal is to spend the same amount of time running over each hill. In order to do so, you will need to run much faster over the tall hill because you need to cover a greater distance.
Similarly, in the case of the prairie dog burrow, the air that flows over the tall mound moves faster because it has to travel a longer distance. The velocity of air that flows over the different entrances of the prairie dog burrow is slightly different. Bernoulli discovered that the air that travels faster has lower pressure. Therefore, the two entrances of the burrow are at different pressures.
This slight pressure difference causes the air to flow through the burrow as shown in the diagram. Pretty amazing!
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Sea Anemones
Sea
anemones are carnivorous marine animals found below
the water surface along all seashores. They have tentacles,
which they use to catch food and transfer it to their
mouths. Most sea anemones attach themselves to hard
surfaces, such as rocks and other animals. They depend
on the flowing water to bring them food and nutrients.
However, if the flow becomes too fast, the anemones
will be dislodged from the surface and swept away.
In order to avoid being washed out to sea,
sea anemones have developed the ability to shrink in order to reduce
the force of water on their bodies. As they shrink, the force from
the flowing water becomes smaller and will not dislodge them. They
also have the ability to expand their bodies to increase the area
exposed to the flow. When it is feeding time, this expansion maximizes
food intake as the anemones filter small food particles from the flow
with their tentacles. Sea anemones do not feed when the water flow
becomes too fast.
Sea anemones can change their shape because of their skeletal system. The "skeleton" consists of:
- an internal cavity that holds water
- a muscular system
- a mouth, which can take in, hold, and expel water as needed
By regulating the amount of water in their bodies, anemones can stretch or shrink. And when they shrink, they reduce the area exposed to the water flow and the drag force the flow creates on their bodies.
See the principle at work for yourself. Imagine moving your hand through water. If you try to pull your open palm against the water, you can feel the drag force created by your hand coming in contact with the water. Now if you pull the edge of your hand through the water, you will feel less drag. That's because drag force is directly related to area.
- When a skydiver's parachute opens, it creates drag force, slowing the skydiver's fall enough to let the skydiver drift to the ground. High school students can learn more about drag force in Physics Explorer: Highly Damped Fall.
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The Comparative Biomechanics Laboratory at Tufts University is taking a serious look at other animals as well. A major field of study is the way butterflies use scientific and engineering principles to heat their bodies. Another example is how hermit crabs select their shells. There are also many other cases where animals use scientific principles to their own advantage. See if you can figure out the answers to the following questions:
- How do butterflies heat their bodies?
- Why would a hermit crab living in a fast-flowing river choose a heavy shell to carry around when lighter ones are available?
- Why are a fish's eyes on the side of its head instead of the front?
- How do birds use their wings to create enough lift to fly?
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Spider Engineering Humans want to know what spiders know: how to make spider silk. Find out why in this Riverdeep archive article. |
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Deep-Diving Dolphins For teachers: See how watching dolphins dive has helped scientists understand oxygen use in this archive article. |
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Drag
Force Activity High school students can investigate drag force with this Physics Explorer activity. |
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