Get in Line!

One day in 2014, Zhiming Yuan (juh-mihng yoo-ahn) and his daughter were walking in a park. They noticed a family of geese in a pond. The goslings, or baby geese, paddled in a line behind their mother. “My daughter asked me why they did that, but I didn’t know,” Yuan says. “I decided to find the answer.”

Yuan likes to investigate these types of questions. He studies hydrodynamics, the science of how water moves, at the University of Strathclyde in Glasgow, Scotland. In past research, Yuan had studied how to design ships so they travel easily through water. He also researched how swimmers can use the movement of water to their advantage.

Yuan found that when boats or swimmers travel together in a line, they use less energy. He wondered if waterbirds might also save energy by swimming single file. Yuan set out to investigate.

Zhiming Yuan (juh-mihng yoo-ahn) went for a walk in the park in 2014. He was with his daughter. They saw a family of geese in a pond. The goslings, or baby geese, were swimming in a line following their mother. “My daughter asked me why they did that,” Yuan says. “But I didn’t know. I decided to find the answer.”

Yuan likes to learn about these topics. He studies hydrodynamics. That’s the science of how water moves. He works at the University of Strathclyde in Glasgow, Scotland. Yuan has studied how to design ships so that they travel easily through water. He’s also studied how swimmers use the motion of water to help them. 

Yuan found that boats and swimmers use less energy when they travel together in a line. He wondered about birds. They might also save energy by swimming single file. Yuan set out to investigate.

For his past research, Yuan had built a computer model to look closely at how objects move through water. The model is a computer program that imitates an object’s motion in calm water. When Yuan enters an object’s size and shape into the model, the model predicts the waves that the object will make. The model also calculates the drag the object will experience. That’s a backward force that resists forward motion.

As a mama duck paddles through water, she makes waves. Yuan thought that her ducklings might avoid some drag by riding these waves, like a person on a boogie board. Could swimming in a straight line help the ducklings do that?

Yuan turned to his old computer model. He entered the dimensions of the mother duck and one duckling. Yuan found that swimming behind mom saved that duckling energy. Would swimming single file benefit the ducklings at the end of the line too?

Yuan had built a computer model for his past research. The computer program re-creates an object’s motion in calm water. That allows Yuan to look closely at how the object moves. Yuan enters the object’s size and shape into the model. Then the model predicts the waves the object will make. The model also measures drag. This force pushes against a moving object. That makes it harder the object to move forward. 

A mama duck makes waves as she paddles through the water. Yuan thought that might help her ducklings avoid some drag. They could ride the waves like a person on a boogie board. Could swimming in a straight line help the ducklings do that?

Yuan turned to his old computer model. He entered the measurements of the mother duck and one duckling. Yuan found that swimming behind its mom saved that duckling energy. Would swimming single file help ducklings farther down the line too?  

The answer was yes! Yuan’s model showed that swimming in a line saved all of the ducklings energy. The baby ducks were able to ride the peak of their mother’s wave. That reduced the drag they experienced. And it gave them a small energy boost!

Yuan also found that each duckling was able to pass the mom’s wave to the duckling behind it. The duckling right behind the mom got the biggest benefit. The ducklings farther down the line got a smaller boost. But they still experienced less drag than if they were alone. “The mother looks after her ducklings by generating a wave,” Yuan explains.

Next, Yuan wants to study how ducks’ feathers and feet help them move. He hopes to use these findings to build more-efficient ships. “Animals always find the best position to save energy,” Yuan says. “There are so many lessons to learn from these ducks.”

The answer was yes! Yuan’s model showed swimming in a line saved all the ducklings energy. The baby ducks rode the peak of their mother’s wave. That reduced the drag on their bodies. And it gave them a small energy boost! 

Yuan also found something else. Each duckling passed the mom’s wave to the duckling behind it. The duckling right behind the mom got the biggest benefit. The ducklings farther down the line got a smaller boost. But they still felt less drag than if they were alone. “The mother looks after her ducklings by generating a wave,” Yuan says. 

Next, Yuan wants to study ducks’ feathers and feet. How might they help the animals move? He hopes to use these findings to build better ships. “Animals always find the best position to save energy,” Yuan says. “There are so many lessons to learn from these ducks.”