Why Do They Do That? The Physics Behind 3 Famous Animal Behaviors

By Amber Bennett

Have you ever wondered about the origins of the phrase, "get your ducks in a row"? What about how the "doggy paddle" works or why squirrels are such amazing jumpers? The answers to all of these questions have one thing in common: physics. Keep reading to learn about the science behind these three famous animal behaviors.

How Do Squirrels Leap from Branch to Branch?

A squirrel leaps through the air. Photo Credit: caroline legg, CC BY 2.0, via Wikimedia Commons

The death-defying acrobatic maneuvers performed by squirrels look a lot like parkour tricks. But how do they know how to land tricky jumps between bendy tree branches that move with the wind? Researchers say it's a combination of learned behavior (practice makes perfect) and inherited adaptations. 

To see what determines how far a squirrel is willing to jump and how the leaps are timed, researchers set up an obstacle course in an artificial forest. Then, they used peanuts to encourage 12 fox squirrels to move through the course. First, the squirrels learned how to jump between branches of varying stiffness to claim the peanuts. The furry test subjects completed 96 jumps during this phase of the trial.

Next, the researchers ran computer simulations of the jumps. In the version that matched the actual animal behavior, they found that the stiffness of a branch was more important than the length of the jump when the squirrel was deciding when to leap.

The next step was to increase the difficulty of the course for five of the squirrels. The gaps between branches were larger, and the branches were bendier. The squirrels did not fall, but their landings were less than graceful. Within five attempts, all five of the squirrels had mastered the more difficult jumps by adjusting their speed. 

The squirrels' quick learning surprised researchers, as did their unusual tactics for jumping longer distances or to branches at a different height than the starting point. The furry test subjects actually rotated in midair and pushed off of other obstacles, greatly resembling parkour maneuvers. They also could slow themselves down with similar midair maneuvers.

If you're interested in seeing some of these acrobatic moves for yourself, check out Mark Rober's Backyard Squirrel Maze 1.0 and the follow-up 2.0 video on YouTube. They are highly entertaining.

Why Do Ducklings Swim in a Row?

Ducklings swim in a line behind their mother. Photo Credit: Public Domain

The phrase "get your ducks in a row" was inspired by how baby ducklings often swim in a single line behind their mother. An article in the Journal of Fluid Mechanics determined that the ducklings are saving energy by riding their mother's waves. Researchers used computer models to discover the most efficient formation for the ducklings to swim in and just how much energy the ducklings saved. 

The duckling in the "sweet spot" receives the most energy-saving benefits. However, researchers found that the ducklings that are farther back in the line still reap the rewards of this swimming formation because their siblings in front pass along waves. If a duckling were to fall out of formation, it would have to work a lot harder than its siblings to keep up. These wave-riding and wave-passing behaviors reduce the wave drag felt by the ducklings, so they can maintain the mother duck's velocity without expending too much energy.

You can check out some newly hatched ducklings moving into position while swimming in a pool with their mother in this video from Lily's Channel - Around the world.

Do Dogs Really Paddle?

A dog paddles in a pool. Photo Credit: Public Domain

Researchers at West Chester University in Pennsylvania examined the swimming habits of six different dog breeds and determined they all used the distinctive "doggy paddle." Using underwater video of the dogs swimming, they also found that the doggy paddle is not a trot, as previously thought. Instead, it's more of a running motion.

When an animal trots, the left-front paw lifts at the same time as the right-back paw. Likewise, the right-front paw moves in sync with the left-back paw. The movement of dogs' paws while swimming is more complex than a trot and looks more like running. Plus, all six breeds, from the Newfoundland to the Yorkshire terrier, used the same style of paddling.

The researchers found that although the doggy paddle is not particularly efficient, it does have an upside. When a dog swims, a paw is extended as it pushes down and back, propelling the dog forward. The paw is then tucked closer to the body as it slowly returns to the starting position, reducing drag. 

You can see the doggy paddle in action in this video of 39 dogs swimming together in a pool from Daily Mail.

What Other Animal Behaviors Do You Want to Learn More About?

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