Researchers Better Understand Animal Propulsion Systems

Researchers have been studying the science behind animal movements, from insects to fish, for ages. According to a new study, there are almost infinite types of animal propulsion systems, but there are also limits the movements, beyond which breakdown occurs.

The research team, lead by Nathan Johnson, a graduate student at Texas A&M-Galveston who also teaches in the marine biology department, studied complex animal movements and their evolution through millions of years and hundreds of species. Their findings are published in Nature Communications.

The team concentrated their study on the propulsion methods of 59 species.

A common trait that researchers found among all the species was the animals' ability to "bend" their means of propulsion. The bend is not limitless, and can only occur to a certain point, according to the press release announcing the findings.

"If you take the wing of a bird or a bat, or the fins on a fish or a manta ray, you find that their means of propulsion are flexible," Johnson explained. "They can move back or forth or sideways easily, or they bend. But this bending and flexibility will only go so far, and it can't bend any more."

According to Johnson, nature has had millions of years to adapt more flexible means of travel. For him, the next step was "to see if there any patterns to this flexibility."

"For most creatures, there is a certain angle that these propulsion devices will reach and won't exceed. It's not that they probably can't exceed these angles, but rather doing so is just not energetically efficient for them," Johnson explained. "There does seem to be a universal range of movement in the species we looked at, from the fruit fly to the humpback whale."

On average, the range of bending for the studied species fell between a 30 and 60 degree angle. "This appears to be especially true with bird wings, while insect wings typically bend slightly less than other organisms we looked at," Johnson added.

While environmental factors influenced the range of movement for animals, it also lead to convergence of vastly different species. For example, the study found that the fin of most fish moves just like the wing of a typical bird.

Johnson said he hopes humans can learn from the result of millions of years of evolution.

"We need to understand a lot of these motion patterns in much more detail," Johnson said. "There are some current day tests being done with man-made materials to see if they can duplicate animal motion, such as some being done with jellyfish. The more we learn about animal propulsion and the way it's been developed over millions of years of evolution, the more it can help us with human engineering and how we can improve our own movement."