Sun Bear Tongues and Frog Tongues

The animals at Zoo Atlanta represent so many opportunities for biologists around the world to learn basic information about, well, animals! We get research proposals all the time from researchers, both among our own staff and globally, seeking permission to include the animals in their research. We approve the proposals that are of the greatest scientific value, that have potential to help us even further improve our qualities of animal care, and that are certain to cause no harm of any form to the animals. Recently two papers were published in major academic journals by scientists from regional universities that contribute some fascinating information to the global body of knowledge about animals.

Dr. Bonnie M. Perdue (Department of Psychology, Agnes Scott College) published:

Perdue, B.M. 2016. The effect of computerized testing on Sun Bear behavior and enrichment preferences.
          Behavioral Sciences 6, 19; doi:10.3390/bs6040019
The field of comparative cognition investigates species’ differences and similarities in cognitive abilities, and sheds light on the evolutionary origins of such capacities. Dr. Perdue realized that, while cognitive studies commonly are conducted with animals such as dogs, elephants, primates, and even giant pandas, many animals have never been studied. So, she applied some standard methods, using an ingenious rugged computerized touchscreen apparatus, to the sun bears at Zoo Atlanta. Bears typically use their tongues to explore and manipulate their environment and, she found that the bears actively engaged the touchscreen menus with their tongues. The screens had dabs of honey on them in the earlier trials, to draw the bears’ attention to these novel objects. Once familiarized with the screens, the bears proceeded to learn to interact with specific color- or shape-targets on the screen in exchange for treats. Soon, the bears were preferring to interact with the computer screens more than any of the other enrichment items available to them. This study discovered a new method by which bears can be studied and showed that the experiments were preferred by the bears who actively involved themselves at every opportunity. This is fascinating stuff!

Alexis Noel (a graduate student in Mechanical Engineering, Georgia Tech) and her colleagues published:

Noel, A.C., Guo, H-Y., Mandica, M., Hu, D.L. 2017 Frogs use a viscoelastic tongue and non-Newtonian saliva to catch prey.
          Journal of the Royal Society Interface 14: 20160764.
          http://dx.doi.org/10.1098/rsif.2016.0764
Frogs can capture insects, mice and even birds using only their tongue, with a speed and versatility unmatched in the world of synthetic materials. How can the frog tongue be so sticky? In this multi-faceted study that included some frogs at Zoo Atlanta, used high-speed films of frog feeding to understand the behaviors involved in tongue-feeding. Then they used high-tech measurements and characterizations of frog tongues at Georgia Tech to investigate the structural properties of frog tongues and saliva. They found that the tongue’s unique stickiness results from a combination of an incredibly soft and stretchable anatomy soft and a saliva that simply does not follow the normal rules of how liquids respond to pressure. The tongue acts like a car’s shock absorber during insect capture, absorbing energy and so preventing separation from the insect. The unique saliva spreads over the insect during impact, grips it firmly to the tongue, and yet it slides off easily once it is back in the mouth. This combination of properties gives the tongue 50 times greater work of adhesion than known synthetic material (such as everyone’s favorite, the sticky-hand toy). These insights offer many new ideas and models for applications in industry and engineering. Yet more proof that frogs are the coolest animals on Earth (according to me, anyway)!

More information (and very cool videos!) are available here:
http://www.news.gatech.edu/2017/01/31/reversible-saliva-allows-frogs-hang-next-meal
https://www.youtube.com/watch?v=I5gRRheZf28
Joe Mendelson, PhD
Director of Research