Frog spit is a non-Newtonian fluid

Frog spit is a non-Newtonian fluid
Its thickness depends on the forces it experiences.
The saliva is normally thick like honey but when its tongue hits a bug, the force of the impact turn the saliva watery. The spit can now flow over the bug like a gooey net. After impact, the saliva turns sticky and thick again. The tongue pulls the bug back like a bungee cord.

Once the bug is in its mouth the frog uses its eyeballs to push the bug down. This eyeball-force turns the saliva watery again, releasing the bug into the throat of the frog.

Journal article:
http://rsif.royalsocietypublishing.org/content/14/127/20160764

Source:
http://www.npr.org/sections/thetwo-way/2017/01/31/512622260/to-catch-prey-frogs-turn-to-sticky-spit

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