(See photos of alligators and crocodiles.)
The animals were fed a diet of dry, dog-treat-like biscuits, and they shed tears during most meals.
Some of the reptiles even produced more dramatic foaming around their eyes.
"At times you can see big bubbles coming up in the corner of the eye, sort of like soap bubbles," Vliet said.
In crocodiles, Vliet believes the weeping may be a byproduct of another feeding behavior: the hisses and huffs that crocs make while dining.
These acts may force air though the reptiles' sinuses, where they stimulate fluid in the tear, or lacrimal, glands and force them into the eyes—sometimes to the point of overflow.
Even simpler explanations could also account for crocodiles' tears.
"The general contraction of jaw muscles during the bite reflex may help to squeeze tears out of the lacrimal glands [and] ducts," croc expert Britton said.
"[Another] explanation is that accumulated tears that well up below the eye are simply displaced and run down the jaws when the crocodile moves its head to eat, and it's easy to associate that 'crying' with eating."
In the violent world of crocodiles, tears likely play a protective role.
"There's a lot of drama going on around the head while they are subduing prey," Vliet said. He noted that a croc's eyes also recede into its head as the animal manipulates its mouth.
"They may just be trying to protect the eye."
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