SAN DIEGO -- Wali's blue tongue rapidly flickers in and out. She swivels her head toward the visitors, reptilian eyes bright.
Wally is a northern blue-tongued skink. These Australian lizards display their azure intakes appendage to ward off predators. Bright colors often mean danger, such as with the highly venomous blue-ringed octopus.
But no worries, blue-tongued skinks are harmless. The color display is all a bluff. Gently handled by keeper Benjamin Fan, Wally even permits a visitor to caress her supple, squamate skin.
The display of lingual lapis lazuli provides one of the intimate moments between human and animal at the Roos and Mates tour. It opened last year at the new Walkabout Australia attraction at the San Diego Zoo Safari Park.
Wali is one of several "animal ambassadors" guests might meet.
Even more intimately, those on the two-hour tour can offer leafy treats to kangaroos, which gently take them from your grasp.
Housed with Wali in an off-exhibit area for "animal ambassadors," is Adelaide, a red kangaroo. Adelaide jumped on request, and allowed a visitor to feed her with one hand, leaving the other free to stroke her dense, luxuriant fur.
You're also allowed to feed the native Australian geese and ducks. They get dried millet; cricket; and writhing giant mealworms that undulate uncomfortably between your fingers before you throw them to the ground.
And you also learn from a guide and keepers the general principles that allow such closeness. Animals willingly modify their behavior if given the right incentives, and well treated.
This is done by proven psychological methods such as operant conditioning. They get a reward for performing the desired behavior, or approximating it. If they don't, nothing happens.