Time Scout by Robert Asprin & Linda Evans

Then she heard the unmistakable grunting roar of lions. A prickle ran straight up her back. Other wild screams reached her. The crowd leaned forward. The stink of sweat and anticipation hung on the bright air. The familiar snapping sound of the opening gates cracked through the arena. Margo peered toward the starting stalls.

A dozen frantic zebras broke into a gallop, veering to avoid the trees, leaping miniature walls of shrubbery, braying and bucking as they entered the arena. Behind them came a dozen ostriches, their black and white plumage bobbing gracefully as they ran down the long course of the track, weaving between the potted trees in visible confusion. Tiny beautiful antelopes darted into the sunlight and milled about in a frightened herd near the finish line.

Down at the starting gates, slaves had closed the big doors again, resetting the bars which held them shut. Once the job was done, they scrambled up ladders which were hastily pulled up after them. Margo leaned forward, watching in morbid fascination as the racing official who’d presided over the morning’s races once again lifted his white cloth as a signal. The cloth fluttered toward the ground. The gates slammed open. A defiant roar shook through the arena.

Enormous cats lunged into the sunlight. Maned lions snarled at one another and drew blood. Sleek, deadly lionesses shot past the quarrelling males, homing in on the terrified game animals already released. The striking pattern of leopard skin flashed past the starting gates as half-a-dozen more big cats were released into the Circus. Margo tried to count Six leopards, twenty lionesses, at least twenty more heavy male lions …