The thought just occurred to me, but how was it the Romans acquired Lions for their game, when tranquilizers didn't exist? Did it make them expensive because of their difficulty to capture? Or did they just throw slaves at it until they caught it?
They were caught by snares. I can't think of any information about the capture of lions. According to Livy's history, 39.22, Lions were first exhibited after the Aetolian war, http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0166%3Abook%3D39%3Achapter%3D22.
Cicero does have an intriguing piece of information regarding the capture of panthers here: https://archive.org/stream/letterstohisfrie01ciceuoft#page/128/mode/2up. It's on page 129. He informs his friend in Rome that hunters laid snares for panthers, but there weren't many left. An interesting tidbit about Roman over-hunting.