I think the caves are a really neat idea for organization purposes, but it is a little annoying to have an extra click whenever I want to glance at the status of my lions. (Levelling up, in heat, about to run away etc)

How about having the option to display the lions from one selected cave in your main den? If lag is an issue then perhaps add an option that limits the list of lions to a set amount - say, 30 - and any over that will be hidden under an accordion style code cut? (An example of what an accordion widget is can be seen here ) This would allow users to 'opt out' of caves by dumping all of their lions in one, but still be able to avoid that extra click while still presumably cutting down on den page lag.