awesome species - I just wish they'd make an appearance more often in Berlin! I've yet to see it there. I recently saw a photo taken by a local zoofan, him jokingly proclaimining that it probably was the first time it had left its burrow in 2-3 years . Based on my very limited experiance with Chester, it seems theirs are less shy.
If I remember correctly, I saw them the first time I visited (2003), they were off-show for enclosure maintenance the second (2005) and no-showed the third time (2011).
Chester's animals show pretty well outside the depths of winter - from Easter-September it's more common to see them than not.
Quite - my two visits earlier this month to Chester are the first times I haven't seen their tuatara, with sightings previously spanning every month of the year bar January.
just for the record, I did see 2 easily (one right up against the window, another half outside its burrow) on the latest Berlin visit earlier this week.