Quote - Can the displacement effect be thus animated? The displacement value altered over time?

Any node parameter can be animated. Click the key next to it and then "Animated" to turn on key framing of that parameter.

Quote - And is there some clever way to make the increase/decrease different for each leg?

Probably the simplest is to use the Group tool to give one leg its own material zone. You would still put the same shader there, but now you have a separate instance of the displacement which you can animate on its own.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)