Making ants crawl up/down hills smoothly

I'm wondering if Unity, physics or mecanim has much to help me with the task of making characters smoothly walk along uneven surfaces. I'd like to use bone based (mecanim) motion for several ants (and other insects/etc) traveling along uneven terrain. I guess the legacy animation system would work fine as well, but I want them to be very smooth so not likely going to use frame based animation (sprite swapping).

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With the physics system I could rig the...

Making ants crawl up/down hills smoothly