Alpacas are smarter than sheep, so they tend to need more enrichment than sheep. If you have open pasture and woodland that provides plenty of interest and diversion (and that's how you would keep sheep) then alpacas would be fine allowed to roam freely and live their own carefree lives. If you have a small, plain pasture or large paddock, your alpacas will need some enrichment to prevent them from going stir-crazy.