As long as your piggies always have access to safe places dotted around the garden, and as your garden is fully enclosed and safe from dogs, cats, foxes, stouts, badgers, rats etc. you still have to consider aerial predators. More and more raptors are moving to urban areas. I have seen one eating its catch in our garden, so it is not simply a theoretical danger! All it takes a few seconds and a piggy that is feeling too safe out in the open...
Please also always keep in mind that those fences are not too high for cats, and that somebody in your neighbourhood may get a roaming cat at some point. There is a good reason why rescues call free-roaming unsupervised set-ups 'cat's takeaways'; my sisters Heulwen and Hedydd have been rescued from such a place.
After losing 3 of our childhood piggies to a neighbour's dog wiggling its way into our garden through a badly maintained fence in two separate attacks and despite my dad having built a supposedly safe cage with a firm lid after the first attack, I have become much more cautious.
I have let my first piggies free roam on a daily basis, but only when I was there to keep an eye on them as we have visiting cats and brown rats coming though tunnels dug by moles looking for new territory; we had several times when they were nesting in the garden and active during the day. Even so, there has been the odd close shave!
I have also always made sure to check the fences' bottoms frequently for areas where other smaller animals have tried to dig/wiggle through to prevent my inquisitive guinea pigs to go walkabout.
This is unfortunately not quite rare. Not quite all wandering piggies are due to being dumped; there are a few escapees but not all are ever found again. If you really want to free roam, I would definitely discuss microchipping with my vet!
My current garden is definitely not safe for any unsupervised roaming, bordering onto open countryside and with too many cats in the neighbourhood, too!
My own dream piggy outdoors space would be like this one in Germany - it is fully enclosed with an outbuilding for the winter, plenty of shade and bushes around to provide amply protection and security as well as a dedicated outbuilding for the winter and any frail piggies. There is a grid overhead to prevent birds of prey and cats from getting into the garden.
Please always remember that it is your piggies that pay the price of any lessons; usually with their lives!
Unsupervised free roaming is not something I would ever recommend, having my own piggy skeletons in the cupboard and having experienced first-hand just how suddenly and quickly attacks can happen. My presence in the garden is still the best deterrence.
