What size door?
Wild rabbits are never seen in open space like hares as they are naturally disposed to hiding and nipping into small places that they can hide in. This keeps them safe and they often dart into a hedge through small gaps and evade capture by running from side to side or disappearing down a burrow.
It is surprising what small gaps they can get through. Domestic rabbits are similar, and larger rabbits like Giant Continentals can also do the quick squeeze to go through a tiny gap. The standard wild burrow has a 4 inch (10cm) entrance but after that it widens and fluctuates throughout the route so some parts will widen while others are tight designed to suit the rabbit but not the fox.
This is how Runaround began with a 4 inch door - and it amazed us all to watch what seemed a big rabbit whizz through it. We had to change to 5 inch (13cm) because many customers just did not believe their bunny would fit through. We tested the 4 inch on many rabbits and they were able to access but 5 became the new normal because most customers always thought their rabbit was too big!
The system still outwitted the fox. The 5 inch aperture door and its twists and turns all suit the rabbit's wiry shape rather than the predator. The large door has a 6 inch aperture and this can be accessed by the giant breeds. Again, this was a source of surprise, but we thoroughly checked it with our own giant continental pair, 5 and 5.5kg respectively. They wouldn't attempt the 6 inch pipe but a 6 inch door proved no problem and they even exited a 5 inch one but with some negotiation. The smaller the doorway the safer - was our thinking which reflected the wild situation.
Dart holes and links (not ever being trapped in one area) allow the rabbit take charge of his own safety. It makes so much sense to Brer Rabbit, it seems odd it was never done before.
Image above from left to right shows: an average bunny with plenty of space in an 8-inch pipe, small wooden peephole, and the standard 5-inch aperture doors.
View our standard Runaround Door here