No, they are not, at least as far as their existence on the Outer Banks. The herd size is at a critical point for sustainability. The problem is that there is not sufficient genetic variability in the herd. This is why they have introduced stallions from herds further south of the Banks to expand the gene pool. The herds from other parts of the Outer Banks are also descendants of the Colonial Spanish Mustangs. The Corolla herd size is currently at about 100 horses. If you have not been to the Outer Banks to see these magnificent creatures, it is well worth the trip.