Why does my mustang accept some handling but shut down for specific body areas?

A mustang that accepts general handling but shows specific defensive responses to particular body areas — common examples include the ears, the legs below the knee, the belly, or the area under the tail — is showing the normal pattern of uneven desensitization that occurs when some areas have been worked more systematically than others, combined with the horse's own map of which body areas carry the highest sensitivity and protective instinct. Different body areas have different levels of sensitivity and different protective instincts in horses generally, and these differences are amplified in mustangs because every area that was touched during the capture and processing experience has an associated memory that may be fear-based rather than neutral. The ears are among the most commonly problematic areas in mustangs specifically, because ear twitching was used during BLM processing to restrain horses for veterinary procedures — a horse that has had its ear twitched will often show extreme defensive responses to any approach toward the ears until the specific desensitization of that area addresses the fear response that the twitching created. The lower legs are another common specific sensitivity area, associated with roping or rope contact during capture and processing. The approach to specific body area sensitivities is to treat each area as a separate desensitization project rather than assuming that general body acceptance transfers to the specific sensitive area — beginning at the edge of the sensitive area where the horse shows the first mild tension signal, confirming acceptance at each level before advancing toward the more sensitive specific location, and using the same advance-and-retreat approach that worked for initial body contact desensitization. Patience with specific area sensitivities is particularly important because the fear response associated with a previously traumatic experience in that area is more resistant to habituation than simple novelty-based fear.