Although posse deputies used to be allowed to carry guns, that privilege was lifted in the late 1970s when peace officers were required to go through more rigorous training. The posse does train regularly, taking part in monthly rides through the Marin wilderness and participating in a huge, annual multi-agency training session complete with simulated injuries. A large part of their orientation includes learning how to interpret maps and handle their horses in the dead of night, when most children, joggers, and hikers are reported missing. However, the riders' training is nothing compared to the stressful sessions the horses have to endure. A lot of horses are not cut out for search and rescue.
Horses are pretty spooky.
Their first impulse is to run. To make sure a horse is ready for search and rescue, the animal is sent to a special, expensive bullet-proofing school, which essentially amounts to five days of what sounds like sheer terror for the horse. The school puts horses through training exercises that subject them to all types of noise and distraction - waving flags, flares on the ground, people beating drums, rounds of exploding firecrackers, smoke bombs, police sirens, cannons, etc. Avoiding strollers All the while, the horse must avoid trampling baby strollers and such. The result is a horse that doesn't have to be pampered in the midst of a late-night search.