They are generally effective against single intruders only, not packs. Guard llamas have been most common on ranches located in the Western United States, where larger predators, such as the coyote, have been more prevalent.
The effectiveness of guard llamas against intruders depends on whether they are facing a lone attacker or a group. They are most commonly used on ranches in the western United States due to the prevalence of coyotes as a predator.