People get llamas and alpacas to protect their other animals from mountain lions.
And Coyotes.
Please do not purchase alpacas thinking they are guard animals. Other than affording chickens some protection from foxes, alpacas are NOT protection animals they are prey animals. When alpacas perceive a threat, they will group together and move as a unit towards the danger. Rearing to look 12ft tall, kicks that are more like hard slaps, and spitting some 2nd stomach upchuck are the only intimidation tactics they have. A coyote can run 40mph+. If chased, the alpacas will run up to 35mph+ for a short distance and then cush, looping its head back over its back in a surrender position and exposing it to a belly attack. The alpaca cannot open its mouth wide enough to effect a really good defensive bite, and it only has teeth on the bottom jaw, so it can’t tear flesh easily - the exception being studs, who have fighting teeth that can castrate competitors but who are not kept with dames so are no help in defending them.
Now, llamas and donkeys are a different story. A llama also can’t outrun a coyote, but both the llama and the donkey are over 500lbs so they have a weight factor. Llamas are less likely to ‘surrender’ than alpacas, will use their head as a battering ram to send a coyote rolling and will stomp it into the ground for good measure. A donkey will shake a coyote to death and then stomp it into the ground.
Since donkeys can end up being a liability in that they do have a murderous streak, the best protection for livestock are LGDs - mostly Great Pyes. They can be a liability when it comes to them ‘eliminating’ neighborhood strays, and young-uns can be a bit thick=headed in training but dogs are more easily managed than a crazy donk and more tolerant of humans around ‘their’ flock.