Llamas have an uncommon serenity. They are very quiet compared to other livestock. Their primary means of vocal communication is humming, which sounds very much like a human hum. They have a variety of hums, addressing each circumstance, as well as other sound including an alarm call you will never forget. The males are noisier than the females, especially when they are chasing each other around trying to establish dominance. At such times they sound much like adolescent human males.
Llamas have an undeserved reputation for spitting. A llama raised in appropriate circumstances will normally not spit at a human unless the human is abusing the llama. A petting zoo is not an appropriate place for a llama (or other animal) and I believe that much of the reputation for spitting comes from those unfortunate llamas who have been subjected to the stress of living in a petting zoo. Llamas use spitting to establish dominance, settle arguments and to protect their food supply.
Llamas are very respectful of fencing and, under normal circumstances, will not jump over a fence to leave a pasture. Llamas do not like to be confined in a small area. Thus we do not normally close them in the barn or a shelter for an extended period. Our llamas have free access to their pastures day and night.
See also: Lama Behavior, an article contributed by Lars Garrison of West Mountain Farm.
Other interesting information about llama behavior may be found in John Mallon's website.