I heard that many llamas can be easily annoyed or scared. The sound of the llama making groaning noises or going "mwa" is often a very good sign of fear or anger. Typically, they are a bit timid or standoffish in nature. If annoyed they make a clucking noise as they are spitting up stomach acid. Llamas can spit so hard that it can bruise the skin. If a llama is agitated, they will lay their ears back. The habit of spitting in the face of persons whose presence annoys them is common to all llamas, as may be witnessed in specimens in confinement in zoos. This is a defense mechanism. However, usually, a llama would prefer to run away than to confront their assumed aggressor, and is not always a frequent occurrence. One of the principal labours to which the llamas were subjected at the time of the Spanish conquest was that of bringing down ore from the mines in the mountains. Gregory de Bolivar estimated that in his day as many as three hundred thousand were employed in the transport of the produce of the mines of Potosí alone, but since the introduction of horses, mules, and donkeys, the importance of the llama as a beast of burden has greatly diminished.
*cough*wikipedia*cough*