The alpaca is a species of South American camelid mammal. It is similar to, and often confused with, the llama. However, alpacas are often noticeably smaller than llamas. The two animals are closely related and can successfully crossbreed. Alpacas can sometimes be aggressive, but they can also be very gentle, intelligent, and extremely observant. For the most part, alpacas are very quiet, but male alpacas are more energetic when they get involved in fighting with other alpacas. Humming is the most common sound alpacas make. They hum softly when they're curious, content, worried, bored, distressed, or cautious. When startled or in danger, one of them will announce a threat with a staccato alarm call and the rest will follow suit. When they breed, the male emits a unique throaty vocalization known to the alpaca-raising community as “orgling.”