What's the difference between an alpaca and a llama?

The average llama is roughly twice the size of the average alpaca. There are differences in the body and head also, especially the shape of the ears. While the alpaca has been carefully bred for over 6,000 years as a luxury fiber-producing animal, the llama was bred as a pack animal. Its purpose has traditionally been to carry packs in mountainous terrain. The llama has coarse guard hair which protects it's fine, inner coat of fleece from the chafing of the pack on its back. Alpacas do not have guard hair in the prime fleece of this "blanket" area. Despite its much larger size, the llama produces far less fleece per animal than the alpaca. The llama shown here has not been shorn; the alpaca shown here was shorn a few months earlier. The fleece of the alpaca is so dense that the animals could not remain healthy in the heat of the summer with their fleeces unshorn. In addition to its packing use, the llama makes a very good guard animal for alpacas, sheep and other small livestock. Llamas and alpacas can interbreed and produce live, fertile offspring, but this offspring would not be either as strong as a true llama nor have as lovely a fleece as a true alpaca, so this "intermediate" animal would not be very useful. New research has confirmed that, while the alpaca was bred by the Incas out of a Vicuna ancestor, the llama was bred by the Incas from a Guanaco ancestor. All four of these animals are members of the camel family, but the rare and endangered Vicuna is famous as the animal with the finest fleece in the world. The much larger llama is easily distinguished by its banana-shaped ears, impending size, and coarser fiber. The smaller, more readily handled alpaca has straight ears and a much softer fiber devoid of guard hairs.