The leader of Charles Muntz's dog pack is named Alpha.
Alpha is the imposing Doberman Pinscher who commands Charles Muntz's trained pack in Up. Muntz uses the dogs to search Paradise Falls for Kevin, the rare giant bird he believes will restore his reputation. Alpha communicates through a special collar that translates the dogs' thoughts into human speech, although the device gives his voice an unusually high, distorted pitch.
The pack also includes Beta and Gamma, whose names follow the same Greek-letter pattern. Dug is another member of the pack, but he is treated as an outsider because he is clumsy and repeatedly fails to satisfy Alpha's expectations. Dug's friendship with Carl and Russell ultimately places him against Muntz and his former packmates.
A notable production detail is that Pixar consulted veterinarian and dog behaviorist Ian Dunbar while developing the dogs' communication and pack behavior. Alpha was voiced by Bob Peterson, who also voiced Dug and co-wrote the film. Delta, Gamma and Beta may sound plausible as pack names, but Alpha is the established leader in the film.