Thala-siren

Thala-sirens were large, fin-footed, marine mammals indigenous to the island planet of Ahch-To. Characterized by their udders, large flippers, and long snout, they were found lying on the cliffs of the sacred temple island, the site of the first Jedi Temple, when Rey traveled to the island to find Jedi Master Luke Skywalker. They were docile mammals who were not hunted and thus did not fear the natives of the island. They enjoyed sunning themselves along the coastal rocks of the island. The females, which were known as sea sows, produced a nutritious green milk, which was harvested by Luke Skywalker and the native Lanai.

Behind the scenes
The thala-siren which Luke Skywalker interacts with in Star Wars: Episode VIII The Last Jedi was a full-sized animatronic puppet, about 18 feet tall. It was sculpted to fit into the rocks of the filming location and had a mechanism on the inside so its head could tilt forward. The puppet was so big that it had to be transported to location by helicopter. Two puppeteers were inside the puppet during filming; one would operate the shoulders and the flippers at the top, while the other person would operate the belly and the udder mechanism at the bottom. Two smaller thala-sirens were staged in the background

Appearances

 * Star Wars: Episode VIII The Last Jedi
 * Star Wars: The Last Jedi: Expanded Edition
 * Star Wars: The Last Jedi: A Junior Novel
 * The Last Jedi: Rey's Journey