DCA files are a model animation format used in Pikmin. DCA files use frame-by-frame animation to show precise movements.
DCA files cannot be found outside of any archive, and are instead located in bundle archives.
Sorry that's all I really know right now. If you make the animation play slowly with the KEY files, they look really jittery and mess with timing. It's the IEEE-754 float after the "spd" label.