I filed a report on the tracker for this. I captured 4 of these from an AI homeworld and while they are fine in system and use their regeneration chamber to stay alive, they will not get in the Mark II Transport I sent to go get them and bring them to the new front-line. The transport has plenty of capacity, it only has 49 vultures on board. I wasn't sure if they are supposed to be untransportable but just not listed in their description, or if it's an actual bug.