question:  Why was the Volpla vocabulary limited when the narrator took a few into the valley?
context: Volpla By WYMAN GUIN Illustrated by [Transcriber's Note: This etext was produced from Galaxy Science Fiction May 1956. Volplas at last. Yet I had always been so sure I could create them that I had been calling them volplas for ten years. I had called them volplas since the day old Nijinsky's elongated arms and his cousin's lateral skin folds had given me the idea of a flying mutant. Again in the laboratory, I entered the metabolic accelerator and withdrew the intravenous needles from my first volplas. I carried their limp little forms out to a mattress in the lab, two girls and a boy. The accelerator had forced them almost to adulthood in less than a month. It would be several hours before they would begin to move, to learn to feed and play, perhaps to learn to fly. Meanwhile, it was clear that here was no war of dominant mutations. I thought, "All this and three volplas, too." I wiped the back of my hand across my mouth and said aloud, "Yes, sir, the dangerous age. I kissed her until I heard rollerskates coming across the terrace from one direction and a horse galloping toward the terrace from the other direction. Outside this little town, I found a litter of flat stones that had young black-snakes under each slab. I filled a pail with them and took them into town and dumped them on the walk in front of the movie just as Theda Bara's matinee let out. Even in the basically mutating colony, there had been a decidedly simian appearance in recent years, a long shift from the garbage-dump rats I had started with. Except for the face, chest and belly, they were covered with a soft, almost golden down. The spars had been common to the basic colony for years and were the result of serial mutations effecting those greatly elongated fifth fingers that had first appeared in Nijinsky. Suddenly, as I teased the male volpla, this happened.
output:  They were encountering concepts that were unfamiliar from the lab environment
options:  They had not been alive long enough to learn enough English to communicate well  They were encountering concepts that were unfamiliar from the lab environment  They are not smart enough to have a fully developed language, no matter how hard they try  They were confusing their own language with English, having trouble keeping the languages separate