Pesachim 52B

אוכלין על של בין הכיפין, ואין אוכלין על שבין השיצין.

One may continue eating dates based on those that have fallen off the tree and are stuck between the palm branches. But one may not continue eating on the basis of the dates that have fallen between the thorn branches, as animals are unable to reach them there. According to the first tanna in the Mishnah cited, one may continue eating fruit as long as an animal has access to its type, parallel to the opinion of the Rabbis with regard to removal. Rabban Shimon ben Gamliel’s opinion is parallel to the opinion of R' Yehuda: If the fruit from a certain place is not available to all, one is required to remove it.

תנן התם, שלש ארצות לביעור: יהודה, ועבר הירדן, וגליל. ושלש ארצות בכל אחת ואחת. ולמה אמרו שלש ארצות לביעור? שיהיו אוכלין בכל אחת ואחת עד שיכלה האחרון שבה.

Since the Talmud discussed the point when Sabbatical Year produce must be removed in different places, it cites a Mishnah from tractate Shevi’it that deals with a similar topic. We learned there in a Mishnah: Eretz Yisrael is divided into 3 separate lands with regard to removal, Judea, Transjordan, and the Galilee. And there are 3 lands in each and every one of them: The valley, the mountains, and the plains, in which the halakhot of removal differ. And why did the rabbis say that there are 3 lands with regard to removal if those lands themselves are further divided? It is so that people will eat in each and every one until a certain crop ceases from the field in the last of the regions that comprise it. Therefore, even if a certain fruit is no longer available in a particular region within the land, it may still be eaten there as long as it is available in one of the other regions.