Or HaChaim on Numbers 22:4/אור החיים על במדבר כ״ב:ד׳

1 ילחכו הקהל את כל סביבותינו, "the multitude will lick up all that is around us, etc." Perhaps the Moabites did not want to reveal to the elders of Midian the extent of their fear of the Israelites and that is why they described the presence of the Israelites in that part of the world as an ecological disaster. They spoke of "our environment" (pl) to include the Midianites as potential victims of such a disaster. The words ובלק בן צפור are what the Torah reports not part of what the Moabites told the Midianites. It is even possible that these words were also spoken by the Moabite messengers to the elders of the Midianites; they wanted to emphasise to the Midianites that inasmuch as they had appointed one of the Midianite princes as their king, the Midianites had a special interest in cooperating with them. Should anything happen to them, this would reflect negatively on Midian because of their king's origin. The Torah emphasises that Balak was king בעת ההיא, "at that time," i.e. not earlier and not subsequently. Once Bileam told the Moabites that they had nothing to fear from the Israelites in the foreseeable future, they dismissed Balak from his position and sent him home. The best proof of that is the fact that when the Torah enumerates the princes who were slain in the punitive expedition the Israelites launched after Pinchas' famous deed (Numbers 31,8), Tzur was amongst the princes listed as having been killed.