One might I saw in my yard a large amount of ants coming up out of the ground.(no mound).they were moving to a new spot app. 30 ft.away.the amount of ants was at.least 6 ft. wide. What causes this much movement from literally thousands of ants?
Grayson County Texas insect issues
I've seen a couple of these 'mass relocations'---wondering about the same thing....why them, why now and why in general? And of course, other entomologists interested in the finer points of ant behavior have theorized why some ant species apparently relocate repeatedly, while other species in the same vicinity do so rarely.
Apparently, there are species differences noted in some of these studies---in some rather exotic locations (e.g. Central American tropics), but field studies none-the-less. Some species exhibit more 'stay-at-home' behavior while others seemingly have no trouble picking up all of their larvae, pupae, the queen(s) and nest mates and relocating.
Some of these frequent movers seem to be relocating to mounds they previously occupied. Probably some mark-and-recapture methods were used by the observers to determine this sort of behavior.
For other species, they are searching for available food resources or maybe even water for some ants or other insect species. As various food sources dwindle seasonally, ants continue to forage but explore newer and larger areas in pursuit of replacement food sources. lt's advantageous to be closer to your food source, so the colony might move closer, if it can. And it might move repeatedly over the course of a year.
For some species, colony competition might come into play. If resources are limited and ants from 2 different colonies or different species are competing for the same food source, the winners continue to use a food resource while the losers must relocate to survive.
Nest quality might be involved in some cases. If a food source is being exploited by a particular ant colony but the available nesting area isn't the most favorable for some reason, that particular ant colony may relocate to a 'better neighborhood' or perhaps one that offers better opportunities for thriving or surviving.
For some ants, escaping natural enemies of various sorts---or natural 'disasters' (flooding, fire, landslides, etc.)--- might be another reason for relocating.
I did locate another research paper on colony relocation in ants where members of some colonies seemed to respond positively to nest mate behavior; if one ant was exhibiting relocation behavior, recruiting a nest mate to do the same didn't seem to be a problem. In these situations, it might be that food availability, environmental changes and increasingly 'dangerous situations' might be triggering relocation responses in some nest members but not necessarily others. However, the latter might 'soften' their 'stances' in response to recruitment behavior as conditions worsen.
When you think about it for a while, these scenarious could apply to human behavior, too.
If a neighborhood urban supermarket goes out of business, all residents must find another supermarket to do business. Those who have cars to travel to other supermarkets have no problem doing so while those that lack cars might be looking for rides to take them to previously unknown neighborhood supermarkets. The indiviual that managed to find a really good food store---and communicates that to friends, relatives and anyone who will listen---could easily recruit neighbors (nest mate ants) to go with her to the new location. But if distance becomes an issue for the foragers and their recruits, all may be more amenable to just relocating the whole colony. Colony members are all related in the ant world, as opposed to most human neighborhoods where the residents are generally not related to each other. In the latter case, when one family moves somewhere else, the others remain. Perhaps that vacant house would be filled by another individual---or not, but the residents have no reason to move---or they can't be convinced to move.
It's interesting to find out how human-like ants can be---and that there are behaviorists and entomologists that study ant and human behaviors---drawing some similarities as well as differences. Maybe this is helpful?