Between 1968 and 1970, American ethologist John B. Calhoun (1917-1995) conducted a behavioral study of captive mice within a nine-square-foot enclosure at a rural facility in Poolesville, Maryland. Within the enclosure known as Universe 25, several pairs of mice bred a population, which ultimately swelled to 2,200. Eventually, they established social orders that created inside and outside factions, and soon mating ceased altogether.

The enclosure could easily accommodate a population of 3000 but without the need for endeavour and no predators, protection skills and will for survival of the species was lost

. Would a universal basic income have a similar affect?

What Humans Can Learn from Calhoun's Rodent Utopia (victorpest.com)