Pervasive loose sociality can drive demographic Allee effects

Sociality can, in theory, lead to positive relationships between population density and per capita growth rates (demographic Allee effects), but evidence of such relationships remains rare. Here, we consider the demographic consequences of sociality, highlight a historic bias favoring studies of species that socialize in relatively fixed groups, and present evidence that 'loose sociality', whereby individuals do not form fixed groups, could be a more likely driver of Allee effects. We show that loose sociality can drive Allee effects if local density increases with population density, that this condition could be widespread in the animal kingdom, and that there are measurable traits that can determine a species' susceptibility to such socially-driven population collapse.