Coati species exhibit a level of sociality uncommon among carnivores, and coatis can provide a valuable test of models relating ecology to social behaviour. This chapter draws principally on the authors’ research in Panama (Nasua narica) and Argentina (Nasua nasua), but also discuss insights gained from work conducted in the United States, Mexico, Guatemala, Costa Rica, and Brazil. Based on these comparisons, the authors posit that predation and feeding competition have been two of the strongest forces shaping coati social patterns and discuss how socio-ecological pressures affect almost every aspect of coati biology, including; morphology, feeding ecology, reproduction, demography, and disease spread.