As they mature, they lose this yellow colour and the markings become less distinct. Adults are dull olive-green. The different subspecies vary in colour, size and skull shape. As they grow, various vertebrates take up a greater percentage of the diet. These include fish, amphibians, reptiles and water birds.
Observations show that as conditions become drier, caimans stop feeding.
Cannibalism has been reported under such conditions. In areas where this species has become depleted, fish populations have also shown a decline. They are also reputed to control piranha numbers. While it has been stated that little evidence is available to support this, C. yacare does demonstrate this particular dietary preference. In reality, it is likely that C. crocodilus is very much a generalist and adaptive predator, given its ecological success.