 Like all Cyclura species , the blue iguana is primarily herbivorous , consuming leaves , flowers , and fruits from over 45 species of plant . This diet is very rarely supplemented with insect larvae , crabs , slugs , dead birds , and fungi . The iguanas are presented with a special problem for osmoregulation : plant matter contains more potassium and as it has less nutritional content per gram , more must be eaten to meet the lizard 's metabolic needs . As they are not capable of creating urine more concentrated than their bodily fluids , they excrete nitrogenous wastes as uric acid salts through a salt gland in the same manner as birds . As a result , they have developed this lateral nasal gland to supplement renal salt secretion by expelling excess potassium and sodium chloride . 
