Determining the percentage of any specific food item in a crocodile's diet is difficult because their defecation in water makes scat analysis impossible, and capturing individual animals to analyze their stomach contents is painstaking. In addition, as an animal that feeds rarely, sometimes only a few times in a year, even the individual stomach content examinations sometimes prove to be unsuccessful. However, as crocodiles grow, relying solely on small and agile food items such as fish becomes difficult, this causes a shift in the diet as the animal matures, for energy conservation purposes, as in other predators. Nonetheless, starting around , they can become capable mammalian hunters and their ability to overpower a wide range of mammals increases along with their size. Crocodiles less than may take a variety of medium–sized mammals up to equal their own mass, including various monkeys, duikers, rodents, hares, pangolins, bats, dik-dik, suni ("Neotragus moschatus"), oribi ("Ourebia ourebi") and other small ungulates up to the size of a Thomson's gazelle ("Eudorcas thomsonii").