Abstract
Caiman crocodilus is found most frequently in relatively warm, shallow or grassy areas in the
larger rivers, lakes and canals of Amazonia. The habitats that it uses are increasing in area because of
human activities. Paleosuchus trigonatus appears to be restricted to small forest streams in dense forest.
Water temperatures are relatively low and constant in the streams and opportunities to bask are limited
in the forest. Paleosuchus palpebrosus and M. niger are both found most commonly in the parts of
major lakes, rivers and canals which have steep banks and little floating grass. To what extent the present
distributions are influenced by intensive hunting of M. niger is unknown. Animals had similar injury
rates in all habitats but in the Lago Amanã area individuals in the lake had higher leech, and lower
nematode infestation than individuals in the surrounding canals. The giant rotifer Limnias ceratophylli
is reported for the first time as an epizoic on the ventral surfaces of M. niger.
