Home range and movement patterns of male dwarf caimans (Paleosuchus palpebrosus and Paleosuchus trigonatus) living in sympatry in Amazonian floodplain streams

Abstract

Dwarf caimans (Alligatoridae: Paleosuchus palpebrosus and Paleosuchus trigonatus), are small crocodilians exhibiting cryptic behaviour and complex habitat use that occur throughout the Amazon region. Our goals were to evaluate individual home range, habitat occupancy and movement patterns where they occur in sympatry in relation to seasonal water-level variation. We tracked five P. palpebrosus and seven P. trigonatus using VHS radio transmitters along the shores of two streams directly influenced by the flooding pulse of the Purus River. Paleosuchus palpebrosus individuals moved greater distances on a daily basis and had larger home ranges than P. trigonatus, and the species had different responses to increases in water levels. Paleosuchus palpebrosus moved into flooded forests, as do their principle prey species. Conversely, larger P. trigonatus individuals usually remained near the main stream, and were relatively sedentary. Intraspecific home-range overlap was higher than interspecific overlap in both species. Thus, habitat occupancy patterns as a function of water-level variation might facilitate coexistence of the two species of dwarf caimans in the same location. This study shows that when living in sympatry under a seasonal flooding regime, Paleosuchus species show a degree of habitat partitioning evidenced by different daily movement rates, home-range sizes and home-range locations.