The riverside fisherman who made the videos, Rainilson Souza, 34, said that the recordings were made in Lago do Rei, near the municipality of Careiro da Várzea, 20 km from the capital Manaus.
The videos show several alligators on sandbanks, which appeared in the lake amid the severe drought in the region.
The animals are of the black caiman species, which can reach up to five meters.
The riverside dweller says that he was not afraid to pass by boat among the animals, but recognizes that the situation was dangerous.
According to him, a black caiman has already attacked a resident of the region.
Ildean Fernandes, a biologist specializing in Amazonian crocodiles, explained that the animals of the black caiman species do not usually gather together, as they appear in the images.
Fernandes emphasizes, however, that the animal exhibits the behavior of gathering in groups in some circumstances, including during periods of drought.
The specialist states that, normally, caimans of this species do not usually pose a risk to humans, except during the reproductive period.
During this period, the males try to protect their territories on the banks of rivers and lakes, while the females can become aggressive to defend their young.

Fuente: Agencia Amazon