Detectabilidade, área de vida e movimentação de Sucuri-amarela (Eunectes notaeus COPE 1862) no Pantanal

Abstract

Movement ecology is an important tool for understanding animal behavior toward basic needs such as reproduction and foraging. Animals usually do not move randomly and use preferentially some habitats more than others. These habitats comprise a portion of a region defined as the home range of an animal. The Yellow Anaconda (Eunectes notaeus) is one of the largest snakes in Brazil. Little is known about aspects of its natural history and this gap poses difficulties to the assessment of population variation due to habitat lost and illegal hunting. Our goal was to study the detection probability and movement patterns of Eunectes notaeus in the Pantanal floodplain, in the Paraguay River basin. We were specifically interested in evaluating: 1) home range size and 2) total and monthly distance traveled by the snakes. We conducted the study in the RPPN SESC Pantanal, a private reserve located in the municipality of Barão de Melgaço, state of Mato Grosso, Brazil. We actively searched for yellow anacondas, both during the day and at night. To calculate detectability we used data from 29 random transects and a total of 13 individuals of yellow anacondas sighted. For movement studies, we captured eight individuals (two males and six females) for surgical implantation of VHF radio transmitters. After surgical procedures, the snakes were released at the capture site and monthly monitored from November 2015 to September 2016. The best model associated with detectability of anacondas was the search time, with a slight improvement of the constant, from 0.26 to 0.30. The home range size of radio tracked yellow anacondas ranged from 0.03 to 16.36 ha. We observed an overlap of the home range of some individuals and, apparently, bigger individuals had larger home ranges. The total distance traveled in a straight line ranged from 121.96 to 4,280.98m, with a monthly average of 367.16m. Monitored individuals moved more intensely during August. The results of this research contributed to the understanding of dispersal patterns of large aquatic snakes in wetlands from central Brazil, and help to clarify aspects of the natural history of Eunectes notaeus.