Ecologia espacial e comunicação vocal de Ariranhas (Pteronura brasiliensis) no Pantanal

Abstract

Giant otters live in cohesive groups, which defend territories during the dry season. Little is known about the spatial ecology of the species during the flooding period, when it is believed that groups abandon their territories. The strong cohesion between group members and the territorial behavior of the species indicate that giant otters use a complex vocalization system, to provide the stability and communication within and among groups. The present study aimed to: 1) to describe the activity pattern of giant otter groups in the Pantanal; 2) to estimate home range size of groups and landscape selection patterns between dry and wet seasons in Pantanal; 3) to look for the effect of season on territory size, territory exclusivity and territorial behaviour of giant otter groups; 4) to describe the vocal repertoire of the species, according to the behavioral context in which sound were emitted; and 5) to test if alarm sounds may present potential identity coding. Ten giant otter groups were monitored through visual observations between June 2009 and June 2011 in the Vermelho and Miranda Rivers, and another seven groups were monitored in the Negro River from September 2009 to June 2011. Three adult males of different groups were monitored with radio-telemetry between November 2009 and June 2011 in the first study area. Camera traps were located on active dens and latrines to record activity patterns in 24-h cycles. Vocalizations and the behavior of senders were recorded during the field campaigns. Groups presented a crepuscular and diurnal activity pattern, but 31% of photographic records occurred at night. The home range size of groups increased from 4 to 59 times during the wet seasons and some groups left their territories during flooding. Some groups overlapped the territories boundaries of neighboring groups. Territory size was correlated with group size in both seasons. The size of exclusive territories of giant otter groups was negatively related with intruder pressure. The vocal repertoire of the species was classified from 15 sounds emitted in different behavioral contexts. Alarm sounds varied significantly among groups and individuals, with a higher discrimination between females and males, which may be related to the body size of the senders and, consequently, sexual dimorphism.