Estudo do comportamento territorial da ariranha (Pteronura Brasiliensis, Carnivora: Mustelidae, Zimmermann 1780) no Parque Estadual do Cantão, Estado do Tocantins

Abstract

The giant otter is a recognized social species, living in groups of 2 to 16 individuals with reproductive cooperative. Individuals of the same group often perform most of daily activities together. One form of organize spatially of animals living in society is defending a territory. The giant otter groups actively defend its territory with high vocalizations and agonism between groups. Therefore, the aim of this study was to know how the social organization is related in space and time. Assess whether there is a change in the group’s composition and size, as well as any difference between the size of the territories in the seasons – drought/dry season (DS) and flood/rainy season (RS). We observed 48 individuals in 12 groups (35 adults or sub-adults and 13 cubs of the year) and one solitary, totaling 49 individuals studied, 40 of these identified. The group sizes ranging from 2 to 12 individuals. The study took place between December 2013 and December 2014 at the State State Park of Cantão, Tocantins State, Brazil. We recorded 130 events of territorial marking in 5 groups, with 80 events during the RS and 50 during the DS. For the RS period, 100% of the marking records took place in communal latrines, meanwhile most of the marking records during the DS season happened in dens’ and latrines’ complexes. A total of territories marking was observed, with 10,2 minutes in the RS period and 8 minutes in the DS period. The time was recorded in continuous hours at the presence of the groups, corresponding to 4h 34 min (n = 10) during the RS, and 52 h 41min (n = 5) during the DS. To estimate each group areas a MPC 100% method was applied. The sizes of the territories in the RS (0.1 - 16.2 km2) have been 2 to 27 times greater than in the DS (0.4 - 1.49 km2); with the linear estimate averaging 4.19 km in the DS and 7.72 km in the RS. There was a significant correlation between the size of territories and groups in the RS period (r= 0.81, t = 3.16, p= 0.02) however, there was no significant relationship for the DS period (r= -0.26, t = -0.47, p= 0.66). During the ebb months, we observed a strong negative correlation between the size of the territory and the clutch (r= -0.76, t= -1.19, p= 0.44). At Cantão, especially in RS period, most groups overlapped each other territories at some point; reaching up to 4 different groups patrolling the same lake during short periods of time, with territorial overlaps ranging from 6% to 28%. Giant otters societies are probably shaped by the spatial dispersion of lakes combined through the food abundance and dispersion of both inside Igapó Forest in RS period. The sharing of latrines used in lakes indicates an interesting path to new research on the behaviors that can arise when different groups of giant otters are either patrolling or using their enlarged scales during the RS.