Variação e multidimensionalidade no uso do espaço em muriquis-do-norte (Brachyteles hypoxanthus)

Abstract

Studies carried out over almost 40 years in the population of northern muriquis (Brachyteles hypoxanthus) in the Private Natural Heritage Reserve – Feliciano Miguel Abdala, in Minas Gerais, Brazil, offer a great opportunity to assess the variation in the movement patterns of animals that live in groups and its relationship with ecological, social and behavioral phenomena that vary in space-time. The muriqui groups showed some changes in this period, from cohesive groups that became fluid, formation of new groups, increase and decrease in population, or the increase in the use strata of the forest, such as the ground use. So, in the first chapter social groups of northern muriquis have fluid grouping patterns, which results in subgroups that vary in size and composition throughout the year. In this study, we investigate whether group size adjustments can influence spatial variables such as daily path lengths and the distances between subgroups. These results show that daily path lengths were positively correlated with subgroup size only in the rainy months and only to the proportion of females, and suggest that the daily path length are linked to the availability and/or need of more resources for females. The greater distance between subgroups in the dry months reduces competition that results from the lower availability of resources, and, is consistent with the benefits of maintaining proximity between subgroups during intergroup encounters. Both results show the flexibility that the fission-fusion dynamics may offer, and indicate the importance of considering inter and intragroup relations. Another change observed was the reduction of the muriquis population by about 10%. Therefore, in the second chapter we verify if variation over time in the demography of primate populations can influence how available space is used. We analyzed the space use by five groups, when the population had reduced, and we compared the results from when the population was bigger. During the period of this study, the five groups of muriquis used 12% less than previously observed, with a 35.8% reduction of space use outside the area of the reserve. The home ranges of the groups were also between 2.7% to 32.5% smaller than previously observed. The size of the core area was not influenced by the reduction in the number of individuals, remaining stable in largest group, but in the other groups there was an increase. Home ranges and core area overlaps among all groups were small or did not occur, however the formation of a new group with the fission generated a moderate overlap between these groups even after a few years. Tracking long-term space use patterns after demographic changes demonstrates the ability of groups to adapt to ecological changes, such as more available space, greater availability of resources and less competition, and can provide a better understanding of space use in other populations as well as in other species. In the third chapter, to represent the reality of the space use those most arboreal animals occupy, it would be more appropriate if we characterize it in 3 spatial dimensions (3D), where the inclusion of the vertical axis can improve the understanding of the spatial ecology of various organisms. We investigated the three-dimensional (3D) space use in a group of muriquis, which are able to explore a variety of vertical substrates, such as canopy layers, understory and even ground use. We found that the percentage of time that the muriquis occupied the forest strata varied from 3% on the ground (0 m) to 35% (strata between 5 and 10 m). When we included in our analysis the altitude of elevation and the height of the forest strata where the behavioral activities take place, the annual volume of the 3D home range was 118 million cubic meters, and the volume of the 3D core area was 20 million cubic meters, there was no correlation between 3D home range and 2D home range, which means that we are measuring different types of space use. However, 3D core areas were correlated with 2D core areas, which indicates that muriquis need a minimum area for their activities. These results show the importance of the vertical space in analysis of the space use of species that live in limited areas and in high density, as they show the importance of understanding the possible benefits of accessing varied resources intensively in various strata, and the energy costs to explore slopes and the disturbed forests compared to a flat area forest and less used strata. The search for knowledge about the use of space by muriquis can help in the maintenance or management of isolated populations