Ecologia e comportamento do Bugio-Ruivo (Alouatta guariba clamitans Cabrera, 1940) em fragmentos florestais na depressão central do Rio Grande do Sul, Brasil

• Autor(a) principal: Fortes, Vanessa Barbisan
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional PUCRS
• Texto Completo: http://hdl.handle.net/10923/5421
• topic: ZOOLOGIA; MACACOS; ANIMAIS - HÁBITOS E CONDUTA; HABITAT DOS ANIMAIS

Howler monkeys (genus Alouatta) are known for their ability to live in fragmented habitats. Their folivorous diet and capacity to use small home ranges play an important role in this adaptability. However, habitat fragmentation may hamper long-term persistence of small and isolated populations through deleterious effects. This study aimed at evaluating the effects of habitat fragmentation on the ecology and behavior of brown howler monkeys (Alouatta guariba clamitans) at the Campo de Instrução de Santa Maria (CISM), Santa Maria (29o43’-29o44’S; 53o42’-53o44’W), State of Rio Grande do Sul, Brazil. A population survey conducted from March to December 2004 recorded 378 individuals (63 bisexual groups, two unisexual groups and eight solitary individuals) living in 18 out of 20 forest fragments. Mean group size (5. 8 individuals) was similar to that observed in brown howler populations living in continuous forests. Groups contained on average 1. 4 adult and subadult males, 2. 5 adult females and 1. 9 immature individuals (IFR=0. 7). Analyses of the influence of landscape (fragment size and isolating distances) and vegetation (species richness and diversity, tree height, density and mean DBH, dead trees density, total IVI, density and dominance of food sources, and density of Fícus spp. ) characteristics on howler monkey demographic variables (abundance, density and group size) indicated howler monkey abundance was positively related to fragment size (r=0. 78, p<0. 001), mean isolating distance (r=0. 56, p<0. 05) and distance to the nearest fragment (r=0. 70, p<0. 01). Population density was inversely related to fragment size (r=-0. 52, p<0. 05) and directly related to total basal area of food sources (r=0. 52, p<0. 05). On the other hand, there was no relationship between group size and any variable.From January to December 2005, the activity budget, use of space and diet of three social groups inhabiting fragments varying in size were studied by the instantaneous scan sampling method. Group P (7 individuals) was studied during 59 days (654 hours) in a 1. 8 ha fragment, group M (6 individuals) was studied during 58 days (623 hours) in a 20 ha fragment, whereas group G (5 individuals) inhabited the largest forest tract at the study site (977 ha) and was followed for 54 days (577 hours). Both groups G and M fed on 48 plant species belonging, respectively, to 29 and 24 families, whereas group P used 52 species (27 families) as food sources. Diet similarity was highest between groups G and M (Horn index, Ro=0. 61), whose fragments also showed more similar plant compositions (Ro=0. 60). Leaves composed the bulk of the diet of all groups (G: 78%; M: 59%; P: 67%), whereas fruit showed the greatest contribution to the diet of group M (35%) compared to P (18%) and G (9%). Feeding (G: 23%; M: 19%; P: 24%) and moving (G: 6%; M: 8%; P: 5%) differed among groups, whereas resting (G: 55%; M: 58%; P: 58%) and travel (G: 11%; M: 9%; P: 9%) did not. The longest (1,463 m) and shortest (92 m) day ranges were performed by group M. Home range was similar among all groups (G: 4. 9 ha; M: 5. 0 ha; P: 1. 8 ha). Group M contained an adult female showing an uncommonly lighter pelage color. Three other howler monkeys belonging to two additional groups inhabiting the same fragment also showed abnormal pelage colors.The spatial isolation of this population is a putative cause of this trait that requires further investigation. The present research represents the largest database of A. g. clamitans populations inhabiting fragments within the same microregion. Fragment size and vegetation quality (related to food availability) are suggested as the most important environmental variables affecting brown howler monkey metapopulation dynamics at the study area.