Effects of Habitat Structure and Fragmentation on Diversity and Abundance of Primates in Tropical Deciduous Forests in Bolivia

Abstract

Habitat structure and anthropogenic disturbance are known to affect primate diversity and abundance. However, researchers have focused on lowland rain forests, whereas endangered deciduous forests have been neglected. We aimed to investigate the relationships between primate diversity and abundance and habitat parameters in 10 deciduous forest fragments southeast of Santa Cruz, Bolivia. We obtained primate data via line-transect surveys and visual and acoustic observations. In addition, we assessed the vegetation structure (canopy height, understory density), size, isolation time, and surrounding forest area of the fragments. We interpreted our results in the context of the historical distribution data for primates in the area before fragmentation and interviews with local people. We detected 5 of the 8 historically observed primate species: Alouatta caraya, Aotus azarae boliviensis, Callithrix melanura, Callicebus donacophilus, and Cebus libidinosus juruanus. Total species number and detection rates decreased with understory density. Detection rates also negatively correlated with forest areas in the surroundings of a fragment, which may be due to variables not assessed, i.e., fragment shape, distance to nearest town. Observations for Alouatta and Aotus were too few to conduct further statistics. Cebus and Callicebus were present in 90% and 70% of the sites, respectively, and their density did not correlate with any of the habitat variables assessed, signaling high ecological plasticity and adaptability to anthropogenic impact in these species. Detections of Callithrix were higher in areas with low forest strata. Our study provides baseline data for future fragmentation studies in Neotropical dry deciduous forests and sets a base for specific conservation measures.

Distribution, habitat and status of the white-coated titi monkey (<i>Callicebus pallescens</i>) in the Chaco - Chiquitano forests of Santa Cruz, Bolivia

“…Sources of these records included review papers (Hershkovitz, 1990;Anderson, 1997;Martínez and Wallace, 2010), broad wildlife surveys (Parker et al, 1993;Cuéllar and Noss, 1997;Miserendino et al, 1998;Navarro et al, 1998;Ayala and Noss, 2000;Arispe and Rumiz, 2002;Brooks et al, 2002;Maffei, 2005), specific primate studies (Justiniano, 2004;Thurley, 2009;Pyritz et al, 2010;Ayala 2011), unpublished photos and related personal communications (Table 1). The presence of C. pallescens was supported by collected specimens in two sites (# 15 and 22) and by new photos and a video in nine sites (# 1, 2, 7, 8, 10, 14, 23, two in 24), while undefined observations in 21 sites and local reports in nine other sites completed the 'assumed' and 'suspected' localities for this species.…”

“…comm.). Square dots near Santa Cruz city (around # 32) included two collecting sites of C. donacophilus (Anderson, 1997), subsequent reviews (Martínez and Wallace, 2010) and several recent sightings nearby that can be confidently assigned to the gray titi monkey (Pyritz et al, 2010; Dingess, unpublished; Rumiz pers. obs.).…”

“…It is likely that size of the trees, availability of tree holes and other shelters, and water-rich foods (such as succulent leaves, flowers and fruits of arboreal cacti) become the key habitat features for C. pallescens (and for Aotus). In humid Chiquitano forest patches near Santa Cruz city (Pyritz et al, 2010), forest maturity, surrounding forest area and understory density have been identified as factors affecting diversity and abundance of primates, although only the high understory density seemed to have a significant and negative effect on the abundance of C. donacophilus. Field studies are needed to identify and conserve the main habitat features that allow these monkeys to survive in these extremely dry forests.…”

“…Moreover, their habitat and distribution records are often uncertain because the species is not identified as the white-coated or the Bolivian gray titi monkey (C. donacophilus). The Bolivian gray (or whiteeared) titi monkey lives in wet but seasonal forests from southern Rondonia in Brazil through the departments of Beni, the east of Cochabamba and the north of Santa Cruz in Bolivia (Veiga et al, 2008b), reaching patches of the drier Chaco-Chiquitano transitional forest around Santa Cruz city (Pyritz et al, 2010). However, along the estimated range limit between these two species there is a wide expanse of dry forest habitats where the presence, absence or identity of titi monkeys is uncertain.…”

Threats to the Bengal slow loris Nycticebus bengalensis in and around Itanagar Wildlife Sanctuary, Arunachal Pradesh, India: impediments to conservation

“…Habitat structure, quality and anthropogenic disturbance are known to affect primate diversity and abundance in tropical forests (Rylands 1987, Chapman & Peres 2001, Pyritz et al 2010. Thus, any kind of habitat alteration or disturbance elicits varied levels of responses among primate species (Schwitzer et al 2011).…”