Conservation planning for primate communities in rapidly transforming landscapes

Abstract

Deforestation in tropical forests is a leading cause of biodiversity loss, including for primate species. In this context the processes, habitat loss and fragmentation are two of the main drivers of primate population declines. However, we still know little about the importance of each of these processes (i.e. habitat loss and fragmentation) across different scales for understanding impacts on primate populations. In particular, the vast majority of primate studies on the effect of habitat loss and fragmentation have been conducted only at the patch scale, without paying attention to patterns and processes at broader landscape scales. Understanding how habitat loss and fragmentation affect primate species’ occurrence, abundance, group structure is important to propose improved management actions for primates in fragmented landscapes. This thesis evaluates the effect of landscape change on primate species occupancy, abundance, group structure at different scales and incorporates them into a systematic conservation planning process. The thesis has four aims: 1) determine what we currently know about the effects of patch size in primates and whether or not it varies across life history traits; 2) determine the relative importance of site-scale, patch-scale and landscape-scale variables for primate species occupancy and abundance in the Colombian Llanos; 3) determine the relative importance of site-scale, patch-scale and landscape-scale variables for primate species group density, composition and size in the Colombian Llanos; and 4) based on the model from (3) identify priority conservation areas for primate conservation in the Colombian Llanos, using systematic conservation planning. To address these, I first conducted a systematic review of the published literature to determine what we know about the effects of habitat loss and fragmentation on primate species and whether or not those effects relate to life history traits. Then I use a multi-scale analysis of the variables affecting the occurrence, abundance, group size and composition of primate species in fragmented landscapes, using four primate species of the Colombian Llanos as examples. I then incorporate the models developed for the Colombian Llanos primate species into a prioritization process using systematic conservation planning. My systematic review shows that density, parasitic prevalence and diversity, and time spent feeding are generally positively correlated with patch size, while species presence and genetic diversity are negatively correlated. Time spent resting and moving did not show clear patterns with changes in patch size. I found little evidence that the effect of patch size varies consistently with traits but this may be due to confounding factors and/or low sample sizes. My novel application of a multi-scaled analysis to primates in the Colombian Llanos demonstrated that occupancy was associated with a combination of patch-site variables, site-landscape or patch-landscape variables depending on the primate species, with site and patch scale variables being the most important in general. Landscape-scale variables were most important at the 1000 m buffer distance (i.e. 1000 m radius distance at which landscape variables were measure from the focal sampling patch) for dusky titi monkeys (Callicebus ornatus), black-capped capuchins (Sapajus apella fatuellus) and Colombian squirrel monkeys (Saimiri cassiquiarensis albigena), and at the 2500 m buffer distance for red howler monkeys (Alouatta seniculus). In further examining the effect of these variables on group densities, groups sizes and group composition I show that group densities are primarily associated with landscape variables for most species, while group size is associated primarily by site-scale variables. Group composition for all primate species studied here was largely influenced by group size and therefore, indirectly influenced by site-scale variables. This gives a much more nuanced understanding on how process operating across multiple scales impact on primate populations that can be achieve through the analysis of abundance and occupancy alone. Finally, I apply a multi-scaled approach to conservation planning for primates. The incorporation of combined spatially explicit models and conservation planning tools for primates benefits the prioritising process by considering primate species features such as group size and composition that affects the long-term persistence of these species in fragmented areas. My analysis also leads to an understanding of the role of cost in driving priorities for primate species in fragmented landscapes. My novel approach to the effects of landscape change on primate species highlights five important contributions for primate conservation. First, I made a quantification of the general effects of patch size on primate species responses finding consistent patterns on primate responses. Second, through this thesis I gained a multi-scaled understanding of the effect of landscape change on primates. Third, an expansion on the multi-scale approach lead to explicitly link landscape change simultaneously to occupancy, abundance and group structure. Fourth, I include a comparative assessment across multiple species in the same landscape. Finally, this is the first study to apply a multi-scaled approach to conservation planning for primates. My thesis highlight how conservation strategies in fragmented landscapes will affect in different way the group density, size and composition of the primate species studied depending on the scale at which conservation actions are taken. This thesis offers a comprehensive analysis of the importance of landscape approach in primate studies to assess the effects of landscape change at multiple scales.