The distribution of non-human primates in tropical forests is highly influenced by vegetation structure, interspecific interactions and human-induced threats. Reported disturbance in the form of charcoal burning, farming, tree extraction for construction poles or timber, encroachment along the forest boundaries and unplanned infrastructure interferes with the forest edges and interiors, which affect the distribution of primate species. The purpose of this study was to assess the population of the Black and White Colobus (Colobus guereza), Blue Monkey (Cercopithecus mitis) and Red-tailed Monkey (Cercopithecus ascanius) in the forest edge and interior in South Nandi Forest during the dry and wet seasons. Their interspecific interactions as well as effects of factors such as human-induced threats, canopy cover, height of trees and stem density were also assessed. The study adopted an ecological survey design with 7 random line transects being established at both the interior and edge locations. The population densities of Black and White Colobus and Blue Monkey were derived using distance sampling. Observations for the Red- tailed Monkey did not attain the minimum required for distance sampling to be used hence their densities were not estimated. Overall, there was a high density of Blue Monkey (0.88±0.19 animals/ha) as compared to the Black and White Colobus (0.63±0.16 animals/ha). The forest interior had high populations of the Blue Monkey (0.99±0.30 animals/ha) and Black and White Colobus (0.89±0.30 animals/ha) as compared to the forest edge. Primate observations were high during the wet season as compared to the dry season. More observations (78 observations) were made for the Black and White Colobus in the wet season as compared to the Blue Monkey (59 observations) and Red-tailed Monkey (9 observations). Blue Monkey interacted more with both the Black and White Colobus and the Red-tailed Monkey with the level of interaction being high (45%) between the Black and White Colobus and the Blue Monkey. These two species form feeding associations especially during the dry season when food is scarce. Major trees utilized included Prunus africana and Croton megalocarpus. Even though the highest averages for stem density (Mean= 56.2), height (Mean= 20.3) and canopy cover (Mean= 64.0) were recorded in the forest interior, independent samples t-test showed there was no significant difference (p>0.05) of these factors in the forest edge and interior. Awareness raising among the locals through the Community Forest Associations should be carried out to sensitize them on impacts of illegal activities to the primate populations. Monitoring should be done for long term effects of human activities on primate populations and distributions

Background information
According to FAO (2015), the total land covered by forests has reduced by 3% from 4128 million ha in 1990 to 3999 million ha in 2015, largely due to deforestation. Tropical forests are often subject to both legal and illegal human activities resulting in forest loss and fragmentation. These activities increase accessibility and exposure of the forest interior to anthropogenic activities and wild species become vulnerable especially where hunting of species is involved (Michalski and Peres, 2005).

Some primate species are very sensitive to slight changes in vegetation structure and composition (Cowlishaw and Dunbar, 2000), because they have specific ecological requirements, with about 90% living in tropical forests (Mittermeier, 1988). Furthermore, many such species are locally endemic or are rare and exhibit disjunct distribution (Richards, 1996). Such narrow distributions predispose many tropical forest species to increased risk of extinction when habitats are modified (Terborgh, 1992) because protected areas even if effectively protected cannot conserve species whose range fall outside the protected area. Despite the fact that these diverse ecosystems should be under legal protection, only a paltry 12% of forests are legally protected from human exploitation (Bruinsma et al., 2015). Still, many of these areas are subject to illegal exploitation (Redford, 1992; Oates, 1996; Chapman and Onderdonk, 1998; Chapman et al., 1999). Therefore, the future of these important species is threatened by escalating rates of forest conversion and degradation (Johns and Skorupa, 1987; Struhsaker 1987; Brown and Lugo, 1990).

Effects of forest loss and degradation on species have been demonstrated through various studies on birds (Newmark, 1991; Githiru and Lens, 2007; O’Dea and Whittaker, 2007; Mac Nally et al., 2009), insects (Warren et al., 2001; Tscharntke et al., 2002) and mammals (Andren, 1994; Chapman and Onderdonk, 1998; Cowlishaw, 1999; Crooks 2002). Most primates however have decreased in population due to loss of their habitats e.g. Orangutans (Cawthon, 2005; Johnson et al., 2005: Geladas, Dunbar, 1998; Yihune et al., 2009) and Lemurs (Irwin et al., 2005; Bodin et al., 2006). However, for primates, effects of disturbance vary depending on the primate species and habitat (Skorupa, 1988; Plumptre and Johns, 2001). A study conducted by Plumptre and Johns (2001) showed that Chimpanzee (Pan troglodytes) densities increased with disturbance in Lope, Gabon but decreased in Kalinzu, Uganda.

The three focal species of this study; Cercopithecus ascanius (Red-tailed Monkey), Cercopithecus mitis (Blue Monkey) and Colobus guereza (Eastern Black and White Colobus) belong to the Cercopithecidae family and are found in tropical forests in Africa including South Nandi Forest. Even though they are listed as Least Concern (LC) according to the IUCN 2015, continuous habitat destruction and fragmentation poses a great threat to the future survival of these species. It is also important to understand the interspecific interaction of these species because these interactions in some cases could influence the spatial distribution of primates within a given habitat (Kingdon et al., 2013).

While some research has been undertaken at the South Nandi Forest, especially on insects (NMK, 2012) there has been no research focus on primates despite their economic importance and increased disturbance from humans which affect their distribution. Any form of disturbance could alter their habitat to an extent that it influences spatial distribution, population density, habitat selection and use by a given species or an assemblage of primate species. It is against this background that this study was conceived to understand the population status of the three primate species in South Nandi Forest, their spatial distribution and the factors influencing the distribution. This is vital in the implementation of proper habitat management interventions, overall decision making as well as policy formulation and implementation at various hierarchical levels such as at the forest management level, national level and regional levels.

Statement of the Problem
Loss and destruction of forest ecosystems is happening all over Kenya and South Nandi is not an exception. Despite the documentation of the presence of the three primate species through a biodiversity survey conducted in South Nandi Forests in 2012 by NMK, presence-absence in function of a given species is not adequate for effective management of species. The current population status of the three primate species remained unknown for South Nandi Forest. Illegal human activities such as unsustainable honey harvesting and logging target specific tree species e.g. Prunus africana which comprise the major diet trees for the primate species especially the Black and White Colobus Monkey. Logging also causes habitat destruction and fragmentation and this affects the distribution of the primates. Additionally, the effect and response by the primates to habitat changes such as vegetation structure both at micro-habitat and macrohabitat levels was hitherto unknown at this forest. This may make it difficult for management and decision making process that involves restoration of degraded forest areas, enhanced enforcement and improved management effectiveness in South Nandi Forest. Primates are also very good indicators of the status of the environment and the adverse changes in their habitats could havean effect such as food availability on other taxonomic groups.

Study Objectives
Broad Objective
To ensure effective conservation and management of primate populations through increased biological knowledge.

Specific Objectives
1. To determine the population density of the three monkey species in South Nandi Forest during dry and wet season

2. To assess the interspecific interaction between the different species of monkeys

3. To evaluate the factors affecting spatial distribution of the three monkey species in the forest edge and interior

Research Questions
1. What is the population density per hectare of the Black and White Colobus, Blue Monkey and Red-tailed Monkey species in South Nandi Forest during the dry and wet seasons?

2. How do the three species interact among themselves?

3. How are the population density, spatial distribution, occurrence and of the three primate species influenced by factors affecting vegetation structure in the forest interior and forest edge?

Justification of the Study
Most primate populations today face ongoing habitat disturbance (Mittermeier et al., 2007) and its effects are likely to increase as human populations increase. Disturbance negatively influence primates through habitat change and reduced food availability (Fimbel et al., 2001) which affects their distribution and densities within a given area (Johns, 1988, 1991). Census data of primate populations are an integral part of primate conservation for two reasons. First, population density estimates are important variables to consider when determining conservation priorities and creating management plans for primate populations (Ganzhorn et al., 1997). Secondly, these estimates are valuable to researchers trying to understand socio- ecological differences between primate populations (Butynski, 1990).

South Nandi Forest is a gazetted forest area and information on population sizes and population densities across a gradient of forest disturbance was very useful to the forest managers because it identified the areas of the forest which require great conservation interventions. Knowledge generated maybe useful for red-listing process in cases where the species populations are significantly reducing. Mapping the spatial distribution of each species provided useful baseline information for future monitoring of the species. Such information was also useful in promoting primates as wildlife-based tourism for the region. The information was applied in awareness creation of the surrounding local communities on their sustainable use of the forest so as to reduce anthropogenic pressure that could negatively impact the population of these species. Information on disturbance is to be used by Kenya Forest Service(KFS) to effectively enforce existing regulations against illegal activities as well as unsustainable use of the forest for increased conservation outcomes. Distribution maps provided information on the areas highly preferred by the three different species and will be used in forest management initiatives, land use planning and decision making at site, national or global level.

Scope of the Study
The study was confined to the South Nandi Forest even though the species are also present in the adjacent forests of North Nandi and Kakamega Forest. Other forests around South Nandi Forest were not considered during the study. In as much as there may be other primate species (e.g. Baboons, bushbabies), this study was only focusing on the three species of primates Blue Monkey (Cercopithecus mitis), Red-tailed monkey(Cercopithecus ascanius) and Black and White Colobus monkey(Colobus guereza). In order to understand the effect of seasonality on the distribution of the primate species, the study was confined to the dry season (February and March) and wet season (April and May) of 2015. The study was also confined to the natural forest only.

Limitations and Assumptions
Heavy rains which are usually experienced in the area occasionally interfered with the sampling schedule. This was addressed by postponing the transect walks which prolonged the research period. The major assumption was that the number of sightings for the different species of monkeys would reach the minimum number of observations required for population density estimates to be established using Distance Sampling analysis procedure. The observations for the Red-tailed Monkey did not attain the minimum observations required hence averages were used to represent the population numbers.

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