Landscape and habitat quality for proboscis monkeys: its variation in space and time, and use in management

The status of Proboscis Monkeys' ecosystems was assessed inside and outside the protected areas of Sarawak. Assessment variables were based on known habitat use of Proboscis Monkeys. Sampling units were laid out in different categories of habitats for assessment of forest structure, food plants, canopy connectivity and human disturbance. Recording of forest attributes was based on rapid assessment, and ecological and forestry survey techniques. Spatial configuration of landscape in the study sites was assessed using satellite imagery. Observation of behavioural activities and foraging behaviour of the monkeys was undertaken in Bako National Park and Kuching Wetland National Park over a period of at least one year. A one-male group was selected from each study site and was followed continuously during the day for three to four days a week. Each age/gender category from the selected one-male group was followed on different days. Feeding, resting, travelling and "other" activities of each category of animal were systematically sampled and recorded in five-minute intervals every 30 minutes from 6:30 am to 6:30 pm. The group was continuously observed outside the five-minute intervals. Patterns of habitat use was formalised into a spatial configuration across the sites and some aspects of the behavioural data was collated and analysed according to that configuration. Behavioural activities occurred within different forest strata and crown levels were also observed and analysed. Feeding behaviour and types of food plants the monkey ate were observed using binocular. Food plants eaten by the monkeys were identified on the spot after they left the feeding area. Food plants that could not be identified were marked with ribbon taps, photographed and samples were collected. Sampling quadrats were established in the heath and the mangrove forests and phenology of plants inside the quadrats were monitored once a week. Trail users' activities on-trail in Bako National Park were identified and their impacts on Proboscis Monkeys' behaviour were analysed. Observation of the interaction between trail users' activities on-trail and Proboscis Monkeys was undertaken weekdays and over the weekend at the entry point on selected days of each month. A single stationary vantage point was located 20 m from the entry point which was screened by undergrowth. Each trail user's activity was observed and recorded from the vantage point. A trail user for observation was randomly selected dependent on trail users whose activity firstly triggered the monkeys' response behaviour. If the observed trail user became invisible, another trail user who remained visible was selected from the vantage point. One animal was also randomly selected from the group of Proboscis Monkeys for observation without selecting either female or male. If the observed one disappeared, another one that was visible from the vantage point was selected. Proboscis Monkeys behaviour were observed and recorded in response to trail users' activities on-trail. Interaction was only recorded when there was an encounter from both present at the entry point at the same time. The results suggest that the forest structure and composition in the study sites differed with more small trees colonized the areas. More fragmented habitats were detected outside the study sites. The medium closed heath forest had higher density of food plants, a few emergent trees, and minimal canopy gaps such that more suitable for the monkeys compared to other study sites. Behavioural activities were higher in the habitat of good forest attributes with higher density of food plants. Behavioural activities were significantly higher in the upper crown level and the upper canopy particularly feeding activity. Male monkeys engaged in more feeding compared to females. Feeding was significantly higher during the wet season as opposed to the dry season in Bako National Park. Young leaves were the most preferred food plant parts to all age/gender categories. Feeding on young leaves was significantly different between wet and dry seasons. Higher feeding on young leaves during the wet season coincided with higher foliation of mangrove stands during the same season. This explains the availability of food resources in the mangrove habitat influence feeding and diet category of the monkeys. Lower feeding activity during the dry season at the time when lower availability of food resources contribute to our understanding that the monkey may be more vulnerable to human disturbance during a time of lower food availability and hence at a time when they can least afford it. Specifically, disturbance derived from off-trail and laughing activities inflicted an adversely disturbing effect on the monkeys' foraging behaviour. Moreover these results indicate that human disturbance have more adverse effects on the monkeys' foraging behaviour as opposed to variability in the availability of food resources