Fruit Phenology of Tree Species and Chimpanzees’ Choice of Consumption in Kalinzu Forest Reserve, Uganda

One hundred and eighteen (118) tree species were identified, among which 58 species produced fruit within the two-year study. Fruit of only 26.3% of the latter is eaten by chimpanzees. The consumption of each of these fruits was generally low, with only two species constituting more than 25% consumption. Only about 1.7% of woody biomass is relied upon by chimpanzees in Kalinzu for food. The major tree species in chimpanzee diet monitored showed that fruit production varies monthly and seasonally. Apart from Musanga leo-errerae and Ficus spp. whose fruiting was consistent throughout the year, general fruit phenology was positively correlated with rainfall. Only three species namely: Craterispermum laurinum, Aframomum angustifolium and Beilschmiedia ugandensis produced fruit in the dry seasons. Correlation between fruit availability and consumption was significantly positive for only one species, Landlophia dawei. This indicated that frugivory of chimpanzees in Kalinzu was not opportunistic;they search for what they like to eat. Chimpanzees would have to range furthest in periods of scarcity and asynchronous fruiting hence a lot of energy expenditure in the food search alone. Therefore, diversity in fruit phenology is important for chimpanzees’ energy conservation, health and survival. Selective logging and other selective human activities that involve cutting down trees that are palatable would in future affect the food diversity and consequently the health of frugivores if not done sustainably. Since patterns of fruit phenology are also linked to patterns of rainfall, changes in the former can assist in predicting the influence of climate change on food availability for big frugivores like chimpanzees.

Fruits’ Nutrient Composition and Their Influence on Consumption by Chimpanzees in Kalinzu Forest, South Western Uganda

This study determined the influence of nutritional fruit content on their consumption by chimpanzees in Kalinzu forest. Fruits consumption frequencies were obtained from analysis of chimpanzee faecal samples picked over a period of two years. Fruit content was analyzed using freeze dried fresh samples using standard techniques. Musanga leo-errerae (76.14%), Ficus spp (66.05%) and (18.68%) were the most commonly eaten fruits of all faecal samples (N = 2683). Generally, fruit consumption increased for fruits with total phenols and tannins below 1% per gram except for Musanga leo-errerae, Uvariopsis congoensis and Aframomum angustifolium. Multiple regression revealed that of the 15 nutrient parameters investigated, only calcium, tannins, crude fat, protein and energy content of the fruits that constitute the major food components for basic animal body needs and functioning of energy, body building and a healthy skeleton significantly predicted 76.86% of consumption (R2 = 76.86%;P = 0.019). However, the fact that some of the most eaten fruits like Aframomum angustifolium and Musanga leo-errerae were recorded to have the highest amounts in tannins shows that there must be additional factors into play. Other than fruit availability, consideration of effect of fruit size and handling within the existing models of chimpanzees’ diet could hence enhance further the understanding of fruit consumption.

Estimation of Population of Ten Selected Forest Tree Species Used by Communities around Kalinzu Forest Reserve, South-Western Uganda

Local communities depend on Kalinzu Forest Reserve (KFR) for plant resources. This resource utilization affects the population of tree species in the forest. This study set out to estimate the population of ten tree species in the forest. Results of this study are hoped to provide a basis for studying future changes in population dynamics of the species. The ten species selected were: Newtonia buchananii, Cynometra alexandrei, Teclea nobilis, Prunus africana, Entandrophragma exelsum, Sapium ellipticum, Diospyros abyssinica, Zanthoxylum gilletii, Rytiginia kigeziensis and Spathodea nilotica. Their selection was based on the results of a study (Aine-Omucunguzi et al., 2010) about utilization of plant resources by the local people around KFR. Species with high demand from the local people were selected. Alternate nested quadrants along five line transects, were used to estimate the population. The plants were categorized into three classes as trees (>5 cm diameter at breast height), saplings (2 cm root collar diameter-5 cm diameter at breast height) and wildings (<2 cm root collar diameter). Population, population density, relative density, frequency, and relative frequency of each species were determined. Generally, the number of wildings, saplings and trees of each species increased away from the forest edge inwards. For all the species, wildings had the highest population density followed by saplings and then trees. Teclea nobilis had the highest number of individual per hectare, followed by Newtonia buchananii, while Rytiginia kigeziensis and Spathodea nilotica had the lowest number of individuals per hectare.

Population Structure and Regeneration Status of <i>Trichilia dregeana</i>Sond. in Heavily and Less Disturbed Areas of Kalinzu Forest Reserve, South Western Uganda

The population structure and regeneration status of Trichilia dregeana in heavily and less disturbed habitats of Kalinzu forest reserve were assessed in 2013. The species was used locally for medicines, fire wood and making household utensils, a situation that rendered it vulnerable. Given this dependence by local communities, the population of the species was under human pressure due to demand. This necessitated a critical understanding of how the population structure was affected by such disturbance although in some species, population structure disturbance increased resilience. Size-class distribution and regeneration status were used to determine the population structure as influenced by human disturbance. Four plots of 20 × 10 m were randomly established in each forest type and all T. dregeana trees of diameter ≥ 10 cm were counted and their DBH was measured at 1.3 m from the ground. In each of these plots, a 10 × 10 m plot was made and saplings DBH ≥ 2 - 10 cm were enumerated. Inside each 10 × 10 m plot, a 5 × 5 m plot was made and T. dregeana seedlings (<2 cm diameter) were identified and counted. The density of T. dregeana in the heavily disturbed forest was higher than in the less disturbed forest type. The size-class distribution exhibited a characteristic inverse J-shaped distribution pattern in the heavily disturbed forest whereas it was bell-shaped in the less disturbed forest type. In both forest types, the population of T. dregeana was found to be actively regenerating. This study concludes that the population structure of Trichilia dregeana is dominated by juveniles with total absence of individuals of DBH ≥ 22 cm, due to selective harvesting of mature individuals. In order to stop harvesting of this species from the natural forest, there should be an effort to provide seedlings to local communities so that they grow it on their farms.