Two new species of the Trichostrongylidae (Nematoda: Trichostrongyloidea), parasitic in Gorilla gorilla beringei in Uganda

Two new species of trichostrongylid parasites of a mountain gorilla in Uganda are described. Paralibyostrongylus kalinae n. sp. is characterised by a short dorsal ray, a dorsal oesophageal tooth and two median longitudinal ridges in the vulvar region. The species is more closely related to leporid parasites than to P. hebrenicutus, another species known from the gorilla. A “transfuge” phenomenon, i.e. transfer to a new host without speciation is suggested. Hyostrongylus kigeziensis n. sp. has several specific morphological characteristics and in particular a synlophe with many strong ridges, rays 4 and 5 divergent at the apex, and the dorsal ray with two branches. Hyostrongylus appears to be an Ethiopian genus which has radiated in many archaic mammals. With the technical collaboration of Mrs. N. Caillaud and Mr R. Tchesprakoff. With the technical collaboration of Mrs. N. Caillaud and Mr R. Tchesprakoff.     

Primate population dynamics over 32.9 years at Ngogo, Kibale National Park, Uganda

We present census data for eight primate species spanning 32.9 years along the same transect at Ngogo, Kibale National Park, Uganda, demonstrating major changes in the composition of the primate community. Correlated with an estimated decline of ～89% in the red colobus population was an increase in encounter rates with chimpanzee parties. Our data, along with the unusually high rates of predation by chimpanzees on red colobus at Ngogo and the fact that the chimpanzee community at Ngogo is the largest ever recorded, support the conclusion that the red colobus decline was caused primarily by chimpanzee predation. This seems to be the first documented case of predation by one nonhuman primate causing the population decline in another. We evaluated disease and interspecific competition as other possible causes of the red colobus decline, but judged them to be relatively insignificant compared with predation by chimpanzees. Notable changes in encounter rates with other primate species may have resulted from forest expansion. Those for mangabeys, redtails, and black and white colobus increased significantly. Encounter rates increased for l'Hoest's monkeys too, but the increased sightings may have been an artifact of increased habituation. Sightings of blue monkey and baboon groups declined. There was no significant change in encounter rates for all species combined. The Ngogo primate community seemed to be in a nonequilibrium state, changing from one dominated by two species, a folivore (red colobus) and a frugivorous omnivore (redtails), to one dominated by three species of frugivorous omnivores (redtails, mangabeys, and chimpanzees). This study demonstrates the importance of long-term monitoring in understanding population dynamics and the role of intrinsic variables in shaping the species composition of a community.     

Tree population dynamics in Kibale National Park, Uganda 1975–1998

Changes in species composition, stem abundance, and basal area of trees taller than or equal to 10 m in a medium altitude tropical rain forest at the Ngogo study area, Kibale National Park, Uganda are described for the period between 1975 and 1998 ( n  = 23 years). Two enumeration episodes were conducted in 263 plots of 5 m by 50 m during 1975–80 and 1997–98. During this period, species richness decreased by 3% (from 92 to 89). Species diversity (H') also declined slightly from 2.97 to 2.86. The number of trees recorded in the sample plots decreased by 8% (from 2545 to 2329), while basal area decreased from 49.48 m² ha⁻¹ to 48.68 m² ha^−1. However, stem abundance and basal area increased for some species.     

Abundance of Diurnal Primates in Mwanihana Forest, Udzungwa Mountains, Tanzania

Many individual researchers have used line transect counts to estimate forest primate abundance. They have devoted less attention to the interpretation of line transect data obtained by several observers, as is often the case in long-term monitoring programs. We present primate relative abundance data that 5 observers collected over 6 yr (not continuous) along 4 different transects each 4 km long in the Mwanihana Forest, Udzungwa Mountains National Park, Tanzania. Total distance walked during transect repetitions is ca. 700 km. The species we saw most frequently was the endemic Udzungwa red colobus Procolobus gordonorum (mean 0.59 groups/km walked), followed by the Angolan black-and-white colobus Colobus angolensis (0.43 groups/km) and Sykes’s monkey Cercopithecus mitis (0.35 groups/km). We sighted the endemic Sanje mangabey Cercocebus galeritus sanjei and the yellow baboon Papio cynocephalus infrequently, the latter being confined to the deciduous forest parts of the transects. We analyzed sighting frequency by gross habitat type, transect, season, and observer. Interobserver differences in the relative abundance of each species were moderate and the few cases of significant variations were due to discordance of only 1 observer from the others. Estimated distances of primate group sightings differ significantly among observers, thus preventing us from deriving estimates of absolute density. Frequency distributions of distance-class intervals are not significantly different among observers, which may indicate gross interobserver consistency in the width of the area sampled. We conclude that unless consistency in data collection is checked, as we did for 2 observers who collected data simultaneously, potential interobserver differences remain an underlying source of variance in the results that cannot be separated from other sources of variance.     

Gorillas of Bwindi-Impenetrable Forest and the Virunga Volcanoes: Taxonomic implications of morphological and ecological differences

Based on their geographic proximity to the Virunga Volcanoes (≈ 25 km), the Bwindi-Impenetrable Forest gorillas have been referred to the subspecies Gorilla gorilla beringei. Differences in anatomy, habitat, ecology, and behavior, however, suggest Bwindi gorillas are distinct from those in the Virungas. Relative to Virunga gorillas, Bwindi gorillas live at lower elevations, in warmer temperatures, are much more arboreal, have longer day ranges and larger home ranges, and eat much more fruit and pith, and less bamboo and leaves. Morphological differences reflect the differences in ecology, habitat, and behavior. Bwindi gorillas measured have smaller bodies, relatively longer limbs, hands, and feet, shorter trunks, thumbs, big toes, and tooth row lengths, and narrower trunks and orbital breadths than Virunga gorillas. These differences indicate Bwindi gorillas do not belong to G.g. beringei and should not be referred to as “mountain gorillas.” How unique the distinguishing features of Bwindi gorillas are, and whether or not they should be assigned to a new taxon, depends on the expression of these features in eastern lowland gorillas (G.g. graueri). © 1996 Wiley-Liss, Inc.     

Patterns of intestinal parasitism in the mountain gorilla Gorilla gorilla in the Bwindi-Impenetrable Forest, Uganda

The intestinal parasite fauna of the mountain gorillas of Bwindi—Impenetrable Forest, Uganda was studied by means of faecal examination and a single post-mortem. The fauna was remarkably uniform between social groups and individuals, showing only slight differences between age groups; there is no evidence of any interaction between the parasites observed. The only protozoa were entodiniomorph ciliates; amoebae and flagellates were absent. Helminths included a single host-specific cestode species and at least five nematodes, three of which are hostspecific. The closest relatives of the host-specific parasites are found in ungulates and paenungulates, not in hosts phylogenetically related to the gorilla.
This unique and specialized parasite fauna deserves to be monitored so that any effects of the habituation of the gorillas for tourism can be assessed.     

The Vanishing De Brazza's Monkey (Cercopithecus neglectus Schlegel) in Kenya

We conducted a trail survey of De Brazza's monkey (Cercopithecus neglectus) on Mt. Elgon and the Cherangani Hills between October 1994 and February 1995. The objectives were to assess the status and distribution of the species and its habitats and to formulate recommendations on its conservation. We counted a total of 49 monkeys: 3 groups and 6 lone individuals near Kimothon River (Mt. Elgon) and 4 groups and 6 lone individuals at Kapolet Forest Reserve and its environs (Cherangani Hills). The mean group size is 6.6. Wanton habitat destruction was evident in all the forest habitats. The species now inhabits unprotected remnant strips of riverine forest. Furthermore, the Kapolet Forest Reserve offers little or no protection to De Brazza's monkeys or their habitat. Translocation of the monkeys from unprotected areas to a protected habitat is recommended as an urgent conservation measure to save the De Brazza's population in Mt. Elgon and the Cherangani areas of Kenya.