Behavioral Responses of Gorillas to Habituation in the Dzanga-Ndoki National Park,Central African Republic

We monitored the impact of habituation for tourism through changes in gorillas' behavior during the habituation process at Bai Hokou (Dzanga-Ndoki National Park, Central African Republic) from August 1996 to December 1999. From August 1998 onwards we focused on one gorilla group: the Munye. During the habituation process, it became increasingly easier to locate and to remain with the gorillas. Their initial reactions of aggression, fear and vocalization upon contact were replaced increasingly by ignoring us. Curiosity appeared to be an intermediate stage in the process. The way in which contacts with the Munye ended became more subdued over time. Regular daily contact is important in promoting habituation. Likewise, contacting gorillas while they are in a tree or in dense forest provides positive results compared to open habitat. Contacts within 10 m and contacts without forewarning the gorillas of observer presence, e.g., via tongue clacking, should be avoided. As of December 1999, habituation had progressed well; habituation of western gorillas is feasible. However, the gorillas experience negative effects during the habituation process, showing, for example, an increase in daily path length, and reactions of aggression, fear and vocalization upon contact. Impacts diminish over time. Given these and other potentially negative effects, the decision to begin habituation should not be taken lightly.     

Ranging Patterns of a Western Gorilla Group During Habituation to Humans in the Dzanga-Ndoki National Park,Central African Republic

The ranging patterns of western gorillas have been described in relation to their more frugivorous diet as compared to mountain gorillas. However, the lack of data from habituated groups prevents a full understanding of their ranging behavior and its implications for western gorilla social behavior. Unhabituated gorillas often flee from approaching researchers, possibly resulting in longer daily ranges and home range expansions and/or shifts. I report on the influence of habituation on the ranging patterns of a western gorilla group. I analyzed progress in habituation through changes in gorilla reactions, displayed upon detecting the observers. I measured daily path length and home range while following the group's trails and monitored diet via fecal analyses and direct observations. During the study period, habituation progressed and the gorillas increasingly ignored the arrival of observers. As a result, daily path lengths were longer during the early stages of habituation, when the gorillas were avoiding observers. There was no range expansion or shift, though the measure is more difficult to investigate, being subject to error due to variation in sample size. We recorded seasonal changes in the consumption of fruit by gorillas, but no direct effect on ranging patterns is detectable with the data available, which is likely a consequence of the combined effect of habituation and seasonality on group movements. The findings are not only important for understanding the extent of human influence while conducting research on wild gorillas but also suggest the need for caution when interpreting results from non-habituated gorillas.     

Factors Affecting Nesting Site Choice in Chimpanzees at Tshibati,Kahuzi-Biega National Park: Influence of Sympatric Gorillas

We recorded 310 fresh chimpanzee night nests at 72 nest sites to determine their choice of tree and site for nesting vis-à-vis the effects of sympatric gorillas. Chimpanzees did not use trees for nesting according to their abundance, but instead tended to nest in fruit trees that they used as food sources. Nesting patterns of chimpanzees may vary with nesting group size, the type of vegetation, and fruit species eaten or not eaten by gorillas. When chimpanzees lodged as a small group in the secondary forest, they nested more frequently in trees bearing ripe fruits eaten only by themselves than in those with fruit eaten also by gorillas. When they lodged as a large group in the primary forest, they nested more frequently in trees bearing ripe fruits eaten by both apes. Nest group size is positively correlated with the availability of preferred ripe fruits in secondary forest. These findings not only reflect the larger foraging groups at the larger fruiting trees but also suggest that chimpanzees may have tended to occupy fruiting trees effectively by nesting in them and by forming large nest groups when the fruits attracted gorillas. Competition over fruits between gorillas and chimpanzees, due to their low productivity in the montane forest of Kahuzi, may have promoted the chimpanzee tactics.     

Brain Evolution: Mammals,Primates, Chimpanzees,and Humans

Though many modern techniques are available for studying brains, they are difficult to use in evolutionary contexts that require examination of large numbers of specimens and species, and all major parts of the brain. Thus, evolutionary studies of many species and of whole brains still tend to be based upon simpler data such as sizes of brains and brain components. Such investigations, carried out over many decades, have usually employed univariate and bivariate analyses, though a few investigators used early multivariate methods. In mammals, these studies generally show the primacy of the relationship between brain and brain-part sizes with overall body size. More recent multivariate applications have confirmed this (Finlay, B. L., and Darlington, R. B. (1995). Science 268: 1578–1584) and some have also separated the highest level phylogenetic groups: strepsirrhines and haplorrhines (Barton, R. A., and Harvey, P. H. (2000). Nature 405: 1055–1058). Both findings were, in fact, evident in earlier multivariate studies (Holloway, R. L. (1979). In Hahn, M. E., Jensen C., and Dudek, B. C. (eds.), Development and Evolution of Brain Size: Behavioral Implications, Academic Press, New York, pp. 59–88; Sacher, G. A. (1970). In Noback, C. R., and Montagna, W. (eds.), The Primate Brain: Advances in Primatology. Vol. 1, Appleton-Century-Crofts, Educational Division, Meredith Corporation, New York, pp. 245–287). However, new studies employing proportional data aimed at conveying input/output relationships between brain components show further groupings of species that share convergences in lifestyles (de Winter, W., and Oxnard, C. E. (2001). Nature 409: 710–714). The convergences are brought about by combinations of brain variables that seem to be associated with brain functions implied by the specific lifestyles. Our most recent results demonstrate that chimpanzees and humans are especially different from one another, and the difference is not due to size alone. Part of this difference is merely a continuation, from chimpanzees towards humans, of a trend already present across all other primates that relates mainly to neocortical increase. But several other large and independent differences are not in the direction of the overall primate trend, but are differences of humans from all other mammals examined including all nonhuman primates. The combinations of brain variables associated with the latter differences are not related simply to enhancement of the neocortex, but seem to reflect other internal relationships. The overall separation of humans and chimpanzees is so large that it goes far beyond the conventional 98.6% commonality in their DNAs. It fits better with more recent molecular, developmental and evolutionary studies implying a considerably greater difference between chimpanzees and humans than usually recognized.     

Variation over Time in Parasite Prevalence Among Free-ranging Chimpanzees at Gombe National Park,Tanzania

From January to September, 2005, we collected fecal samples from 60 chimpanzees at Gombe National Park, Tanzania and examined them for parasites. We compared current parasite prevalence data with previous studies to obtain a pattern of parasitism over time. There were considerable similarities in the parasite species composition and prevalence, although we noted some variations. Generally, parasite prevalence decreased over time, with the present prevalence being lower than in previous surveys. We identified 8 types of parasites, all of which had previously been documented in the chimpanzees of Gombe. Three nematodes — Oesophagostomum sp., Strongyloides fulleborni, and Abbreviata caucassica— occurred at higher prevalence (41.2–45.5%) but relatively lower than previous findings of 50–91%. We also diagnosed unidentified strongyles at a moderate prevalence (33%), lower than a previous record of 41%. Probstmayria gombensis occurred at relatively low prevalence (16.4%) vs. past observations (23–59%), while the prevalence of Trichuris sp. (7.3%) was closely similar to previous records of 5–9%. We also observed unidentified ciliate at 9% within the same range as in previous studies (5–28%). The prevalence of Troglodytella abrassarti was 78%, closely similar to previous findings of 75%. There was no significant variation in parasite prevalence between chimpanzees of the Kasekela community and those of the Mitumba community, although the former tended to have higher prevalence of helminths than the latter. The causes of the similarities and variations in parasite prevalence over time are discussed. The study provides baseline data for monitoring of chimpanzee health at Gombe.     

Behavioral Ecology of Sympatric Chimpanzees and Gorillas in Bwindi Impenetrable National Park,Uganda: Diet

Via a field study of chimpanzees (Pan troglodytes schweinfurthii) and gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, we found that their diets are seasonally similar, but diverge during lean seasons. Bwindi chimpanzees fed heavily on fruits of Ficus sp., which were largely ignored by the gorillas. Bwindi gorilla diet was overall more folivorous than chimpanzee diet, but was markedly more frugivorous than that of gorillas in the nearby Virunga Volcanoes. During 4 mo of the year Bwindi gorilla diet included more food species than that of the chimpanzees. Three factors in particular—seasonal consumption of fibrous foods by gorillas, interspecific differences in preferred fruit species, and meat consumption by chimpanzees—contributed to dietary divergence between the two species. When feeding on fruits, gorillas ate Myrianthus holstii more frequently than chimpanzees did, while chimpanzees included more figs in their annual diet. Chimpanzee diet included meat of duikers and monkeys; gorilla frequently consumed decaying wood.     

Temporal Variation in Insect-eating by Chimpanzees and Gorillas in Southeast Cameroon: Extension of Niche Differentiation

I studied insect-foraging strategies of great apes and aimed to define niche differentiation in their insect diet. I investigated seasonality in fruit-, foliage-, insect-, and meat-eating by great apes in southeast Cameroon via indirect methods and measured activity and nest densities of insect prey. I used a multinomial logistic regression to analyze the data. Gorilla and chimpanzee insect-, ant-, and termite-eating does not correlate with rainfall. Ant- and nonwinged termite-eating by chimpanzees increased in periods of succulent fruit scarcity and provided protein and energy, which might have compensated for the protein-low foliage eaten then. The apes ate winged termites when succulent fruit was abundant. Ant and winged termite consumption by gorillas correlates positively with that of chimpanzees. Ant-eating by gorillas increased when fruit was scarce, but was also associated with temporal ant activity and nest density. Both ape species also encountered more ant nests and trails in that period, as they predominantly foraged for herbs in vegetation types with high ant availability. In contrast, fruit-eating correlates positively with nonwinged termite-eating by gorillas, but again temporal prey availability is also associated. Termites might have provided 1) supplemental iron when tannin-rich fruits were eaten or 2) antidiarrheal properties when gorillas ate too much laxative fruit. Termite-eating by both ape species is not associated with spatial termite availability. In conclusion, there is niche differentiation in their insect diet. Based on the trade-off between foraging effort and nutritional gain, chimpanzees use a high-energy and gorillas a low-energy strategy when feeding on termites, but both use a low-energy strategy when feeding on ants. However, more information on the consumption of ant larvae is necessary to define niche differentiation in their ant diet.     

A Survey of Chimpanzees (Pan troglodytes troglodytes) and Gorillas (Gorilla gorilla gorilla) in the Selectively Logged Ngotto Forest,Central African Republic

Currently, the timber company Industrie Forestiére du Batalimo is selectively logging the Ngotto Forest in the Central African Republic. The forest is home to a population of chimpanzees (Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) and provides the Bofi-speaking people of Grima with food, medicine, housing material, and other commodities. Over a 7-month period, the research team conducted a line-transect survey of the great ape population in the forests to the south of Grima to document their distribution. For comparison purposes, the team also surveyed a section of adjacent forest that had already been logged. Ape nests were significantly rarer in the logged forest than in the unlogged forest, and ape nests were most common in the more pristine forests to the south. This report further discusses the effects of logging and other human activities.     

Prevalence of Microsporidium and Other Intestinal Parasites in Children from Malatya,Turkey

Parasite infections are common during the critical developmental period in children. The occurrences of intestinal parasites are also common in orphanage, nurseries and schools in Turkey. The study was carried out to determine the percentage of microsporidium and intestinal parasites in children from Malatya, Turkey. This study was carried out at the Department of Parasitology of Inonu University, Turgut Ozal Medical Center, during January–December 2006. Totally, 1,181 stool samples were examined using the native-Lugol, sedimentation-techniques, modified trichrome (MTS), acid-fast-trichrome stain and calcofluor staining methods. In addition, perianal region material was taken from the children to examine with cellophane tape method. Power analyses were performed for statistical analyses used. Microsporidia were found in 92 (7.8%) of the samples, and also intestinal parasites were detected in 329 (27.8%). The numbers of infections according to the species were as follows: 69 (5.8%) Entamoeba coli, 7 (0.6%) Blastocystis hominis, 114 (9.7%) Giardia intestinalis, 15 (1.3%) Iodomoeba butchlii, 8 (0.7%) Dientamoeba fragilis, 7 (0.6%) Taenia spp. 70 (5.9%) Enterobius vermicularis, 11 (0.9%) Hymenolepis nana, 25 (2.1%) Trichomonas intestinalis, 1 (0.1%) Ascaris lumbricoides and 2 (0.2%) Chilomastix mesnilii. Also, greater than 90% power values were achieved for statistical analyses. Whereas the detection rates of microsporidium and intestinal parasites were found to be low, it was concluded that in addition to intestinal parasites, microsporidium should be also searched for in children with complaints of intestinal system.     

Nutritional Aspects of Western Lowland Gorilla (Gorilla gorilla gorilla) Diet During Seasons of Fruit Scarcity at Bai Hokou,Central African Republic

Traditionally, gorillas were classified as folivores, yet 15 years of data on western lowland gorillas (Gorilla gorilla gorilla) show their diet to contain large quantities of foliage and fruit, and to vary both seasonally and annually. The consumption of fruit by gorillas at Bai Hokou, Central African Republic, is correlated with rainfall and ripe fruit availability (Remis, 1997a). We investigated the nutritional and chemical content of gorilla foods consumed at Bai Hokou during two seasons of fruit scarcity as measured by phenological observations and compared our findings with the nutrient content of gorilla foods at other African sites. We conclude that during lean times, Bai Hokou gorillas consumed fruits with higher levels of fiber and secondary compounds than those of other populations of western lowland or mountain gorillas. Conversely, leaves consumed by Bai Hokou gorillas were relatively low in fiber and tannins. Bai Hokou gorillas appeared to meet their nutritional needs by eating a combination of fruit and foliage. They ate fruits comparatively high in secondary compounds and fiber when necessary. While gorillas are selective feeders, wherever and whenever preferred foods are scarce, their large body size and digestive anatomy enable them to consume and process a broader repertoire of foods than smaller bodied-apes.     

Rift Valley Fever Virus Circulating among Ruminants,Mosquitoes and Humans in the Central African Republic

BackgroundRift Valley fever virus (RVFV) causes a viral zoonosis, with discontinuous epizootics and sporadic epidemics, essentially in East Africa. Infection with this virus causes severe illness and abortion in sheep, goats, and cattle as well as other domestic animals. Humans can also be exposed through close contact with infectious tissues or by bites from infected mosquitoes, primarily of the Aedes and Culex genuses. Although the cycle of RVFV infection in savannah regions is well documented, its distribution in forest areas in central Africa has been poorly investigated.

Methodology/Principal Findings

To evaluate current circulation of RVFV among livestock and humans living in the Central African Republic (CAR), blood samples were collected from sheep, cattle, and goats and from people at risk, such as stock breeders and workers in slaughterhouses and livestock markets. The samples were tested for anti-RVFV immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. We also sequenced the complete genomes of two local strains, one isolated in 1969 from mosquitoes and one isolated in 1985 from humans living in forested areas. The 1271 animals sampled comprised 727 cattle, 325 sheep, and 219 goats at three sites. The overall seroprevalence of anti-RVFV IgM antibodies was 1.9% and that of IgG antibodies was 8.6%. IgM antibodies were found only during the rainy season, but the frequency of IgG antibodies did not differ significantly by season. No evidence of recent RVFV infection was found in 335 people considered at risk; however, 16.7% had evidence of past infection. Comparison of the nucleotide sequences of the strains isolated in the CAR with those isolated in other African countries showed that they belonged to the East/Central African cluster.

Conclusion and significance

This study confirms current circulation of RVFV in CAR. Further studies are needed to determine the potential vectors involved and the virus reservoirs.     

Intestinal parasite infections in pigs and beef cattle in rural areas of Chungcheongnam-do, Korea

The present study was performed to investigate the infection status of intestinal parasites in pigs and beef cattle in rural areas of Chungcheongnam-do, Korea. From November 2009 to April 2010, a total of 241 fecal samples of pigs and beef cattle (136 and 105, respectively) were examined by direct smear and centrifugal sedimentation methods. The overall positive rates of intestinal parasites among pigs and beef cattle were 73.5% and 4.8%, respectively, and the double-infection rate was 10.3% in pigs. Of 136 specimens from pigs, Balantidium coli, Ascaris suum, and Entamoeba spp. infections were found in 88 (64.7%), 24 (17.6%), and 5 cases (3.7%), respectively. Of 105 beef cattle, Entamoeba spp. infections were detected in 5 cases (4.8%). From these results, it is shown that pigs raised on rural farms in Chungcheongnam-do had a high B. coli infection rate and a moderate A. suum infection rate. These results demonstrate that environmentally resistant cysts or eggs could be widespread on the farms examined, and thus an effective hygienic management system is needed to prevent them from serving as the source of infection for human beings.     

Dietary Variability of Mountain Gorillas in Bwindi Impenetrable National Park,Uganda

Data on intraspecific dietary variability has important implications for understanding flexibility in foraging behavior, habitat utilization, population dynamics, and social behavior and may also assist in conservation efforts. We compared food availability and diet of a group of mountain gorillas (Gorilla beringei beringei) at a high altitude site and 2 groups at a low altitude site in Bwindi Impenetrable National Park, Uganda, from September 2001 to August 2002. Plant species diversity was greater at the low altitude site than at the high altitude site. The two groups at the low elevation consumed more plant species (140 species vs. 62 species), and a greater number of fruit species per mo (7 vs. 3 species) and per yr (36 vs. 11 species) than the high altitude group did. Furthermore, each group shared <51% of important fibrous food items in their diet with the 2 other groups. There is no significant difference in the proportion of days fruit remains were found in the dung among groups. Finally, according to Ivlev's electivity index, all groups positively selected the majority of food items in their diets. We attribute a large proportion of dietary variation between locations to differences in fruit availability and plant species composition between sites. Differences between groups at the low altitude site may be due to variation in food profitability—more profitable foods available to choose in the same area—within their overlapping home range, or group traditions. A comparison of our results with the diets of gorillas of the Virunga Volcanoes in Rwanda and Kahuzi-Biega, DRC shows that eastern gorilla populations have highly variable dietary patterns with limited overlap in species consumed among groups and populations.     

Intestinal Parasites of Free-ranging,Semicaptive,and Captive <Emphasis Type="Italic">Pongo abelii</Emphasis> in Sumatra,Indonesia

We collected fecal samples from 32 free-ranging, 19 semicaptive, and 54 captive Sumatran orangutans on Sumatra from 1998 until 2004 and screened them for gastrointestinal parasites. Our objectives were to compare the intestinal parasites of free-ranging, semicaptive, and captive orangutans and to evaluate the risk of parasite transmission in orangutan reintroduction programs. We identified 4 genera of Protozoa, 7 genera of nematodes, 1 trematode sp., and 1 cestode sp. The prevalence of Balantidium coli in free-ranging orangutans was significantly higher than in captive individuals. However, the prevalence of Strongyloides sp. was higher in captive than in free-ranging orangutans. Free-ranging female orangutans had a significantly higher total prevalence of intestinal parasites than that of males. We found no significant difference between parasite prevalences in different age groups. Compared to gorillas and chimpanzees, orangutans carry a smaller variety of protozoan and nematode species. Strongyloides sp. infections form the highest risk in reintroduction programs as crowding, ground-dwelling, and poor hygiene in captive and semicaptive orangutans may cause a constant reinfection.     

Intestinal parasites and bacteria of mountain gorillas (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda

A survey in 1994 examined intestinal helminths and bacterial flora of mountain gorillas (Gorilla beringei beringei) in Bwindi Impenetrable National Park, Uganda. Parasites and bacteria were identified to genus in the feces of two groups of tourist-habituated and one group of non-tourist-habituated mountain gorillas. Eggs were identified as those of an anoplocephalid cestode, and nematode eggs representative of the genera: Trichuris, Ascaris, Oesophagostomum, Strongyloides, and Trichostrongylus. This is the first report of Ascaris lumbricoides-like eggs in mountain gorillas. Fecal samples (n=76) from all groups contained helminth eggs, with strongyle eggs and anoplocephalid eggs being the most common. Salmonella and Campylobacter were found in both gorilla groups. Regular long-term non-invasive fecal monitoring of the populations of mountain gorillas is essential for the prevention and identification of potential health threats by intestinal parasites and bacteria in this highly endangered subspecies.This revised version was published online in April 2005 with corrections to the cover date of the issue.     

Home Range and Frugivory Patterns of Mountain Gorillas in Bwindi Impenetrable National Park,Uganda

Mountain, western, and Grauer's gorillas exhibit broad differences in ecological patterns with western gorillas eating more fruit and having larger home ranges than their largely folivorous counterparts in the Virunga Volcanoes. We studied the home range and frugivory patterns of one group of Gorilla beringei beringei in the little-studied population of Bwindi Impenetrable National Park, Uganda, to compare with other populations and to investigate whether there was any relationship between patterns of frugivory and home range size. During the 3-year study, the gorillas ate 16 species of fruit on 27% of observation days. There was high variability in frugivory among the 3 years and no consistent seasonal pattern. Annual home range size was ca. 21 km² for Years 1 and 2, and it increased dramatically to 40 km² in Year 3. Home range size varied considerable between months and seasons, but there is no clear relationship between occurrence of fruit-eating and home range size. The group exhibited more fruit-eating and a larger home range size those ofthe gorillas in the Virunga Volcanoes. Their home range size is comparable to that of western gorillas, though Bwindi gorillas consumed less fruit. Home range size and utilization by all gorillas probably depends on a complex relationship between the distribution and abundance of both fruit and herbaceous vegetation and social factors such as male mating tactics.     

Primate Community Dynamics in Old Growth Forest over 23.5 Years at Ngogo,Kibale National Park,Uganda: Implications for Conservation and Census Methods

Few data exist regarding long-term changes in primate populations in old-growth, tropical forests. In the absence of this information, it is unclear how to assess population trends efficiently and economically. We addressed these problems by conducting line-transect censuses 23.5 years apart at the Ngogo study area in Kibale National Park, Uganda. We conducted additional censuses over short time intervals to determine the degree to which the temporal distribution of censuses affected estimates of primate numbers. Results indicate that two species, blue monkeys and red colobus, may have experienced significant reductions over the past 23.5 years at Ngogo. In contrast, five other species, baboons, black-and-white colobus, chimpanzees, mangabeys, and red-tailed guenons, have not changed in relative abundance. Additional findings indicate that different observers may vary significantly in their estimates of sighting distances of animals during censuses, thus rendering the use of measures of absolute densities problematic. Moreover, censuses conducted over short periods produce biased estimates of primate numbers. These results provide guidelines for the use of line-transect censuses and underscore the importance of protecting large blocks of forests for primate conservation.     

Movement Patterns and Home Range Of The Bongo (Tragelaphus Eurycerus) In The Rain Forest Of The Dzanga National Park, Central African Republic

Bongos ( Tragelaphus eurycerus Ogilby) were studied for 8 months in the Dzanga National Park, Central African Republic. Tracks were followed and mapped with a compass and a pedometer to study movement patterns and home range. Natural licks were shown to be central points in the home range of the bongos: they visited the licks recurrently to consume soil, but also to forage on grass and herb species, and for social reasons. Forest areas far from licks were used much less than forest areas close to licks. When a lick was visited, distances between two resting sites were longer than in the forest without lick visits, caused by a direct and straight movement from the denser forest areas toward a lick. The study area of about 150 km² was presumably occupied by two groups of bongos. One of them seemed to split temporarily into two subgroups. Groups were not larger than 10–20 individuals. Estimated home ranges were at least 49 km² and 19 km² for the two groups, respectively. Estimated density in the Dzanga National Park was 0.25 bongos per km^2. This study shows the importance of natural licks for the largest social forest antelope, the bongo, and provides information which is important for its future conservation.