Geophagia by mountain gorillas (Gorilla gorilla beringei) in the Virunga Mountains,Rwanda

Mountain gorillas (Gorilla gorilla beringei) occasionally eat material from weathered regolith (subsoil) sediments in the Virunga Mountains of northwestern Rwanda. The possible nutritional significance of this behaviour has been investigated by analyzing the geochemistry, primary mineral composition, and clay content of several regolith and surface soil (paleosol) samples. Iron, Na, and Br content may be important in geophagy, and clay present in the soil may also have nutritional importance.     

Bed and bed-site reuse by western lowland gorillas (<Emphasis Type="Italic">Gorilla g. gorilla</Emphasis>) in Moukalaba-Doudou National Park,Gabon

In this paper we describe bed (nest) and bed-site reuse by western lowland gorillas (Gorilla g. gorilla) in Moukalaba-Doudou National Park, south-eastern Gabon. During an eight-month study 44 bed sites and 506 beds were found. Among these, 38.6% of bed sites and 4.1% of beds were reused. We analyzed the monthly frequency of bed-site reuse in relation to rainfall, fruit abundance, and fruit consumption by the gorillas. The different frequency of bed-site reuse in the rainy and dry seasons was not significant. More bed-site reuse was observed during the fruiting season than during the non-fruiting season. Results from fecal analysis suggested that gorillas ate more fruit in the fruiting season than in the non-fruiting season. The frugivorous diet of western gorillas may possibly cause gorillas to stay in some areas and, consequently, reuse their bed sites. Reuse of bed sites by gorillas suggests their frequent return to an area where preferred fruit is readily available. A higher percentage of arboreal beds may also affect bed-site reuse, because of the shortage of bed material.     

Diet and seasonal changes in sympatric gorillas and chimpanzees at Kahuzi–Biega National Park

Based on 8 years of observations of a group of western lowland gorillas (Gorilla beringei graueri) and a unit-group of chimpanzees (Pan troglodytes schweinfurthii) living sympatrically in the montane forest at Kahuzi–Biega National Park, we compared their diet and analyzed dietary overlap between them in relation to fruit phenology. Data on fruit consumption were collected mainly from fecal samples, and phenology of preferred ape fruits was estimated by monitoring. Totals of 231 plant foods (116 species) and 137 plant foods (104 species) were recorded for gorillas and chimpanzees, respectively. Among these, 38% of gorilla foods and 64% of chimpanzee foods were eaten by both apes. Fruits accounted for the largest overlap between them (77% for gorillas and 59% for chimpanzees). Gorillas consumed more species of vegetative foods (especially bark) exclusively whereas chimpanzees consumed more species of fruits and animal foods exclusively. Although the number of fruit species available in the montane forest of Kahuzi is much lower than that in lowland forest, the number of fruit species per chimpanzee fecal sample (average 2.7 species) was similar to that for chimpanzees in the lowland habitats. By contrast, the number of fruit species per gorilla fecal sample (average 0.8 species) was much lower than that for gorillas in the lowland habitats. Fruit consumption by both apes tended to increase during the dry season when ripe fruits were more abundant in their habitat. However, the number of fruit species consumed by chimpanzees did not change according to ripe fruit abundance. The species differences in fruit consumption may be attributed to the wide ranging of gorillas and repeated usage of a small range by chimpanzees and/or to avoidance of inter-specific contact by chimpanzees. The different staple foods (leaves and bark for gorillas and fig fruits for chimpanzees) characterize the dietary divergence between them in the montane forest of Kahuzi, where fruit is usually scarce. Gorillas rarely fed on insects, but chimpanzees occasionally fed on bees with honey, which possibly compensate for fruit scarcity. A comparison of dietary overlap between gorillas and chimpanzees across habitats suggests that sympatry may not influence dietary overlap in fruit consumed but may stimulate behavioral divergence to reduce feeding competition between them.     

Going to extremes for sodium acquisition: use of community land and high‐altitude areas by mountain gorillas Gorilla beringei in Rwanda

Space use in mammals may be influenced not only by their primary foods, but also by localized sources of physiologically critical resources such as sodium‐rich plants. We examined how sodium acquisition influences habitat use in mountain gorillas (Gorilla beringei) in Rwanda which have increased the amount of time they forage on community land outside of Volcanoes National Park (VNP), where eucalyptus (Eucalyptus spp.) tree bark is their most frequently eaten food. We measured sodium content in samples from 34 main dietary items and quantified sodium intake by 22 gorillas in three social groups over one year. On a dry weight basis, eucalyptus bark contains 3100 mg Na/kg. In contrast, the four herbs most frequently exploited for food inside the park are relatively sodium‐poor (<70 mg/kg each). Further, sodium intake rates were highest when the gorillas were on community land. Of the two groups that fed outside of the park, one obtained 73% and the other one 45% of their sodium in that habitat despite only feeding for minimal amounts of time there. However, one group that did not feed on community land acquired 78% of its sodium in the subalpine and alpine zones through the consumption of pith of giant lobelias and groundsels. Obtaining sodium thus likely creates an incentive for the gorillas to leave the park and make forays into high‐altitude habitat. Both strategies are not without risks: exiting their natural habitat and feeding on crops may increase human‐wildlife conflict and visiting high‐altitude areas may increase the risk of hypothermia.     

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.     

Day-journey length and daily diet of solitary male gorillas in lowland and highland habitats

We compared day-journey length and daily diets of solitary male gorillas in lowland versus highland habitats. Solitary males in tropical forests of Zaire tend to travel longer distances, to visit more types of vegetation, and to consume more kinds of food than a solitary male mountain gorilla in the Virunga Volcanoes did. The number of feeding sites per day is larger and the mean distance between feeding sites is far longer for the former than the latter. These observations may reflect differences in food breadth and availability between highland and lowland habitats. The herbaceous plants that are eaten by mountain gorillas are densely and evenly distributed in the higher montane forest of the Virungas, where gorillas need not cover long distances to search for food. In contrast, herbaceous plants are scarce in primary and ancient secondary forests of lowland habitats, where gorillas travel long distances and eat various fruits and insects. The patchy and unpredictable distribution of foods may extend the distances over which gorillas search for food in the lowland habitat. However, solitary males showed a prominent reduction in day-journey length and changed their choices of food during the nonfruiting season (the long rainy and dry seasons) in the lowland habitats. This strategy may have developed during the Pleistocene and may have enabled them to enlarge their ranges to the higher montane forests, where fruits are sparse throughout the year.     

Are the gorillas in Bwindi Impenetrable National Park “true” mountain gorillas?

The gorillas that inhabit Bwindi Impenetrable National Park in Uganda are the least known of the eastern gorillas. Because they are an allopatric population living a minimum of 25 km from the well‐studied population of mountain gorillas (Gorilla beringei beringei) in Rwanda and have certain morphological and ecological differences from these gorillas, their taxonomic status has been in question in recent years. This study presents new craniodental metrics from Bwindi individuals and compares them to Virunga individuals as well as to eastern lowland gorillas, G. gorilla graueri. Multivariate statistics, including MANCOVA, least‐squares, regression, and principal components analyses, were used to evaluate how closely the Bwindi crania resemble the Virunga crania and how both relate to G. g. graueri. Results indicate that the Bwindi gorillas have generally smaller crania than the Virunga gorillas, but when metrics are log‐transformed, the only variable that distinguishes the Bwindi individuals is a longer face. When both populations are compared to G. g. graueri, they cluster together separately from the eastern lowland gorillas, sharing such features as higher rami, wider bigonia, longer mandibles, and wider and shorter mandibular symphyses in relation to G. g. graueri. Functional morphological explanations for these differences are discussed, but lacking measurements of the physical properties of G. g. graueri, they cannot fully be explained. Results clearly indicate that at least pertaining to the cranium, upon which most gorilla taxonomy is based, the Bwindi gorillas are proper mountain gorillas (G. b. beringei). Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Tree structure and sex differences in arboreality among western lowland gorillas (Gorilla gorilla gorilla) at Bai Hokou, Central African Republic

The aim of six months of research in 1995 on the gorillas (Gorilla gorilla gorilla) at Bai Hokou, Central African Republic, was to study the effects of tree structure, relative numbers of arboreal feeding sites, and sex differences in body size on arboreal foraging. The analysis presented here also documents inter-annual variation in fruit availability and climbing by silverback gorillas by comparing the 1995 results to those from earlier research, 1990–1992. This analysis suggests that female gorillas maintain similar levels of arboreality in fruit-rich and fruit-poor seasons and years, but silverbacks may be more terrestrial when fruit is scarce or difficult to access. Trees of different shapes present different numbers of feeding sites to bigger males and smaller females. Male climbing is affected by the availability of fruit, and small trees with narrow crowns that lend easy access to fruit from the core. This study suggests that the energetics of vertical climbing and biomechanical constraints imposed by small branch feeding sites in the periphery of trees may constrain the arboreal behavior of male gorillas. Fine-tuned comparisons of food availability, tree structure, and variation in social context of behavior across habitats, will assist efforts to understand differences in ecology among populations and species of African apes.     

Social and ecological factors alter stress physiology of Virunga mountain gorillas (Gorilla beringei beringei)

Living in a rapidly changing environment can alter stress physiology at the population level, with negative impacts on health, reproductive rates, and mortality that may ultimately result in species decline. Small, isolated animal populations where genetic diversity is low are at particular risks, such as endangered Virunga mountain gorillas (Gorilla beringei beringei). Along with climate change‐associated environmental shifts that are affecting the entire population, subpopulations of the Virunga gorillas have recently experienced extreme changes in their social environment. As the growing population moves closer to the forest's carrying capacity, the gorillas are coping with rising population density, increased frequencies of interactions between social units, and changing habitat use (e.g., more overlapping home ranges and routine ranging at higher elevations). Using noninvasive monitoring of fecal glucocorticoid metabolites (FGM) on 115 habituated Virunga gorillas, we investigated how social and ecological variation are related to baseline FGM levels, to better understand the adaptive capacity of mountain gorillas and monitor potential physiological indicators of population decline risks. Generalized linear mixed models revealed elevated mean monthly baseline FGM levels in months with higher rainfall and higher mean maximum and minimum temperature, suggesting that Virunga gorillas might be sensitive to predicted warming and rainfall trends involving longer, warmer dry seasons and more concentrated and extreme rainfall occurrences. Exclusive use of smaller home range areas was linked to elevated baseline FGM levels, which may reflect reduced feeding efficiency and increased travel efforts to actively avoid neighboring groups. The potential for additive effects of stress‐inducing factors could have short‐ and long‐term impacts on the reproduction, health, and ultimately survival of the Virunga gorilla population. The ongoing effects of environmental changes and population dynamics must be closely monitored and used to develop effective long‐term conservation strategies that can help address these risk factors.     

Ecological Constraints on the Foraging Effort of Western Gorillas (Gorilla gorilla gorilla) at Bai Hoköu, Central African Republic

Recent studies demonstrate that western lowland gorillas incorporate much more fruit into their diet than Virunga mountain gorillas do. Very little is known, however, about how the frugivorous behavior of western gorillas influences their daily ranging behavior, which may ultimately affect social factors such as group size and structure. I examined the influence of diet and the spatiotemporal availability of plant foods on the foraging effort of nonhabituated western lowland gorilla groups during 17 months at Bai Hoköu in the Dzanga-Ndoki National Park, Central African Republic. I determined diet from indirect methods and gorilla plant food availability and spatial distribution from phenology and line transects. Daily path length gives an estimate of foraging effort and was the distance paced, following fresh gorilla trails, from morning to evening nest sites. The availability and distribution of fruit and its consumption by gorillas varied seasonally. When concentrating on fruits, gorillas traveled significantly farther (mean = 3.1 km/day) than when their diet consisted mostly of nonfruit vegetation, such as leaves and woody pith, stems, and bark (mean = 2.1 km/day). The amount of herbaceous vegetation in the diet did not vary seasonally and did not influence daily path length. The best environmental predictor of foraging effort was fruit density, or a measure combining both density and spatial pattern: coefficient of dispersion. In addition, when fruit patches were small, path length tended to increase but not significantly. Compared with results of other studies, gorillas at Bai Hoköu travel farther (mean = 2.6 km/day) than gorillas in Gabon (mean = 1.7 km/day) and five times farther than mountain gorillas in the Virungas (mean = 0.5 km/day). Increased foraging effort of gorillas in this region, especially during the fruiting season, may have profound effects on group size and structure.     

Sympatric Chimpanzees (<Emphasis Type="Italic">Pan troglodytes troglodytes</Emphasis>) and Gorillas (<Emphasis Type="Italic">Gorilla gorilla gorilla</Emphasis>) in Loango National Park,Gabon: Dietary Composition,Seasonality, and Intersite Comparisons

Dietary overlap of sympatric apes is complex and understudied, but its examination is essential to further our understanding of species distribution, abundance, and community ecology. Over 3 yr we studied food availability and dietary composition of central chimpanzees (Pan troglodytes troglodytes) and western gorillas (Gorilla gorilla gorilla) in Loango National Park, Gabon. We predicted that living in a habitat dominated by mature forest with sparse terrestrial herbaceous vegetation would lead to an increase in frugivory by gorillas, resulting in increased dietary overlap between the 2 ape species vs. other sites, but that chimpanzees would remain more frugivorous than gorillas. Through fecal analysis we measured overlap in fruit consumption between the 2 species on a bimonthly basis using the Renkonens method. Mean overlap was 27.5% but varied greatly seasonally, ranging between 0.3% and 69%, indicating that when examined on a finer scale, the degree of overlap appears much lower than at other study sites. In contrast to studies elsewhere, there was not a positive correlation between rainfall and fruit availability in Loango, and the long dry season was a period of high fruit production. As observed elsewhere, we found a positive correlation between fruit consumption and fruit availability for both chimpanzees and gorillas and we found that chimpanzees were more frugivorous than gorillas. A very low availability of herbs did not lead to increased frugivory by gorillas nor increased overlap between the 2 ape species vs. other field sites. We conclude that forest composition, fruit availability, and dietary variability of sympatric species can vary greatly between locations, and that chimpanzees and gorillas can adapt to primary forest with little undergrowth, where they concentrate their diet on fruit and leaves.     

Insect-eating by sympatric Lowland gorillas (Gorilla g. gorilla) and chimpanzees (Pan t. troglodytes) in the Lopé Reserve,Gabon

Sympatric populations of lowland gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes troglodytes) in the Lopé Reserve in central Gabon consumed insects at similar average frequencies over a 7-year period (30% versus 31% feces contained insect remains). Data came mostly from fecal analysis supplemented by observation and trail evidence. The weaver ant (Oecophylla longinoda) was the species eaten most frequently by both gorillas and chimpanzees. Other species of insects wore eaten but there was virtually no overlap: Chimpanzees used tools to eat Apis bees (and their honey) and two large species of ants; gorillas ate three species of small ants. Thus, despite their shared habitat, the esources utilized were not identical as gorillas do not show the tool-use “technology” of chimpanzees. The frequency of insect-eating by both species of ape varied seasonally and between years but in different ways. This variation did not seem to be related to the ratio of fruit to foliage in their diets. Gorillas of all age-classes ate insects at similar rates. Comparisons with insectivory by other populations of gorillas indicate differences exist. Mountain gorillas (Gorilla g. beringei) in the Virunga Volcanoes, Rwanda, consume thousands of invertebrates daily, eating them inadvertently with handfuls of herbaceous foods but they deliberately ingest insect-foods only rarely. Lowland gorillas at Lopé habitually ate social insects, and their selective processing of herbaceous foods probably minimizes inadvertent consumption of other invertebrates. Gorillas at Belinga in northeastern Gabon, 250 km from Lop6, ate social insects at similar rates but ignored weaver ants in favor of Cubitermes sulcifrons, a small species of termite that occurs at Lopé but was not eaten by gorillas. This indicates that local traditions similar to those reported for chimpanzees also exist amongst populations of gorillas. © 1992 Wiley-Liss, Inc.     

Gorillas (Gorilla gorilla gorilla) in the Likouala swamp forests of north central Congo: Preliminary data on populations and ecology

Until recently it was generally believed that gorillas avoid water. In two recent, independent faunal surveys in the Likouala swamp of north central Congo, we have found that gorillas occur at high densities, extending the known range of Gorilla gorilla gorillavery close to the Oubangui River. The gorillas in this area fed on the abundant ground vegetation of herbaceous monocotyledons in the swamp forest. In adjacent islands of terra firmathere was little evidence of gorilla nesting or feeding, indicating that they spend at least part of the year almost exclusively in the swamp forests. Recent reports from several sites in West Africa indicate that swamp forests may generally provide abundant food resources that are used regularly by gorillas.     

Newly Discovered Gorilla Population in the Ebo Forest,Littoral Province,Cameroon

We report on a new population of gorillas discovered in November 2002 in the Ebo Forest, Littoral Province, Cameroon. We observed A group of q7 gorillas directly for 83 min, and they were in auditory range for 155 min. Further evidence of gorilla presence included 8 nest groups totaling 38 nests, distinctive feeding signs accompanied by footprints, and a gorilla cranium collected from the nearby village of Iboti. This newly discovered gorilla population is geographically intermediate between the 2 extant populations of western gorillas: Gorilla gorilla gorilla, the most populous gorilla subspecies living in Gabon, Equatorial Guinea, Congo-Brazzaville, Central African Republic and Cameroon to the south of the Sanaga River, and G. g. diehli or the Cross River gorilla, a small population of ca. 250 individuals on the Cameroon-Nigeria border. It is not possible to assign the new gorilla population to either subspecies on the basis of measurements of the single male cranium. Genetic analyses of freshly shed hairs, collected from gorilla nests, may help to resolve the taxonomic status of the Ebo gorillas.     

An experimental study of nettle feeding in captive gorillas

Mountain gorillas (Gorilla beringei beringei) in Karisoke, Rwanda, feed on the stinging nettle Laportea alatipes by means of elaborate processing skills. Byrne [e.g. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 358:529–536, 2003] has claimed that individuals acquire these skills by means of the so‐called program‐level imitation, in which the overall sequence of problem‐solving steps (not the precise actions) is reproduced. In this study we present western lowland gorillas (Gorilla gorilla gorilla) with highly similar nettles. Twelve gorillas in three different groups (including also one nettle‐naïve gorilla) used the same program‐level technique as wild mountain gorillas (with differences mainly on the action level). Chimpanzees, orangutans, and bonobos did not show these program‐level patterns, nor did the gorillas when presented with a plant similar in structural design but lacking stinging defenses. We conclude that although certain aspects (i.e. single actions) of this complex skill may be owing to social learning, at the program level gorilla nettle feeding derives mostly from genetic predispositions and individual learning of plant affordances. Am. J. Primatol. 70:584–593, 2008. © 2008 Wiley‐Liss, Inc.     

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.     

EFFECT OF CULTURE AND BLOOM DEVELOPMENT AND OF SAMPLE STORAGE ON PARALYTIC SHELLFISH POISONS IN THE CYANOBACTERIUM ANABAENA CIRCINALIS

Paralytic shellfish poisons (PSPs) were detected in 24 of 31 bloom samples dominated by the cyanobacterium Anabaena circinalis Rabenhorst, collected from across Austraia. The ability to produce PSPs has been maintained in everal non-axenic strains of A. circinalis kept in culture, whereas strains that were non-toxin-producing when isolated have remained as such. PSPs were detected and quantified by high-performance liquid chromatography (HPLC), and the structures were confirmed by electrospray mass spectroscopy. The concentration of toxins in PSP positive samples ranged from 50 to 3400 μg.g^-1 dry weight. Toxin profiles were always dominated by the N-sulfocarbamoyl-11-hydroxysulfate C toxins, C1 and C2 (44–85 mol%), with the remainder consisting of gonyautoxins-2, −3, and −5, decarbamoylgonyautoxins-2 and −3, saxitoxin, and decarbamoylraxitoxin. N₁-_-hydroxy PSPs, commonly found in marine dinoflagellates, were absent, suggesting that A. circinalis lacks the enzyme responsible for N₁-_-hydroxylation. On a dry weight basis, the amount of toxin in cultured Anabaena circinalis (strain ACMB06)rose significantly (P < 0.05)over time from 570 to 3400 μg.g.^-1 cells in late stationary phase. However, there was no significant trend in cellular toxin quota (toxin per cell) over the life of the culture; this may be explained by variation in cell mass. On average, batch cultures of Anabaena circinalis contained 19% extracellular toxin, which increased slightly over the growth cycle and had a composition similar to that of the intracellular toxins. As cultures aged, the formation of decarbamoyl toxins and increases in theα-/β-epimer ratios of C toxins and gonyautoxins were observed. The variation in these components during stationary phase in culture was sufficient to explain the variation in relative PSP composition observed among natural bloom samples. Because decarbamoylgonyautoxins are much more toxic than C toxins on a molar basis, these transformations also lead to an increase in toxicity of the sample or bloom over time. The transformations of PSPs, which occur during aging and sample storage, render the comparison of PSPs by HPLC unreliable for phenotyping Anabaena circinalis, unless strains are cultured, harvested, and analyzed under standard conditions.     

Species and sex identification of western lowland gorillas (Gorilla gorilla gorilla), eastern lowland gorillas (Gorilla beringei graueri) and humans

Methods for the identification of the sex and species of individuals from samples non-invasively taken from humans and gorillas were established. Amplification of a segment of amelogenin (AMG), which is an X–Y homologous gene, using two pairs of primers from human AMG, revealed both X- and Y-specific bands. The possibility of sex identification was examined by typing the AMG gene using hair and fecal samples from captive western lowland gorillas (Gorilla gorilla gorilla) in Japan and hair samples from wild eastern lowland gorillas (Gorilla beringei graueri) in the Kahuzi-Biega National Park, Democratic Republic of Congo, which were sexed by direct observation. Species-specific bands of AMG in gorillas and humans were identified by restriction fragment length polymorphisms analysis. These tests could be used for sexing unidentified individuals of wild western and eastern lowland gorillas, and screening contamination of human DNA from non-invasively acquired samples.     

Investigation of the RH locus in gorillas and chimpanzees

The human Rh blood-group system is encoded by two homologous genes,RhD andRhCE. TheRH genes in gorillas and chimpanzees were investigated to delineate the phylogeny of the humanRH genes. Southern blot analysis with an exon 7-specific probe suggested that gorillas have more than twoRH genes, as has recently been reported for chimpanzees. Exon 7 was well conserved between humans, gorillas, and chimpanzees, although the exon 7 nucleotide sequences from gorillas were more similar to the humanD gene, whereas the nucleotide sequences of this exon in chimpanzees were more similar to the humanCE gene. The intron between exon 4 and exon 5 is polymorphic and can be used to distinguish the humanD gene from theCE gene. Nucleotide sequencing revealed that the basis for the intron polymorphism is anAlu element inCE which is not present in theD gene. Examination of gorilla and chimpanzee genomic DNA for this intron polymorphism demonstrated that theD intron was present in all the chimpanzees and in all but one gorilla. TheCE intron was found in three of six gorillas, but in none of the seven chimpanzees. Sequence data suggested that theAlu element might have previously been present in the chimpanzeeRH genes but was eliminated by excision or recombination. Conservation of theRhD gene was also apparent from the complete identity between the 3′-noncoding region of the human D cDNA and a gorilla genomic clone, including anAlu element which is present in both species. The data suggest that at least twoRH genes were present in a common ancestor of humans, chimpanzees, and gorillas, and that additionalRH gene duplication has taken place in gorillas and chimpanzees. TheRhCE gene appears to have diverged more thanRhD among primates. In addition, theRhD gene deletion associated with the Rh-negative phenotype in humans seems to have occurred after speciation. Correspondence to: C.M. Westhoff     

Nutritional quality of gorilla diets: consequences of age,sex, and season

We tested the effects of age, sex, and season on the nutritional strategies of a group of mountain gorillas (Gorilla beringei) in the Bwindi Impenetrable National Park, Uganda. Through observations of food intake of individual gorillas and nutritional analyses of dietary components over different seasons and environments, we estimated nutrient intake and evaluated diet adequacy. Our results suggest that the nutritional costs of reproduction and growth affect nutrient intake; growing juveniles and adult females ate more food and more protein per kilogram of metabolic body mass than did silverbacks. The diets of silverback males, adult females, and juveniles contained similar concentrations of protein, fiber, and sugar, indicating that adult females and juveniles did not select higher protein foods than silverbacks but rather consumed more dry matter to ingest more protein. Juveniles consumed more minerals (Ca, P, Mg, K, Fe, Zn, Mn, Mo) per kilogram of body mass than adult females and silverback males, and juveniles consumed diets with higher concentrations of phosphorous, iron, and zinc, indicating that the foods they ate contained higher concentrations of these minerals. Seasonally, the amount of food consumed on a dry weight basis did not vary, but with increased frugivory, dietary concentrations of protein and fiber decreased and those of water-soluble carbohydrates increased. Energy intake did not change over the year. With the exception of sodium, gorillas ate diets that exceeded human nutrient requirements. A better understanding of the relative importance of food quantity and quality for different age–sex classes provides insights into the ways in which gorillas may be limited by food resources when faced with environmental heterogeneity.