To explore sources of variation in tropical forest primate biomass, and, in particular, to test the hypothesis that soil conditions are a major ultimate determinant of the biomass of colobine monkeys and other primates, we compared data on the soils, vegetation, and primate community at a site in West Africa (Tiwai Island, Sierra Leone) with information from other sites, especially two other African sites (Douala—Edea in Cameroon, and Kibale Forest in Uganda). The biomass of eight anthropoid primate species in old secondary high forest on Tiwai was estimated from data on population densities assessed by transect samples combined with data on social group densities and individual body masses. Samples of soil and tree foliage were collected at the same site, and subjected to a variety of chemical and mechanical analyses. Our estimate of anthropoid biomass at Tiwai is 1229—1529 kg/km2, including 682—889 kg/km2 of colobines. This is one of the highest primate biomasses recorded anywhere. The soils at Tiwai were found to be relatively high in sand content and low in pH, and to have low levels of mineral nutrients. Levels of condensed tannins in the mature foliage of the trees comprising a major part of the forest canopy were higher than at other sites, but the ratio of protein to fiber in this foliage was also higher than at any other site except Kibale. It is argued that a wide range of environmental factors affect primate population densities, and that nutrient—poor soils and high tannin levels in tree foliage do not necessarily produce a low primate (or colobine) biomass, as some earlier studies had suggested. Furthermore, seeds (an important food source for Tiwai colobines) are apparently a common part of the colobine dietary repertoire and are not consumed largely as a response to a scarcity of digestible foliage.

All living trees (>_ 30 cm gbh) were enumerated in 135 80× 80 m plots, each subdivided into four 40x40 m subplots, and arranged along four 5 km transect lines in the Korup Forest Reserve, Cameroun. For each plot altitude, slope and the extent of permanent and seasonal swamps were recorded.Four hundred and eleven taxa were recognized of which 66% were identified to species. Mean tree density was 471 ha -1, basal area 27.6 m 2 ha -1 and number of species per plot 75. The subfamily Caesalpinioideae (Leguminosae) was the most abundant family/subfamily in terms of basal area, but the Scytopetalaceae the most frequently represented, mainly on account of Oubanguia alata. Ten plots had at least three quarters of their area permanently swamped, and three, to a similar extent, were seasonally swamped. The ranges in sand, silt and clay content were 60-91, 0-24 and 4-20% respectively. The pH value, organic carbon content and nitrate-nitrogen concentration ranged between 4.0-5.8, 1.3-5.7% and 0-35 ppm respectively. The largest soil variations were in available phosphorus, range 2-29 ppm, and potassium, 38-375 ppm.Correspondence analysis ordination of all plots showed a major indirect floristic gradient correlated with increasing altitude, slope and soil phosphorus and potassium. Removal of the topographic effect by separate re-ordinations of four groups of plots at low, middle (2) and high altitude/slopes highlighted a strong correlation of the main floristic gradients of the middle altitude/slope groups with the concentration of available soil phosphorus.Direct gradient analysis using all plots with respect to available soil phosphorus concentration confirmed the indirect analyses. Individual species response to phosphorus were also shown by direct comparisons in the vegetation on plots of high and low available soil phosphorus concentration. Low available phosphorus soils (_< 5 ppm) are strongly associated with species of the subfamily Caesalpinioideae, especially of the tribes Amherstieae and Detarieae. It is suggested that this result is probably due to the ability of these particular legume tribes to form associations with ectotrophic mycorrhizae.

Black colobus monkeys (CO~U/JU\ wlnruir) in the Douala-Edea Reserve, a rain-forest on the coast of Cameroon, have been shown to avoid young and mature leaves of most of the common plants in their habitat and to feed disproportionately heavily on leaves of rare plants. The proportion of leaves in the diet was low compared to most colobines studied, and the monkeys spent over half their feeding time eating seeds. Patterns of food selection were analysed in relation to distribution of nutrients, digestion-inhibitors and toxins in the vegetation. Colobw ~a t r m c~ select food items that are rich in mineral nutrients and nitrogen and low in content of the general digestion-inhibitors, lignin and tannin. They achieve this in the following ways: (i) by feeding preferentially on young leaves, which have higher nutrient content and lower contents of digestion-inhibitors than mature leaves; (ii) by eating those mature leaves with highest nument content relative to content of digestioninhibitors; and (iii) by eating seeds, which are sources of readily available energy and which, as an item class, are less rich in digestion-inhibitors. Seeds at Douala-Edea appear to contain Ins nitrogen than leaves and C. J&UUU selects those seeds with highest nitrogen content. It is suggested that seedfeeding may be facilitated by the ability of the forestomach flora of these ruminant-like monkeys to detoxify some of the secondary compounds contained in seeds. Avoidance of most unused young and mature leaf items is correlated with a low nutrienudigestion-inhibitor ratio; avoidance of most unused seeds could be accounted for by their low nitrogen contents. Most items whose avoidance could not be explained in terms of these major constraints on food selection possess secondary compounds likely to be toxic. It is proposed that relative importance of digestion-inhibitors, low nutrient content and toxins as constraints on food selection by generalist herbivores will vary greatly among forests with different nutrient and secondary chemistry profiles.KEY WORDS:-Community ecology -tropical rainforest -plant-animal interactions -generalist herbivores -plant chemical defences -food selection -ruminant-like digestion -C o l h sutmw.

The leaf-monkey Presbytis johnii has been found to exhibit considerable selectivity in its dietary utilization of mature foliage in a rain-forest habitat. To investigate the basis of this selectivity and to examine the hypothesis that the observed selection is related to the digestibility and toxicity of the available foliage, chemical analyses have been made on 16 of the most important tree species in the monkey's habitat. It has been found that the most heavily used items, which form a staple part of the diet of P. johnii, are characterized by a low fibre content and a very low condensed tannin content. However, neither class of compound is an absolute feeding deterrent as minor, but still significant, mature leaf food items contain considerable amounts of both. It is suggested that the feeding deterrents in these minor items, which may be ingested to supply specific dietary requirements, can perhaps be tolerated because of their dilution in the gut by the dietary staples. An examination of the pepsin/cellulase digestibility of available mature foliage showed that the staple food items tended to be highly digestible. Little correlation has been found between alkaloid content and food selection and it is suggested that the colobine forestomach microflora has the ability to detoxify at least some alkaloids. Additional data on mature leaf petioles and young leaves suggest that the high ratio of cell-sap to cell-wall in these items, and their related high digestibility, explain the high relative abundance of these items in the P. johnii diet.

Some Astragalus species are used as forage for livestock and wild animals. Many species are used in folk medicine for their hepatoprotective, antioxidative, immunostimulant, and antiviral properties, whereas others are toxic, and in many cases the toxic principles can pass to humans through milk and meat. Three groups of chemicals have been described as pharmacologically active principles: polysaccharides, saponins and phenolics. In addition, three kinds of toxic principles have been reported: indolizidine alkaloids, aliphatic nitro compounds and selenium. © 1997 John Wiley & Sons, Ltd.

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A comparative floristic survey of lowland tropical rain forest at Kuala Lompat, Krau Game Reserve, West Malaysia and at Sepilok Virgin Jungle Reserve, Sabah, East Malaysia, revealed significant differenres in the composition of canopy species, notably in the relative paucity of Dipterocarpaceae and abundance of Leguminosae at Kuala Lompat. A further comparison with data from other sites in Malesia indicated that Kuala Lompat was rather atypical, representing an extreme example of the relatively legume rich and dipterocarp poor forests of West Malaysia. Conversely, the predominance of dipterocarps and lack of legumes a t Sepilok was similar to other sites in Borneo. Young and mature leaves were collected from a representative sample of the canopy flora of the two study sites; the levels of nitrogen, fibre, total phenolics and condensed tannins, and degree of digestibility by cellulase and pepsin, were measured. Levels of fibre, nitrogen and phenolics differed significantly between the two floras; foliage from Kuala Lompat being, on the whole, richer in nitrogen but lower in phenolics and fibre. As a consequence of the lower levels of fibre, and less certainly of phenolics, the Kuala Lompat foliage was comparatively more digestible. Possible reasons for the differences in foliar biochemistry between the two sites are discussed. Differences in rainfall and in soil quality are regarded as potential evolutionary causes. A further comparison of the chemical profiles with data for other forests in India and Africa indicate that Sepilok is a site in which trees invest heavily in quantitative defences such as fibre and phenolics whereas trees at Kuala Lompat place a lower emphasis on the production of these. Finally, attention is drawn to the use of foliar chemical profiles in predicting the carrying capacity for colobine monkeys at each of the five Old World forests where data are available. It was found that the ratio of nitrogen to fibre correlated well with the biomass of colobines at the five sites. KEY WORDS:-SouthEast Asian lowland rain forests ~ comparative floristicscomparative phytochemistrydifferential investment in chemical defencescolobine monkeyscarrying capacity of forests in relation to leaf chemistry.

The diets of the banded leaf monkey (Presbytis melalophos) at Kuala Lompat in the Krau Game Reserve of West Malaysia and the red leaf monkey (Presbytis rubicunda) in Sepilok Virgin Jungle Reserve, Sabah, East Malaysia have been examined in relation to plant chemistry. Both monkeys spent about half their time eating foliage, and about half their time eating fruits and seeds. 'l'hey both favoured leaves with high digestibility (due to relatively low levcls of fibre) and high levcls of protein, a combination found predominantly in young leaves and some flowers. The monkeys appeared to favour seeds and fruits with high concentrations of storage carbohydratcs or fats, but not those rich in simple sugars. Selection of seeds and fruits was not correlated with protein content.An analysis of the fibre and protein contents of foods showed that, on an annual basis, the two monkeys achieved a comparable intake for both items. However, these diets were obtained in radically different ways. Presbyfis melalophos was able to eat foliage from many of the common tree species in its home range, whereas P. rubicunda relied on rare trees and lianas. This difference is attributed to the very high density of Dipterocarpaceae at Sepilok, a tree family that provides little food for colobines. The rarity of P. rubicunda's food plants at Sepilok is considered to be the main reason for the greater home range size and lower population density in comparison to P. melalophnr.Finally, the biochemical profiles of the young leaf diet of these two monkeys were compared with previously published information on two African and one south Indian colobines. In many respects the intake of supposed critical components, protein and fibre, showed marked similarities between different animals, considering contrasts in their habitats.