Feeding ecology of the proboscis monkey (Nasalis larvatus)

Proboscis monkey (Nasalis larvatus) feeding behavior and ecology were studied at the Natai Lengkuas Station, Tanjung Puting National Park, Kalimantan Tengah, Indonesia. Data on feeding behavior were collected using scan sampling during group follows. Three vegetational plots containing 1,732 trees were established and monitored monthly for changes in fruit, flower, and young leaf production. Basal area and canopy cover were calculated and used in estimating food abundance. Proboscis monkeys were found to be folivore/frugivores, specializing in seed consumption. At least 55 different plant species were used as food sources, with a marked preference for Eugenia sp. 3/4,Ganua motleyana and Lophopetalum javanicum. These tree species were among the most frequent and most dominant. However, proboscis monkeys were selective feeders; use of tree species as food sources was not based simply on relative density. During times of low food abundance and/or availability proboscis monkeys switched dietary strategies and increased dietary diversity. The average total home range was estimated to be 130.3 ha, with an average group density of 5.2 groups per km². The average biomass per km² was estimated to be 499.5 kg. Given their high biomass and predilection for consuming seeds of dominant species, proboscis monkeys may help to maintain and increase vegetational diversity.     

The diet and feeding behavior of the silver leaf monkey (Trachypithecus auratus sondaicus) in Indonesia

I describe the diet and feeding behavior of silver leaf monkeys (Trachypithecus auratus sondaicus) in the Pangandaran Nature Reserve, West Java, Indonesia, and compare a group living in old secondary rain forest with a group living in mixed plantation/secondary forest to determine intraspecific variation in feeding behavior and the importance of the plantation species in the diet of the monkeys. Young leaves and leaf buds made up slightly less than half of their diets, with both groups showing a preference for a few species when seasonally available. Fruits and flowers of a few species were also preferentially selected when available. These included sweet, fleshy fruits, which most other colobines tend to avoid. Young leaf intake was greatest in months when fruit intake was low. Mature leaves were rarely eaten. Both groups spent approximately 20% of feeding time foraging on Moraceae species. Differences in the diet of the two groups were related largely to differences in vegetational composition and the availability and abundance of food items for the species common to both sites. Teak (Tectona grandis) was the top food species of the group living in mixed plantation/secondary forest, with the midribs of young leaves preferentially selected. Young leaves ofT. grandis, available throughout the study, provided a staple food and were eaten when preferred foods were scarce. More favored food items were available to the group living in old secondary forest, though none was a staple food.     

The feeding ecology and activity budget of proboscis monkeys

A group of proboscis monkeys (Nasalis larvatus) consisting of an alpha‐male, six adult females, and several immatures was observed from May 2005–2006. We collected over 1,968 hr of focal data on the adult male and 1,539 hr of focal data on the six females in a forest along the Menanggul River, Sabah, Malaysia. Availability and seasonal changes in plant species consumed by the focal monkeys were determined by vegetation surveys carried out across an area of 2.15 ha along 200–500 m trails in riverine forest. A total of 188 plant species were consumed by the focal monkeys. The activity budget of members of our study group was 76.5% resting, 19.5% feeding, and 3.5% moving. Young leaves (65.9%) and fruits (25.9%) accounted for the majority of feeding time. Over 90% of fruit feeding involved the consumption of unripe fruits and in the majority of case both the fruit flesh and seeds were eaten. Although fruit eating was rare in some months, during other times of the year time fruit feeding exceeded the time devoted to young leaves. We found that monthly fruit availability was positively related to monthly fruit eating and feeding activity, and seasonal fluctuations in dietary diversity were significantly affected by fruit eating. These results suggest that fruit availability and fruit‐eating behaviors are key factors that influence the activity budget of proboscis monkeys. Earlier assumptions that colobine monkeys are obligate folivores do not apply well to proboscis monkeys and certain other colobines. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of Asian colobines. Am. J. Primatol. 71:478–492, 2009. © 2009 Wiley‐Liss, Inc.     

Dietary breadth and resource use of François' langur in a seasonal and disturbed habitat

Previous studies of Trachypithecus species indicated that they were selective feeders that concentrated on relatively few food species/items. From January to December 2005, I quantified potential food availability and the food species/items eaten by five groups of François' langur (Trachypithecus francoisi) in the Mayanghe Nature Reserve (MNR), People's Republic of China. These langurs fed on 164 species, of which the top ten accounted for 51% of all feeding records. Langurs consumed more species (91) in the spring than in other seasons (73 summer, 75 autumn, and 67 winter), and only 38 species were consumed in all seasons. Nontree food species, such as bushes and lianas, accounted for 47% of the total feeding records and for a majority (68%) of the feeding records in winter. The annual diet consisted of leaves (64% of feeding records), fruit and seed (32%), and other nonfoliage items (4%); the langurs switched from being more folivorous in spring (93%) and summer (79%) to being more frugivorous in autumn (53%) and winter (56%). There was no correlation between the proportion of feeding records and the food availability in the most frequently consumed species, indicating that these langurs were selective feeders; there were significant correlations between consumption and abundance in both the entire set of 112 food species and the set of 86 infrequently consumed species, indicating that foods that are more available are eaten more frequently. It appeared that in the seasonal and disturbed habitat, feeding decisions and diet composition of the langur may be driven more by food availability, and less by animal's selectivity, than at other sites. The results indicate that François' langur copes with habitat alterations by broaden its dietary breadth; this has implications for the adaptive significance of dietary breadth, and has implications for future conservation strategies for species which exist in degraded habitats. Am. J. Primatol. 73:1176–1187, 2011. © 2011 Wiley Periodicals, Inc.     

Morphology and phenology of seeds and whole fruit eaten by Milne-Edwards’ sifaka,Propithecus diadema edwardsi,in Ranomafana National Park,Madagascar

Although it is an anatomical folivore, the diet of the Milne-Edwards’ sifaka (Propithecus diadema edwardsiA. Grandidier, 1871) in Ranomafana National Park contained 35% seeds, 30% whole fruit, and 28% leaves. Plant species used as seed sources differed from those used as whole fruit sources in terms of temporal variation in consumption, taxonomic affiliation, morphology, and phenology. Although seeds were destroyed in both exploitation styles used by the sifakas—seed and whole fruit-eating—the gross morphology of species used as seed sources conformed to the complex of traits typical for fruits experiencing seed predation, while species used as whole fruit sources conformed to traits typical for fruits that do not experience predispersal predation. Many of the 19 plant species from which the seed was extracted and eaten contained a single seed with moderate testa thickness, and fruits containing this type of seed were medium-sized with dry or fibrous flesh, moderate skin thickness, and a dull color. In contrast, brightly colored, juicy fruits with minimally protected seeds were characteristic of the 38 plant species from which both pericarp and seed were eaten. Compared to transectwide measures of fruit availability or patterns restricted to whole fruit sources, fewer species of seed sources produced fruit per month and fruiting activity was more seasonal.     

Behavioral responses of Cao Vit gibbon (Nomascus nasutus) to variations in food abundance and temperature in Bangliang, Jingxi, China

The Cao Vit gibbon is a critically endangered species with only about 110 individuals remaining in a degraded karst forest along the China-Vietnam border. Behavioral data from this site are particularly useful in understanding gibbon behavioral adaptations to different sets of ecological conditions and will contribute to the conservation of the species. We studied seasonal variation in the time budget and diet of the Cao Vit gibbon in response to variation in food availability and ambient temperature by observing two groups for 1,379 hr between January and December 2009. We used 5-min scan samples to record the activity of gibbons. Both ambient temperature and food availability varied from month to month. Gibbon groups increased resting time and huddled together in sleeping places in cold months. Gibbons spent more time feeding on fruit when fruit was more abundant suggesting that fruit was their preferred food. Alternatively, leaf eating was negatively correlated with leaf availability which suggested that leaves may be used as a fallback food. Gibbons increased their diet diversity when they ate more leaves. This might be a strategy to cope with toxins or digestion inhibitor accumulation associated with feeding from a limited number of leaf species. Individuals consumed more buds when Broussonetia papyrifera produced buds in March and April. During this period, they decreased traveling time and engaged in less frequent social interactions. Gibbons spent more time searching for and feeding on invertebrates during June and October. However, we did not collect data on invertebrate abundance and therefore cannot determine the relationship between invertebrate feeding and availability. We conclude that flexibility in consuming diverse food types and food species, and in responding to the availability of preferred foods, has enabled the Cao Vit gibbon to survive in a degraded karst forest habitat.     

Patterns of Frugivory in Three West African Colobine Monkeys

We studied the comparative feeding ecology of three species of colobus (Procolobus badius, Procolobus verus, and Colobus polykomos) on Tiwai Island, Sierra Leone. We collected dietary data on each species by scan-sampling habituated groups. Because these groups were observed in the same study area during overlapping time periods, the confounding effects of temporal and spatial variability in food availability were reduced. Our results show that the annual diets of the two larger species (Procolobus badius and Colobus polykomos) include roughly equal proportions of fruits (including seeds), young leaf parts, and mature leaf parts, although P. badius had a greater intake of floral parts. Procolobus verus consumed almost no mature leaf parts, few fruits and seeds, and many young leaf parts. Colobus polykomos commonly fed from lianas. Seeds were the dominant fruit item eaten by all three colobus, and the fruits they selected were generally dull and non-fleshy, in contrast to the brightly-colored, pulpy fruits eaten by guenons. Leguminous plants contributed substantially to the diets of both the larger species, but comparisons with other African forest sites indicate that colobine biomass is not closely correlated with the abundance of leguminous trees in the forest. (Deceased)     

The role of phytochemistry in dietary choices of Tana River red colobus monkeys(Procolobus badius rufomitratus)

We conducted a phytochemical survey of tree species growing within the riverine forests of the Tana River National Primate Reserve in Kenya to understand better the feeding ecology of an endangered resident primate, the Tana River red colobus monkey (Procolobus badius rufomitratus).Young leaves, which make up a large percentage of this monkey's diet, are significantly higher in nitrogen and lower in acid detergent fiber than more abundant mature leaves are. Phenolic chemistry had little inhibitory effect on feeding by P. b. rufomitratus.Choice among tree species by P. b. rufomitratusappears to be influenced largely by leaf availability,once an acceptable threshold of nitrogen and fiber is reached When mature leaves are eaten, they selected species that are high in nitrogen and low in fiber. A significantly higher nitrogen content was found for the mature leaves of all leguminous versus nonleguminous tree species. Consequently, the availability of certain types of mature leaf species during periods of preferred food scarcity may prove critical to groups of Tana River red colobus monkeys.     

Plant feeding of yellow baboons (Papio cynocephalus) in Mikumi national park,Tanzania, and the relationship between seasonal feeding and immature survival

Focal-animal feeding data obtained from 64 adult baboons during a 3-year period were used together with equivalent data from 46 infants to evaluate hypotheses predicting selection for a birth peak and to study the baboon’s eclectic/selective feeding adaptation, with emphasis on differential feeding by sex, developmental trends, and seasonal use of food classes (fruit, leaf, flower, grass, etc.). The findings suggest that feeding conditions are better in the wet season than in the dry season. Despite large sexual dimorphism, estimates of total amounts eaten were virtually identical for males and females. Infants used all of the same plant-food classes as adults, but proportional differences occurred for some food classes in amounts eaten. Foods eaten proportionately less by infants were probably harder for them to obtain and process or were chosen through inexperience or for exploration. There was considerable between-year variation in amounts of food classes eaten, but the within-year standard deviations were similar, as were also the mean amounts eaten per year. An eclectic/selective feeding adaptation has the advantage of permitting long-run acquisition of adequate nutrition within a context of high feeding variation from season to season and year to year. Mixed results were obtained from hypotheses about selection for a birth peak. Although a peak occurred in the early dry season, this was not the optimal time of birth for survival. Survival was highest for individuals born in the late wet season, when the availability and probably the quality of food for lactating mothers were greatest.     

Baboon diet: a five-year study of stability and variability in the plant feeding and habitat of the yellow baboons (Papio cynocephalus) of Mikumi National Park, Tanzania

The habitat and plant feeding of 64 well-habituated, individually identified adult male and female yellow baboons was studied for 5 years at Mikumi National Park, Tanzania. Variation across the years showed that a study of only one or two years would have been incomplete and misleading. The list of baboon food species obtained from Mikumi is considerably larger and more diverse than any previously reported. One to six plant parts were eaten from each of more than 180 species. The 25 most common tree genera all contained species used for food. Of the 50 most common grass, shrub and herb genera, 93% included plant foods. Using months in which a species was eaten during at least one year of the study, 21 staple species were eaten during a mean of 8.86 months and 7 were eaten in all 12 months. Although many foods were from commonly available plant species, 15 such species were only rarely eaten. The number of parts of a species eaten per month and an estimate of the amounts eaten per month both varied with temperature and rainfall, being lowest near the end of the cool, dry season. There were substantial differences from year to year in the timing and amount of food production of many species; nevertheless, the same broad feeding pattern was repeated in each of the 5 years of the study. Despite yearly variation in food availability, 14 or more staples and other common foods were eaten in any given month. If crops of many of these foods were to fail, a large number of less commonly eaten species could be substituted. Baboons are eclectic feeders that appear to be optimizing their diet by selective feeding from among a wide array of available foods in an ever-changing floristic environment.     

Diets of Two Lemur Species in Different Microhabitats in Beza Mahafaly Special Reserve,Madagascar

Studies of primate diets usually focus on differences that distinguish species or populations. However, variation in diet can occur at a more local level of groups within a population, especially in a non-homogeneous habitat. I compared dietary variation in food composition and toughness across groups of 2 lemur species in Beza Mahafaly special reserve, Madagascar. Beza Mahafaly contains an 80-ha reserve (Parcel 1) that, while small, hosts a dense population of Lemur catta (ring-tailed lemurs) and Propithecus verreauxi verreauxi (sifakas). Microhabitats in the eastern vs. western sides of the parcel are structurally and floristically distinct. Sifakas in this parcel have small, discrete home ranges and are morphological folivores. For these reasons, I expected that the 6 groups studied would eat a different menu of food plants but with similar toughness values. Ring-tailed lemurs have comparatively large, overlapping home ranges, and I expected that the 5 study groups would eat similar foods. Despite living in different microhabitats across the parcel, sifakas exhibit high dietary uniformity both in dietary plant species composition and the toughness of the foods. Food selection in sifakas operates on two distinct levels. Sifaka groups share many key food species that appear independent of local abundances, but the ranking of the foods within each group appears related to availability. Ring-tailed lemur groups are more heterogeneous in the composition of their diets relative to sifakas, though the time spent feeding on individual foods reveals a marked preference for the fruits of Tamarindus indica by all groups. Food toughness is consistent across the parcel with the exception of the most western group. Ring-tailed lemurs are highly specific feeders, but indiscriminate nibblers. Sifakas are targeted, balanced feeders. There does not appear to be a consistent microhabitat effect operating across species. Differences within sifaka and ring-tailed lemur populations in food composition and toughness, however, correspond to an east-west microhabitat gradient. Measures of dietary flexibility must take into account not only the plant species consumed and the different parts eaten but also their associated food properties and proportion of time spent feeding on them.     

Influence of Forest Seasonality on Gibbon Food Choice in the Rain Forests of Barito Ulu,Central Kalimantan

We describe the diet of two hybrid gibbon groups (Hylobates mulleri x H. agilis) in relation to forest seasonality. We collected data over 12 mo in lowland dipterocarp forest in the Barito Ulu research area, Central Kalimantan, Indonesia. Although non-fig fruit was the main dietary item (52–64% of diet), gibbon diet was most strongly influenced by the availability of flowers. During periods when flowers were most abundant and the gibbons increased consumption of them, they also ate figs or young leaves more often. We suggest that although flowers are nutritionally rich sources of food, providing relatively high levels of protein compared to fruit, they are unlikely to satiate gibbon hunger and they seek dietary bulk from figs or young leaves, because they are easily obtained. Rainfall also influenced food choice, and non-fig fruit availability had a weak influence on fruit selection for one group. The group concentrated feeding on the fruit of a few species when fruit was most abundant and ate a greater diversity of species when fruit was scarce. Gibbon diet appeared not to be influenced by changes in availability of figs, young leaves and diversity of fruiting species.     

Fallback Foods of Red Leaf Monkeys (Presbytis rubicunda) in Danum Valley, Borneo

Animals in Southeast Asia must cope with long periods of fruit scarcity of unpredictable duration between irregular mast fruiting events. Long-term data are necessary to examine the effect of mast fruiting on diet, and particularly on the selection of fallback foods during periods of fruit scarcity. No such data is available for colobine monkeys, which may consume substantial amounts of fruits and seeds when available. We studied the diet of red leaf monkeys (Presbytis rubicunda, Colobinae) in Danum Valley, Sabah, northern Borneo, using 25 mo of behavioral observation, phenology and vegetation surveys, and chemical analysis to compare leaves eaten with nonfood leaves. The monkeys spent 46% of their feeding time on young leaves, 38% on seeds, 12% on whole fruits, 2.0% on flowers, 1.0% on bark, and 1.2% on pith. They spent more time feeding on seeds and whole fruit when fruit availability was high and fed on young leaves of Spatholobus macropterus (liana, Leguminosae) as fallback foods. This species was by far the most important food, constituting 27.9% of the total feeding time, and the feeding time on this species negatively correlated with fruit availability. Consumed leaves contained more protein than nonconsumed leaves, and variation in time spent feeding on different leaves was explained by their abundance. These results suggest that red leaf monkeys show essentially the same response to the supra-annual increase in fruit availability as sympatric monogastric primates, increasing their seed and whole-fruit consumption. However, they depended more on young leaves, in particular Spatholobus macropterus, as fallback foods during fruit-scarce periods than did gibbons or orangutans. Their selection of fallback food appeared to be due to both nutrition and abundance.     

Seasonally Consistent Small Home Range and Long Ranging Distance in <Emphasis Type="Italic">Presbytis rubicunda</Emphasis> in Danum Valley,Borneo

Seasonal fluctuation in food availability is a universal problem for wild animals. One common response to dietary changes is to modify ranging patterns. We studied the ranging pattern of one group (8–12 individuals) of red leaf monkeys (Presbytis rubicunda) in the lowland dipterocarp forest of Danum Valley, Borneo from December 2006 to December 2008. The seasonal availability of fruits varies significantly in this forest because of mast fruiting. We tested the hypothesis that changes in ranging pattern are linked with seasonal changes in diet in this species. We recorded activity, foods eaten, and location every 10 min from around 06:00 until 16:00 h, 5–10 days/mo. The home range size was 21.4 ha over the 25-mo study (95% kernel contour). There were no statistically significant relationships between feeding times on the four major nonexclusive dietary components (all species of seeds, all species of young leaves, young leaves of Spatholobus macropterus, and other species of young leaves) and either the home range (95% kernel contour) or the core area (50% kernel contour). The areas used in the seed-eating and non-seed-eating seasons overlapped to a large extent. The daily path length was 1160 ± 340 m (mean ± SD, range: 550–2140 m). Neither daily path length nor monthly mean travel rate was significantly related to feeding time on any of the four major dietary components. The group’s ranging patterns may be related to the unusual fallback strategy of this population, which depends on the young leaves of an abundant liana (S. macropterus), which are available in small patches. The monkeys need only a small home range because of the high abundance of these leaves. However, they range a relatively long distance because the patches of S. macropterus are easily depleted; thus the ranging distance does not decrease in non-seed-eating periods.     

Resource use by howler monkeys (Alouatta palliata) in the rain forest of Los Tuxtlas,Veracruz, Mexico

The feeding preferences of howler monkeys at their northernmost distribution in the Neotropics are reported for an annual cycle. A remarkable selectivity for 27 species representing 15 families was observed. The Moraceae and Lauraceae plant families were the most important in the diet. The howlers spent an almost equal proportion of their feeding time eating leaves and fruit, and displayed a marked preference for young leaves and mature fruit. The consumption of different plant parts was markedly seasonal and the howlers’ ranging behavior was closely associated with the availability of young leaves and mature fruit. Their home range was unusually large (ca. 60 ha) for howlers and the food species exploited occur at very low densities (93%, ≤ 4 ind/ha). They chose food items richer in protein and energy. Alkaloid compounds, present in some of the leaves, play a secondary role in their dietary selectivity.     

Dietary generalists and nutritional specialists: Feeding strategies of adult female blue monkeys (Cercopithecus mitis) in the Kakamega Forest,Kenya

Generalist primates eat many food types and shift their diet with changes in food availability. Variation in foods eaten may not, however, match variation in nutrient intake. We examined dietary variation in a generalist‐feeder, the blue monkey (Cercopithecus mitis), to see how dietary food intake related to variation in available food and nutrient intake. We used 371 all‐day focal follows from 24 adult females (three groups) in a wild rainforest population to quantify daily diet over 9 months. We measured food availability using vegetation surveys and phenology monitoring. We analyzed >700 food and fecal samples for macronutrient content. Subjects included 445 food items (species‐specific plant parts and insect morphotypes) in their diet. Variation in fruit consumption (percentage of diet and total kcal) tracked variation in availability, suggesting fruit was a preferred food type. Fruits also constituted the majority of the diet (by calories) and some fruit species were eaten more than expected based on relative availability. In contrast, few species of young leaves were eaten more than expected. Also, subjects ate fewer young leaves (based on calories consumed) when fruit or young leaves were more available, suggesting that young leaves served as fallback foods. Despite the broad range of foods in the diet, group differences in fiber digestibility, and variation that reflected food availability, subjects and groups converged on similar nutrient intakes (grand mean ± SD: 637.1 ± 104.7 kcal overall energy intake, 293.3 ± 46.9 kcal nonstructural carbohydrate, 147.8 ± 72.4 kcal lipid, 107.8 ± 12.9 kcal available protein, and 88.1 ± 17.5 kcal structural carbohydrate; N = 24 subjects). Thus, blue monkeys appear to be food composition generalists and nutrient intake specialists, using flexible feeding strategies to regulate nutrient intake. Findings highlight the importance of simultaneously examining dietary composition at both levels of foods and nutrients to understand primate feeding ecology.     

Monthly and diurnal variations in food choice byMacaca fuscata yakui during the major fruiting season at Yakushima Island, Japan

An ecological survey was conducted on two groups of wild Japanese macaques (Macaca fuscata yakui) inhabiting the warm-temperate, broad-leaved forest of Yakushima Island. The survey was designed to determine and explain monthly and diurnal variations in both duration of feeding and food choice, and to explain these variations from a nutritional perspective. Feeding activity increased during the hour before sunset, while leaf eating in particular tended to be observed later in the day throughout the study period. A diverse and unstable diet promoted monthly differences in fat and protein consumption. The mean lipid and calorific content of the food and the rate of protein intake were high in early autumn.Ficus fruits were not selected when unripeArdisia sieboldii fruits were available, but were an important food resource in a general context. Differences in nutritional intake at different times of the day were determined by the combination of species eaten although no single species was preferred at a particular time. Similarities with experimental results in laboratory animals suggest that a physiological, rather than a behavioural, response was regulating nutritional intake. A high consumption of proteins before rest might produce satiety in the macaques and give them the opportunity to digest and absorb complicated or toxic metabolites slowly during the night.     

Diet and Feeding Behavior of <Emphasis Type="Italic">Leontopithecus chrysomelas</Emphasis> (Callitrichidae) in Degraded Areas of the Atlantic Forest of South-Bahia,Brazil

Habitat disturbance alters plant diversity and food resource availability, affecting the ecology, and ultimately the survival and reproduction, of species depending on those plants. Studies in degraded areas serve to improve our understanding of the consequences of habitat modification for endangered species and to guide conservation actions. We studied diet composition, monthly variation in feeding behavior and fruit feeding time, and dietary diversity in two golden-headed lion tamarin (Leontopithecus chrysomelas) groups ranging in a degraded area of the Atlantic Forest in South-Bahia, Brazil, over a 12-mo period. We recorded feeding behavior and food items consumed through continuous observations and focal animal sampling, and performed dietary analyses on samples from consumed fruits. Substrate manipulation to search for animal prey was the feeding activity most frequently observed, followed by fruit consumption. We observed nectar drinking and exudate feeding at low frequencies from April through July. Bromeliads were the principal foraging substrate. We observed the use of 114 plant species, confirming the large dietary diversity reported for the species. Individual trees from the family Melastomataceae, common in degraded forests, accounted for the highest visiting frequencies (40%). Fruit availability was the main factor explaining variation in monthly fruit feeding time, despite the absence of climatic seasonality. Nutritional or energetic characteristics did not affect fruit choice. Differences in floristic composition appear to be a major determinant of the species’ diet in different study areas. Regional forest restoration programs should consider including advanced forest species, to improve both forest quality and animal mobility between fragments.     

Seasonal variation in activity and diet in a small-bodied folivorous primate,Hapalemur griseus,in southeastern Madagascar

How small-bodied (500–1,200 g) folivorous prosimian primates cope with large amounts of foliage in their diet seasonally has yet to be determined for many species such as Hapalemur griseus, which specializes on bamboo. To address this issue, we present results on seasonal variation in activity and diet from a wild group of H. griseus in southeastern Madagascar. Throughout the study (which was conducted from July–November 1994 and July 1995–February 1996), H. griseus primarily fed on new growth from three species of bamboo: two species of liana bamboo and Cephalostachyum perrieri. Bamboo species were used in different ways seasonally; liana bamboo was consumed more during the dry, cool season, and C. perrieri was eaten more often during the wet, warm season. H. griseus also spent more of their time feeding and traveling than nocturnal folivores of similar body size during the dry season. During the warm wet season, H. griseus decreased the amount of time spent feeding and traveling and rested more often. We hypothesize that seasonal changes in activity may be primarily related to the distribution and availability of food sources and/or reproductive cycles. Am. J. Primatol. 43:211–223, 1997. © 1997 Wiley-Liss, Inc.     

Dental topography and diets of platyrrhine primates

Abstract

More than half a century ago, Percy Butler touted the importance of analyzing teeth to understand their function in an evolutionary context. There have been many advances in the study of dental functional morphology since that time. Here we review the various approaches to characterizing and comparing occlusal form that have been developed, especially dental topographic analysis. We also report on a new study of dental topography of platyrrhine primates (n = 341 individuals representing 16 species) with known differences in both dietary preferences and other food items eaten. Results indicate frugivores, gummivores, folivores, and seed eaters each have a unique combination of slope, relief, angularity, sharpness, and occlusal orientation patch size and count values. Likewise, among frugivores, those that supplement their diets with hard objects, insects, leaves, and seeds, also each have a distinctive suite of topographic features. We conclude that both primary and secondary diet choices select for occlusal form, and that functional morphology more reflects the types of foods and mechanical challenges they pose rather than the frequencies in which they are eaten.