Diet of samango monkeys (Cercopithecus mitis erythrarchus) in the Cape Vidal dune forest, South Africa

The samango monkey ( Cercopithecus mitis erythrarchus Peters, 1852) is the southernmost representative of the widely-distributed polytypic Cercopithecus mitis species-group. At Cape Vidal (28 S) climatic seasonality causes significant seasonal fluctutation in food abundance. There are, however, no congeneric competitors, and few arboreal frugivores (birds, bats). In spite of seasonality of food abundance at Cape Vidal, samango monkeys maintain a high quality diet, dominated by fruit (51.7%), throughout the year. To a large extent this is made possible by their broad dietary tolerances and the effect of competitive release on food choice. Seasonal insect abundance does, however, place serious constraints on the availability of readily-digestible protein and the acquisition of protein-rich foods must be seen as the critically limiting factor in the dietary behaviour of the samango monkey. Adaptation of gut morphology and symbiotic microflora permit samangos to supplement the diet with large amounts of protein-rich foliar and floral items. Where necessary, even large quantities of less palatable items, such as unripe fruits and mature leaves, may be ingested. Although insects form a small part of the diet a larger variety, than used by equatorial C. mitis populations, are included in the diet. Given that there are no congeneric competitors, nor are the monkeys particularly food stressed, I suggest that the diet of the samango monkey at Cape Vidal most closely reflects the intrinsic food choices of the C. mitis species-group.     

Diet and feeding behaviour of samango monkeys (Cercopithecus mitis labiatus) in Ngoye Forest, South Africa

The samango monkey occurs at the southern limit of the range of Cercopithecus mitis. Greater climatic seasonality at this latitude results in more predictable fruiting patterns. In addition, there are no diurnal sympatric primate frugivores. Under these conditions, the diet and feeding strategies of samango monkeys would be expected to differ notably from those of central or east African C. mitis subspecies. Contrary to these expectations, the preliminary observations reported here indicate that diets of samango and blue monkeys differ only superficially in the proportions of items eaten. Similarities in feeding behaviour are especially marked during the dry season period when fruit is not abundant. Both samango and blue monkeys tend to be less selective in their choice of food species and to eat available food species regardless of their energy content; a shift toward less nutritious items such as leaves is also noted. Feeding behaviour during the summer wet season is characterized by the selection of fruits with high-energy values. A high proportion of visits by the monkeys to areas of greater food availability suggests a concentration of feeding effort in food patches and the selection of higher energy food species within patches.     

Seasonal variation in the behavioural ecology of samango monkeys (Cercopithecus albogularis schwarzi) in a southern latitude montane environment

Samango monkeys (Cercopithecus albogularis schwarzi) in the Soutpansberg Mountains, South Africa, experience a highly seasonal climate, with relatively cold, dry winters. They must show behavioural flexibility to survive these difficult conditions near the southern limit of the species’ distribution and maintain the minimum nutritional intake they require. Through environmental monitoring and behavioural observations of a habituated group of samango monkeys, we explored how they adapted to the highly seasonal climate they experienced in the mountains. Our results indicated that the monkeys varied their foraging behaviours to account for changes in climate and daylight availability. The samangos increased their food intake in colder months, specifically leaves, likely due to an increased need for calories during winter to maintain body temperature. Samango monkeys have anatomical and physiological adaptations for digesting leaves, and these are likely important in explaining their ability to adapt to the broad range of climatic conditions they experience.

     

Gut microflora of vervet and samango monkeys in relation to diet

The microflora in the gastrointestinal tracts of wild vervet and samango monkeys (Cercopithecus aethiops and C. mitis, respectively) were studied, using fermentation acid analysis, electron microscopy, and culturing methods. The diets of the two species of monkey differ considerably, with that of the samango including a greater proportion of cellulose-rich leaf material, and this is reflected in the microflora. Volatile fatty acid measurements along the gut of both species showed that these end products of bacterial metabolism were concentrated in the cecum and colon. Electron microscopy indicated that morphologically similar bacteria were present in the cecum and colon of both species, but the samango possessed a distinct stomach microflora. Bacteria in the lumina of the four main regions of the gut of the monkeys (stomach, small intestine, cecum, and colon) were plated on a number of anaerobic media (Mann, Rogosa, and Sharp; clostridial basal; and complex media). The cecum and colon were found to contain higher numbers of microbes per gram (wet weight) of gut content than the stomach and small intestine. Microbial isolates were able to catabolize carboxymethyl cellulose and other polymers. This may aid the monkeys, particularly samangos, in the digestion of fibrous dietary components such as leaves.     

The effects of water on patch use by two Simpson Desert granivores (Corvus coronoides and Pseudomys hermannsburgensis)

Abstract Water loss while foraging may affect the overall value of food to desert animals. When water is scarce, foragers may alter activity and shun certain types of food due to elevated water loss. When water is abundant, foragers can exploit food patches more thoroughly and remain active over a broader range of ambient conditions. In short, food and water may be complementary resources. The presence of water raises the marginal value of food, particularly those foods low in water content. We tested for the complementarity of food and water to foragers at a sand dune site in the Simpson Desert of arid Australia. To do so, we quantified patch exploitation of foragers in the presence or absence of bowls filled with water. In order to quantify patch use, we provisioned feeding trays with granulated peanuts mixed into a sand substrate. In these trays we measured giving-up densities (GUD; the amount of food left in a tray after a foraging bout) of diurnal (mostly Australian ravens, Corvus coronoides) and nocturnal foragers (mostly sandy inland mouse, Pseudomys hermannsburgensis). The presence of water affected the GUD of ravens but not of rodents. For the ravens, GUD dropped about 50% in response to added water. For ravens, water and food are strongly complementary. In addition, ravens had lower GUD in the open than the bush microhabitat, and lower GUD at the bottom than the tops of sand dunes.     

Gut microflora of vervet and samango monkeys in relation to diet.

The microflora in the gastrointestinal tracts of wild vervet and samango monkeys (Cercopithecus aethiops and C. mitis, respectively) were studied, using fermentation acid analysis, electron microscopy, and culturing methods. The diets of the two species of monkey differ considerably, with that of the samango including a greater proportion of cellulose-rich leaf material, and this is reflected in the microflora. Volatile fatty acid measurements along the gut of both species showed that these end products of bacterial metabolism were concentrated in the cecum and colon. Electron microscopy indicated that morphologically similar bacteria were present in the cecum and colon of both species, but the samango possessed a distinct stomach microflora. Bacteria in the lumina of the four main regions of the gut of the monkeys (stomach, small intestine, cecum, and colon) were plated on a number of anaerobic media (Mann, Rogosa, and Sharp; clostridial basal; and complex media). The cecum and colon were found to contain higher numbers of microbes per gram (wet weight) of gut content than the stomach and small intestine. Microbial isolates were able to catabolize carboxymethyl cellulose and other polymers. This may aid the monkeys, particularly samangos, in the digestion of fibrous dietary components such as leaves.     

Patch use behaviour of Elephantulus myurus and Micaelamys namaquensis: the role of diet,foraging substrates and escape substrates

We investigated the role of diet and substrate features in the coexistence and habitat affinities of the rock elephant shrew, Elephantulus myurus, and the Namaqua mouse, Micaelamys namaquensis. We measured giving‐up densities at experimental food patches that varied in foraging substrate, escape substrate surrounding the food patch and food type. In terms of food consumption, E. myurus favoured pebble (63% total harvest) over sand and sawdust, whereas M. namaquensis favoured foraging in sand (48% total harvest) over sawdust (29%) and pebbles (23%). Mealworms comprised most of E. myurus’s harvest, and M. namaquensis harvested seeds the most, followed by alfalfa and mealworms. In terms of escape substrates, M. namaquensis had significantly higher GUDs when the food patch was surrounded by tussocks of sedge (average 28.11 seeds/patch) than rock surfaces (17.41) or by bush/crevice (14.36). In conjunction with morphologic adaptations, E. myurus detects and recovers food using its snout and long tongue, and M. namaquensis digs and handles foods with its forepaws. The different foraging preferences of E. myurus and M. namaquensis suggest that the interaction of substrates with food types characterize their niches and promote coexistence. Elephantulus myurus travelled greater distances, whereas M. namaquensis was selective for microhabitats offering refuge or traction.     

Habitat selection of an endangered primate,the samango monkey (Cercopithecus albogularis schwarzi): Integrating scales to prioritize habitat for wildlife management

AimAs habitat loss continues to accelerate with global human population growth, identifying landscape characteristics that influence species occurrence is a key conservation priority in order to prevent global biodiversity loss. In South Africa, the arboreal samango monkey (Cercopithecus albogularis sp.) is threatened due to loss and fragmentation of the indigenous forests it inhabits. The aim of this study was to determine the habitat preferences of the samango monkey at different spatial scales, and to identify key conservation areas to inform management plans for this species.LocationThis study was carried out in the western Soutpansberg Mountains, which represents the northernmost population of samango monkeys within South Africa, and the only endangered subspecies (C. a. schwarzi).MethodsWe used sequentially collected GPS points from two samango monkey groups followed between 2012 and 2017 to quantify the used and available habitat for this species within the western Soutpansberg Mountains. We developed 2nd‐order (selection of ranging area), 3rd‐order (selection within range), and 4th‐order (feeding site selection) resource selection functions (RSFs) to identify important habitat features at each scale. Through scale integration, we identified three key conservation areas for samango monkeys across Limpopo Province, South Africa.ResultsHabitat productivity was the most important landscape variable predicting probability of use at each order of selection, indicating the dependence of these arboreal primates on tall‐canopy indigenous forests. Critical habitat across Limpopo was highly fragmented, meaning complete isolation between subpopulations is likely.Main conclusionsUnderstanding the habitat characteristics that influence samango monkey distribution across South Africa is crucial for prioritizing critical habitat for this species. Our results indicated that large, contiguous patches of tall‐canopy indigenous forest are fundamental to samango monkey persistence. As such, protected area expansion of large forest patches and creation of forest corridors are identified as key conservation interventions for this species.     

Samango Monkeys (<Emphasis Type="Italic">Cercopithecus albogularis labiatus</Emphasis>) Manage Risk in a Highly Seasonal,Human-Modified Landscape in Amathole Mountains,South Africa

Wild species use habitats that vary in risk across space and time. This risk can derive from natural predators and also from direct and indirect human pressures. A starving forager will often take risks that a less hungry forager would not. At a highly seasonal and human-modified site, we predicted that arboreal samango monkeys (Cercopithecus albogularis labiatus) would show highly flexible, responsive, risk-sensitive foraging. We first determined how monkeys use horizontal and vertical space across seasons to evaluate if high-risk decisions (use of gardens and ground) changed with season, a proxy for starvation risk. Then, during a subsequent winter, we offered equal feeding opportunities (in the form of high-value, raw peanuts) in both gardens and forest to see if this short-term change in food availability and starvation risk affected monkeys’ foraging decisions. We found that during the food-scarce winter, monkeys foraged outside indigenous forest and in gardens, where they fed on exotic species, especially fallen acorns (Quercus spp.), despite potential threats from humans. Nevertheless, and as predicted, when given the choice of foraging on high-value foods in gardens vs. forest during our artificial foraging experiment, monkeys showed a preference for a safer forest habitat. Our experiment also indicated monkeys’ sensitivity to risk in the lower vertical strata of both habitats, despite their previous extensive use of the ground. Our findings support one of the central tenets of optimal foraging theory: that risk of starvation and sensitivity to the variation in food availability can be as important drivers of behavior as risk of predation.     

Food choice in the laboratory pigeon

Although food reward plays a large role in learning and behavioral experiments, there have been few studies examining the most motivating food reward for pigeons. Brown (1969) found that pigeons had a tendency to prefer peas, while Killeen et al. (1993) found pigeons to prefer peas and popcorn in Experiment 1A. We looked to further explore these options as well as expand upon the types of foods examined beyond mainly grains and seeds. Pigeons were presented with six novel foods (granulated peanuts, popping corn, freeze-dried mealworms, bread crumbs, split peas, and sunflower hearts) allocated into two sets of three food items. Once the most consumed food from each food set was determined, they were pooled together with sorghum seeds (a familiar food) to form a third set. Sunflower hearts were the most consumed of all the food items, followed by corn and granulated peanuts. We discuss the potential factors mediating consumption choice, including nutritional profile and food particle size.     

Foraging and community consequences of seed size for coexisting Negev Desert granivores

We examined the effects of seed size on patch use and diet selection for three co-existing Negev Desert granivores: Allenby's gerbil ( Gerbillus allenbyi ), greater Egyptian sand gerbil ( Gerbillus pyramidum ), and crested lark ( Galerida cristata ). We manipulated size and spatial distribution of seeds in experimental food patches and quantified foraging behavior by measuring giving-up densities (GUDs: the amount of food remaining in a resource patch following exploitation by a forager). In one experiment, we presented small (<1.4 mm in diameter cracked wheat), medium (2.0–3.3 mm), and large (>3.4 mm) seeds in separate trays; in a second, we presented small and medium seeds separately and mixed together. Gerbils had a higher handling time efficiency on smaller seeds, but a much higher encounter probability on larger seeds (20 times higher on large than medium seeds, and 2–5 times higher on medium than small seeds). This led gerbils to have significantly lower GUDs on larger seeds than smaller seeds and to harvest a higher proportion of the larger seeds. When presented with rich and poor patches, G. allenbyi tended to equalize GUDs in both patches, indicating a quitting harvest rate rule for patch exploitation. In contrast, larks appeared to use a fixed time rule for patch exploitation. For larks, seed size did not influence encounter probabilities, and they showed no seed-size selectivity. Still, larks had higher handling efficiencies on smaller than larger seeds, and consequently had a significantly lower GUD on small than medium seeds. Despite large differences between the gerbils and larks in their foraging, our results do not support species coexistence via seed-size partitioning: the larks had much higher GUDs than the gerbils on all seed sizes. Nonetheless, seed size, seed abundance, seed distribution and the animal's patch use behavior all played major roles in determining gerbils' and larks' diet selectivities and GUDs.     

High flexibility in diet and ranging patterns in two golden monkey (Cercopithecus mitis kandti) populations in Rwanda

Many primates exhibit behavioral flexibility which allows them to adapt to environmental change and different habitat types. The golden monkey (Cercopithecus mitis kandti) is a little-studied endangered primate subspecies endemic to the Virunga massif and the Gishwati forest in central Africa. In the Virunga massif, golden monkeys are mainly found in the bamboo forest, while in the Gishwati forest they live in mixed tropical montane forest. Here we describe and compare the diet of golden monkeys in both fragments. Over 24 consecutive months from January 2017 we used scan sampling to record feeding and ranging behavior of two Virunga groups and one Gishwati group totaling ca. 240 individuals. We also examined the phenology of bamboo and fruit trees, key seasonal food plant species for the monkeys. Golden monkeys fed on more than 100 plant species. The Virunga groups were mostly folivorous (between 72.8% and 87.16% of the diet) and fed mostly on young bamboo leaves and bamboo shoots, while 48.69% of the diet of the Gishwati group consisted of fruit from 22 different tree and shrub species. Bamboo shoots and fruit are seasonally available foods and were consumed regularly throughout the period when they were available. Despite being the smallest of the three study groups, the Gishwati group had a larger home range area (150.07 ha) compared to both Virunga groups (25.24 and 91.3 ha), likely driven by the differences in availability and distribution of fruit and bamboo in the habitats. Like other blue monkey subspecies, golden monkeys appear to have a flexible dietary strategy enabling them to adjust diet and ranging behavior to local habitats and available food resources. Additional studies and continuing conservation efforts are needed to better understand how variation in feeding and ranging ecology affects reproduction, population growth, and carrying capacity.     

Effect of bone strain on cortical bone structure in macaques (Macaca mulatta)

It has recently been shown that the consistency of food significantly affects levels of bone strain in the mandible during mastication (Hylander, '79a). Mandibular bone histology was examined to test the effects of a diet of hard food compared to a diet of soft food in two group of monkeys. One group of rhesus macaques (Macaca mulatta) was fed a diet of commercially prepared hard biscuits. The second group was fed a soft diet the consistency of fudge. Both diets were nutritionally adequate for normal growth and development. As a control for other factors influencing cortical bone structure, fibular morphology was also examined. At the end of the test period, mandibular and fibular tissue samples from the two groups were prepared to determine the amount of secondary Haversian bone present. Mandibular depth at M₂ and fibular anteroposterior diameter were also measured and compared between the two dietary groups. The soft-diet monkeys showed low levels of remodeling in their mandibles. There were large patches of unremodeled bone and resorption spaces were common. The hard-diet monkeys exhibited more extensive evidence of secondary Haversian remodeling in their mandibles. The hard-diet monkeys also had deeper mandibles. In contrast, the fibulae from the two groups had similar mean diameters and showed comparable levels of secondary remodeling. We infer that the higher mandibular bone remodeling levels in the hard-diet monkeys represent an adaptive response to remove and replace fatigued mandibular bone due to higher stress levels associated with the ingestion and mastication of hard foods. We also infer that greater depth of the mandible at M₂ found in the harddiet group represents an adaptive response to higher stress levels associated with the ingestion and mastication of hard foods.     

Patch use by Dipodomys deserti (Rodentia: Heteromyidae): profitability,preference, and depletion dynamics

Summary Granivorous desert rodents of the family Heteromyidae forage nonrandomly among microhabitats that vary in substrate, seed densities, and seed species composition. To explore the hypothesis that microhabitat use is sensitive to seed patch profitability, we quantified effects of seed size (1.96 vs. 5.21 mg/seed) and density (0.4–10.6 seeds/cm²) on Dipodomys deserti harvest rates, which is a measure of profitability when expressed as mg of seed taken per min. By manipulating seed density, we created large-seed and small-seed patches of known relative profitability and exposed D. deserti individuals to pairwise choices in the laboratory and field. We used three treatment classes: 1) large-seed patches that were more profitable than small-seed patches (equal seed densities); 2) large-seed and small-seed patches that were equally profitable (small-seed densities somewhat higher): and 3) large-seed patches that were less profitable than small-seed patches (small-seed densities much higher). Harvest rate increased nearly linearly with seed density, and profitability of large-seed patches was greater than small-seed patches of the same density. Cumulative harvest from a patch increased linearly with residence time up to a plateau; this gain curve indicates that animals move systematically within patches and hence avoid resampling already depleted areas. In the laboratory, animals visited small-seed patches first more often and visited them more frequently when they were more profitable than large-seed patches. When large-seed patches were of greater or equal profitability, large-seed patches were preferred by both measures. The expressed preference for large-seed patches, when animals were presented with equally profitable patches, suggests an underlying preference for large seeds. In the field, animals depleted all patches to a constant low profitability, in accord with qualitative predictions of optimal patch use models. These results suggest that patch preferences by D. deserti are affected by the economics of seed harvest.     

川金丝猴食谱的地域性差异比较

对不同地区川金丝猴食物组成的比较有助于了解其对不同生境食物供应的适应性。本研究通过对陕西川金丝猴猴群食谱的长期记录,并汇集了国内对四川-甘肃和湖北的川金丝猴食性研究结果,集成了这三个地理种群川金丝猴各自的地域性食谱,共计有136 种植物(隶属35 科)被该物种作为采食对象。对来自这三个不同区域(陕西、四川-甘肃、湖北)的川金丝猴食谱组成的比较,发现有近半数的植物是三个地理种群共同的采食对象,但其食谱组成差异明显。这可能源于各地植物本身的多样性差异,及不同地理种群对各种食物采食偏好的不同所致。对其相关聚类分析结果显示,陕西和湖北的猴群在食谱组成上相近,但四川-甘肃的猴群与前两个地区猴群的食谱组成差异极大。然而湖北和四川-甘肃种群在食物的选择上采用了近乎相同的偏好倾向,而陕西的猴群与它们明显不同。我们初步分析认为造成食谱组成和采食偏好差异的原因可能是各地理种群活动地海拔带重叠度不同、森林类型不同、它们在不同林型中活动的时间分配不一。很明显,就我们目前所掌握的有关川金丝猴食谱组成来看,该物种不应该仅仅被认为是一个叶食性灵长类动物,而应该是一个泛化采食者。     

Food Preferences Among Captive Western Gorillas (Gorilla gorilla gorilla) and Chimpanzees (Pan troglodytes)

I used a zoological park setting to address food preferences among gorillas (Gorilla gorilla gorill) and chimpanzees (Pan troglodytes). Gorillas and chimpanzees are different sizes, and consequently, have been traditionally viewed as ecologically distinct. Sympatric western gorillas and chimpanzees have proved difficult to study in the wild. Limited field data have provided conflicting information about whether gorillas are fundamentally different from chimpanzees in diet and behavior. Fruit eating shapes the behavior of most apes, but it is unclear whether the large-bodied gorillas are an exception to this rule, specifically whether they are less selective and more opportunistic fruit eaters than chimpanzees are. My research provides experimental observational data to complement field data and to better characterize the diets and food preferences of the African apes. During laboratory research at the San Francisco Zoological Gardens, I examined individual and specific differences in food preferences of captive gorillas and chimpanzees via experimental paired-choice food trials with foods that varied in nutritional content. During the study, I offered 2500 paired-food choices to 6 individual gorillas and 2000 additional pairs to them as a group. I also proffered 600 food pairs to 4 individual chimpanzees. Despite expectations of the implications of body size differences for diet, gorillas and chimpanzees exhibited similar food preferences. Both species preferred foods high in non-starch sugars and sugar-to-fiber ratios, and low in total dietary fiber. Neither species avoided foods containing tannins. These data support other suggestions of African apes sharing a frugivorous adaptation.     

Food preference of young rhesus monkeys fed marginally zinc deficient diets

Zinc deprivation has been shown to produce hypogeusia in rhesus monkeys but the possible consequences of altered taste sensitivity for food preference and selection is not known. We studied 13 rhesus monkeys (2.5 to 3 years of age) for food preference in a structured choice situation. These animals were fed two levels of dietary zinc: marginally zinc deprived (fed 4 μg zinc/g diet from conception and throughout development;N=6), or control (fed a 100 μg zinc/g diet throughout the study;N=7). Preference for familiar vs unfamiliar food items, order of food preferences, persistence in retrieval of preferred and nonpreferred foods, and preference under four deprivation periods were examined. Animals were offered a choice of two food items, both containing minimal zinc levels, and food choice and latency of choice were measured. Results indicate that animals fed the marginal zinc diets had reduced preference for unfamiliar foods relative to controls and different patterns of food preference. These results may be relevant to maintenance of appropriate food selection in marginally zinc deprived populations.     

Parental Self-Feeding Effects on Parental Care Levels and Time Allocation in Palestine Sunbirds

The trade-off between parents feeding themselves and their young is an important life history problem that can be considered in terms of optimal behavioral strategies. Recent studies on birds have tested how parents allocate the food between themselves and their young. Until now the effect of food consumption by parent birds on their food delivery to their young as well as other parental activities has rarely been studied. I have previously shown that parent Palestine sunbirds (Nectarinia osea) will consume nectar and liquidized arthropods from artificial feeders. However, they will only feed their young with whole arthropods. This provided a unique opportunity to experimentally manipulate the food eaten by parents independent of that fed to their offspring. Here, I hypothesized that parents invest in their current young according to the quality of food that they themselves consume. Breeding pairs with two or three nestlings were provided with feeders containing water (control), sucrose solution (0.75 mol) or liquidized mealworms mixed with sucrose solution (0.75 mol). As food quality in feeders increased (from water up to liquidized mealworms mixed with sucrose solution): 1) Parents (especially females) increased their food delivery of whole arthropod prey to their young. 2) Only males increased their nest guarding effort. Nestling food intake and growth rate increased with increasing food quality of parents and decreasing brood size. These results imply that increasing the nutrient content of foods consumed by parent sunbirds allow them to increase the rate at which other foods are delivered to their young and to increase the time spent on other parental care activities.     

Patch area, substrate depth, and richness affect giving-up densities: a test with mourning doves and cottontail rabbits

We compared the foraging behavior of mourning doves Zenaida macroura and cottontail rabbits Sylvilagus floridanus in patches that varied in initial food abundance, surface area and substrate depth. We measured giving‐up densities (GUD), food harvest and proportion of food harvested to investigate their ability to respond to characteristics of resource patches. GUDs have been analyzed in three ways: grams of per patch, grams per unit surface area (GUD_AREA), and grams per unit volume of sand (GUD_VOL). Mourning doves and cottontails exhibited similar responses to resource density and sand depth. Both foragers detected and responded to variation in initial food abundance. The proportion of food harvested from a patch increased from 40.7, 43.8 to 48.3% (for the doves) and 34.9, 35.8 to 38.4% (for the rabbits) in patches of low, medium and high initial food abundance, respectively. Deeper substrates reduced the foragers’ encounter probability with food, decreased patch quality and resulted in higher GUDs (60% higher in the deepest relative to shallowest substrate) and lower harvests. A significant interaction between initial food abundance and substrate depth showed that both species were willing to dig deeper in patches with higher resource density. Patch size (surface area) had no effect on food harvest or the proportion of food harvested. Consequently, GUD_AREA and GUD_VOL increased in patches with a smaller surface area. Smaller patches appeared to hamper the dove's and cottontail's movement across the surface. Our results revealed that mourning doves and cottontails forage under imperfect information. Both species were able to respond to patch properties by biasing their feeding efforts toward rich and easy opportunities, however, mourning doves were more efficient at food harvesting. The interaction of patch area, volume and food abundance directly influenced food harvest. Such resource characters occur under natural situations where food varies in abundance, area of distribution, and accessibility.     

Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima

The feeding behavior of the southern subspecies of Japanese macaque (Macaca fuscata yakui) was studied over a period of 18 months in warm temperate broad-leaved forest on the island of Yakushima, Japan. Focal animal data were collected for the eight adults in the troop. Over a full annual cycle, 35.0% of foraging on identified foods was on leaves and shoots, 30.2% on fleshy fruit, 13.2% on seeds, and 5.5% on flowers. Invertebrates and other animal matter accounted for 10.3% of foraging and fungi for 4.6%. There was marked seasonal variation in the use of different food categories, and seeds, leaves, fleshy fruit, and animal matter were each predominant at different times of year. There was also evidence of annual cyclicity in patterns of foraging on all major food types. The monkeys spent less time moving and ate a greater variety of foods when feeding on leaves than when feeding on fruit and seeds, or on insects. Time spent foraging was positively correlated with diversity of the diet, but there was no simple relationship between time spent foraging and the predominant food type. This suggests that a wide variety of foods takes longer to harvest and process, irrespective of the food type. The diet of the study troop was flexible and could not be assigned to a simple dietary category, such as frugivorous or folivorous. If these data are representative of the subspecies, the Yakushima macaque is much more of a dietary generalist than most primates for which there are adequate data. Am. J. Primatol. 43:305–322, 1997. © 1997 Wiley-Liss, Inc.