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.     

Time Allocation Patterns of Lowland Woolly Monkeys (Lagothrix lagotricha poeppigii) in a Neotropical Terra Firma Forest

We investigated the time allocation decisions of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a terra firma forest in eastern Ecuador where they occur sympatrically with 9 other primate species. Woolly monkeys spent considerable amounts of time searching for and attempting to procure animal prey—roughly as much time as they spent consuming plant material: ripe fruits, leaves, and flowers. The amount of time spent foraging for animal prey is positively related to the habitat-wide availability of ripe fruits (the predominant component of the woolly monkey diet), and negatively related to both ambient temperature and the abundance of potential prey items in the habitat. Time spent resting showed exactly the opposite pattern with respect to these ecological variables. These results suggest that woolly monkeys follow an energy-maximizing strategy of food acquisition during times of fruit abundance—focusing on animal foods and perhaps laying down fat reserves to utilize when ecological conditions worsen—and follow an energy-minimizing strategy when fruit resources are scarce. Such a strong and seasonal commitment to animal prey foraging is unique among the ateline primates and is not ubiquitous even among lowland woolly monkeys. We suggest that this foraging strategy, and the greater intragroup cohesion that characterizes some populations of Lagothrix, are both opportunistic responses to regional differences in habitat quality. Identifying and accounting for such intraspecific variation should be a goal of any analysis of comparative socioecology.     

Responses of squirrel monkeys to seasonal changes in food availability in an eastern Amazonian forest

Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal shifts in fruit availability. In this study, I examined seasonal changes in diet and foraging behaviors of two groups of squirrel monkeys (Saimiri sciureus), studied for 12 months in Eastern Brazilian Amazonia, an area characterized by seasonal rainfall. Squirrel monkeys were primarily insectivorous (79% of feeding and foraging time), with fruit consumption highest during the rainy season. Although monkeys fed from 68 plant species, fruit of Attalea maripa palms accounted for 28% of annual fruit-feeding records. Dietary shifts in the dry season were correlated with a decline in ripe A. maripa fruits. Despite pronounced seasonal variation in rainfall and fruit abundance, foraging efficiency, travel time, and distance traveled remained stable between seasons. Instead, squirrel monkeys at this Eastern Amazonian site primarily dealt with the seasonal decline in fruit by showing dietary flexibility. Consumption of insects, flowers, and exudates increased during the dry season. In particular, their foraging behavior at this time strongly resembled that of tamarins (Saguinus sp.) and consisted of heavy use of seed-pod exudates and specialized foraging on large-bodied orthopterans near the forest floor. Comparisons with squirrel monkeys at other locations indicate that, across their geographic range, Saimiri use a variety of behavioral tactics during reduced periods of fruit availability.     

Seasonal changes in food resource distribution and feeding sites selected by Japanese macaques on Koshima Islet,Japan

Feeding sites of Japanese macaques (Macaca fuscata) change according to seasonal fluctuations in food resource distribution. To examine what characteristics of food items affect feeding site selection, I describe herein the seasonal changes in food items, feeding sites, and food resource distributions of this species. Feeding behavior of monkeys and their food resource distributions were investigated on Koshima Islet, southern Japan, for four study periods (i.e., seasons) in 2002. Monkeys showed large variations in their diet between seasons. To weigh the relative influence of the distribution and abundance of food items on feeding site selection in each season, multiple regression analyses were performed by 100 m × 100 m grid. In the analyses, feeding time was a dependent variable and the abundance of staple food items, for which feeding time was over 5% in each season, in each grid square was an independent variable. There was no correlation between the resource distribution of most food items and the distribution of feeding time by monkeys in each season. Monkeys spent more feeding time where multiple staple food items were available. Food items that affected feeding site selection by monkeys had the following three characteristics: (1) clumped distribution, (2) seasonal availability, and (3) fruit. This suggests that monkeys are likely to select feeding sites to consume food items whose availability is limited temporally and spatially, which may enable them to simultaneously use other widely distributed, abundant food items efficiently.     

Seasonal variation of diet and food availability in a group of Sichuan snub-nosed monkeys in Shennongjia Nature Reserve, China

We studied the diet and food availability of a group of Sichuan snub-nosed monkeys for 14 months (July 2003 to September 2004, except for February) in the Shennongjia Nature Reserve, China. This species is primarily a lichen eater, with lichens (Usneaceae) accounting for 43.28% of feeding records (n=3,452). Other food types in the diet were young leaves (28.71%), fruits or seeds (14.57%), buds (5.36%), mature leaves (3.51%), herbs (2.09%), bark (1.36%), and flowers (1.13%). The monkeys used 23 plant species. Their diet showed a complicated seasonal variation: the monthly diet varied from primarily lichens in November-April, to a mixture of leaves and lichens in May-July, to a mixture of fruits or seeds and lichens in August-October (the latter depended on annual fruit and seed availability). The proportion of fruits or seeds in the diet was negatively correlated with that of lichens, which suggests that the monkeys prefer fruits or seeds to lichens when all of these items are available. The fruit or seed availability varied greatly between the two study years. The proportion of lichens, young leaves, flowers, and fruits or seeds in the diet was positively associated with their availability. The monkeys appeared to be selective feeders. They preferred 10 tree species for plant parts, and nine tree species for lichens. The selection index of tree species for lichens was positively related to lichen coverage per branch on tree species, demonstrating that the monkeys preferred tree species with abundant lichens, as well as dead trees for lichens. The results suggest that dead-tree harvesting in the reserve could significantly reduce the quality of habitat for these monkeys, and should therefore be prohibited. Connus controversa, Cerasus discadenia, Salix willichiana, and Malus halliana should be conserved as top priority species because the monkeys preferred them for both their vegetative parts and the lichens that grow on them.     

Seasonal fluctuations of resource abundance and avian feeding guilds across forest–farmland boundaries in tropical Africa

Seasonal fluctuations in climatic factors are expected to increase in future decades. However, little is known about the response of tropical species communities to seasonal fluctuations in climate and resource availability, particularly across different habitat types. We examined the relationship between spatio‐temporal fluctuations in the abundance of fruits and invertebrates and two avian feeding guilds, i.e. frugivores and insectivores, in forest and farmland habitats in western Kenya. Fruits and invertebrates fluctuated substantially throughout the year, but seasonal fluctuations were asynchronous between the two habitat types. Species richness and total abundance of frugivores and insectivores also fluctuated strongly and were closely related to the abundance of their respective resources. Frugivore species richness fluctuated anti‐cyclical in forest and farmland habitats, suggesting that several frugivorous species tracked fruit resources across habitat boundaries. In contrast, insectivorous bird richness fluctuated synchronously in the two habitat types, suggesting a lack of local‐scale movements across habitat boundaries. We conclude that bird communities strongly respond to seasonal fluctuations in resource availability, but responses differ between feeding guilds. While frugivores seem to respond flexibly to seasonal fluctuations, for instance by tracking fruit resources across habitat boundaries, insectivorous birds appear to be more susceptible to the expected increase in seasonal fluctuations in resource availability.     

Fruit eating and seed dispersal by howling monkeys (Alouatta palliata) in the tropical rain forest of Los Tuxtlas,Mexico

The frugivory and ranging habits of howling monkeys living in the rain forest of Los Tuxtlas, Veracruz, Mexico, were studied for 5 consecutive years with the aim of investigating the role of seed dispersal agents played by the howling monkeys. The howling monkeys' consumption of fruit occupied half of their feeding time, and 80% of this time was spent feeding on mature fruit. Observations confirmed use of 19 tree species and a preference for a few species of Moraceae and Lauraceae. Fruit exploitation was very seasonal; only two species provided fruit year-round. Home range size was about 60 ha, and animals in the troop (N = 16) showed a day range of 10–893 m. Monthly collection of fecal samples during 2 years indicated that 90% of the seeds (N = 7,928) in the samples belonged to eight tree species and to one liana; the rest belonged to 15 unidentified species of vines. Germination success for the seeds in the feces was about 60% and for control seeds was 35%. Howling monkeys created diverse seed shadows in the vicinity of their leaf and fruit sources, and while they dispersed the seeds of some plant species, they also produced a great deal of fruit and seed waste for others.     

Ecological strategies of woolly monkeys (Lagothrix lagotricha) at Tinigua National Park,Colombia

Information on the use of space, activity patterns, diet, and social interactions were recorded for a group of woolly monkeys (Lagothrix lagotricha) during 13 months at Tinigua National Park, Macarena, Colombia. In this region, fruit abundance changes throughout the year with a peak during March–April (beginning of the rainy season) and less fruit during September-November (end of rainy season). Woolly monkeys spent most of their time in mature forest where fruit abundance is higher than in opendegraded or flooded forests. Changes in habitat used by monkeys were coupled with changes in fruit supply across vegetation types. On an annual basis, woolly monkeys spent 24% of point samples locomoting, 36% resting, 36% feeding, and 4% on other activities. However, these proportions varied across the year depending on fruit availability. Based on instantaneous samples, the diet consisted mostly of fruits (60%), arthropods (23%), vegetative parts and flowers (17%), and other items (1%). Non-lactating females and juveniles spent more time eating insects than adult males and lactating females; however, significant differences between classes were detected only during the period of fruit scarcity. These differences are probably due to the high extent to which non-lactating females and juveniles were excluded from fruiting trees by males. The high proportion of arthropods in their diet is unusual for primates with large body size and is a possible factor influencing group cohesiveness in woolly monkeys. © 1994 Wiley-Liss, Inc.     

Bats, flowers and fruit: evolutionary relationships in the Old World

Old World phytophagous bats (Megachiroptera: Pteropodidae) number 173 species of which 79% are Asian and 21% African. Bats arose, presumably monophyletically, in the early Tertiary, the Megachiroptera soon diverging from the Microchiroptera. By the Cretaceous-Tertiary boundary the major groups of modern angiosperms were present, some of these probably being pollinated nocturnally by large insects and non-flying mammals and others with seeds dispersed by terrestrial vertebrates. Early bats were perhaps initially attracted to such flowers and fruit by the insects found around them, later finding the plants themselves nutritious. Megabats today feed upon floral resources, fruit and leaves from a total of at least 188 plant genera in 64 families. They may effect both pollination and seed-dispersal, and both bat-flower and bat-fruit syndromes are commonly recognized. Individual species are generally catholic in their feeding, favoured food varying with locality and season. Depending upon roosting habits and season, megabats may travel considerable distances each night to feed and may undertake seasonal migrations. Their feeding in orchards may sometimes require their control, but the future of certain species is more seriously threatened by slaughter for food and particularly by habitat destruction.     

Reliance on Exotic Plants by Two Groups of Threatened Samango Monkeys, <Emphasis Type="Italic">Cercopithecus albogularis labiatus</Emphasis>, at Their Southern Range Limit

Understanding how threatened species adapt their behavior to landscapes shaped by humans is increasingly important to ensuring they persist in a changing world. Matrix habitats can be shared spaces where human and nonhuman primates coexist. We set out to determine how an endemic, threatened forest specialist, the frugivorous, arboreal samango monkey (Cercopithecus albogularis labiatus), has responded to a matrix habitat made up of residential gardens and commercial plantations in Eastern Cape province, South Africa. We followed two groups from dawn to dusk for a mean of 3 days/mo for 12 mo (February 1, 2011 to January 31, 2012) using scan sampling to collect data on their diet, activity, and ranging patterns. We used resource abundance transects to describe the groups’ home ranges and monitored tree phenology to calculate fruit and seed availability indices. Monkeys from both groups consumed large quantities of exotic plant species, accounting for >50% of their overall annual diet, with seeds of the invasive black wattle (Acacia mearnsii) the most commonly consumed exotic species followed by acorns of two oak species (Quercus robur and Q. palustris.). However, monkeys responded to the availability of indigenous rather than exotic fruits and seeds and increased their consumption of exotics when indigenous fruits were less available. Although monkeys spent less time moving when feeding on exotic species compared to indigenous species, eating exotics did not free up monkeys’ time to rest or socialize, as additional time was required to process exotic foods. To offset the possible negative consequences of the monkeys’ reliance on exotic seeds, including escalating conflict between monkeys and people in gardens, we suggest gradual removal of exotic plant species in the habitat and replacement with indigenous species as one mitigation strategy.     

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.     

Diet and nutrition in wild mongoose lemurs (Eulemur mongoz) and their implications for the evolution of female dominance and small group size in lemurs

Data collected on the feeding behavior, food intake, and chemical analyses of plant foods were used to document seasonal variation in diet and nutrition in Eulemur mongoz in northwestern Madagascar. E. mongoz conforms to the general Eulemur dietary pattern, with a predominantly frugivorous diet supplemented mainly by leaves, flowers, and nectar. Phytochemical analysis revealed high water contents in all the main plant foods; mature fruit and flowers contained the most water-soluble carbohydrates; immature leaves were richest in protein and essential amino acids; the limiting amino acids in all plant foods were methionine and cystine; ash (mineral) content was highest in petioles and mature leaves; crude lipid content was highest in seeds; and crude fiber content was indistinguishable between immature and mature fruit and leaves. High-fiber foods were eaten during both seasons; the wet season diet was dominated by high-energy foods (mature fruit, nectar, and seeds), while the dry season diet contained foods high in energy (mature fruit and flowers) and high in protein (immature leaves) and minerals (mature leaves and petioles). However, nutrient intake did not vary between seasons, implying that nutrient requirements are met throughout the year. These results suggest we draw more conservative conclusions when interpreting dietary variability in the absence of chemical analysis, and also draw into question the idea that nutritional stress is a factor in the timing of reproduction in lemurs and, by extension, is linked to the prevalence of female dominance and small group size in lemurs.     

Diet and activity budget of <Emphasis Type="Italic">Rhinopithecus roxellana</Emphasis> in the Qinling Mountains,China

We collected data on diet and daytime activity budget, and investigated the phenology of food trees and food abundance for a group of Rhinopithecus roxellana on the East Ridge of Yuhuangmiao in the Qinling Mountains from November 2001 to December 2003. We calculated the seasonal activity budget using data collected by scan sampling from 84 full-day observations (winter 16, spring 18, summer 28, autumn 22 days). During scan sampling we recorded behavioral states, and the food items and species consumed. The subjects consumed 84 plant species, including trees and shrubs of 29 families, and lichens. Food species varied seasonally. The overall diet of R. roxellana consisted of 29.4% fruit/seeds, 29.0% lichens, 24.0% leaves, 11.1% bark, 4.2% buds, 1.3% twigs and 1.0% unidentified items. Because the abundance of different food items varied seasonally, the monkeys had to shift their major food items seasonally. The annual activity budget of R. roxellana was 36.2% time spent resting, 35.8% feeding, 22.9% moving, and 5.1% other behavior. Seasonal changes in activity budget were observed. R. roxellana spent more time moving in autumn, when the quality of the food might be highest, and least time moving in winter when the food quality might be lowest. Thus, this type of monkey has a passive foraging strategy.     

Feeding ecology and activity pattern of black-fronted titi monkeys (<Emphasis Type="Italic">Callicebus nigrifrons</Emphasis>) in a semideciduous tropical forest of southern Brazil

Most aspects of the ecology and behavior of Callicebus nigrifrons are still unknown. The information available about this species is mainly based on a few studies that also focused on other Callicebus. We examined the feeding behavior and activity pattern of a free-ranging pair of C. nigrifrons between March and November 2007 in an area of semideciduous tropical forest of southeastern Brazil. The study site is located at the southern limit of the Tropical Zone and is characterized by pronounced seasonality. As observed for other Callicebus monkeys, fruits were the most consumed food resource, accounting for 53% of the diet, which was complemented mainly by leaves (16%) but also by invertebrates and flowers (10% of each). A great variety of plant families (28) and species (62) were included in the diet. The titis spent 35% of their time feeding, distributing the remaining time between resting (30%) and traveling (24%). Data presented here indicate that C. nigrifrons prefer high-quality food items (fruit pulp), adding low-quality food items (such as leaves) as the availability of the higher-quality foods decreases. The amount of time spent traveling and resting did not change between seasons, but the time invested in feeding increased during the lean period. The activity pattern was not related to fruit availability, but in months with lower temperatures, monkeys spent more time feeding. We suggest that the feeding ecology and activity pattern of C. nigrifrons reflect adaptations related to annual fluctuations in food availability and temperature, respectively.     

Chimpanzee feeding ecology and fallback food use in the montane forest of Nyungwe National Park,Rwanda

Almost all primates experience seasonal fluctuations in the availability of key food sources. However, the degree to which this fluctuation impacts foraging behavior varies considerably. Eastern chimpanzees (Pan troglodytes schweinfurthii) in Nyungwe National Park, Rwanda, live in a montane forest environment characterized by lower primary productivity and resource diversity than low‐elevation forests. Little is known about chimpanzee feeding ecology in montane forests, and research to date predominantly relies on indirect methods such as fecal analyses. This study is the first to use mostly observational data to examine how seasonal food availability impacts the feeding ecology of montane forest chimpanzees. We examine seasonal changes in chimpanzee diet and fallback foods (FBFs) using instantaneous scan samples and fecal analyses, supported by inspection of feeding remains. Chimpanzee fruit abundance peaked during the major dry season, with a consequent change in chimpanzee diet reflecting the abundance and diversity of key fruit species. Terrestrial herbaceous vegetation was consumed throughout the year and is defined as a “filler” FBF. In contrast to studies conducted in lower‐elevation chimpanzee sites, figs (especially Ficus lutea) were preferred resources, flowers were consumed at seasonally high rates and the proportion of non‐fig fruits in the diet were relatively low in the current study. These divergences likely result from the comparatively low environmental diversity and productivity in higher‐elevation environments.     

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.     

Seasonal, sex, and interspecific differences in activity time budgets and diets of patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus), living sympatrically in northern Cameroon

I examined seasonal, sex, and interspecific differences in activity time budgest and diets of patas (Erythrocebus patas) and sympatric tantalus monkeys (Cercopithecus aethiops tantalus) on the basis of 5-day data sets collected in three and two different seasons, respectively, by the method of focal animal sampling. The seasons included species-specific mating and birth seasons. As compared with not only the birth season but also conspecific females, both patas resident male and tantalus male spent less time feeding and more time resting, day and night, in their respective mating seasons. Given that day-resting time includes time for vigilance for non-resident males and receptive females, this may reflect that males should minimize time spent feeding to allow maximum participation in other fitness-increasing activities such as mating-relating activities asSchoener (1971) predicted. In both species, the males consumed fruits containing less protein but more calories and showed a high feeding rate to compensate for the shorter time spent feeding in the mating season. In contrast, females consumed protein-rich food types (i.e. animals, protein-rich seeds, leaves, and flowers) in the birth season to meet the high demand for protein due to pregnancy and lactation. Given that the season for males was considered to be not a calendar but a reproductive “season” (i.e. mating or birth season), both sexes of patas spent more time moving and less time day- and night-resting than did the tantalus counterparts irrespective of the “season”. Patas subsisted on fruits, gums, and supplementarily lipid-rich seeds as an energy source and animal matters and protein-rich seeds as a protein source. In contrast, tantalus subsisted on fruits and lipid-rich seeds as energy and flowers and leaves as protein.     

Food diversity and choice of white-headed langur in fragmented limestone hill habitat in Guangxi,China

We studied the diet and food choice of three groups of white-headed langurs (Trachypithecus leucocephalus) from July 2002 to June 2003 at Fusui Rare Animal Reserve, Guangxi, China. Data were collected from via focus group sampling, with continuous recording. A total of 109 plant species (including 19 unidentified species) were used as food by the white-headed langur. They spent 91.6% of total feeding time feeding on leaves, 4.2% on fruits and 3.3% on stems. Flowers and other food items accounted for only 0.3% and 0.6% of total feeding time, respectively. There were significant seasonal variations in the langurs’ diets with changes in the total number of species and the diversity of food species consumed. The langurs used significantly more plant species as food in the rainy season than in the dry season (36 species vs. 26.5 species). Dietary diversity was also significantly higher in the rainy season than in the dry season (2.6 vs. 2.4). No significant seasonal variation was found in the percentage of various plant parts in their monthly diets. Though the white-headed langur fed on many plant species, 11 species made up 84.9% of their diet. There were no significant correlations between the percentage of feeding time for main food plant species and their corresponding abundance in the habitat, content of water, crude protein, crude fiber and the ratio of crude protein to crude fiber. These results suggest that food choice of the white-headed langur is not influenced by their abundance and nutritional content.     

邦亮东黑冠长臂猿日食性与活动节律的季节性变化

日食性变化和活动节律是动物行为的重要方面,通过对日食性变化与活动节律的研究,可以了解食物、温度和光照时间等环境因素的变化对动物行为的影响,以及动物在行为上的应对策略。2009 年1 -12 月,在广西靖西县邦亮东部黑冠长臂猿自治区级自然保护区内,采用瞬时扫描取样法对2 群东黑冠长臂猿觅食行为和活动节律进行了研究。结果显示,东黑冠长臂猿的活动和食性在旱季和雨季都具有明显的节律。鸣叫只发生在12:00之前,但旱季的鸣叫时间偏晚。在日节律上,东黑冠长臂猿在离开过夜树后和进入过夜树前各有一个取食高峰,07:00 喜欢取食果实和无花果,16:00 也选择更多的果实,但无花果较少,13:00 - 15:00 取食更多的叶和芽。在10:00 - 12:00,其用于休息和社会活动的时间增加。在雨季,东黑冠长臂猿以果实和无花果为主要食物,并且花大量时间觅食无脊椎动物;但在旱季,其食物以叶和芽为主。与之相适应,东黑冠长臂猿在旱季通过减少移动增加休息来节约能量开支和应对低温,同时它们增加取食的时间以获得等价的能量和营养。雨季时社会行为的比例明显高于旱季,而且其高峰出现在08:00 - 10:00,但旱季社会行为主要出现在11:00 - 14:00。在雨季东黑冠长臂猿没有出现休息高峰,相反在旱季10:00 左右出现一个明显的休息高峰。上述行为节律体现了东黑冠长臂猿对环境季节性变化的良好适应,使其能够在寒冷并且退化的喀斯特森林中生存繁衍。     

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.