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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.  相似文献   

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Primate field studies often identify “lean seasons,” when preferred foods are scarce, and lower‐quality, abundant foods (fallback foods) are consumed. Here, we quantify the nutritional implications of these terms for two diademed sifaka groups (Propithecus diadema) in Madagascar, using detailed feeding observations and chemical analyses of foods. In particular, we sought to understand 1) how macronutrient and energy intakes vary seasonally, including whether these intakes respond in similar or divergent ways; 2) how the amount of food ingested varies seasonally (including whether changes in amount eaten may compensate for altered food quality); and 3) correlations between these variables and the degree of frugivory. In the lean season, sifakas shifted to non‐fruit foods (leaves and flowers), which tended to be high in protein while low in other macronutrients and energy, but the average composition of the most used foods in each season was similar. They also showed dramatic decreases in feeding time, food ingested, and consequently, daily intake of macronutrients and energy. The degree of frugivory in the daily diet was a strong positive predictor of feeding time, amount ingested and all macronutrient and energy intakes, though season had an independent effect. These results suggest that factors restricting how much food can be eaten (e.g., handling time, availability, or intrinsic characteristics like fiber and plant secondary metabolites) can be more important than the nutritional composition of foods themselves in determining nutritional outcomes—a finding with relevance for understanding seasonal changes in behavior, life history strategies, competitive regimes, and conservation planning. Am J Phys Anthropol 153:78–91, 2014. © 2013 Wiley Periodicals, Inc.  相似文献   

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The time spent between sleeping periods, which is called the active period, has to accommodate all essential activities, including feeding, resting, social behavior, and reproduction. To minimize costs in terms of, e.g., predation risk, suboptimal foraging, or sleep deficiency, the active period of diurnal animals should be less than or equal to the daylight period. Thus, the active period of an animal should be shaped by local environmental conditions as well as by metabolic and reproductive demands. Chimpanzees, which exhibit reduced predator pressure and a flexible fission-fusion society, were chosen as a model to explore these links. We investigated the influence of sex, female reproductive status, dominance rank, and season on the duration of the active period of adult chimpanzees at Gombe National Park, Tanzania (1975-1992). Sexually nonreceptive females had shorter active periods compared to males, while receptive females had even longer active periods than males. Dominance rank did not influence the duration of the active period of nonreceptive females, but high- and middle-ranking males had shorter active periods compared to low-ranking males. Nonreceptive females exhibited longer active periods during the dry season than in the wet season. No seasonal effect was discovered for males, perhaps because they already had long active periods in the wet season. Nonreceptive females seem to be able to accommodate all essential activities in the daylight period available, probably because they live less socially than males. Thus, the active period does not reflect differences in female competitive abilities, but does reflect such differences in males. The duration of the active period appears to be a simple, reliable tool for exploring basic responses and constraints in animal societies.  相似文献   

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The newly described Arunachal macaque Macaca munzala occurs largely in sub‐tropical to temperate environments at elevations of c. 1,800–3,000 m in Arunachal Pradesh, northeastern India. We studied its over‐wintering strategy by comparing the diet, ranging, and behavior of a troop of 24 individuals during winter and spring (December 2005 to May 2006) through instantaneous scan sampling (3,002 records, 448 scans, 112 hr of observation). We also monitored the phenology of food plants. The macaques spent more time (41–66%) feeding in the winter than in spring (33–51%), whereas time spent moving and resting was greater in spring. The diet composed largely of plants, with animal matter being eaten rarely. The number of plant species in the diet increased from 18 to 25 whereas food types rose from 18 to 36 from winter to spring, respectively. Although only two species formed 75% of the winter diet, seven species comprised this proportion in spring. Availability of fruits and young leaves increased in spring; the troop moved more and utilized a larger part of its range during this time. Seasonal changes in behavior could be explained by the scarcity of food and the costs of thermoregulation in winter. Our study suggests that the Arunachal macaque inhabits a highly seasonal environment and has an over‐wintering strategy that includes subsisting on a high‐fiber diet by increasing the time spent feeding, and minimizing energy expenditure by reducing the time spent moving. Am. J. Primatol. 71:939–947, 2009. © 2009 Wiley‐Liss, Inc.  相似文献   

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Highly frugivorous primates like chimpanzees (Pan trogolodytes) must contend with temporal variation in food abundance and quality by tracking fruit crops and relying more on alternative foods, some of them fallbacks, when fruit is scarce. We used behavioral data from 122 months between 1995 and 2009 plus 12 years of phenology records to investigate temporal dietary variation and use of fallback foods by chimpanzees at Ngogo, Kibale National Park, Uganda. Fruit, including figs, comprised most of the diet. Fruit and fig availability varied seasonally, but the exact timing of fruit production and the amount of fruit produced varied extensively from year to year, both overall and within and among species. Feeding time devoted to all major fruit and fig species was positively associated with availability, reinforcing the argument that chimpanzees are ripe fruit specialists. Feeding time devoted to figs-particularly Ficus mucuso (the top food)--varied inversely with the abundance of nonfig fruits and with foraging effort devoted to such fruit. However, figs contributed much of the diet for most of the year and are best seen as staples available most of the time and eaten in proportion to availability. Leaves also contributed much of the diet and served as fallbacks when nonfig fruits were scarce. In contrast to the nearby Kanywara study site in Kibale, pith and stems contributed little of the diet and were not fallbacks. Fruit seasons (periods of at least 2 months when nonfig fruits account for at least 40% of feeding time; Gilby & Wrangham., Behavioral Ecology and Sociobiology 61:1771-1779, 2007) were more common at Ngogo than Kanyawara, consistent with an earlier report that fruit availability varies less at Ngogo [Chapman et al., African Journal of Ecology 35:287-302, 1997]. F. mucuso is absent at Kanyawara; its high density at Ngogo, combined with lower variation in fruit availability, probably helps to explain why chimpanzee population density is much higher at Ngogo.  相似文献   

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Evolutionary Consequences of Fallback Foods   总被引:2,自引:2,他引:2  
Primatologists use the term fallback foods to denote resources of relatively low preference that are used seasonally when preferred foods are unavailable. We examine the assumption that fallback foods play an important role in shaping morphological adaptations, behavior, and socioecology in primates. We discuss operational definitions of preferred and fallback foods and suggest that the evolutionary importance of fallback foods applies more to adaptations for processing than for harvesting foods. Equally, we propose that preferred resources tend to drive adaptations for harvesting foods. We distinguish 2 classes of fallback foods according to their roles in the diet and their evolutionary effects. Staple fallback foods are available year-round, tend to be eaten throughout the year, and seasonally can constitute up to 100% of the diet. Filler fallback foods never constitute 100% of the diet, and may be completely avoided for weeks at a time. We suggest that the availability of the 2 classes of fallback foods have different effects on the socioecology of primate species.  相似文献   

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The microscopic traces of use wear on teeth have been extensively studied to provide information that will assist in elucidating the dietary habits of extinct hominin species. 1 - 13 It has been amply documented that dental microwear provides information pertaining to diet for living animals, where there is a strong and consistent association between dental microwear patterns and different types of foods that are chewed. The details of occlusal surface wear patterns are capable of distinguishing among diets when the constituent food items differ in their fracture properties. 14 - 20 For example, the microwear traces left on the teeth of mammals that crush hard, brittle foods such as nuts are generally dominated by pits, whereas traces left on the teeth of mammals that shear tough items such as leaves tend to be characterized by scratches. These microwear features result from and thus record actual chewing events. As such, microwear patterns are expected to be variably ephemeral, as individual features are worn away and replaced or overprinted by others as the tooth wears down in subsequent bouts of mastication. Indeed, it has been demonstrated, both in the laboratory and the wild, that short‐term dietary variation can result in the turnover of microwear. 17 , 21 - 23 Because occlusal microwear potentially reflects an individual's diet for a short time (days, weeks, or months, depending on the nature of the foods being masticated), tooth surfaces sampled at different times will display differences that relate to temporal (for example, seasonal) differences in diet. 24  相似文献   

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Objectives

Insectivory likely contributed to survival of early humans in diverse conditions and influenced human cognitive evolution through the need to develop harvesting tools. In living primates, insectivory is a widespread behavior and frequently seasonal, although previous studies do not always agree on reasons behind this. Since western gorillas (Gorilla gorilla) diet is largely affected by seasonal variation in fruit availability, we aimed to test three non-mutually exclusive hypotheses (habitat use, frugivory and rainfall) to explain seasonality in termite feeding across age/sex classes in three habituated groups (Nindividuals = 27) in Central Africa.

Materials and Methods

We used 4 years of ranging, scan and continuous focal sampling records of gorillas (Nranging days = 883, Nscans = 12,384; Nhours = 891) in addition to 116 transects recording vegetation and termite mound distribution.

Results

Depending on the age/sex classes, we found support for all three hypotheses. Time spent in termite-rich vegetation positively impacted termite consumption in all age/sex classes, but subadults. Lengthier travels increased termite feeding in females but decreased it in subadults. Frugivory decreased termite consumption in adults. Daily rainfall had a positive effect on termite feeding and foraging in silverbacks and juveniles, but a negative effect in subadults. For females, rainfall had a positive effect on termite feeding, but a negative effect for termite foraging.

Discussion

In great apes, seasonal insectivory seems to be multifactorial and primarily opportunistic with important differences among age/sex classes. While insectivory has potentials to be traditional, it likely played a crucial role during primate evolution (including ours), allowing diet flexibility in changing environments.  相似文献   

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Recent findings on the strong preference of gorillas for fruits and the large dietary overlap between sympatric gorillas and chimpanzees has led to a debate over the folivorous/frugivorous dichotomy and resource partitioning. To add insight to these arguments, we analyze the diets of sympatric gorillas and chimpanzees inhabiting the montane forest of Kahuzi-Biega National Park (DRC) using a new definition of fallback foods (Marshall and Wrangham: Int J Primatol 28 [2007] 1219–1235). We determined the preferred fruits of Kahuzi chimpanzees and gorillas from direct feeding observations and fecal analyses conducted over an 8-year period. Although there was extensive overlap in the preferred fruits of these two species, gorillas tended to consume fewer fruits with prolonged availability while chimpanzees consumed fruits with large seasonal fluctuations. Fig fruit was defined as a preferred food of chimpanzees, although it may also play a role as the staple fallback food. Animal foods, such as honey bees and ants, appear to constitute filler fallback foods of chimpanzees. Tool use allows chimpanzees to obtain such high-quality fallback foods during periods of fruit scarcity. Among filler fallback foods, terrestrial herbs may enable chimpanzees to live in small home ranges in the montane forest, whereas the availability of animal foods may permit them to expand their home range in arid areas. Staple fallback foods including barks enable gorillas to form cohesive groups with similar home range across habitats irrespective of fruit abundance. These differences in fallback strategies seem to have shaped different social features between sympatric gorillas and chimpanzees. Am J Phys Anthropol 140:739–750, 2009. © 2009 Wiley-Liss, Inc.  相似文献   

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The most important environmental factor explaining interspecies variation in ecology and sociality of the great apes is likely to be variation in resource availability. Relatively little is known about the activity patterns of western lowland gorillas (Gorilla gorilla gorilla), which inhabit a dramatically different environment from the well‐studied mountain gorillas (G. beringei beringei). This study aims to provide a detailed quantification of western lowland gorillas' activity budgets using direct observations on one habituated group in Bai Hokou, Central African Republic. We examined how activity patterns of both sexes are shaped by seasonal frugivory. Activity was recorded with 5‐min instantaneous sampling between December 2004 and December 2005. During the high‐frugivory period the gorillas spent less time feeding and more time traveling than during the low‐frugivory period. The silverback spent less time feeding but more time resting than both females and immatures, which likely results from a combination of social and physiological factors. When compared with mountain gorillas, western lowland gorillas spend more time feeding (67 vs. 55%) and traveling (12 vs. 6.5%), but less time resting (21 vs. 34%) and engaging in social/other activities (0.5 vs. 3.6%). This disparity in activity budgets of western lowland gorillas and mountain gorillas may be explained by the more frugivorous diet and the greater dispersion of food resources experienced by western lowland gorillas. Like other apes, western lowland gorillas change their activity patterns in response to changes in the diet. Am. J. Primatol. 71:91–100, 2009. © 2008 Wiley‐Liss, Inc.  相似文献   

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Abstract 1. The majority of general life‐history models treat the environment as being invariable through time, even though temporal variation in selective agents could dramatically change the outcomes, e.g. in terms of optimal size and time at maturity. For herbivorous insects, seasonal differences in food quality are reasonably well described, but seasonal dynamics of top‐down selective forces are poorly documented. 2. The present study attempted to quantify seasonal changes in predation risk of folivorous insect larvae in temperate forest habitats. In a series of field experiments, artificial larvae were exposed to predators, and the resulting bird‐inflicted damage was recorded. The trials were repeated regularly throughout the course of two summers. 3. A distinct peak of larval mortality was recorded in mid‐June (the nestling period for most insectivorous passerine birds), after which predation risk declined to a plateau of 20–30% below the peak value. 4. The recorded pattern is interpreted as a consequence of seasonal changes in the number and behaviour of insectivorous birds, and the abundance of alternative food resources for these predators. 5. A quantitative analysis based on field data indicated that considering temporal variation in mortality in life‐history models is crucial for obtaining realistic predictions concerning central life‐history traits, such as final body size in different generations.  相似文献   

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Flowers are included in the diets of many primates, but are not generally regarded as making an important contribution to primate energy budgets. However, observations of a number of lemur, platyrrhine, and cercopithecine populations suggest that some flower species may function as key primate fallback foods in periods of low abundance of preferred foods (generally ripe fruits), and that flowers may be preferred foods in some cases. I report heavy reliance on flowers during some study months for a siamang (Symphalangus syndactylus) population in southern Sumatra. Siamangs at Way Canguk spent 12% of feeding time eating flowers from October 2000 to August 2002, and in 1 month flower‐feeding time exceeded 40% of total feeding time. The overall availabilities of fig and nonfig fruits, flowers, and new leaves in the study area were not significant predictors of the proportion of time that siamangs spent consuming any plant part. However, flower‐feeding time was highest in months when nonfig fruit‐feeding time was lowest, and a switch from heavy reliance on fruit to substantial flower consumption was associated with a shift in activity patterns toward reduced energy expenditure, which is consistent with the interpretation that flowers may function as a fallback food for Way Canguk siamangs. Hydnocarpus gracilis, a plant from which siamangs only consume flowers, was the third‐most‐commonly consumed plant at Way Canguk (after Ficus spp. and Dracontomelon dao), and flowers from this plant were available in most months. It is possible that relatively high local availability of these important siamang plant foods is one factor promoting high siamang density in the study area. Am. J. Primatol. 71:624–635, 2009. © 2009 Wiley‐Liss, Inc.  相似文献   

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Physical anthropologists use the term “fallback foods” to denote resources of relatively poor nutritional quality that become particularly important dietary components during periods when preferred foods are scarce. Fallback foods are becoming increasingly invoked as key selective forces that determine masticatory and digestive anatomy, influence grouping and ranging behavior, and underlie fundamental evolutionary processes such as speciation, extinction, and adaptation. In this article, we provide an overview of the concept of fallback foods by discussing definitions of the term and categorizations of types of fallback foods, and by examining the importance of fallback foods for primate ecology and evolution. We begin by comparing two recently published conceptual frameworks for considering the evolutionary significance of fallback foods and propose a way in which these approaches might be integrated. We then consider a series of questions about the importance of fallback foods for primates, including the extent to which fallback foods should be considered a distinct class of food resources, separate from preferred or commonly eaten foods; the link between life history strategy and fallback foods; if fallback foods always limit primate carrying capacity; and whether particular plant growth forms might play especially important roles as fallback resources for primates. We conclude with a brief consideration of links between fallback foods and primate conservation. Am J Phys Anthropol 140:603–614, 2009. © 2009 Wiley-Liss, Inc.  相似文献   

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Little is known about the biology of long-tailed cuckoos (Eudynamys taitensis). In this study, 79 dead cuckoos, mostly from the wider Auckland region, New Zealand, were examined and dissected to shed light on the sex ratio, morphology, breeding season and diet. There were no statistically significant sexual differences in the means for weight or body measurements. However, immature birds had significantly shorter bill, wing and tail lengths than adults. In adults, gonads were enlarged (for breeding) from October to January, while all cuckoos identified (from plumage) as immatures had small gonads. Of 888 food items identified from 62 gizzards, 94% were insects. The main foods were cicadas and shield-bugs (Hemiptera, 48% of food items), stick-insects (Phasmatodea, 19%) and wētās and katydids (Orthoptera, 13%). Small vertebrates (lizards and birds’ eggs and nestlings) were a minor dietary element (1% of food items; 13% of stomachs). Cicadas, stick-insects and praying mantids (large insects abundant in late summer) made up 57% of the immature diet; in adults these three categories made up just 13% of food items. Immatures leave New Zealand on migration several months after adults, and this delay in late summer and autumn coincides with an opportunity to exploit a seasonal abundance of large insects.  相似文献   

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Colobine monkeys have complex, multichambered, foregut-fermenting stomachs with either three (“tripartite”) or four (“quadripartite,” adding the praesaccus) chambers where a commensal microbiome digests plant cell walls and possibly detoxifies defensive plant chemicals. Although different potential functions for the praesaccus have been suggested, little evidence exists to support any of the proposed functions. To address the issue of the function of the praesaccus, we collated literature data on diet and compared tripartite and quadripartite species. Our results suggest that the praesaccus is an adaptation to a dietary niche with a particularly high reliance on leaves as fallback foods in colobine clades with quadripartite stomachs, and a higher reliance on fruits/seeds as foods at times of high fruit availability in clades with tripartite stomachs. This supports the notion that a large gut capacity is an important characteristic by which folivores survive on a high fiber diet, and that this large gut capacity may not be necessary for some species if there are seasonal peaks in fruit availability.  相似文献   

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