Grouping Patterns and Competition Among Female <Emphasis Type="Italic">Pan troglodytes schweinfurthii</Emphasis> at Ngogo,Kibale National Park,Uganda

In mammals, access to mates is probably the most important influence on male reproductive success, whereas foraging efficiency is probably the most important influence on female reproductive success Emlen and Oring (Science 197:215–223, 1977). Male chimpanzees (Pan troglodytes) are highly gregarious and form cooperative relationships with other males. In contrast, female social relationships vary within and between populations. Females in most East African populations, e.g., Gombe, Mahale, Kibale-Kanyawara, are less gregarious than males and spend most of their time alone or with only their dependent offspring. Researchers have attributed low female gregariousness to the high potential for feeding competition. I provide the first data on association patterns and agonistic interactions of female chimpanzees (Pan troglodytes schweinfurthii) from the unusually large Ngogo community, Kibale National Park, Uganda. Ngogo females were less gregarious than males, but spent a mean of 64% of their time in association with ≥1 other females and as much time in all-female parties as they did alone. Further, female dyads associated nonrandomly and they formed associative cliques. Association levels within cliques were similar to those among the relatively gregarious West African chimpanzee females at Taï (Pan troglodytes verus) and among bonobo (P. paniscus) females. Agonistic interfemale interactions were extremely rare, and monthly mean party size and the numbers of anestrous females per party do not correlate significantly with fruit availability. Thus, Ngogo females maintained relatively high levels of gregariousness, but avoided detrimental feeding competition by preferentially associating with a small subset of other community females.     

Behavioral responses of Barbary macaques (Macaca sylvanus) to variations in environmental conditions in Algeria

In this study, the behavioral responses of Barbary macaques to seasonal and interhabitat variations in resource availability were analyzed over an entire annual cycle. Two groups, one in an evergreen cedar–oak forest (Djurdjura) and the other in a deciduous oak forest (Akfadou), were observed. In this paper, references to data on resource availability published elsewhere are made. Time budget has been studied. Variations in foraging and moving time, in day–range lengths, and in time moving in trees have been considered to estimate the variations in foraging effort and thus energy expenditure. Great monthly variations in foraging effort and other activities were observed in both habitats. In early spring, when resource availabilities were maximal, foraging effort was low while monkeys maximized their feeding time (about 5 h/day). In June, during the peak of the birth season and the rearing period, monkeys minimized their feeding time to the benefit of social interactions (to 1.6–2.7 h/day), whatever the food availability, which was low in Akfadou and high in Djurdjura. In addition, foraging effort remained low in Djurdjura, while it increased in Akfadou. Thus, at the beginning of the dry summer period, monkeys in Akfadou were in a less favorable position than those in Djurdjura. At both sites, in periods of food shortage in summer or in winter, monkeys displayed two different strategies. In the former case, their foraging effort increased, while in the second one it remained relatively low. Whatever the foraging effort, monkeys did not reach the same amount of feeding time as in early spring. In the poorest site of Akfadou, foraging effort was globally greater than in the richest site of Djurdjura, especially for adults. At both sites, adult males spent more time feeding than juveniles and less time in social interactions. Results are discussed according to rearing period, temperatures, and day length constraints. The limits of adaptability to different habitats are considered in light of the demographic parameters. Am. J. Primatol. 43:285–304, 1997. © 1997 Wiley-Liss, Inc.     

Time budgets of Nuthatches Sitta europaea with supplementary food

Individual time budgets during winter and spring were studied in a population of Nuthatches Sitta europaea in south-central Sweden. In late winter birds spent about 90% of daytime foraging, males feeding somewhat less than females, possibly due to male dominance. In early spring, foraging time decreased to about 65% of daytime activity, and sex-related differences became more pronounced. Males then increased time spent resting and singing. Females were nestbuilding, spent less time resting and also devoted more time to foraging than did males. Prior to the observation periods, food density for part of the population was experimentally increased by supplying sunflower seed. In spite of this, time budgets in the experimental group were similar to those of the control group. It is possible that the intensity of foraging, rather than actual time devoted to it, was influenced by food density and that, as a result, birds in the experimental group were able to maintain a higher level of vigilance. Also, an increase in food supply may be less important to a hoarding bird such as the Nuthatch. However, the result remains that Nuthatch time budgets in winter and spring are not readily influenced by an increase in food density.     

Male and female western gorilla diet: Preferred foods,use of fallback resources,and implications for ape versus old world monkey foraging strategies

Most of what is currently known about western gorilla (Gorilla gorilla) diet is based on indirect studies using fecal samples and trail signs rather than measures based on direct observations. Here we report results on adult male and female western gorilla foraging behavior, based on systematic focal observations and nutritional analyses of foods. We found that western gorillas, like other apes, are highly selective ripe fruit specialists, seeking fruit high in energy, low in antifeedants, and rare in the environment. During seasonal fruiting peaks, fruit accounted for up to 70% of feeding time. When ripe fruit was scarce, gorillas increased time spent feeding on leaves and nonpreferred fruits and herbs. Leaves were the major fallback food, accounting for up to 70% of feeding time in males and 50% in females during periods of fruit scarcity. In spite of large differences in body size, the sexes were remarkably similar in their overall diet, not differing in time spent feeding on fruit or preferred herbs. However, the male consistently fed more often and on a greater variety of leaves than did females, whereas females fed more often on fallback herbs and termites. Our findings, when considered in light of previous findings on sympatric mangabeys, indicate that the foraging strategy of western gorillas is broadly similar to that of chimpanzees and orangutans, and distinct from that of old world monkeys. Am J Phys Anthropol 140:727–738, 2009. © 2009 Wiley-Liss, Inc.     

Sex differences in diet and foraging behavior in white-faced capuchins (Cebus capucinus)

I examined sex differences in diet and foraging behavior in two groups of white-faced capuchin monkeys (Cebus capucinus)in a tropical dry forest at Santa Rosa National Park, Costa Rica. I tested three hypotheses: sex differences in diet and foraging behavior are best explained by (1) sexual dimorphism, (2) the energy demands of pregnancy and lactation for females;and (3) avoidance of competition between the sexes. Sexual dimorphism offered the best explanation of sex differences in the diet and foraging behavior of C. capucinus,accurately predicting that males do more strenuous foraging activity, make less use of small foraging supports, and spend more time on or near the ground. Females spent more time foraging than males did but probably obtained a lower protein yield per unit foraging time. Females exploited more small and embedded invertebrates, while males ate more large invertebrates and vertebrate prey. Pregnant and lactating females spent more time resting and less time foraging than other females did, increasing their foraging return by focusing on foods requiring little handling. There was little evidence of competition avoidance between the sexes.     

Orangutan diet,range, and activity at Tanjung Puting,Central Borneo

Previously, wild orangutan feeding and ranging behaviors have been described only from populations in hilly or mountainous regions. The Tanjung Puting study focuses on an orangutan population in a swampy lowland area near sea level. Tanjung Puting also differs from other areas in the virtual absence of large figs, which are significant orangutan food sources elsewhere. During a 4-year period and 6804 hr of observation, focal orangutans were recorded in 11,338 foraging bouts accounting for 3805 hr. Composition and phenology of the forest habitat were documented. The orangutans were predominantly frugivorous, with fruit-eating accounting for 61% of the foraging time. However, the overall variety in their diet was remarkable; 317 different food types have been identified, including fungus, insects, and honey. Orang-utans were strongly opportunistic foragers, with the composition of their diet varying markedly from month to month. During most months orangutans fed on a complex mix of fruit, leaves, bark, insects, and small vines. During some months fruit was not the major component of the diet. All orangutans foraged in both the dry-ground mixed dipterocarp forest and the peatswamp forest habitats found in their ranges. Adult males and females utilized different proportions of certain resources in their diets. Prime adult males also ranged further per day and spent more time on the ground than prime adult females. At Tanjung Puting contact with other orangutans usually increased a focal orangutan’s day length, day range, and amount of time spent moving. This suggests that foraging alone maximized each orangutan’s foraging returns by minimizing the day range traveled. Orangutan solitariness is the result of a large body size and of a predominantly frugivorous and opportunistic diet.     

State-dependent incubation behaviour in the high arctic barnacle geese

Energetic trade-offs between time spent on incubation and times spent on foraging for nesting birds give individuals in good body condition the possibility to incubate more continuously. In the present paper, the incubation behaviour of female barnacle geese Branta leucopsis was quantified in a colony in Svalbard. Females were weighted in early incubation and feeding recess lengths and frequencies were recorded. The feeding behaviour during the course of incubation was significantly correlated to by body mass, and heavy females had both fewer and shorter feeding recesses than lighter females. Moreover, there was an increase in the number of feeding recesses and the total feeding time as the incubation period progressed. Neither clutch size nor egg laying date had an effect on incubation behaviour. However, clutch size was positively related to female body mass suggesting that high-quality females produce large clutches but also allocate more body reserves to incubation. Females left the nest to feed at all times of the day, but more frequently during day time. This was not related to their body mass. Females presumably leave their nest at the time of day when the costs to reheat eggs are at a minimum. The diurnal rhythm may also be adjusted to the activity by egg predators. Overall the results support the state-dependent hypothesis for incubation behaviour, suggesting that body condition at the start of incubation is an important factor for incubation behaviour in barnacle geese.     

Environmental factors influencing the seasonality of estrus in chimpanzees

Although the energetics of the estrous cycle in primates is not well understood, evidence suggests that energy and nutrient acquisition influence ovulation and the timing of conception. Energy for estrus has to compete with energy allocated for cellular maintenance, thermoregulation, movement for food, and predation avoidance. While some chimpanzee (Pan troglodytes) populations do not have a seasonal birth period, evidence suggests that there is seasonality in the number of estrous females. Similarly, the onset of postpartum cycles has been reported to be seasonal. We used 33 months of data from the Taï National Park, Côte dIvoire, to examine how the number of estrous females in a given month was influenced by the abundance and distribution of food, diet, rainfall and temperature. In a second analysis, we examined if there was a seasonal effect on first estrous swellings in adolescent females and postpartum adult females. Results demonstrated that the number of females in estrous in a given month was positively related to food abundance and percent foraging time spent eating insects, and negatively related to mean rainfall in the two preceding months and the mean high temperature. The timing of first estrous swellings of postpartum females and prepartum young females was positively related to the food abundance, and negatively related to mean high temperature. These results showed that environmental conditions can seasonally limit the energetically demanding estrus cycle. The presence of estrous females increases gregariousness in chimpanzee communities, and this study identified environmental factors that affect estrus directly and hence social grouping indirectly.     

Time Allocation during the Reproductive Season in Vicuñas

Vicuñas (Vicugna vicugna) are wild South American camelids that live in high-altitude grasslands (Puna). Their social organization is based on family and bachelor groups. The amount of time they allocated to walking, running, lying, grazing and alert behaviour was studied in Abrapampa, northwestern Argentina, during the 1988–1990 reproductive seasons. Females and yearlings spent significantly more time grazing, and less time walking, running and alert than territorial males and bachelors. This result suggests that females maximized the time spent foraging to fulfil the energetic demands of reproduction. The alertness of the territorial males increased and the grazing decreased with the number of females in the families, suggesting that males that incurred a higher cost of lost feeding time through vigilance activities increased their mating success.     

Estimation of food intake and ingested energy in Daubenton’s bats (Myotis daubentonii) during pregnancy and spermatogenesis

We studied food intake of and estimated ingested energy in female and male Myotis daubentonii during the periods of pregnancy (period 1, 8 May–4 June) and of intense spermatogenetic activity (period 2, 24 July–22 August) over 8 years (1996–2003) in central Germany. We used radiotelemetry to determine the time spent foraging and marked animals with chemiluminescent light-sticks to determine prey attack rates. Body length, body mass, moisture content, and caloric content of chironomids, the main prey of Daubenton’s bats, were measured to estimate the nightly food intake and, in consequence, energy intake. Pregnant females spent significantly more time foraging than males during period 1 and females during the post-lactation period. In contrast, male foraged longer during the period of highest spermatogenetic activity than during late spring and also significantly longer than post-lactating females. Based on a mean number of 8.3 prey attacks per minute, the time spent foraging, and a capture success rate of either 50 or 92%, calculated intake values with a feeding rate of 7.6 insects per minute (=92% capture success) were more consistent with literature data for other insectivorous bats than that of values calculated on the basis of a capture success rate of 50%. In the high capture-success model, calculated insect intake of female bats was 8.0 g during pregnancy and 4.9 g per day during post-lactation, providing 5.0 and 3.0 kJ of ingested energy per gram body mass per day. Calculated intake of male bats was 3.6 g insects per day during late spring and 8.0 g during period of intensive spermatogenesis, providing 2.6 and 5.7 kJ of ingested energy per gram body mass.     

To Feed or Not to Feed? Testing Different Hypotheses on Rut‐Induced Hypophagia in a Mountain Ungulate

In many ruminant species, males dramatically reduce forage intake during the rut. To date, different hypotheses have been suggested to explain this rut‐induced hypophagia. To assess the predictions of the main hypotheses, we analysed Alpine ibex (Capra ibex) activity budget and compared the behaviour of males and females before, during, and after the rut. Only males spent significantly less time foraging during the rut than outside of it, whereas females allocated a similar proportion of time to foraging before, during, and after the rut. Our results showed that during the rut males also reduced lying time, while the ratio of time spent feeding to time spent lying did not change for males among periods. In conclusion, during the breeding season males maximized energy intake when not actively engaged in mating activities and rut‐induced hypophagia appeared to result from time budget constraints generated by mating‐related activities. Accordingly, the foraging constraint hypothesis seems appropriate to explain this phenomenon in Alpine ibex males.     

Floral resources impact longevity and oviposition rate of a parasitoid in the field

1. The use of floral resource subsidies to improve herbivore suppression by parasitoids requires certain trophic interactions and physiological changes to occur. While the longevity and fecundity of parasitoids are positively affected by nectar subsidies in laboratory studies, the impacts of floral subsidies on the fecundity and longevity of freely foraging parasitoids have not been studied. 2. We studied the longevity and per capita fecundity of naturally occurring Diadegma insulare foraging in cabbage plots with and without borders of flowering buckwheat, Fagopyrum esculentum, as well as relationships between longevity, fecundity, sugar feeding and parasitism rates on larvae of the diamondback moth, Plutella xylostella. 3. Relative longevity was estimated by counting broken setae on the fringe of the forewing. Floral borders increased the longevity of males and females in adjacent cabbage plots. 4. The egg maturation rate of D. insulare was estimated by comparing egg loads of females collected early in the day with egg loads of females held without hosts in field cages throughout the day. Females in buckwheat cages matured 2.7 eggs per hour while females in control cages resorbed 0.27 eggs over the same time period. 5. The fecundity of females collected in the afternoon was estimated by comparing their actual egg load to the estimated egg load in the absence of oviposition for females in a given plot. Females foraging in buckwheat plots had marginally fewer eggs remaining in their ovaries, and laid marginally more eggs than females in control plots. Females from both treatments carried 30-60 eggs by the afternoon and therefore were time-limited rather than egg-limited. 6. Plots where a greater proportion of females had fed on sugar had longer-lived females. This suggests that feeding enhanced longevity of D. insulare. However, plots with longer-lived and more fecund females did not exhibit higher parasitism rates, although the power of these tests were low.     

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.     

Activities and feeding behavior of free-ranging pregnant baboons

The activities and feeding behavior of pregnant baboons, Papio cynocephalus,were studied in two free-ranging groups in Amboseli National Park, Kenya. Both the environmental conditions and the age of their fetuses influenced females’ activity budgets and feeding behavior. Females fed more and rested less during the dry season than during the wet season, and most females spent progressively more time feeding and less time grooming than expected (based upon the amount of recent rainfall) as their fetuses matured. During the wet season, females also devoted significantly greater proportions of feeding time to consumption of grass blades, leaves, and flowers and significantly smaller proportions of their feeding time to feeding upon seeds, corms, and fruit. As their fetuses became older, the proportion of time spent feeding upon seeds increased, and the proportion of time spent feeding upon grass blades and fruit declined.     

Changes in Orangutan Caloric Intake,Energy Balance,and Ketones in Response to Fluctuating Fruit Availability

I used novel quantitative measures to assess the impact of fruit seasonality on changes in diet and energy balance during 4918 hours of observation on <60 orangutans in Gunung Palung National Park, West Kalimantan, Indonesia, from September 1994 through September 1995. During this period a mast fruiting occurred, resulting in large fluctuations in fruit availability, measured by monitoring of 558 orangutan fruit trees. Orangutan diet varied tremendously in accordance with these fluctuations. During the month of highest fruit production, 100% of the orangutan diet was composed of fruit. In contrast, during the fruit-poor period as little as 21% of the diet was fruit, while 37% was bark. Nutritional analyses of 78 of the foods most commonly eaten during this study show that mast foods were significantly higher in caloric content than were nonmast foods, which translates into substantial changes in caloric intake. During the month of highest fruit consumption (January), males consumed an estimated 8422 kcal/day and females consumed 7404 kcal/day. During the month of lowest fruit consumption (May), males consumed 3824 kcal/day and females consumed 1793 kcal/day. These differences were significantly different between the 2 months for both males and females. In May, males ate significantly more kcal/day than females did. Time spent feeding did not differ between the two periods for either males or females. I assessed the impact of these changes in diet and caloric intake on orangutan physiological functioning by measuring ketones in 257 urine samples collected from adult males and females. Ketones—products of fat metabolism—were present in urine only during the fruit-poor period. These data suggest that orangutans are highly efficient at storing fat during fruit-rich periods and utilizing the reserves during times of fruit shortfall. This response may have important implications for orangutan survivorship, reproduction, and behavior.     

Sex differences in the use of daily torpor and foraging time by big brown bats (Eptesicus fuscus) during the reproductive season

Temperate zone bats can use daily torpor as a means of saving energy. Some argue, however, that torpor is costly for both males and females and that individuals should only use it during times of poor foraging conditions. Others hypothesize that the costs are greater for females and that males should enter torpor more regularly. We tested these alternative hypotheses by using temperature-sensitive radiotransmitters to monitor use of torpor and foraging by free-ranging big brown bats ( Eptesicus fuscus ). During the pregnancy period, males used torpor at night more and foraged less often than did females. Males also went into deep torpor more often and remained in torpor longer than did females. When they foraged, males and females were away from the roosts for equal periods of time. During the lactation period, males and females rarely failed to forage and foraging times were again no different between the sexes, although males may roost at night away from the maternity colonies. Males again used torpor and deep torpor more often and for longer than females did. These results support the hypothesis that the fitness costs of using torpor are lower for males than for reproductive females and that males regularly use torpor as an energy-saving mechanism. Females enter torpor only when foraging conditions are poor, presumably because torpor prolongs gestation and slows neonatal growth thereby leaving less time for females and their young to prepare for hibernation.     

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.     

From nest to nest--influence of ecology and reproduction on the active period of adult Gombe chimpanzees

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.     

Eating for two: Behavioral and environmental correlates of gestation length among free-ranging baboons (Papio cynocephalus)

Variation in environmental conditions during pregnancy and differences in the feeding behavior of females during pregnancy were consistently associated with variation in gestation length among free-ranging yellow baboons, Papio cynocephalus,in Amboseli National Park, Kenya. Females whose pregnancies ended during the wet season gave birth after shorter pregnancies than females whose pregnancies ended during the dry season. When rainfall is held constant, another source of variation in gestation length emerges. Females that spent progressively less time feeding over the course of their pregnancies gave birth after longer pregnancies than females that spent progressively more time feeding over the course of their pregnancies. These two factors, which provide rough indices of maternal nutritional status, accounted for a substantial fraction of the observed variation in gestation length among these female baboons.