Activity and Ranging Patterns of <Emphasis Type="Italic">Colobus angolensis ruwenzorii</Emphasis> in Nyungwe Forest,Rwanda: Possible Costs of Large Group Size

With group sizes sometimes >300 individuals, the Angolan black-and-white colobus (Colobus angolensis ruwenzorii) population in Nyungwe Forest, Rwanda is an intriguing exception to the tendency for folivores to live in smaller groups than expected relative to body size. Researchers have hypothesized that the unusually high quality of foliage at Nyungwe allows colobus there to avoid intragroup feeding competition, releasing constraints on the formation of large groups (Fimbel et al., 2001). We collected data on the activity and ranging patterns of a >300-member Nyungwe colobus group and compared our results to those from smaller groups in other black-and-white colobus (Colobus spp.) populations. Colobus at Nyungwe spent far more time feeding and moving (62%) and far less time resting (32%) than black-and-white colobus at any other site. The annual home range of the Nyungwe colobus was also many times larger (95% minimum convex polygon: 20.7 km ² ; 95% fixed kernel: 24.4 km ² ) than those for other populations. We terminated our research after the group engaged in an unprecedented migration among black-and-white colobus by moving 13 km south of their former range. Our results suggest that intragroup scramble competition may be more intense than originally believed within the large colobus groups at Nyungwe and that long periods of resource renewal may be necessary after a large colobus group passes through an area, thereby potentially helping to explain their wide ranging patterns. We discuss the socioecological convergence between the Nyungwe colobus and Chinese snub-nosed monkeys (Rhinopithecus spp.) and suggest directions for future research on the unique black-and-white colobus population at Nyungwe.

Correlates of Ranging Behavior in a Group of Red Colobus Monkeys (Colobus badius tephrosceles)

Data are presented from 17 months of systematic sampling ofthe food habits, ranging patterns and distribution of food ofa group of red colobus monkeys. No positive or negative correlationswere found between the diversity of ranging patterns and thediversity of diet, distribution of food species, or percentageof young growth in the diet. There was, however, a significantcorrelation between the diversity of ranging pattern and thenumber of days per monthly sample that the group was proximalto or had aggressive encounters with another group of red colobusmonkeys.     

A note on the ecology of the red-colobus monkeys (Colobus badius tephrosceles) living in the Mahali Mountains

Red-colobus monkeys of the Mahali Mountains utilize many vegetation types; although their main habitat is composed of forest vegetation (gallery forest and montane forest), they sometimes penetrate into even theMiombo woodland.Red-colobus monkeys mainly live on leaves of trees, but sometimes eat flowers, fruits, and barks. Most of the plant leaves which the chimpanzees eat have proved to be delicacies to colobus monkeys also. Colobus monkeys live in compact bisexual groups, ranging from 30 to 50 in size. No solitary male has so far been observed.A colobus group living in the gallery forest moved 100 to 200 meters daily within its welldocumented home range. The home ranges of groups do not seem to overlap each other extensively.Their natural enemies are leopards, birds of prey and probably chimpanzees. The Tongwe inhabitants avail themselves of the colobus coat as part of their native bellows (mufuba) and some pagan inhabitants kill them for their meat.The research was financed by the Scientific Research Fund of the Ministry of Education and in part by the Wenner-Gren Foundation. This report is a part of the results of the Kyoto University Africa Primatological Expedition.     

Ecology of the Zanzibar Red Colobus Monkey: Demographic Variability and Habitat Stability

We examined the Zanzibar red colobus' (Procolobus kirkii) social structure and population dynamics in relation to the density, diversity and dispersion of food resources in ground-water forest and agricultural land, which we characterized in terms of red colobus food species density, diversity, basal area and dispersion. We used transect sampling and group follows to describe population dynamics and social systems. Two agricultural areas, SJF Shamba and Pete Village, had higher densities and more uniformly dispersed red colobus food tree species than those of the ground-water forest. Red colobus at these two sites had greater population densities and natality, and smaller home ranges than red colobus in the ground-water forest. However, these findings apply to a very small area of agricultural land (approximately 18 ha) that is contiguous with an area of the forest reserve having a high density of red colobus. It is not representative of agricultural areas elsewhere on Zanzibar which support much lower densities or no red colobus. Although agricultural areas contiguous with the forest reserve had high densities of red colobus, they appear to be very unstable. Within the agricultural areas, we observed higher intergroup variation in group size and composition, study groups that decreased dramatically in size and disappeared from the study site, significantly lower levels of juvenile recruitment, and red colobus food trees that exhibited definite signs of overbrowsing. This apparent instability in the subpopulation of red colobus utilizing agricultural systems probably reflects the lower basal area of food trees and the greater fragmentation of suitable habitat and floristic dynamics due to human activities in these areas. A fusion-fission social system occurred only in the ground-water forest subpopulation, which we hypothesize to be due to highly clumped food resources.     

Group Size and Composition of Colobus guereza in Kyambura Gorge, Southwest Uganda, in Relation to Chimpanzee Activity

We documented and assessed the influence of chimpanzee activity on group size and composition of Colobus guereza in Kyambura Gorge, southwest Uganda, from July to September, 1994 and in February and March 1996. The population density of colobus is very high: 347 individuals per km ². Density differed outside activity centers of chimpanzees (525 individuals per km ² ) and within the centers (186 per km ² ). We identified a total of 24 colobus groups, ranging between 3 and 13 individuals. Of the 24 groups, 22 were one-male groups. Groups were smaller and the percentage of subadults and juveniles was lower in groups within chimpanzee activity centers. Estimates of home ranges are between 1.7 and 6.2 ha, but neighboring home ranges overlapped 80%. Only a territory of approximately 0.5 ha was defended by the alpha male.     

Effect of Group Size on Activity Budgets of Colobus vellerosus in Ghana

Group size influences foraging efficiency in several primates. We examined the activity budgets of 3 groups of Geoffroy's pied colobus (Colobus vellerosus) at the Boabeng-Fiema Monkey Sanctuary in Ghana to determine whether larger group size induces scramble competition. We studied 2 groups (B1; N = 7-8 and WW; N = 31-33) occupying slightly overlapping home ranges from August to November 2000. We observed the third group, B2 (N = 15-16), comprising B1 and 7 male invaders in the same home range as B1 from August to November 2001. By comparing groups belonging to the same population and occupying sligthly overlapping or similar home ranges, we were able to control, to a certain extent, for differences in food distribution. We recorded a total of 3353 scans, yielding 14,886 activity records, over 73 days. As with other black-and-white colobus, resting was their most common activity (59%). Intergroup comparisons suggest that time spent feeding, resting and moving did not vary in relation to group size. However, intragroup comparisons between the sexes show that females in the large group spent more time feeding than males did, whereas this was not the case in the small group, which suggests that scramble competition may be occurring among female Colobus vellerosus at BFMS. It is also possible that this may be due to greater nutritional requirements because of a higher proportion of infants in the large group. In fact, the proportion is quite similar between the two groups, lending support to the idea that females in the two groups had comparable nutritional demands due to lactation. This suggests that increased feeding in females in the large group was partly an effect of scramble competition. Group size and group composition also influenced the frequency of social behavior. There was more grooming in the large group, and it was performed mostly by females. The distribution of activities throughout the day was similar to the pattern reported for other black-and-white colobus.     

Effects of habitat disturbance on the behavioral ecology and demographics of the Tana river red colobus (Colobus badius rufomitratus)

Annual surveys in 1985–1987 revealed that, since 1975, the total population of the Tana River red colobus (Colobus badius rufomitratus)declined by approximately 80%. An intensive study in 1986–1988 of two groups of colobus in the Tana River Primate National Reserve indicated that habitat disturbance from the changing river course and shifting agricultural practices were primarily responsible for the decline. Clearcutting around Mchelelo forest in the late 1960s compressed colobus populations to levels probably above the carrying capacity. Between 1975 and 1986 primate population density declined dramatically, the number of red colobus groups in Mchelelo forest decreased by half, and the size of the remaining group was greatly reduced. In 1986, there were fewer solitary colobus and small parties in the forest, harem male takeovers did not occur, infant survivorship increased, and demographic parameters generally had improved. The colobus groups in Mchelelo in 1973–1975, living at higher densities, showed different feeding and ranging behaviors than 1986–1988 groups. Range size was smaller in 1975, range overlap occurred, and a greater portion of the forest was used per day and per month. Mature leaves accounted for a much higher proportion of the diet. Time spent feeding and resting was the same in both studies. Social organization in predominantly one- male groups was maintained and adult and subadult females transferred between groups.     

Monkey Abundance and Social Structure in Two High-Elevation Forest Reserves in the Udzungwa Mountains of Tanzania

The effects of human activity on population and social structure are a pantropical concern for primate conservation. We compare census data and social group counts from two forests in the Udzungwa Mountains, Tanzania. The main aim is to relate differences within and between the forests to current theory on the effect of human disturbance on primate abundance and group size. The survey reveals the presence of the restricted-range red colobus, Procolobus gordonorum, in New Dabaga/Ulangambi Forest Reserve (NDUFR). The primate community of NDUFR is impoverished compared to that in Ndundulu forest. Red colobus and black-and-white colobus (Colobus angolensis palliatus) abundance and group size are lowest in NDUFR. Fission-fusion of red colobus social groups may be occurring in previously logged areas of both forests. Our observations are consistent with current theory on the effect of habitat degradation and hunting on primates, but the relative effects of the 2 factors could not be differentiated. We pooled the results with previous data to show that abundance of red colobus in the Udzungwa Mountains is lowest at high elevations. Low red colobus group sizes appear to be related to human activity rather than elevation. Black-and-white colobus and Sykes monkeys (Cercopithecus mitis) show no relationship with elevation. Future studies will require more detailed information on vegetation, diet and ranging patterns to interpret fully intraspecific variation in population demography and social structure in the Udzungwa Mountains.     

Comparison of habitat quality and diet of Colobus vellerosus in forest fragments in Ghana

The forest fragments surrounding the Boabeng-Fiema Monkey Sanctuary (BFMS) in central Ghana shelter small populations of Colobus vellerosus. Little is known about these populations or the ability of the fragments to support them, despite the fact that these fragments represent potentially important habitat for the colobus in this region. We compared the diet of three groups of C. vellerosus in the fragments to two groups in BFMS. We also examined the differences in plant species composition and food abundance among fragments. The study took place from June to November 2003. Dietary data were collected using scan sampling. Plant species composition and food abundance were evaluated using tree plots and large tree surveys. As in BFMS groups, leaves constituted the highest proportion of the diet of fragment groups, yet the colobus in fragments fed on more lianas than did those in BFMS. Over 50% of all species observed eaten by colobus in the fragments were not consumed in BFMS groups during the same season. Food abundance was similar between fragments and BFMS, although species composition differed. There was no relationship between the density of colobus and the density of food trees or percentage of food species, suggesting that other factors may be influencing the number of colobus present. This study highlights the broad dietary range of C. vellerosus, which may be a factor allowing its survival in these fragments.     

Ranging behaviour and its relation to diet selection in Tana River Red colobus (Colobus badius rufomitratus)

Ranging behaviour of a group of Red colobus monkeys, Colobus badius rufomitratus, on the Tana River, Kenya, is described. The main study group had a mean day journey of 603 in and an annual range area of 9 ha (measured in 0.25 ha quadrats). Relationships between ranging patterns and diet selection are sought on both spatial and temporal dimensions. Differential use of the annual range is related to the distribution of major food species, while the diversity of monthly ranging patterns is inversely related to the availability of young growth in the canopy. These findings lead to a discussion of why range areas at the Tana are much smaller than those reported from rain-forest sites.     

Influence of Chimpanzee Predation on Associations Between Red Colobus and Red-tailed Monkeys at Ngogo,Kibale National Park,Uganda

Colobines often associate with cercopithecines at various African sites. Such polyspecific associations presumably have an antipredation function. At Ngogo, Kibale National Park, Uganda, red colobus (Procolobus rufomitratus) spend considerable time in association with red-tailed monkeys (Cercopithecus ascanius), and they are also heavily hunted by chimpanzees (Pan troglodytes). I conducted behavioral observations and playback experiments to test the hypothesis that red colobus and red-tailed monkeys obtain mutual protection and predator-related benefits by associating. Despite high chimpanzee hunting pressure on red colobus and much lower hunting pressure on red-tailed monkeys, red-tailed monkeys initiate, maintain, and terminate the associations. The results suggest that rather than providing red colobus with protection against chimpanzees, the associations occur mostly because they protect red-tailed monkeys against predation by eagles.     

Group size in folivorous primates: ecological constraints and the possible influence of social factors

The ecological-constraints model assumes that food items occur in depletable patches and proposes that an increase in group size leads to increased day range due to more rapid patch depletion. Smaller groups become advantageous when an increase in travel costs is not repaid by an increase in energy gained or some other fitness advantage. On the other hand, we also know that group size can be influenced by social factors. Here we contrast the diet and group size of red colobus (Procolobus badius) and black-and-white colobus (Colobus guereza) in Kibale National Park, Uganda to consider how ecological and social factors are affecting their group sizes. Subsequently, we examine whether the insights gained from this detailed comparison can provide an understanding of why the social organization and group size of mantled howlers (Alouatta palliata) and black howlers (A. pigra) differ. Two groups of red colobus and two groups of black-and-white colobus were studied over 10 months. Red colobus groups were larger (48 and 24) than black-and-white colobus groups (9 and 6). The two groups of red colobus overlap home ranges with the two groups of black-and-white colobus; 75% and 95% of their home ranges were within red colobuss home range. There was a great deal of similarity in the plant parts eaten by the two species and both species fed primarily on young leaves (red colobus 70%, black-and-white colobus 76%). In terms of the actual species consumed, again there was a great deal of similarity between species. The average dietary overlap among months for the two neighboring groups of red colobus was 37.3%, while the dietary overlap between the red colobus and the black-and-white colobus group that had its home range almost entirely within the home range of the red colobus groups averaged 43.2% among months. If ecological conditions were responsible for the difference in group size between the two colobine species, one would expect the density of food trees to be lower in the home ranges of the black-and-white colobus monkeys, since they have the smaller group size. We found the opposite to be true. Both black-and-white colobus groups had more food trees and the cumulative size of those trees was greater than those in the red colobuss home ranges. We quantify how these differences parallel differences in mantled and black howlers. The average group size for mantled howlers was 12.9 individuals, and for black howlers it was 5.3 individuals. We explore possible social constraints, such as infanticide, that prevent black-and-white colobus and black howlers from living in large groups.This revised version was published online in April 2005 with corrections to the cover date of the issue.     

Charcoal Consumption by Zanzibar Red Colobus Monkeys: Its Function and Its Ecological and Demographic Consequences

The Zanzibar red colobus monkey is the only primate, aside from humans, known to eat charcoal in the wild. All age classes and both sexes eat charcoal, but only those groups living in perennial gardens or near human dwellings do so. The habit appears to be transmitted from mother to offspring by imitation, but how it developed in the first place is unknown. Sources of charcoal include charred stumps, logs, and branches, as well as that produced in kilns by humans. These charcoals adsorb organic materials, such as phenolics, particularly well and, as a consequence, remove these compounds, which have the potential to be toxic or interfere with digestion or both. The extreme inertness of charcoal makes it an unlikely source of minerals to the colobus. We conclude that, by eating charcoal, monkeys living in gardens with a high density of food species dominated by exotic trees — Indian almond and mango — are able to exploit this abundant food resource that is high in total phenolic content much more effectively than in the absence of charcoal. The young leaves of these exotic tree species are also very high in protein and highly digestible. The benefits of charcoal eating are most likely due to the fact that charcoal adsorbs phenolics better than proteins. This may explain in large part why the birth rates and population densities of the colobus living in the Indian almond and mango habitat adjacent to the Jozani Forest are significantly higher than those in the ground-water forest. The population density of colobus in this small area is the highest ever recorded for a nonhuman anthropoid (700/km ² ). It may not, however, be a stable situation, as there are indications of higher levels of aggression, lower recruitment into the medium-juvenile size class, and overbrowsing.     

Population Sizes and Distribution of Primates in the Lower Tana River Forests,Kenya

We studied the population size and distribution of diurnal primates in the lower Tana River forests, Kenya. They are the only remaining habitats for 2 threatened primates: the Tana River red colobus (Procolobus rufomitratus) and the Tana River crested mangabey (Cercocebus galeritus galeritus). We conducted censuses in 73 forest patches from January through March 2001. We estimate population size of the red colobus to be 788 individuals in 82 groups and that of the crested mangabeys to be 2,070 individuals in 59 groups. The data suggest that over a 7-year period (1994-2001), there was an 18% increase in the crested mangabey population and a 5% decline in red colobus numbers. Further, the red colobus range has expanded both north and south, whereas that of crested mangabeys has only expanded south. Fifty-six percent of crested mangabeys and 46% of red colobus groups were inside the Tana River Primate National Reserve (TRPNR). Other primates encountered included 170 groups of Sykes' monkeys (Cercopithecus mitis), 70 groups of yellow baboons (Papio cynocephalus) and 4 groups of grivets [Chlorocebus (Cercopithecus) aethiops]. Mean group densities of the 2 endangered primates and of baboons were higher inside than outside the TRPNR, reinforcing the importance of TRPNR for their conservation. An intervention program is required to stem further decline in the red colobus population and to protect small isolated groups in forest patches outside TRPNR.     

Interspecific interactions between wild pygmy chimpanzees (Pan paniscus) and red colobus (Colobus badius)

Interspecific interactions accompanied by physical contacts between wild pygmy chimpanzees (Pan paniscus) and red colobus (Colobus badius) were observed on three occasions at Wamba, Republic of Zaire. In all cases, the red colobus initiated the interactions by approaching the pygmy chimpanzees. Most of the pygmy chimpanzees, which were within 5 m of the red colobus, were juveniles or infants but the adult male pygmy chimpanzees never showed any interest in the red colobus. The red colobus groomed the chimpanzees in two cases, but the latter never groomed the former. No true aggressive interactions were observed between the two species. The lack of any evidence of hunting of red colobus through longitudinal studies of the pygmy chimpanzees of Wamba, together with the present observations, suggests that red colobus are probably not targets of hunting by the pygmy chimpanzees.     

Vigilance in ursine black and white colobus monkeys (Colobus vellerosus): an examination of the effects of conspecific threat and predation

Vigilance is thought to have evolved as an antipredator defense but, in primates, conspecific threat often better explains this behavior. We examined vigilance in one group of Colobus vellerosus inhabiting the Boabeng‐Fiema Monkey Sanctuary in Ghana. We aimed to (1) describe factors affecting vigilance in this population, and (2) examine the importance of predation avoidance and conspecific threat in explaining vigilance patterns. Because of a male takeover preceding the study, our focal group (B2) consisted of six adult males and three adult females. We collected 490 10‐min focal samples (82 hr) from all adults in the group (N=9) from July to November, 2001. To avoid predators, individuals should be more vigilant (i) with fewer neighbors, and (ii) in areas of the canopy with higher predation risks. Conspecific threats can be divided into extra‐ and intra‐group threats. Extra‐group threats should lead to higher vigilance levels (iii) during intergroup encounters, and (iv) in areas where the home range overlaps with other groups of colobus. Intra‐group threats should lead to greater vigilance (v) in the presence of neighbors and (vi) while feeding or occupying food patches (if resources are limiting). Our results best support the hypothesis that vigilance functions primarily to detect extra‐group, conspecific threats. Individuals were most vigilant during intergroup encounters and in areas of range overlap, and monthly vigilance rates were associated with monthly encounter rates. Individuals tended to scan less in proximity to familiar vs. unfamiliar group mates, suggesting that relationship quality may affect colobus vigilance. Finally, predation pressures or anthropogenic disturbances might have influenced vigilance, as individuals were more vigilant low in the canopy. However, this last result could also be due to the lower visibility because of dense foliage or to the fact that the monkeys have access to fewer escape routes when ranging lower in the canopy. Am. J. Primatol. 71:919–927, 2009. © 2009 Wiley‐Liss, Inc.     

Better to Live with Allogenerics Than to Live Alone? The Case of Single Male Cercopithecus pogonias in Troops of Colobus satanas

We report the integration of single male crowned guenons (Cercopithecus pogonias) into troops of black colobus (Colobus satanas). We observed one male Cercopithecus pogonias in three troops of Colobus satanas on 30% of observation days (n = 231). Activities of single males guenons did not differ significantly from those of the colobus with which they associated. Moreover, both species performed simultaneously the same activities more often than expected by chance. Interspecific grooming occurred on several occasions. Furthermore, single male guenons spent as much in time social activities when part of a colobus troop, as they typically do when part of a conspecific group. Unlike solitary male crowned guenons, which are silent, a male that is integrated into a troop of colobus is vocal and emits social alarm calls to which colobus monkeys respond. During the single file movements of colobus troops, single male crowned guenons were integrated in the core of the troop and used the same branches at the same height with the colobus. Thus, the life of a single male crowned guenon with black colobus was social. We suggest that the main benefits that he gained is the possibility to live in a social context. Social interactions could be the key element to explain why single males Cercopithecus pogonias join troops of monkeys so different from their natal groups.     

Some observations on the ecology ofColobus badius temmincki,Abuko Nature Reserve,the Gambia,West Africa

Three groups of red colobus (Colobus badius temmincki) were observed at the Abuko Nature Reserve in the Gambia, West Africa between December 1973 and August 1974. The population of the three groups ranged from 24–40 animals with home ranges measuring 4.3–12.8 hectares. The red colobus fed on a wide variety of flora and their diet included fruit, flowers, shoots, and bark, as well as new and mature leaves. There was a change in diurnal activity patterns over the two seasons (dry and rainy), with more definitive activity peaks occurring during the dry season.     

Population Declines of Colobus in Western Uganda and Conservation Value of Forest Fragments

The processes of habitat loss and fragmentation are probably the most important threats to biodiversity. It is critical that we understand the conservation value of fragments, because they may represent opportunities to make important conservation gains, particularly for species whose ranges are not in a protected area. However, our ability to understand the value of fragments for primates is limited by the fact that researchers have conducted many studies in protected areas, which do not represent most fragments, and studies are typically short term. Here we determine the long-term survival probability of red (Procolobus pennantii) and black-and-white colobus (Colobus guereza) inhabiting forest fragments outside of Kibale National Park, Uganda. Local communities use the fragments primarily for subsistence agriculture and fuelwood. We surveyed primate populations 3 times over 8 yr, made a total inventory of all trees 2 times, contrasted behavior of groups inhabiting 1 fragment with groups in the continuous forest, and judged the conservation value of the fragments by quantifying patterns of forest use by local people. Of the 20 fragments surveyed, 16 supported resident populations of colobus in 1995, 2 were cleared in 2000, and an additional 2 fragments were cleared by 2003. In 1995 we counted 165 black-and-white colobus, whereas in 2000 and 2003, we counted 119 and 75 individuals, respectively. Seven fragments supported red colobus in 1995, 11 in 2000, and 9 in 2003. In 2000 we counted 159 red colobus, while in 2003, we saw 145 individuals. For both species, activity patterns in continuous forest were similar to those in a fragment, with the exception that individuals in the fragment rested more. Colobus in the fragment ate more mature leaves than colobus in the continuous forest did. Fragments supported all the fuelwood needs of an average of 32 people who lived immediately adjacent to them, and partially supported families up to 3 farms away (ca. 400 m), representing 576 people. Intensive harvesting for fuelwood occurred when neighboring households engaged in beer brewing (an average of 9.6% of the households), gin distilling (8.8%), or charcoal production (14.5%). Overall, between 2000 and 2003, the average density of trees declined by 14 trees/ha (range = 0–60 trees/ha). If current rates of clearing continue, the probability that the fragments will continue to support colobus populations is low.     

Interactions among foraging honey bees from different apiaries in the same field

Summary The extent to which honey bee foragers from an apiary are influenced by the presence of bees from other colonies in the same field was studied with the aid of colonies whose bees were made radioactive with P³². It was found that the concentration of tagged bees decreased more near large apiaries than near a small group of eight colonies. The population density of all bees was found to be slightly greater near the three larger apiaries than elsewhere on the experimental fields.The total population of both marked and unmarked foragers was more uniform in a field in which no colonies were located, although a heavier concentration of marked bees was still evident at sampling stations within 110 yards of the edge nearest the experimental apiary from which they had flown.The experimental fields included two varieties of alfalfa, Narragansett and Ranger. A higher bee population existed on the Narragansett field of alfalfa than on the adjacent field of Ranger. Its greater attractiveness may have been because of its thinner stand density or of varietal differences.

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Zusammenfassung Inwiefern Trachtbienen aus einem Bienenstand durch die Anwesenheit von Bienen aus anderen Völkern in demselben Feld beeinflusst werden, wurde mit Hilfe von Völkern studiert, deren Bienen mit radio-aktivem P³² markiert worden waren. Es wurde festgestellt, dass die Konzentration markierter Bienen nahe grossen Bienenständen stärker abfiel als nahe einer kleinen aus acht Völkern bestehenden Gruppe. Weiter wurde festgestellt, dass die Bevölkerungsdichte aller Bienen nahe den drei grösseren Bienenständen ein wenig höher war als anderswo auf den Versuchsfeldern.Die Gesamtbevölkerung sowohl der gezeichneten als auch der ungezeichneten Trachtbienen war gleichmässiger in einem Feld, in dem keine Völker aufgestellt waren, obgleich es an den Sammelstellen noch offensichtlich war, dass die gezeichneten Bienen innerhalb 100.6 Meter (110 Yards) des Feldrandes nächst dem Versuchsbienenstand, von dem sie anflogen, stärker konzentriert waren.Die Versuchsfelder umfassten zwei Abarten der Luzerne: Narragensett und Ranger. Eine stärkere Bienenbevölkerung existierte auf dem Feld mit Narragansett als auf dem angrenzenden Feld mit Ranger. Die grössere Anlockung ist möglicherweise durch die geringere Wachstumsdichte oder durch die Verschiedenheiten der Abarten verursacht worden.

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Résumé Le degré auquel les Abeilles butineuses d'un rucher sont influencées par la présence d'Abeilles d'autres colonies dans le même champ a été étudié à l'aide de colonies dont on a marqué les Abeilles avec du P³² radio-actif. On a trouvé que la concentration des Abeilles marquées diminuait plus près des grands ruchers que près d'un petit groupe de 8 colonnies. On a trouvé que la densité de toutes les Abeilles était légèrement plus forte près des 3 plus grands ruchers que dans d'autres parties des champs expérimentales.La population totale et de butineuses marquées et de celles non marquées était plus uniforme dans un champ où aucune colonie n'était pas placée, bien qu'une plus forte concentration d'Abeilles était encore évidente aux lieux d'échantillonnage à 100,6 m (110 yards) du bord du champ le plus près du rucher expérimental d'où provenaient les Abeilles.Les champs expérimentaux renfermaient 2 variétés de luzerne: Narragansett et Ranger. Une plus forte population d'Abeilles existait sur le champ de Narragansett que sur le champ voisin de Ranger. La plus grande attractivité de la première était peut-être due à sa moindre densité de croissance ou à des différences de variété.

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In cooperation with theUtah Agricultural Experiment Station.