Accepting loss: the temporal limits of reciprocity in brown capuchin monkeys

Delayed reciprocity is a potentially important mechanism for cooperation to occur. It is however rarely reported among animals, possibly because it requires special skills like the ability to plan a loss. We tested six brown capuchin monkeys (Cebus apella) in such skills. Subjects were studied in exchange tasks in which they had to retain a food item for a given time lag before returning it to an experimenter and obtaining a more desirable reward. Experiments showed that the subjects could wait for several minutes when allowed to return only part of the initial item. When required to return the full item intact, however, most subjects could not sustain a time lag longer than 10 s. Although the duration of waiting increased with the amount of return expected by subjects, in most cases it did not extend beyond 20 s even when the eperimenter offered a food amount 40 fold the initial item. The failure of capuchin monkeys to sustain long-lasting waiting periods may be explained by limited self-control abilities. This would prevent them achieving reciprocal altruism.     

Exchange of objects between humans and captive western lowland gorillas

An experiment was carried out to assess the ability of captive western lowland gorillas (Gorilla g. gorilla) to exchange objects with a human partner. Before the exchange itself, individuals had to learn to give an item to the experimenter. Four individuals out of nine performed active giving. After that familiarization with giving behaviour, two kinds of exchanges, of increasing complexity, were tested with gorillas. Simple exchange (give C to obtain D) was the first procedure and six gorillas out of nine succeeded. Double exchange (give B to receive C, then give back C to obtain D) was performed only by three individuals and triple exchange (give A to receive B, give back B to receive C, then give back C to obtain D) was performed only by two individuals. Different types of errors were scored, as well as social constraints on learning. Results showed that (1) naive gorillas are able to get a reward (D) in an experimental exchange situation; and (2) the complex rules of multiple successive exchanges were not easily understood by gorillas.     

Problem solving and functional design features: experiments on cotton-top tamarins, Saguinus oedipus oedipus

In any problem-solving situation, there are features associated with the problem that are relevant from a functional perspective and other features that are irrelevant. To determine whether animals are sensitive to the distinction between functionally relevant and irrelvant features of a problem, we conducted two main experiments with a New World monkey, the cotton-top tamarin. In the first condition of both experiments, subjects were required to pull a piece of cloth to gain access to a piece of food. The first experiment involved choosing between food that was on the cloth and food that was off the cloth. The second experiment involved choosing between food that was on a connected piece of cloth and food that was on two pieces of cloth separated by a horizontal gap. Having learned to solve either of these two problems, we conducted a series of probe conditions to determine whether the tamarins would generalize to changes in the shape, size, colour, and texture of the cloth and food, the position of the food relative to the cloth, and the type of connection between two pieces of cloth. For most of the probe conditions, the tamarins readily generalized, showing no decrement in performance, even on the first trial. For other conditions, involving apparently more subtle discrimination (e.g. a narrow vertical gap between the two pieces of cloth), explicit training was required. These results indicate that tamarins solve means-end relationships, and that their ability depends on a discrimination between properties that are functionally relevant as opposed to irrelevant. Copyright 1999 The Association for the Study of Animal Behaviour.     

Bt抗虫棉秸秆还田对土壤养分特征的影响

【目的】研究转基因作物秸秆或残茬还田可能对土壤养分特性造成的影响。【方法】以不同抗虫水平Bt棉花和常规棉花(泗棉3号)为研究材料,分别在经过一、二个生长周期后将秸秆机械粉碎后原位还田,40 d后测定分析土壤中Bt蛋白含量及肥力相关的养分含量变化。【结果】Bt棉秸秆还田后,所有品种棉花土壤中Bt蛋白含量与还田前无显著增加,且转Bt基因棉与非转基因棉还田对土壤Bt蛋白含量的影响并无显著差异。同时,棉秸秆还田可显著提高土壤有机质、速效磷、碱解氮、速效钾、全氮、全磷和全钾含量,提升土壤pH值;增加幅度在不同抗虫水平Bt棉花间及与非转基因常规棉花品种间皆无显著性差异。【结论】秸秆还田对土壤肥力的提升与Bt棉的抗虫水平无关。“转Bt基因”不成为Bt棉秸秆还田提高土壤肥力的限制性因素,其秸秆还田不会对土壤肥力质量产生负面影响,可使土壤养分含量增加,有效提升土壤肥力。秸秆原位还田简单、无害又提升肥力,有条件作为转Bt基因植物秸秆无害化处理的理想方式。     

The effect of individual and food characteristics on food retrieval and food sharing in captive Guinea baboons (Papio papio)

Access to food is of major importance to the fitness and survival of every individual, particularly in group-living animals, in which individual characteristics and food distribution can affect food intake. Additionally, several species of primates are known to share food under certain conditions. Such unresisted transfer of food from one individual to another appears to be adaptive, for instance as a tool to maintain and reinforce social bonds. In this study, we aimed to test how food retrieval and food sharing varies depending on the social relationship between individuals, and on the characteristics of the food. In six different test conditions, we provided a captive group of Guinea baboons (Papio papio, N = 23) with multiple food items, differing in quality, quantity, density, monopolizability, and effort required to obtain it. We further used behavioral observations to assess individual relationships and possible variations in grooming exchanges linked to food sharing events. Out of 424 events in which food items were retrieved by the subjects, we detected no instances of active food sharing and only 17 of passive food sharing. The way food was retrieved was affected by individual and food characteristics (i.e., quantity, quality, and monopolizability of food): Males and central individuals (i.e., those connected to many partners, and/or having partners with many connections in the social network) were more likely to retrieve food during test conditions. In particular, events of passive food sharing mostly happened when the quality of food was low, and between individuals belonging to the same community (i.e., having close relationships). No other food characteristics affected the probability to share food, and the occurrence of food sharing had no immediate effect on grooming exchanges. Overall, our findings suggest that food sharing is relatively rare in Guinea baboons unless the food has a low quality and individuals form close social bonds.     

Tonkean Macaques Orient Their Food Search From Olfactory Cues Conveyed by Conspecifics

We investigated the ability of monkeys to use referential information about environmental resources from cues passively transmitted by conspecifics. The subjects and their companions were four young males belonging to a group of semifree‐ranging Tonkean macaques (Macaca tonkeana) raised in a 2‐acre wooded park. In a first experiment, a subject had to orient its search strategy from the information obtained from a conspecific. It first had to smell the mouth of a companion having just eaten a food item, and then search for same quality food in the field. The results showed that subjects adjusted their foraging speed according to the value of the reward to be found. They were able to recognize the food resource on the basis of the item previously eaten by their companion. In a second experiment, we asked whether the subjects could anticipate a given food quantity from smelling a companion associated with that given food quantity. When testing whether subjects oriented their search strategy on the basis of companion's identity, they did not appear to use it as a referential cue to food quantity. They nonetheless adapted their foraging speed according to food value. Both experiments indicated that macaques are liable to assess and select food from information extracted from conspecifics, and hence avoid some costs associated with individual food searching.     

Aimed Throwing as a Means of Food Transfer Between Tufted Capuchins (Cebus apella)

We examined aimed throwing as a means of food transfer in tufted capuchins (Cebus apella). We conducted this research in three phases. In Phase 1 we provided food to monkeys in one of two groups housed 1 m apart. We did not provide food to subjects in the second group. An observer recorded each instance in which a subject in the first group threw food toward one in the second group. In Phase 2 we provided a group of capuchins with food and noted each instance in which a subject threw food toward an empty cage. In Phase 3 we provided food simultaneously to two groups of capuchins and noted each instance of food-throwing between them. In Phase 1 subjects in one group threw food toward subjects in a second group, which, when provided the opportunity, did not throw food toward capuchins in the first group. Thrown food was either caught, retrieved, or lost on the test room floor. The rate of throwing decreased significantly when subjects were presented with an empty cage and when both groups of subjects were given food. We propose that psychological processes which underlie aimed throwing and food sharing came into existence through convergent evolution in large-brained, extractive foraging primates. We further speculate that although a well-developed system of exchange, based on contingent reciprocity, may occur among primates only inHomo,simpler transfer systems involving voluntary unidirectional passing of food from one individual to another appear to be more widespread among primates than previously thought and can be expressed in rather unusual circumstances such as those in this experiment.     

Sex differences in food acquisition and aggression in captive common marmosets (Callithrix jacchus)

Competition for food within the social group has been postulated as an important factor affecting primate social organization. This study examined how factors such as sex, aggression, dispersion of food, and amount of difficulty involved in obtaining food affect the distribution of food in common marmoset (Callithrix jacchus) social groups. Mated pairs of adultC. jacchus were presented with food that was either dispersed or concentrated, and either difficult or easy, to obtain. The number of food pieces obtained, aggressive displays, incidents of physical aggression, and amount of time spent searching for food were recorded for each animal. Neither dispersion nor difficulty in obtaining food had significant effects on the distribution of food or any of the other behaviors examined. The primary factors affecting food distribution were aggression and amount of time spent searching. Females obtained more food than males in all situations because they were more aggressive and apparently more motivated to search for food than were males.     

Can Monkeys Make Investments Based on Maximized Pay-off?

Animals can maximize benefits but it is not known if they adjust their investment according to expected pay-offs. We investigated whether monkeys can use different investment strategies in an exchange task. We tested eight capuchin monkeys (Cebus apella) and thirteen macaques (Macaca fascicularis, Macaca tonkeana) in an experiment where they could adapt their investment to the food amounts proposed by two different experimenters. One, the doubling partner, returned a reward that was twice the amount given by the subject, whereas the other, the fixed partner, always returned a constant amount regardless of the amount given. To maximize pay-offs, subjects should invest a maximal amount with the first partner and a minimal amount with the second. When tested with the fixed partner only, one third of monkeys learned to remove a maximal amount of food for immediate consumption before investing a minimal one. With both partners, most subjects failed to maximize pay-offs by using different decision rules with each partner' quality. A single Tonkean macaque succeeded in investing a maximal amount to one experimenter and a minimal amount to the other. The fact that only one of over 21 subjects learned to maximize benefits in adapting investment according to experimenters' quality indicates that such a task is difficult for monkeys, albeit not impossible.     

Delay Maintenance in Tonkean Macaques (<Emphasis Type="BoldItalic">Macaca tonkeana</Emphasis>) and Brown Capuchin Monkeys (<Emphasis Type="BoldItalic">Cebus apella</Emphasis>)

Animals commonly face choices requiring them to wait and postpone action. The ability to delay gratification is a prerequisite for making future-oriented decisions. We investigated the ability of brown capuchins (Cebus apella) and Tonkean macaques (Macaca tonkeana) to delay benefits in several experiments. In exchange tasks, subjects had to return a piece of cookie after a given time lag to obtain a larger one from an experimenter. Capuchins could wait 10–40 s and macaques 20–80 s depending on subjects and the size of rewards. Both groups were able to anticipate delay durations, but unlike macaques, capuchins discounted all sizes of reward at the same speed, meaning that their delay-maintenance was not affected by the reward size. When the subjects could give the initial piece of cookie back immediately and then wait for the return, performances increased to 10–21 min for capuchins and 21–42 min for macaques, demonstrating the role of consumption inhibition in postponing gratification. In a further task, we presented subjects with an accumulation of food pieces added at short intervals until they seized them. On average, brown capuchins could wait 33–42 s and macaques 38–72 s before seizing the rewards. Our results confirmed that brown capuchins were more impulsive than Tonkean macaques in several tasks. We did not find significant differences between the waiting performances of the Tonkean macaques and those previously reported in long-tailed macaques. The contrasting performances of macaques and capuchins might be related to their different skills in the physical and social domains.     

Polymorphism and size-pairing in the harvester antPogonomyrmex badius: a test of the ecological release hypothesis

Summary The role of caste polymorphism in the foraging strategy ofPogonomyrmex badius was studied in the field by measuring food items collected by foragers, and correlating food item size variables with forager size variables. The diet ofP. badius included seeds and insects. In two colonies examined, these food types comprised different proportions of the diet sample.Although some forager size variables showed close or significant correlations with food item size variables, we could identify no overall significant relationship between worker size and seed or prey size. Polymorphism inP. badius may be associated with omnivory. However, since minor workers serve as foragers and represent a portion of the total worker size variation, dietary expansion through caste proliferation appears to be only one aspect of the functional significance of polymorphism in this species.     

Do capuchin monkeys, Cebus apella, know what conspecifics do and do not see?

Capuchin monkeys were tested in five experiments in which two individuals competed over food. When given a choice between retrieving a piece of food that was visible or hidden from the dominant, subordinate animals preferred to retrieve hidden food. This preference is consistent with the hypotheses that either (1) the subordinate knew what the dominant could and could not see or (2) the subordinate was monitoring the behaviour of the dominant and avoiding the piece of food that it approached. To test between these alternatives, we released subordinates with a slight head start forcing them to make their choice (between a piece of food hidden or visible to the dominant) before the dominant entered the area. Unlike chimpanzees, Pan troglodytes, subordinates that were given a head start did not preferentially approach hidden pieces of food first. Therefore, our experiments provide little support for the hypothesis that capuchin monkeys are sensitive to what another individual does or does not see. We compare our results with those obtained with chimpanzees in the same paradigm and discuss the evolution of primate social cognition. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Descriptive study of antennation during trophallactic unloading contacts in honeybees <Emphasis Type="Italic">Apis mellifera carnica</Emphasis>

Summary  Trophallaxis, the mouth-to-mouth transfer of food, is a widespread behavior occurring between individuals of eusocial insect societies. Antennal movements during food transfer are, in honeybees, too rapid to be characterized using standard video recordings. Using a high-speed camera (200 frames/s), we recorded nectar unloading performed by forager honeybees (Apis mellifera carnica Spinola) within the hive once they returned from collecting sugar solution at a feeder that delivered nectar at a variable rate. Frequency patterns attained a mean value of 13 Hz. Antennation intensity showed a tendency to increase with the reward rate recently exploited by the food donor. This raises the question whether or not antennation intensity is a reliable parameter providing modulatory information related to food-source profitability.Received 12 September 2002; revised 21 March 2002; accepted 24 April 2003.     

Experimental assessment of problem solving by <Emphasis Type="Italic">Milvago chimango </Emphasis>(Aves: Falconiformes)

We report a preliminary assessment of problem solving as an estimate of behavioural innovation and learning ability of a generalist and abundant raptor, Milvago chimango, under controlled conditions in aviaries. Experimental tests consisted in presentation of a Plexiglas box with four lids leading to isolated pieces of meat. We recorded time to first contact with the box and time from this first contact to gaining access to the pieces of meat. We recorded the number of attempts to open the box and reach the first portion of meat, and the total number of lids opened by each individual during five successive daily sessions. We found that individuals of M. chimango quickly approached and made contact with the Plexiglas box, and responded successfully to the novel feeding problem of reaching the food inside. In our study, performance of individuals was enhanced after solution of the novel task for the first time, as indicated by the progressively reduced time taken to access the food. Further, some individuals gained access to an increasing number of sections of the Plexiglas box during subsequent sessions, suggesting significant learning ability. Our results indicated M. chimango has a remarkable ability to obtain food in a novel situation, an observation that agrees with anecdotal reports of opening of receptacles to obtain food in urban environments. The results support the idea of behavioural plasticity in this species.     

Do chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) use cleavers and anvils to fracture <Emphasis Type="Italic">Treculia africana</Emphasis> fruits? Preliminary data on a new form of percussive technology

Wild chimpanzees (Pan troglodytes) are renowned for their use of tools in activities ranging from foraging to social interactions. Different populations across Africa vary in their tool use repertoires, giving rise to cultural variation. We report a new type of percussive technology in food processing by chimpanzees in the Nimba Mountains, Guinea: Treculia fracturing. Chimpanzees appear to use stone and wooden “cleavers” as tools, as well as stone outcrop “anvils” as substrate to fracture the large and fibrous fruits of Treculia africana, a rare but prized food source. This newly described form of percussive technology is distinctive, as the apparent aim is not to extract an embedded food item, as is the case in nut cracking, baobab smashing, or pestle pounding, but rather to reduce a large food item to manageably sized pieces. Furthermore, these preliminary data provide the first evidence of chimpanzees using two types of percussive technology for the same purpose.     

Aggressive communication in fulmars (Fulmarus glacialis) competing for food

A simple model which considers communication of subjective resource value during aggressive encounters is developed. If different behavioural patterns differ in effectiveness (probability of winning) the model predicts that: (1) the expected cost should differ for different behaviour patterns; (2) when effectiveness increases, the associated cost should increase; and (3) the optimal choice should be influenced by the value the resource represents for the animal. These predictions were tested on field data from 1383 interactions between fulmars competing for food. In these interactions, one bird was the ‘owner’ who defended the food item and during the time of ownership ate pieces of the food item. The owner was regularly challenged and take-overs occurred in 22% of interactions. The effectiveness of a given behaviour pattern was measured as the proportion of interactions won. The cost was measured as the proportion of interactions that entailed physical fighting. Resource value was estimated indirectly by comparing time as owner with choice of behaviour. The results indicate that an animal's choice of behaviour influenced its probability of victory, and expected cost, and that effectiveness and cost correlate positively. Furthermore, the frequency with which different behaviours were observed is influenced by the value of the resource for the bird.     

Trophallaxis in a primitively social sphecid wasp

Summary In a total of six hours of observation of severalMicrostigmus nigrophthalmus nests with two or more adult wasps, nine buccal contacts, six between females and three between females and males were observed. Except for two cases, these occurred soon after one of the females involved (the apparent donor) had returned to the nest and involved transfer from older to younger individuals. Experimental feeding of colored solution confirmed the occurrence of trophallaxis. InM. nigrophthalmus, trophallaxis seems to have arisen as a prolongation of maternal care since food is transferred from an older to a younger individual.     

The Effect of Food Size and Dispersion Pattern on Retrieval Rate by the Argentine Ant, Linepithema humile (Hymenoptera: Formicidae)

Food acquisition in central-place foraging animals demands efficient detection and retrieval of resources. Most ant species rely on a mass recruitment foraging strategy, which requires that some potential foragers remain at the nest where they can be recruited to food once resources are found. Because this strategy reduces the number of workers initially looking for food, it may reduce the food detection rate while increasing the postdiscovery food retrieval rate. In previous studies this tradeoff has been analyzed by computer simulation and mathematical models. Both kinds of models show that food acquisition rate is greatly influenced by food distribution and resource patch size: as food is condensed into fewer patches, the maximal acquisition rate is achieved by a shift to fewer initial searchers and more potential recruits. In general, these models show that a mass recruitment strategy is most effective when resources are clumped. We tested this prediction in two experiments by letting laboratory colonies of the Argentine ant (Linepithema humile) forage for resources placed in different distributions. When all prey were small, retrieval rate increased with increasing resource patch size, in support of foraging models. When prey were large, however, the mass of prey returned to the colony over time was much lower than when prey were small and widely distributed. As more ants reached a large prey item, the distance the prey item was transported decreased due to a greater emphasis on feeding rather than transport. Because Argentine ants can transport more biomass externally than they can ingest, food retrieval that depends only on ingestion can depress the biomass retrieval rate. Thus, our results generally support theoretical foraging models, but we show how prey size, through differential prey-handling behavior, can produce an outcome greatly different from that predicted only on the distribution of resources.     

Foraging,Delayed Maturation,and Advantages of Cooperative Breeding in White-winged Choughs,Corcorax melanorhamphos

White-winged choughs live in groups which cooperate in all aspects of rearing young, affording an opportunity to examine the influence of cooperation on foraging behavior. The amount of food choughs forage for themselves and feed to young increases with age, supporting the idea that individuals which dispersed to breed would have difficulty in rearing young. When feeding nestlings, individuals in the two larger groups returned to the nest less often and with larger loads than the individuals in the smallest group. Choughs in the smallest group also consumed less food at the beginning of each trip from the nest than those in the larger groups. We suggest that these measures indicate the greater efficiency allowed to individuals in larger groups when foraging from the nest. In all groups, individuals returning to the nest simultaneously with other group members carried smaller loads than those returning alone. We propose that returning in groups enables all nestlings of asynchronously hatched broods to obtain sufficient food.     

Nectar distribution and its relation to food quality in honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis>) colonies

In honeybees (Apis mellifera), the process of nectar collection is considered a straightforward example of task partitioning with two subtasks or two intersecting cycles of activity: (1) foraging and (2) storing of nectar, linked via its transfer between foragers and food processors. Many observations suggest, however, that nectar collection and processing in honeybees is a complex process, involving workers of other sub-castes and depending on variables such as resource profitability or the amount of stored honey. It has been observed that food processor bees often distribute food to other hive bees after receiving it from incoming foragers, instead of storing it immediately in honey cells. While there is little information about the sub-caste affiliation and the behaviour of these second-order receivers, this stage may be important for the rapid distribution of nutrients and related information. To investigate the identity of these second-order receivers, we quantified behaviours following nectar transfer and compared these behaviours with the behaviour of average worker hive-bees. Furthermore, we tested whether food quality (sugar concentration) affects the behaviour of the second-order receivers. Of all identified second-order receivers, 59.3% performed nurse duties, 18.5% performed food-processor duties and 22.2% performed forager duties. After food intake, these bees were more active, had more trophallaxes (especially offering contacts) compared to average workers and they were found mainly in the brood area, independent of food quality. Our results show that the liquid food can be distributed rapidly among many bees of the three main worker sub-castes, without being stored in honey cells first. Furthermore, the results suggest that the rapid distribution of food partly depends on the high activity of second-order receivers. Received 31 August 2006; revised 8 December 2006; accepted 11 December 2006.