Responses of wild chimpanzees (<Emphasis Type="Italic">Pan troglodytes schweinfurthii</Emphasis>) toward seismic aftershocks in the Mahale Mountains National Park,Tanzania

This is the first report documenting the responses of wild chimpanzees (Pan troglodytes schweinfurthii) to seismic activities. During our long-term fieldwork in Mahale Mountains National Park, Tanzania, a high-intensity earthquake with a Richter magnitude of 6.8 occurred at 15:19 hours local time on 5 December 2005. During the main tremor, the chimpanzees displayed the “wraa” call, “scream,” and “pant bark” or “bark” vocalizations. Many mild aftershocks followed the main tremor, and the wild chimpanzees displayed a variety of responses to these. In several cases, they climbed trees or stopped activities such as grooming, moving, and feeding. These responses are similar to those previously reported in nonhuman primates. During the observations, a unique behavior, one never reported before was exhibited by a female chimpanzee. She placed her right palm on the ground giving the impression she was inspecting the trembling of the ground.     

Acquisition and transfer of visual Go/No-go discrimination by a chimpanzee

An adolescent female chimpanzee was trained to press a key in the presence of a computer-graphic geometric figure (“Go” stimulus) within 5 sec and not to press the key during 5-sec presentations of another figure (“No-go” stimulus) with food reinforcement. In the acquisition training, the accuracy of performance increased primarily as a result of learning to inhibit key presses in No-go trials. The chimpanzee acquired this “Go/No-go” visual discrimination task in 1,260 trials. She was then given 14 successive transfer problems. The results for these problems suggested that learning-set formation and repeated use of the same discriminative stimuli both influenced transfer to new problems.     

Tool-using and -making behavior in wild chimpanzees at Bossou,Guinea

The behavior of wild chimpanzees at Bossou, Guinea, was studied from November 1976 to May 1977 recognizing each chimpanzee without artificial feeding. During the study period some tool-using and tool-making behavior was observed, as follows: (1) Although water drinking using a “leaf-sponge” was not seen, that using a “leaf-spoon” was observed for taking water from the hollow of a tree. (2) “Termite fishing” was not seen in this group although there were many termite hills in the moving range of the chimpanzees. They dug termites from the hollow of a tree by pounding with a small stick. Similar use of a stick was made for digging up the resin from a tree. (3) “Aimed throwing” was frequently observed in adult males for attacking an observer, and in adolescents and juveniles as mischief against an observer or for their own play. (4) “Nut cracking” with a pair of stones was seen for removing the ovule from palm-seeds. Particular stones were repeatedly used by many chimpanzees for a long period. (5) “Branch hauling” represented difficult work. Patient and inventive manufacture of proper sticks was necessary for capturing branches which they were unable to reach normally. Local variations in the tool-using patterns and manufacturing ability of chimpanzees are discussed.     

Development of the hand and wrist bones in chimpanzees

Skeletal developmental of chimpanzees was studied cross-sectionally. By application of the TW2 method, we described the skeletal development of chimpanzees and compared their skeletal development with humans'. A development pattern of chimpanzees repeated accelerations and decelerations displaying “early-juvenile trough,” “pre-adolescent peak,” “mid-adolescent trough,” and “post-adolescent peak” in incremental curves. Sex differences in skeletal development are slower development in males during infant and early juvenile phases, and greater increment around the adolescent phase in males. Females are fully mature at younger ages than males, e.g. about one and a half years. In comparison with chimpanzees, humans have such characteristics as a longer slower period of juvenile development and a shorter spurt-like adolescent fast period which ends with full maturity.     

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.     

Rank and age related feeding strategy observed through field experiments in the Koshima group of Japanese macaques

The feeding process of Japanese monkeys on soy beans which were scattered over a sandy beach on Koshima islet was studied. Younger monkeys were able to pick up more beans when 8 kg of beans were divided and given two times (“two times feeding”) than when the whole amount (8 kg) of beans was given at one time (“one time feeding”). The effect of saturation of the food intake capacity in younger monkeys at the first feeding in “two times feeding” did not appear at the second feeding one hour later. The minutely intake of soy beans (feeding speed) for each age class was analyzed. The decline of feeding speed in adult females after the peak in “one time feeding” was not related to the decline in density of beans on the ground, and this decline was caused by saturation of their food intake capacity. Adult females were divided into four classes according to their dominance rank order: high, lower-high, higher-low, and low classes. The total amount of intake in “one time feeding” was far larger in the high class than in any of the other classes. The total amount of feeding in the first feeding of “two times feeding” increased in accordance with rise in the dominance rank class, and there was no relation to rank and total feeding amount in the second feeding of “two times feeding.” Differences existed in the process of feeding between the rank classes. The feeding speed of the low class was as high as that of the high class on the curve of minutely intake, while the low class stopped feeding much earlier than the high class. The lower-high class displayed a low feeding speed, and stopped feeding the latest. The order of the duration to stay and to feed in the feeding area was lower-high > high > higher-low > low, and this order did not change under the three different feeding conditions, “one time feeding,” and the first and second feedings of “two times feeding.” Adolescent females tended to stay the longest duration in the feeding area among all age classes. Both the lower-high class females and adolescent females had an unstable social status in the Koshima group, and their social status affected their feeding behaviors. The feeding behaviors were similar in attitude depending on social status, and are considered to be maintained for a fairly long time. The feeding strategy of the lower-high class, in staying a longer duration in the artificial feeding area, and departing later, may be effective under the artificial feeding conditions, but it may be a bad strategy in a natural habitat where the food is not so clumped as in artificial feeding, and where choice of other food patches is possible. The above results agree well with previous reports for the Koshima group, indicating that the rank of the lower-high class females was unstable (Mori et al., 1989), and that their reproductive success was low (Watanabe et al., 1992).     

Do bonobos copulate more frequently and promiscuously than chimpanzees?

The copulatory activities of bonobos (Pan paniscus) of Wamba, Zaire, were compared with those of chimpanzees (P. troglodytes schweinfurthii) of Mahale, Tanzania. The copulation rates of adult male bonobos were equal to or lower than those of adult male chimpanzees. The copulation rates of adult female bonobos were approximately equal to those of adult female chimpanzees who were in maximal genital swelling, but it should be much higher than those of the adult female chimpanzees throughout the birth interval. The copulation rates of adolescent male bonobos were lower than those of adolescent male chimpanzees, whereas the copulation rates of adolescent female bonobos were much higher than those of adolescent female chimpanzees. It was suggested that the bonobos of Wamba did not copulate more promiscuously than did the chimpanzees of Mahale. The female bonobos may show “receptivity”, whereas female chimpanzees may show rather “proceptivity”.     

Condensed tannins and sugars in the diet of chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda

Fruits, leaves and bark forming part of the diet of chimpanzees were collected and it was noted whether samples were of a kind being eaten or not eaten. Samples were dried and analysed for condensed tannin content and for three sugars, glucose, sucrose and fructose. It was found that chimpanzees did not select foods according to the level of tannins but did so according to the levels of sugars, preferring the higher levels. Fig seeds contained higher tannin levels than fig pulp, and the chimpanzees made oral boli (“wadges”) of fig seeds which they spat out. Two fig species were compared: the one with lower tannin and higher sugar content was preferred. The bark of one tree species often eaten contained high levels of tannins but also contained sugars. Young leaves with lower tannin levels were preferred to mature leaves with higher levels. Chimpanzees appear to be able to tolerate higher tannin levels than three monkey species in this forest, and considerably higher levels than marmosets (Callitrichidae). Received: 20 October 1997 / Accepted: 1 March 1998     

Olfactory discrimination of eight food flavors in the capuchin monkey (Cebus apella): Comparison between fruity and fishy odors

Operant conditioning was used to investigate how primates discriminate between odor qualities. Eight artificial food flavors, selected from either a “Fishy” or “Aroma/Fruity” category, were used. During the presence of one of the two odors S+ or S−, the monkey was reinforced by pushing a response key when S + was presented. The tufted capuchins discriminated most accurately when both odors were Aroma. Discrimination was more accurate when S+ was Fruity odor and S− was Fishy odor. When both odors were Fishy, discrimination could not be acquired in 20 sessions. All of the flavors used, except apple, were novel for the subjects, which suggests that capuchins can innately discriminate among them. The data also suggest that Aroma odors are more salient than Fishy odors. The results also suggested an innate aversion to Fishy odors.     

Chimpanzee grouping patterns and food availability in Mahale Mountains National Park,Tanzania

The aim of this study was to test for a correlation between party size and food (fruit) availability among the M group chimpanzees (Pan troglodytes) in the Mahale Mountains, Tanzania. Chimpanzee unit groups (or communities) show fission–fusion grouping patterns and form temporal parties. Fruit availability is assumed to be one of the important limiting factors in relation to the size of these parties. Different methods have been proposed to measure party size, but they all appear to focus mainly on two aspects of grouping phenomena. In “face-to-face parties”, party size is measured by scan sampling, whereas in “nomadic parties”, all members observed during a specific time period are counted. The mean monthly group size resulting from these two measures was compared with fruit availability, i.e. fruiting plant density and mean potential patch size. Nomadic party size was correlated with both values. Thus, party formation at this level was considered to be sensitive to overall fruit availability in the habitat. On the other hand, face-to-face party size remained stable and showed weak or no correlations with density and potential patch size. Although large patches are available during the peak fruiting season, Mahale chimpanzees depend on the liana species Saba comorensis, which, when fruiting, encourages individuals to spread out to eat. Thus, the lack of correlation between face-to-face-party size and fruit availability was attributed to the influence of physical limitations countervailing the fluctuation in fruit availability. Maximum face-to-face party size relative to unit-group size, regarded as the cohesiveness of a unit group, was compared among sites. The values differed largely: Mahale groups M and K, Bossou, and, in some years, Budongo, showed high cohesiveness, while others remained low. Thus, the distribution of the most important food during the fruiting season in each study site may be a crucial factor in the grouping phenomena of chimpanzees.     

Chain processes and their biophysical applications: Part I. General theory

A mathematical theory applicable to the biological effects of radiations as chain processes is developed. The theory may be interpreted substantially as a “hit theory” involving the concepts of “sensitive volume” or “target area”. The variability of the sensitivity of the organism to the radiation and its capacity of recovery between single hits is taken into account. It is shown that in a continuous irradiation of a biological aggregate in which the effect of each single hit cannot be observed, recovery and variation of sensitivity are formally equivalent to each other so that a discrimination between these two phenomena is possible only by discontinuous irradiation or by using different radiation intensities. Methods for the calculation of the “number of hits” and for the determination of the kinetics of the processes from “survival curves” or similar experimental data are given. The relation between the recovery and the Bunsen-Roscoe law is discussed. The case in which the injury of the organism is dependent on the destruction of more than one “sensitive volume” is also considered.     

The neuronal dynamics underlying cognitive flexibility in set shifting tasks

The ability to switch attention from one aspect of an object to another or in other words to switch the “attentional set” as investigated in tasks like the “Wisconsin Card Sorting Test” is commonly referred to as cognitive flexibility. In this work we present a biophysically detailed neurodynamical model which illustrates the neuronal base of the processes related to this cognitive flexibility. For this purpose we conducted behavioral experiments which allow the combined evaluation of different aspects of set shifting tasks: uninstructed set shifts as investigated in Wisconsin-like tasks, effects of stimulus congruency as investigated in Stroop-like tasks and the contribution of working memory as investigated in “Delayed-Match-to-Sample” tasks. The work describes how general experimental findings are usable to design the architecture of a biophysical detailed though minimalistic model with a high orientation on neurobiological findings and how, in turn, the simulations support experimental investigations. The resulting model is able to account for experimental and individual response times and error rates and enables the switch of attention as a system inherent model feature: The switching process suggested by the model is based on the memorization of the visual stimuli and does not require any synaptic learning. The operation of the model thus demonstrates with at least a high probability the neuronal dynamics underlying a key component of human behavior: the ability to adapt behavior according to context requirements—cognitive flexibility. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Action Editor: Peter Dayan     

Influence of chimpanzee predation on the red colobus population at Ngogo, Kibale National Park, Uganda

Frequent hunting of red colobus monkeys (Procolobus rufomitratus) takes place at all long-term chimpanzee (Pan troglodytes) study sites where both species are present. Red colobus are the most commonly selected prey of chimpanzees even when other monkey species are more abundant. In particular, the chimpanzee community at Ngogo, Kibale National Park, Uganda, preys heavily on red colobus monkeys: the chimpanzee hunting success rate is extremely high, and chimpanzees kill many individuals per successful hunt. Census data had suggested that the red colobus population is declining and that predation by chimpanzees may be contributing to this decline. In this paper, I address the impact of hunting on the red colobus population at Ngogo. To test the hypothesis that chimpanzee hunting is sustainable, I am using demographic data collected on red colobus monkeys over a period of 3 years, as well as fecundity and mortality data from previous studies of this species. I apply matrix models and vortex analyses using a sensitivity analysis approach to project future population development. Results show that current rates of hunting are not sustainable, but that chimpanzees are neither more “noble”, nor more “savage” than humans are, but that they also hunt to ensure maximum benefit without regard for the consequences for the prey population.     

Generalization and categorization of spectral colors in goldfish. II. Experiments with two and six training wavelengths

In part I of this study (Kitschmann and Neumeyer 2005), goldfish categorized spectral colors only in the sense that wavelengths in a range of about twice as large as the just noticeable difference were treated as similar to a given training wavelength. Now, we trained goldfish on more than one wavelength to prevent very accurate learning. In one experiment goldfish were trained on six adjacent wavelengths with equal numbers of rewards, and, thus, equal numbers of learning events. Generalization tests showed that some wavelengths were chosen more often than others. This indicated that certain spectral ranges are either more attractive or more easily remembered than others. As this is a characteristic of the “focal” colors or centers of color categories in human color vision, we interpret the findings in goldfish accordingly. We conclude (Figs. 5 and 6) that there are four categories in spectral ranges approximately coinciding with the maximal sensitivities of the four cone types, and three categories in-between. Experiments with two training colors indicate that there is no direct transition between categories analogous to human “green” and “red”, but that there is a color analogous to human “yellow” in-between (Figs. 2, 3; Table 1).     

Suggestions for a mathematical biophysics of some psychoses

We may consider that most of the human behavior is a set of learned responses to certain patterns which recur frequently in the course of human life. Some “abnormal” events or experiences may result in the learning of abnormal responses, and thus in abnormal behavior. The “abnormal” responses may begin to be learned after some of the normal response patterns have been fairly well established. The development of both normal and abnormal behavior may thus be represented by learning curves of the type studied by H. D. Landahl. Applying some of the results of the theory of learning curves and considering that the normal and abnormal reactions may reciprocally inhibit each other, a quantitative theory of some psychoses may be developed. In particular, the effects of shock may be deduced from the assumption that they cause the more recently learned abnormal reactions to be “unlearned” more readily, than the earlier learned “normal” reactions. The effectiveness of shock treatments as a function of the duraction of psychosis is discussed from this point of view.     

Learning how to learn: The significance and current status of learning set formation

In honor of the memory ofHarry F. Harlow, this paper reviews the current status of learning set formation, the discovery of which represents one ofHarlow's major contributions to behavioral science. Learning set formation or “learning how to learn” refers to the learning of visual and other types of discrimination problems progressively more quickly as a function of training on a series of such problems. The general procedure thatHarlow used, his original learning set finding, and its significance are described first. A brief review of theories of learning set formation follows. Lastly, the attempt to use learning set formation as a tool for studying comparative behavior is discussed. This article is based on a paper by the author delivered at:A. M. Schrier andS. J. Suomi (cochairs),Primate Behavior: A Symposium in Memory of Harry F. Harlow. Symposium presented at the IXth Congress of the International Primatological Society, Atlanta, Georgia, August 1982.     

Song dialects in the yellowhammer Emberiza citrinella : bioacoustic variation between and within dialects

The yellowhammer Emberiza citrinella is a common European bird that sings in dialects that for decades have been distinguished by the existence of one single element (called a “specific”). In this study we looked into other possibilities for dialect discrimination, measuring 24 different variables. For the first time, multivariate statistics were used to discriminate dialect in yellowhammer song. Two similar dialects (XlB and XsB) that are not clearly defined in the literature were studied. Statistics incorporated (1) all variables, (2) no variables of “specific” elements, and (3) no variables under the influence of these “specific” variables. Multivariate statistics support dialect discrimination by ear and confirmed that only one element in yellowhammer song characterises dialect. In addition, we looked for local differences within two dialects and found that one local observation area showed a higher separation than the other sites (Meck1). However, as yet there is insufficient evidence for the existence of a new subdialect. The experiments comply with the current laws of the study area.     

The perfect learner

As a “base line” of memorization performance, the behavior of a “perfect learner” is considered. He is characterized by a perfect memory and by the ability to choose the best search procedure in problems where the correct response from a given repertoire is to be found to each of several stimuli under the condition of “right” and “wroing” promptings by the experimenter. Expected learning curves are derived for the case of disjoint response repertoires associated with the stimuli under cyclic and random presentation of the stimuli and for the case of a single response repertoire (a one-to-one matching problem) under cyclic presentation.     

From view cells and place cells to cognitive map learning: processing stages of the hippocampal system

 The goal of this paper is to propose a model of the hippocampal system that reconciles the presence of neurons that look like “place cells” with the implication of the hippocampus (Hs) in other cognitive tasks (e.g., complex conditioning acquisition and memory tasks). In the proposed model, “place cells” or “view cells” are learned in the perirhinal and entorhinal cortex. The role of the Hs is not fundamentally dedicated to navigation or map building, the Hs is used to learn, store, and predict transitions between multimodal states. This transition prediction mechanism could be important for novelty detection but, above all, it is crucial to merge planning and sensory–motor functions in a single and coherent system. A neural architecture embedding this model has been successfully tested on an autonomous robot, during navigation and planning in an open environment. Received: 28 June 1999 / Accepted in revised form: 26 April 2001     

Archaeological Analysis Does Not Support Intentionality in the Production of Brushed Ends on Chimpanzee Termiting Tools

Some chimpanzees use 2 types of tools to extract underground termites for consumption. Chimpanzees insert thin, flexible probes into tunnels or holes in termite mounds (fishing), and sometimes use stouter, rigid sticks to first puncture the holes and also possibly to fish. Many puncturing sticks have distinctive “brushed” ends. Researchers have hypothesized that chimpanzees create the brushed ends intentionally to increase their affixibility to biting termites (Sugiyama, 1985). The results of our archaeological analysis of a large collection of puncturing sticks used by Central African chimpanzees falsifies this hypothesis, and instead agrees with the recent behavioral observations of Sanz et al. (2004; cf. Bermejo and Illera, 1999) that brushing is a coincidental result of procuring sticks from vegetation sources. The results highlight the positive contribution of an archaeological approach to problems in chimpanzee material culture and emphasize to primatologists the value of curating artifacts.