Empathy in chimpanzees: Evidence for theory of mind?

Empathy can be widely defined as the capacity to understand the emotional, visual, or cognitive perspective of another individual and is perhaps reliant on the ability to attribute mental states. Behavioural events that may indicate empathy in chimpanzees,Pan troglodytes, are collated (1) using a questionnaire and (2) from the literature. These case studies are classified in a taxonomy of empathic acts in which empathy is categorized as visual empathy, emotional empathy, concordance and extended empathy. In addition, the circumstances surrounding the empathic acts are discussed: whether the recipient of the empathic act was a relative, an unfamiliar individual, or a heterospecific. The cost to the animal showing empathy, whether it displayed any levels of intentionality and if it communicated to a third party are also analyzed. Rescuing of an individual from a dangerous social or physical situation is the only category where the animal shows empathy under all the specified conditions. From this preliminary analysis it seems the chimpanzees may be capable of showing empathy across a wide range of circumstances.     

Symbolic communication in wild chimpanzees?

The language abilities of captive chimpanzees give rise to the question of the existence and use of similar capabilities in wild chimpanzees. In Taï forest, wild chimpanzees seem to use drumming on buttressed trees to convey information an changes of travel direction, resting periods or both information combined. This communication system is iconic and relies on some arbitrariness. Emergence of symbol-like communication in wild chimpanzees seems mainly dependent on a low visibility environment, a high predation pressure and a large group of males.     

What's in it for me? Self-regard precludes altruism and spite in chimpanzees

Sensitivity to fairness may influence whether individuals choose to engage in acts that are mutually beneficial, selfish, altruistic, or spiteful. In a series of three experiments, chimpanzees (Pan troglodytes) could pull a rope to access out-of-reach food while concomitantly pulling another piece of food further away. In the first study, they could make a choice that solely benefited themselves (selfishness), or both themselves and another chimpanzee (mutualism). In the next two experiments, they could choose between providing food solely for another chimpanzee (altruism), or for neither while preventing the other chimpanzee from receiving a benefit (spite). The main result across all studies was that chimpanzees made their choices based solely on personal gain, with no regard for the outcomes of a conspecific. These results raise questions about the origins of human cooperative behaviour.     

Do chimpanzees cooperate in a learning task?

The aim of this study was to assess the ability of chimpanzees (Pan troglodytes) to cooperate in an instrumental task. A specially constructed fruit distributor was presented to a group of six captive chimpanzees. A cooperative response required two chimpanzees: both had to pull a handle simultaneously to make a fruit fall into the cage. The dominant male of the group and an infant produced most of the operant responses, and the male got nearly all the fruits. Other conspecifics avoided the dominant male at the apparatus. Social influences appear to limit the possibility of co-operation between individuals because a certain level of interindividual tolerance is required. The results revealed a significant increase in the number of pulls each time both chimpanzees were together at the apparatus. Operant chimpanzees learn to coordinate their actions in time and space.     

Physiological adaptation in noncompetitive rock climbers: good for aerobic fitness?

The present investigation aimed to establish whether noncompetitive rock climbing fulfills sports medicine recommendations for maintaining a good level of aerobic fitness. The physiological profile of 13 rock climbers, 8 men (age, 43 +/- 8 years) and 5 women (age, 31 +/- 8 years) was assessed by means of laboratory tests. Maximal aerobic power (VO2peak) and ventilatory threshold (VT) were assessed using a cycloergometer incremental test. During outdoor rock face climbing, VO2 and heart rate (HR) were measured with a portable metabolimeter and the relative steady-state values (VO2 and HR during rock climbing) were computed. Blood lactate was measured during recovery. All data are presented as mean +/- SD. VO2 was 39.1 +/- 4.3 mL.kg.min in men and 39.7 +/- 5 mL.kg.min in women, while VT was 29.4 +/- 3.0 mL.kg.min in men and 28.8 +/- 4.6 mL.kg.min in women. The VO2 during rock climbing was 28.3 +/- 1.5 mL.kg.min in men and 27.5 +/- 3.7 mL.kg.min in women. The HR during rock climbing was 144 +/- 16 b.min in men and 164 +/- 13 b.min in women. The aerobic profile was classified from excellent to superior in accordance with the standards of the American College of Sports Medicine (ACSM). The exercise intensity (VO2 during rock climbing expressed as a percentage of VO2peak) was 70 +/- 6% in men and 72 +/- 8% in women. Moreover, the energy expenditure was 1000-1500 kcal per week. In conclusion, noncompetitive rock climbing has proved to be a typical aerobic activity. The intensity of exercise is comparable to that recommended by the American College of Sports Medicine to maintain good cardiorespiratory fitness.     

Did brain-specific genes evolve faster in humans than in chimpanzees?

One of the most distinctive characteristics of humans among primates is the size, organization and function of the brain. A recent study has proposed that there was widespread accelerated sequence evolution of genes functioning in the nervous system during human origins. Here we test this hypothesis by a genome-wide analysis of genes that are expressed predominantly or specifically in brain tissues and genes that have important roles in the brain, identified on the basis of five different definitions of brain specificity. Although there is little overlap among the five sets of brain-specific genes, none of them supports human acceleration. On the contrary, some datasets show significantly fewer nonsynonymous substitutions in humans than in chimpanzees for brain-specific genes relative to other genes in the genome. Our results suggest that the unique features of the human brain did not arise by a large number of adaptive amino acid changes in many proteins.     

Stress and fitness in parthenogens: is dormancy a key feature for bdelloid rotifers?

Background

Bdelloid rotifers are the most common and abundant group of animals that reproduce by ameiotic parthenogenesis, only. They are common in temporally ephemeral habitats, and it is unclear if they dwell in unstable habitats because are excluded from better conditions by stronger competitors, or because they need unstable conditions for their success. We tested the hypothesis that bdelloids 'require' stressful conditions for their persistence by comparing fitness-related traits of stressed (desiccated, D) and unstressed (hydrated, H) lines of two species, Adineta ricciae and Macrotrachela quadricornifera.

Results

For both bdelloid species, fecundity was significantly lower in H than in parallel D line. Fitness components decreased with time progressively in the H line but not in the D line. Recovery rates of D lines were recorded after every desiccation and did not reveal any trend in time, suggesting that no selection was operating.

Conclusion

Stress in the form of reiterated desiccations seemed to help both bdelloid species to keep fitness stable; in contrast under stable conditions, like permanent hydration, these bdelloid species had poorer performances. Bdelloids, although aquatic animals, are not only efficient in tolerating desiccation, but seem somehow dependent on anhydrobiosis, a circumstance that might represent a key event in their life cycle. If this is true, life in unpredictable habitats should not be seen as the result of competitive exclusion from 'easier' habitats, but a requirement for long-term survival of these parthenogenetic animals.

     

Is each light-harvesting complex protein important for plant fitness?

Many of the photosynthetic genes are conserved among all higher plants, indicating that there is strong selective pressure to maintain the genes of each protein. However, mutants of these genes often lack visible growth phenotypes, suggesting that they are important only under certain conditions or have overlapping functions. To assess the importance of specific genes encoding the light-harvesting complex (LHC) proteins for the survival of the plant in the natural environment, we have combined two different scientific traditions by using an ecological fitness assay on a set of genetically modified Arabidopsis plants with differing LHC protein contents. The fitness of all of the LHC-deficient plants was reduced in some of the growth environments, supporting the hypothesis that each of the genes has been conserved because they provide ecological flexibility, which is of great adaptive value given the highly variable conditions encountered in nature.     

Do chimpanzees build comfortable nests?

Nests built by wild chimpanzees (Pan troglodytes verus) were studied at the Fongoli research site in southeastern Senegal from January 2004-May 2004 to investigate the role of comfort in nest building behavior by relating measures of nest comfort and building effort. Nest comfort across zones of the nest surface were compared with construction effort for 25 nests. Several variables of nest comfort were assessed: (1) physical discomfort, (2) visible discomfort, and (3) softness. Physical discomfort was used as a representative measure of nest discomfort. Building effort was measured by (1) construction force, (2) complexity, and (3) added material. Spearman rank correlations compared Effort and Comfort measures for both whole nests and central versus edge zones. The results show that construction force and complexity do not influence comfort of the nest as a whole. Greater Construction force correlates with more nest edge discomfort, yet the central area shows no difference. More complex nests do result in a more comfortable central area in the nest. Nests built with greater force may result in more discomfort, whereas complexity may allow chimpanzees to maintain comfort in a central area for sleep. Chimpanzees may place additional leaves or twigs over hard branches, protruding from the nest surface after construction, to increase comfort of the central nest area. Functions of chimpanzee nest building are likely to be several, but these results suggest comfort is a factor in nest building behavior.     

The heritability of fitness: Bad news for 'good genes'?

Some models of sexual selection depend on a female preference for 'good genes': females choose conspicuous males as these are advertising their possession of genes for fitness characters which can be inherited by their offspring. In contrast, Fisher's fundamental theorem of natural selection - which underlies much of population genetics theory - predicts that in a population at equilibrium there can be no additive genetic variation in fitness. Recent work on collared flycatchers in the wild shows that characters influencing fitness do indeed have a relatively low heritability. However, other studies of the inheritance of fitness in the laboratory suggest that under some circumstances a population may retain considerable genetic diversity for fitness characters. Genetically based female choice might hence have the potential to control the evolution of male sexual ornaments. More work on natural populations is needed; and birds may be a good place to start looking.     

Behavioral diversity in populations of free-ranging chimpanzees in Africa: is it culture?

Behavioral differences exist among populations of wild chimpanzees (Pan troglodytes, Hominoidea) across Africa. Deciding if these are cross-cultural differences demands careful interpretation and rigorous scrutiny. Even standard patterns like social grooming may show variation in detail between neighboring populations. Some patterns of tool use, such as using hammers to crack nuts, also vary across far western Africa. At least 37 populations of free-ranging chimpanzees show tool use, and 14 show at least one habitual pattern of tool use. Regional differences exist among the three subspecies or geographical races of chimpanzees. Convincing empirical demonstration of social customs and traditions in non-human species is problematical, and even something so simple in principle as innovation is hard to show in practice. However, culture need not depend on imitation, teaching, or language, either in humans or in other species.     

When does play panting occur during social play in wild chimpanzees?

To clarify the social functions of play panting in chimpanzees, I investigated when they emitted play panting in social play and how the interactions were affected by the occurrence of play panting. The subjects were the M-group chimpanzees living in Mahale, Tanzania. The following observations were made: (1) chimpanzees emitted play panting when they were tickled or chased but rarely did so when they tickled or chased others. Chimpanzee play panting does not have the function of a play signal communicating that these aggressive actions are performed not as aggression but as play. (2) Chimpanzees emitted play panting more often when they received aggressive actions that supposedly elicited higher arousal. (3) A chimpanzee tended to continue to perform aggressive actions when the target emitted play panting. Play panting activates the interaction of social play by encouraging the performer to continue tickling or chasing. These results can be summarized as showing that chimpanzee play panting serves as positive feedback to the play partner for continuing somewhat fragile interactions, which may contain the risk of excessive arousal and the risk of confusing defensive actions by the target of the aggressive actions with real efforts to escape the situation.     

Do chimpanzees know what conspecifics know?

We conducted three experiments on social problem solving by chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual competed for food, which was placed in various ways on the subordinate's side of two opaque barriers. In some conditions dominants had not seen the food hidden, or food they had seen hidden was moved elsewhere when they were not watching (whereas in control conditions they saw the food being hidden or moved). At the same time, subordinates always saw the entire baiting procedure and could monitor the visual access of their dominant competitor as well. If subordinates were sensitive to what dominants did or did not see during baiting, they should have preferentially approached and retrieved the food that dominants had not seen hidden or moved. This is what they did in experiment 1 when dominants were either uninformed or misinformed about the food's location. In experiment 2 subordinates recognized, and adjusted their behaviour accordingly, when the dominant individual who witnessed the hiding was replaced with another dominant individual who had not witnessed it, thus demonstrating their ability to keep track of precisely who has witnessed what. In experiment 3 subordinates did not choose consistently between two pieces of hidden food, one of which dominants had seen hidden and one of which they had not seen hidden. However, their failure in this experiment was likely to be due to the changed nature of the competition under these circumstances and not to a failure of social-cognitive skills. These findings suggest that at least in some situations (i.e. competition with conspecifics) chimpanzees know what conspecifics have and have not seen (do and do not know), and that they use this information to devise effective social-cognitive strategies. Copyright 2001 The Association for the Study of Animal Behaviour.     

Does selection intensity increase when populations decrease? Absolute fitness, relative fitness, and the opportunity for selection

The variance in relative fitness, commonly called the “opportunity for selection,” is a measure of the maximum amount of selection that can occur in a population. I review the relation between fitness variance and population growth, showing that fitness variance is higher during periods of population decline. This is true both for survival and for commonly used models for variable descendant number (Poisson, negative binomial, generalized Poisson). Empirical evidence suggests that not just the opportunity for selection but also the actual selection occurring is commonly greater during such periods of population reduction.