Animal Behaviour

We quantified the diet of the Chilean Hawk (Accipiter chilensis) by analyzing 495 prey remains collected during two breeding seasons (2001-2002 and 2002-2003) in an Andean Nothofagus forest of Nevados de Chillán, northern Patagonia. The diet was almost exclusively birds (97.8% of all prey remains), with relatively few rodents (1.6%) and insects (0.6%). At least 19 vertebrate species composed the prey remains (1 small mammal and 18 bird species), with Austral Thrush (Turdus falcklandii), White-crested Elaenia (Elaenia albiceps), Black-chinned Siskin (Carduelis barbata), Fire-eyed Diucon (Xolmis pyrope), and Thorn-tailed Rayadito (Aphrastura spinicauda) being the most common. All identified vertebrate prey are known to use forest habitats; 47% (n ϭ 9) are forest specialists. Prey that inhabit both forest and shrublands accounted for 82% of the remains, and 18% of prey remains were of forest specialists. Our results indicate that during the breeding season, Chilean Hawks in Nevados de Chillán are pre-eminent, bird-eating predators that feed primarily on forest-dwelling birds.

In some social mammals, loud calling not only serves to advertise ownership of a territory and attract mates but also plays a vital role in allowing social companions to maintain contact when they are separated by long distances. Under these circumstances, individuals that are not territory owners but that call in the context of social cohesion or mate attraction could risk inviting escalated contests from territorial competitors. Here we present observations and playback experiments demonstrating that nomadic male lions (Panthera leo) do not roar despite the likely importance of roaring in maintaining social ties with other males in their coalition, on which their subsequent reproductive success depends. Instead, roaring is confined to males that are resident in prides and prepared to escalate in contest situations. Roaring is a flexible behaviour that is sensitive to temporal changes in status; resident males remain silent outside of their territories even when presented with playbacks of unfamiliar males roaring, and nomadic males start roaring only when they are taking over a pride. Our study suggests that individuals of social species may avoid givingimportant long-distance signals in circumstances where it would pay them to conceal their presence from eavesdroppers.

RÉSUMÉ : Nous nous pencherons sur les travaux du jeune Heidegger afin de montrer que, s’il affirme dans Être et temps que les animaux ne sont ni chose, ni Dasein, mais participent d’un énigmatique mode d’être propre – le « simplement vivant », ce qui ne fait « rien de plus que vivre » – cela constitue un revirement dans la pensée heideggérienne. Dans les travaux qui préparent la rédaction de Sein und Zeit, l'animal avait toujours été considéré comme un être qui a un monde, comme un être auquel nous devons reconnaître le mode d'être du Dasein. En s’appuyant sur l’interprétation phénoménologique d’Aristote qu’il présente dans ses cours de 1919 à 1926, nous montrerons que les structures fondamentales de l'être-au-monde ont été élaborées sur le fond des capacités propres à la vie animale que sont l’affection (pathos), la perception (aisthēsis), la discrimination (krinein), la mobilité (kinesis kata topon) et le désir (orexis).

ABSTRACT : Our investigation of young Heidegger’s work aims at showing that, if Being and Time states that animals are neither mere things, neither Dasein, but have their own puzzling mode of being – “mere life”, which does not exist, but simply lives – this constitutes a reversal in Heidegger’s way of thinking. In the works that prepared the way towards Sein und Zeit, animal life was always presented as being-in-a-world, as a being to which we must ascribe Dasein’s way of being. With the help of Heidegger’s phenomenological interpretations of Aristotle presented between 1919 and 1926, we will show that the basic features of being-in-the-world that will become Being and Time's existential structures were developed on the basis of capacities belonging to animal life : affection (pathos), perception (aisthēsis), discrimination (krinein), mobility (kinesis kata topon) and desire (orexis).

Background: Vertebrate predators use a broad arsenal of behaviors and weaponry for overcoming fractious and potentially dangerous prey. A unique array of predatory strategies occur among snakes, ranging from mechanical modes of constriction and jaw-holding in non-venomous snakes, to a chemical means, venom, for quickly dispatching prey. However, even among venomous snakes, different prey handling strategies are utilized, varying from the strike-and-hold behaviors exhibited by highly toxic elapid snakes to the rapid strike-and-release envenomation seen in viperid snakes. For vipers, this mode of envenomation represents a minimal risk predatory strategy by permitting little contact with or retaliation from prey, but it adds the additional task of relocating envenomated prey which has wandered from the attack site. This task is further confounded by trails of other unstruck conspecific or heterospecific prey. Despite decades of behavioral study, researchers still do not know the molecular mechanism which allows for prey relocation. Results: During behavioral discrimination trials (vomeronasal responsiveness) to euthanized mice injected with sizefractionated venom, Crotalus atrox responded significantly to only one protein peak. Assays for enzymes common in rattlesnake venoms, such as exonuclease, L-amino acid oxidase, metalloproteinase, thrombin-like and kallikreinlike serine proteases and phospholipase A 2 , showed that vomeronasal responsiveness was not dependent on enzymatic activity. Using mass spectrometry and N-terminal sequencing, we identified the proteins responsible for envenomated prey discrimination as the non-enzymatic disintegrins crotatroxin 1 and 2. Our results demonstrate a novel and critical biological role for venom disintegrins far beyond their well-established role in disruption of cellcell and cell-extracellular matrix interactions. Conclusions: These findings reveal the evolutionary significance of free disintegrins in venoms as the molecular mechanism in vipers allowing for effective relocation of envenomated prey. The presence of free disintegrins in turn has led to evolution of a major behavioral adaptation (strike-and-release), characteristic of only rattlesnakes and other vipers, which exploits and refines the efficiency of a pre-existing chemical means of predation and a highly sensitive olfaction system. This system of a predator chemically tagging prey represents a novel trend in the coevolution of predator-prey relationships.

To behave in an adaptive way an animal must refer to information. Consider what happens when a motorist comes to traffic lights at red. The motorist usually stops. Stopping avoids the high risk of damage and injury at the cost of one or two minutes. So stopping at red traffic lights is the best way for the motorist to behave.

Barbary macaques (Macaca sylvanus) utter "shrill barks" in response to disturbances in their surroundings. In some cases, the majority of group members react by running away or climbing up a tree. In many other instances, however, group members show no overt reaction to these calls. We conducted a series of playback experiments to identify the factors underlying subjects' responses. We presented calls given in response to dogs that had elicited escape responses and calls that had failed to do so. We also presented calls given in response to snakes and to the observer approaching the sleeping-trees at night. An acoustic analysis of the calls presented in the playback experiments (electronic supplementary material, audioclip S1) revealed significant differences among calls given in response to dogs, the observer approaching at night, and snakes. However, the analysis did not detect any differences between calls given in response to dogs that were related to whether or not they had elicited escape responses in the first place. Correspondingly, after playback of calls given in response to dogs, we observed no difference in subjects' responses in relation to whether or not the calls had initially elicited escape responses. Subjects showed startle or escape responses significantly more often after playbacks of calls given in response to dogs than after calls given in response to observers. Playbacks of calls given in response to snakes failed to elicit specific responses such as standing bipedally or scanning the grass. Although these findings may imply that responses depend on the external referent, they also indicate that there is no clear-cut relationship between the information available to the listeners and their subsequent responses. This insight forces us to extend current approaches to identifying the meaning of animal signals.

Peacocks, Pavo cristatus, defend small display sites and aggregate to form leks. Observations of one lek, consisting of 10 males, showed that there was considerable variance in mating success. The most successful male copulated 12 times whilst the least successful males obtained no copulations. Over 50% of the variance in mating success could be attributed to variance in train morphology; there was a significant positive correlation between the number of eye-spots a male had in his train and the number of females he mated with. Furthermore, analysis of female behaviour provided good evidence that this non-random mating is a result of a female preference. On no occasion did a female mate with the first male that courted her and, on average, females visited three different males. Females thus always reject some potential mates. For 10 out of 11 sequences ending in a successful copulation, the male 'chosen' at the end of a sequence had the highest eye-spot number among the males visited. These data support Darwin's hypothesis that the peacock's train has evolved, at least in part, as a result of a female preference.

Many animal species have complex cognitive abilities previously assumed to be limited to humans. Explanations for how these abilities evolved have focused on ways in which cognitive performance may influence survival, such as solving ecological problems or navigating complex social environments. However, sexual selection (differences in the reproductive success of individuals) can also lead to the evolution of complex traits. This could occur, for example, if females prefer males with better cognitive ability. A common assumption of models of female choice for male cognitive ability is that performance scores on different cognitive tasks are intercorrelated. In the present study, we evaluated performance of male satin bowerbirds on six cognitive tasks. Although we found little intercorrelation amongst males' performance scores of these tasks, males with better scores for two integrative measures of these cognitive tasks had higher mating success, which is a good indicator of reproductive success in this species. In addition, a multiple regression analysis suggested that performance on most cognitive tasks independently predicted mating success. Our results point to an important link between sexual selection and cognitive ability that has not been well appreciated and appears to be quite complex. Ó

Proximity to cover has two contrasting consequences for a prey animal: it provides a hiding place and protection in the event of attack, but obstructs its view of approaching predators (Elton 1939). In different studies prey vigilance has been found to vary with distance to cover in ways predicted for one or other of these protective or obstructive functions, on the 'compensatory' adaptive premise that vigilance increases to compensate for a greater risk of predation. Thus, avian studies in which vigilance increased with distance to cover have interpreted the greater vigilance as an adaptive response to an increased predation risk away from the protection afforded by vegetation (

The study of collective animal behaviour must progress through a comparison between the theoretical predictions of numerical models and data coming from empirical observations. To this aim it is important to develop methods of three-dimensional (3D) analysis that are at the same time informative about the structure of the group and suitable to empirical data. In fact, empirical data are considerably noisier than numerical data, and they are subject to several constraints. We review here the tools of analysis used by the STARFLAG project to characterize the 3D structure of large flocks of starlings in the field. We show how to avoid the most common pitfalls in the quantitative analysis of 3D animal groups, with particular attention to the problem of the bias introduced by the border of the group. By means of practical examples, we demonstrate that neglecting border effects gives rise to artefacts when studying the 3D structure of a group. Moreover, we show that mathematical rigour is essential to distinguish important biological properties from trivial geometric features of animal groups.

Like most solitary carnivores, the home ranges of male American mink overlap with those of several females, but each female typically shares its range with only a single male. Nevertheless, female mink produce multiply sired litters. Unusually among mammals, the physiological characteristics of female American mink make them highly suited to multiple paternity, suggesting that polyandry in the species may result from female behaviour rather than from coercion by males. In a free-choice experiment on captive-bred animals, all female mink mated multiply, with seven of the eight mating with all three available partners. Since females sometimes resisted copulations, multiple mating in this species may result from their behaviour rather than male coercion. Females visited males nonrandomly, but visiting patterns did not predict mating patterns, suggesting disparate social and mating preferences. There was no evidence for precopulatory female choice, since the allocation of copulations among available males did not deviate significantly from the expected distribution. Females mated multiply only around the predicted times of ovulation, contrary to the expectation that they should be more selective at times of peak fertility. Larger males copulated for longer in total: copulation duration is probably under male control, suggesting that larger males could influence mating duration, perhaps increasing their share of paternity by greater sperm transfer. Our observations suggest that in wild populations, mating patterns could be influenced by female preference for multiple partners.

The hypothesis that size assortative mating in Gammarus pulex is due to mal~male competition was examined in three experiments. When males were given a choice of two mates they preferred to enter into precopula with the female that offered the greater utility in terms of eggs fertilized per reproductive effort. When a receptive female was simultaneously encountered by two males it was usually the larger male that entered into precopulatory amplexus. There was more male-male c~nflict in the presence of a receptive female than in that of an unreceptive female. Few take-overs occurred but those that did were by males larger than the male in precopula. These data are consistent with the hypothesis that competition results in size assortative mating; however, it is suggested that the optimal time (relative to female moult) of entry into precopula varies as a function of both male and female size. Thus large males enter into precopula earlier than small males and prefer to take a large female to a small female. Mal~male competition may determine some of the costs and benefits associated with size assortative mating but it is not the mechanism by which it occurs.

Recently, there has been much interest in the role of endogenous and maternal hormones as regulators of offspring begging and mediators of parent–offspring conflict. Here, we review recent work in this field, and identify inconsistencies in the literature. We find good evidence that hormones play a role as regulators of begging: 13 studies report a positive effect on begging and six a negative effect. There is also good evidence that hormones influence offspring fitness, but the direction of reported effects is inconsistent: eight studies report a positive effect on offspring fitness and 10 a negative effect. We explore potential pathways linking hormonal effects on begging and growth. We find that our current understanding of these pathways is incomplete, and suggest a simple model linking hormonal effects on begging and growth. We next discuss the role of hormones as mediators of parent–offspring conflict. We find little evidence that maternal hormones provide a mechanism for parental favouritism. We use graphical models to explore the hypothesis that maternal hormones act as honest signals, and find that costs of hormone production can ensure the honesty of maternal hormones but only under very restricted conditions. We discuss evidence from recent cross-fostering experiments suggesting that maternal hormones act in the context of overlapping interests between parents and offspring. Finally, we highlight the need for more studies on nonavian taxa to establish whether hormonal regulation of begging is specific to birds or general across taxa where offspring beg for food from their parents.

Despite the considerable number of studies of avian mating systems, the reasons for divorce in monogamous birds are still poorly understood. It is now generally believed that divorce is a reproductive strategy by an individual to maximize its own fitness, and that birds are continuously faced with the decision of whether to stay with the old mate or divorce in favour of a different partner. The key to understanding when divorce will occur lies in determining the costs and benefits of both pair fidelity and divorce. These are likely to be species-specific and related to the varying life histories. Individuals are expected to divorce when the benefits outweigh the costs. Although a number of hypotheses have been proposed to explain why and when individuals may divorce, these are scattered throughout the literature and have not been critically compared and contrasted either theoretically or empirically. Confusion still exists as to the underlying assumptions and predictions of the individual models, mainly because a sound theoretical framework is lacking. Empirical studies to date are few and have been mainly post-hoc interpretations. Further advances in the field require sound mathematical modelling of the hypotheses and more experimental studies that rigorously test a priori predictions. These include removal of mates to create vacancies under controlled situations, manipulating sex ratios to increase intra-sexual competition, reducing or enlarging clutch sizes to alter perceived fitness, and manipulating the availability or quality of territories or mates to determine to what extent this affects divorce rates.

The social relationships of newly independent domesticated budgerigars were studied from 1 day to 3 weeks after fledging. Birds were kept in large, outdoor flight cages, so that juveniles fledged into flocks containing many unfamiliar juveniles and adults. When measured on a per available bird basis, fledglings initiated more social interactions than expected with their siblings and their fathers, and many fledglings formed a mutual affiliative relationship with one of their siblings (a partner). Rates at which juveniles initiated social interactions with various categories of flock-mates were studied using principal components analyses; social initiations to fathers and unfamiliar adults and juveniles loaded on one factor, while social initiations to mothers and siblings loaded with opposite signs on a second factor. Conversely, fledglings attracted more social initiations from their siblings, fathers and other fledglings than expected on a per available bird basis. Principal components analyses of social initiations directed by other birds to new fledglings gave no indication that some individuals were generally more attractive to flock-mates than were other individuals. Patterns of social activity for the first 3 weeks were comparable for male and female fledglings, and were unrelated to fledging order. However, family size did affect early social behaviour. Fledglings from broods of one (singletons) tended to initiate and receive more social interactions from parents and strangers than did fledglings with siblings, and individuals from larger families interacted more per unit time with siblings than did birds from smaller families. These results suggest that early social relationships in some birds may be at least as complex as those previously described for mammalian species.

Adult female and male impala engage in a type of allogrooming in which partners alternately deliver bouts of oral grooming to the head and neck. These grooming encounters comprise typically six to 12 tit-for-tat-like exchanges of bouts and are highly reciprocal among adult females, adult bachelor males and subadult males. Although allogrooming among females could be between related individuals, that occurring among adult males would appear to be between unrelated individuals. Unlike allogrooming reported for some primate species and other ungulates, the dominant impala received no more grooming than the subordinate. It is proposed that one function of impala allogrooming is to reduce the ectoparasite load on body areas an animal cannot reach with its own mouth. The impala reciprocal aUogrooming system is unique among free-ranging antelope and other ungulates and may be a candidate for the tit-fortat strategy of evolved cooperation.

In juvenile salmon and trout, there seems to be a positive phenotypic correlation between individual aggression level and growth rate. Aggressive fish are dominant, and they obtain and defend territories, giving them access to good feeding sites. Being aggressive may increase predation risk, and may also carry costs such as increased metabolic demand, with effects on growth. To test the hypothesis that there is a trade-off between individual growth rate and aggression, we mated 12 female coho salmon with two unique males each, creating 24 full-sibling families. Growth of individually marked fish from each family was estimated in a situation where food could not be monopolized. Thereafter, individual fish were tested for mirror-elicited agonistic behaviour. We found significant variation between families in early growth rate, with a high heritability (1.04). There was also significant between-family variation in agonistic behaviour, but activity was generally low and heritability was low (0.25) and not significant. Growth rate and agonistic behaviour were negatively correlated. These results imply that aggressive behaviour has an energetic cost.

We examined the behavioural ecology of mothers and calves during the first year of life to identify variables predicting calf mortality among bottlenose dolphins. Specifically, we investigated whether the primary cause of calf mortality was poor calf condition or shark predation. Seventy-five per cent of calves that died (N Z 12) showed visible signs of poor health compared with 4.7% of the survivors (N Z 21). Calves that spent more time swimming in infant position (in contact under the mother) in the first year of life were more likely to die by 3 years of age than calves that spent less time swimming in infant position. No other behavioural or ecological measures tested were associated with calf mortality. We suggest that the mother and/or calf may compensate for poor calf health by increasing the time spent in contact with the mother. In contrast, frequent mother-calf separation and high rates of calf socializing and foraging are proposed to be indicators of vigour. Although most of our results do not support the predation hypothesis, mothers altered one behaviour in relation to predation risk. Mothers rested less in deep water during the warm months, where and when predation risk was high, than during the cool months, when predation risk was low, suggesting that predation risk influenced maternal vigilance. However, calf mortality was not higher in warm months than in cool months. Our results suggest that poor calf condition, not predation, is the primary cause of calf mortality.

The ontogeny of orientation mechanisms in migratory birds involves a complex of programmed learning rules and calibrations between the several compasses used during migration. Visual information at sunset, especially the pattern of polarized skylight, provides a primary source of orientation information for night-migrating species. To examine the development of visual orientation mechanisms at sunset, hand-raised Savannah sparrows, Passerculus sandwichensis, were given controlled experience with the clear daytime sky during the first 3 months of life. One group of birds saw the daytime sky only within an earth-strength magnetic field with magnetic north shifted 90 clockwise to true east; a control group had similar exposure to the sky within a normal, unshifted magnetic field. Orientation tests were performed on clear evenings between the time of sunset and the first appearance of stars within a vertical magnetic field of normal earth intensity (no directional magnetic information). There was no difference in the orientation of the two groups: both showed southwestward orientation. Contrary to indications from earlier experiments, the visual orientation mechanism at sunset develops independently of magnetic directions and, in this context, is similar to the ontogeny of stellar orientation.

In social foraging, scroungers take a disproportionately large share of the food found relative to their own food-searching efforts, while producers find more food than they manage to monopolize. We present a model of social foraging acknowledging the finder's advantage and foraging role asymmetries among individuals but incorporating the possibility that producers and scroungers differ in vigilance level and in vulnerability to predators. This allows simultaneous examination of both foraging benefits and anti-predatory aspects of grouping behaviour. Instead of seeking for equal payoff conditions, we first look for groups in which foraging character combinations and anti-predatory properties of producers and scroungers minimize the phenotype-specific predation hazard over food-intake rate, R i /I i , that is, fixed phenotype R i /I i minima. In the second approach, we allow individuals to change their foraging status to achieve lower R i /I i and look for combinations where it no longer pays for either producers or scroungers to change their roles, that is, evolutionarily stable group compositions, ESS. Various character combinations allow the phenotype-specific minima. In most cases, however, producers' and scroungers' minima are achievable only in different group compositions. The ESS combinations of producers and scroungers deviate widely from those combinations yielding phenotype-specific minima of R i /I i. If individuals are allowed to be flexible in adopting either a producer or a scrounger role, ESS group compositions will emerge, even though they are more expensive for both producers and scroungers in terms of R i /I i than group compositions yielding the phenotype-specific R i /I i minima.

The bycatch of small cetaceans in commercial fisheries is a global wildlife management problem. We used data from skippers' logbooks and independent observers to assess common bottlenose dolphin (Tursiops truncatus) bycatch patterns between 2003 and 2009 in the Pilbara Trawl Fishery, Western Australia. Both datasets indicated that dolphins were caught in all fishery areas, across all depths and throughout the year. Over the entire datasets, observer reported bycatch rates (n = 52 dolphins in 4,124 trawls, or 12.6 dolphins/1,000 trawls) were ca. double those reported by skippers (n = 180 dolphins in 27,904 trawls, or 6.5 dolphins/1,000 trawls). Generalised Linear Models based on observer data, which better explained the variation in dolphin bycatch, indicated that the most significant predictors of dolphin catch were: (1) vessel-one trawl vessel caught significantly more dolphins than three others assessed; (2) time of day-the lowest dolphin bycatch rates were between 00:00 and 05:59; and (3) whether nets included bycatch reduction devices (BRDs)-the rate was reduced by ca. 45%, from 18.8 to 10.3 dolphins/1,000 trawls, after their introduction. These results indicated that differences among vessels (or skippers' trawling techniques) and dolphin behavior (a diurnal pattern) influenced the rates of dolphin capture; and that spatial or seasonal adjustments to trawling effort would be unlikely to significantly reduce dolphin bycatch. Recent skipper's logbook data show that dolphin bycatch rates have not declined since those reported in 2006, when BRDs were introduced across the fishery. Modified BRDs, with top-opening escape hatches from which dolphins might escape to the surface, may be a more effective means of further reducing dolphin bycatch. The vulnerability of this dolphin population to trawling-related mortality cannot be assessed in the absence of an ongoing observer program and without information on trawler-associated dolphin community size, broader dolphin population size and connectivity with adjacent populations.

Domestic dogs, Canis familiaris, have been shown capable of finding hidden food by following pointing gestures made with different parts of the human body. However, previous studies have reported that hand-reared wolves, C. lupus, fail to locate hidden food in response to similar points in the absence of extensive training. The failure of wolves to perform this task has led to the proposal that the ability to understand others' intentions is a derived character in dogs, not present in the ancestral population (wolves). Here we show that wolves, given the right rearing environment and daily interaction with humans, can use momentary distal human pointing cues to find food without training, whereas dogs tested outdoors and dogs at an animal shelter do not follow the same human points. In line with past studies, pet dogs tested indoors were successful in following these points. We also show that the reported failure of wolves in some past studies may be due to differences in the testing environment. Our findings indicate that domestication is not a prerequisite for human-like social cognition in canids, and show the need for additional research on the role of rearing conditions and environmental factors in the development of higher-level cognitive abilities.

Great tits, Parus major, display their white cheek patches to one another during intraspecific encounters. We measured the size of these patches and the regularity of their borders (immaculateness) as part of an investigation into their function as signals. Patch size was not significantly related to any of our measures of fitness, but male great tits with more immaculate cheek patches had significantly greater access to a safer feeding site in winter and produced heavier chicks in small woods. Females with more immaculate patches bred significantly earlier in 2 of the 3 years of the study in both large and small woods. We decreased the immaculateness of both sexes with dye and found that competition with other tits significantly increased their exposure to danger when feeding. Factors resulting in reduced immaculateness included ectoparasites, fighting with conspecifics, faster feather wear in young birds and the timing of the autumn moult. Selection for immaculateness by conspecifics may be one mechanism responsible for the evolution of regular head and body patterns in several species of birds and in other animals.

We present the first three-dimensional calculations of Radiation Driven Implosion of Molecular Clouds including self-gravity and ionization. We discuss the effects of initial density perturbations on the dynamics of ionizing globules and show that the onset of gravitational collapse can be significantly delayed for a multiple of the implosion timescale. We demonstrate that Radiation Driven Implosion could be an efficient process for injecting disordered kinetic energy into molecular clouds in the vicinity of massive stars.

- After the exceptional influx of Booted eagles Hieraaetus pennatus from Western Europe in October 2004, we reviewed thespecies’ presence in Italy over the period December 2004 - February 2005 and during spring 2005. We documented the size of the spe-cies’ wintering population by gathering the sightings from various regions of Italy. We surveyed the spring migration of the speciesthrough simultaneous raptor counts at several sites (mostly in Sicily and Sicilian islands). The remarkable wintering population of 2004-2005 (estimated range: 173 - 202 individuals) was related to the unusual migratory influx that took place in the previous autumn and itagrees with an apparent trend towards an increasing number of birds wintering in southern Italy, particularly in Sicily (estimated range :132 – 157 individuals). The northward spring migration observed from the southern regions of Italy along the Tyrrhenian coast (towardsFrance), validates the hypothesis of a West European origin of the ind...

There has been a long-standing debate regarding the functions of play during childhood. An important, but neglected, first step in this debate entails documenting the costs associated with play. In this study we analysed energetic costs (expressed in terms of caloric expenditure) associated with physical play in four field experiments of play in primary school children. Experiment 1 established the concurrent validity of an observational check list to estimate caloric expenditure of children's physical play. Experiment 2 compared caloric expenditure of the play (defined as all behaviour exhibited during play time) for two age groups of children during playtime outdoors and during indoor sedentary activity; caloric expenditure of outdoor activity was greater and was significantly correlated with ambient temperature. In experiment 3, children were observed during indoor play to control for the influence of ambient temperature. Outdoor physical play was more energetically costly than indoor physical play. In experiment 4, children's behaviour was observed outdoors and caloric expenditure for play, games and other activities was compared. Physical play was more costly than other forms of behaviour and games. Estimates of total energetic costs of play ranged from 6 to 15%. Results are discussed in terms of the relatively low caloric costs of play.

... In this way reciprocity can occur whether or not individuals differ in their general tendency to direct acts. ... Individual variation in social inter-action frequencies is realistic. For instance, wild malechimpanzees each havetheir own character-istic grooming duration (Simpson ...

Since the early 19th century, graphs have been recognised as an effective method of analysing and representing scientific data. However, levels of graph use have varied widely since then, partly due to increasing reliance on inferential statistics in some fields. Recent studies indicate that graph use is closely related to the 'hardness' of scientific disciplines, and that this finding holds for journal articles and textbooks across the subfields of psychology. In the area of animal behaviour, journals devote about one-sixth of their page space to graphs, a level of graph use approximating that of biology and physics. Implications for the training of scientists in the use of visual displays are considered.

Comparative studies of vocal repertoires over the geographical range of a species can improve our understanding of the function and evolution of animal vocalizations. They may also help to elucidate relationships between populations, where genetic studies are missing or ...

Changes in the visual appearance of the sexual skins of female Theropithecus gelada associated with different stages of the reproductive cycle and with age are analysed using data from a large sample of females in the wild. Changes associated with the oestrous cycle and with pregnancy and birth are confirmed by a more detailed study of particular individuals. These signals are compared with those reported for other primate species. The behaviour of females during the course of the oestrous cycle is examined and compared with that reported for other species of Papio baboons.

Aerobic organisms naturally create reactive oxygen species (ROS) as by-products of energy production. These substances can damage DNA and tissue, and probably are major causes of mutation, ageing and a host of diseases. Oxidative stress occurs when an organism produces an overabundance of ROS relative to ROS-neutralizing antioxidants. In this study, we examined the hypotheses that individual differences in oxidative stress are associated with fluctuating asymmetry and with perceived mate quality. We measured urinary biomarkers of oxidative stress (8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA)) in a sample of healthy, young men and tested their association with fluctuating asymmetry and physical attractiveness. A composite measure of oxidative stress correlated positively with FA and negatively with physical attractiveness (with exposure to toxins, smoking, and their interaction statistically controlled for). Follow-up analyses yielded associations of oxidative stress with both healthy and masculine appearance. No association was mediated by cortisol or testosterone. These findings may yield insights into previously unidentified factors that affect the development of phenotypic features under sexual selection and contribute to the shape of human life histories, and have potential implications for other species as well.

Female frogs of many species show preferences for calls with particular properties. This study focuses on female preferences in Hyla ebraccata for computer-synthesized calls that differ in pulserepetition rate or dominant frequency. Both of these call properties are static acoustic properties of advertisement calls of H. ebraccata (within-male coefficient of variation <5%). Females exerted directional selection on dominant frequency, preferring low-frequency calls (2960 Hz) to calls with the dominant frequency of the population mean (3240 Hz). Because size is negatively correlated with dominant frequency, female choice could explain size-biased mating success observed in natural populations. Females also exerted stabilizing selection on pulse-repetition rate, preferring calls with a pulse-repetition rate of the population mean (99 Hz) to calls with a pulse-repetition rate that was twice as fast . The results of this study show that female choice creates either directional or stabilizing selection on static properties of calls.

Co-orientation with others by using their gaze direction is considered to be adaptive for detecting food or predators or monitoring social interactions. Like the great apes, common ravens are capable of following human experimenters' gaze direction not only into distant space but also behind visual barriers. We investigated the ontogenetic development of these abilities by confronting birds with a human foster parent looking up (experiment 1) and behind visual barriers (experiment 3) and their modification by habituation (experiments 2 and 4). We tested a group of 12 hand-reared ravens during their first 10 months of life. Ravens responded to others' look-ups soon after fledging but could track their gaze behind a visual barrier only 4 months later, at the age they usually become independent from their parents. Furthermore, ravens quickly ceased responding to repeated look-ups by the model, but did not habituate to repeated gaze cues directed behind a barrier. Our findings support the idea that the two modes of gaze following reflect different cognitive levels in ravens and, possibly, have different functions.

In laboratory studies we determined that the defensive responses used by two agamid lizards, Agama savignyi and A, pallida, change as a function of body temperature. At high body temperatures, these lizards flee rapidly from predators. At lower body temperatures, which reduce sprint speed, the lizards rarely run but instead hold their ground and attack aggressively. This temperaturedependent switch in defensive behaviour may have evolved because cold lizards that live in open habitats would have little chance of outrunning predators. Defensive behaviours of animals may in general be sensitive to physiological variables that influence locomotor performance.