Showing papers in "Behaviour in 2017"
TL;DR: It is suggested that the lower ability of the stone marten to avoid interference competition at community-level may play a major role in determining its widespread exclusion from forested areas by the pine marten.
Abstract: Most studies focused on species coexistence have been directed at the differential use of habitat and food resources; nonetheless, the differential use of the diel cycle may enhance the coexistence of same-sized species. We investigated the activity patterns of mesocarnivores (red fox ( Vulpes vulpes ), European badger ( Meles meles ), pine marten ( Martes martes ), stone marten ( M. foina )) in NW Italy via camera-trapping. We hypothesized that the smallest species would tend to avoid competition by selecting time periods when larger species were less active. Foxes, badgers, and stone martens were mainly nocturnal. In lowland areas overlap between coexisting species was generally low, while in Mediterranean habitats all activity patterns tended to be unimodal and overlap was generally high. The pine marten showed a cathemeral pattern. We suggest that the lower ability of the stone marten to avoid interference competition at community-level may play a major role in determining its widespread exclusion from forested areas by the pine marten.
41 citations
TL;DR: This article found that individual differences in activity and aggression, as measured in an open-field trial, were related to natal dispersal distance in a wild population of North American red squirrels ( Tamiasciurus hudsonicus ).
Abstract: Individual natal dispersal behaviour is often difficult to predict as it can be influenced by multiple extrinsic and intrinsic factors. Individual differences in personality have been shown to be an important correlate of dispersal behaviour. However, the relationships between personality traits and dispersal are often inconsistent within and across studies and the causes of these discrepancies are often unknown. Here we sought to determine how individual differences in activity and aggression, as measured in an open-field trial, were related to natal dispersal distance in a wild population of North American red squirrels ( Tamiasciurus hudsonicus ). For 14 cohorts, while individual aggression consistently had no association with dispersal distance, the association between activity and dispersal fluctuated through time, mediated by population density. The environmental-dependence of the relationship between personality and dispersal in this population is indicative of the importance of considering external conditions when predicting dispersal behaviour.
36 citations
TL;DR: In this article, the authors used a speaker occupation experiment to test whether red squirrel rattles function to deter conspecific rivals, and found that the presence of a speaker replacement reduced the probability of intrusion by 34% and increased the latency to first intrusion by 7%, providing support for the hypothesis that rattles play an active role in reducing intrusion risk.
Abstract: In many species, territory advertisement is thought to be one of the primary functions of acoustic communication. North American red squirrels are a territorial species in which ‘rattles’ have long been thought to be the principal signal communicating territory ownership. These vocalizations have been assumed to deter intruders, thus reducing energetic costs and the risk of injury associated with direct aggressive interactions. However, this hypothesis has not been directly tested. Here we used a speaker occupation experiment to test whether red squirrel rattles function to deter conspecific rivals. We studied 29 male squirrels and removed each individual from his territory twice in a paired design. During the experimental treatment, we simulated the owner’s presence after its removal by broadcasting the owner’s rattle from a loudspeaker at the centre of the territory once every 7 min. During the control treatment, the territory was left in silence following the temporary removal of the owner. We found that the presence of a speaker replacement reduced the probability of intrusion by 34% and increased the latency to first intrusion by 7%, providing support for the hypothesis that rattles play an active role in reducing intrusion risk. However, intrusions were not completely averted by the speaker replacement, indicating that for some individuals vocalizations alone are not a sufficient deterrent without other cues of the territory owner.
30 citations
TL;DR: The ontogeny of isolation calls in nectivorous bats, Glossophaga soricina, is studied to find strong statistical evidence for an individual signature encoded in isolation calls and provide evidence for considerable changes in isolation call parameters over a short ontogenetic time span.
Abstract: Bat pups produce isolation calls to solicit maternal care. During maturation, pup isolation calls may gradually develop into echolocation calls or exist in parallel to them, depending on the species involved. We studied the ontogeny of isolation calls in nectivorous bats, Glossophaga soricina. Isolation calls of G. soricina pups were frequency modulated calls uttered in bouts of varying length. Newborn pups already produced both isolation calls and echolocation call precursors (which developed into ‘normal’ echolocation calls), indicating that isolation calls of G. soricina pups occur independently and exist in parallel to echolocation calls during ontogeny. We found strong statistical evidence for an individual signature encoded in isolation calls. Moreover, we provide evidence for considerable changes in isolation call parameters over a short ontogenetic time span. Throughout ontogeny, the call interval decreased significantly whereas most frequency parameters increased significantly and call entropy rose (i.e., isolation calls became less tonal but noisier).
24 citations
TL;DR: In this article, a study conducted off Cape Breton Island, between 1998-2011, confirmed unit membership predicts associations between individuals. And they delineated 21 nearly stable social units, with an average 7 members.
Abstract: Cetacean social structures include fluid and stable elements. Long-finned pilot whales ( Globicephala melas ) live in units that interact forming labile groups. In this study conducted off Cape Breton Island, between 1998–2011, we confirm unit membership predicts associations between individuals. We determine how units are structured and interact. We delineated 21 nearly-stable social units, with an average 7 members. For units where multiple individuals are sexed, both sexes are present. Most units showed long-term stability, while one showed evidence of splitting. Three units shared individuals with the largest unit (K, average size = 29). Splitting is likely triggered by size and difficulties maintaining associations between all individuals. Pilot whales face many pressures driving sociality at a range of temporal and social scales producing a multilevel society. While we have produced a more detailed model of long-finned pilot whale social structure, there are still unanswered questions, particularly whether units are strict matrilines.
23 citations
TL;DR: This article found that nocturnal singing by ovenbirds and white-throated sparrows was related to date, temperature, wind, weather, and the lunar phase of the day.
Abstract: Recent research suggests that many diurnal songbirds also sing at night. The functions of nocturnal singing by diurnally active birds are not well understood. We used automated recorders to record nocturnal singing from May through July 2014. We examined how date, temperature, wind, weather, and lunar phase influenced nocturnal vocal behaviour. We found that nocturnal singing by ovenbirds and white-throated sparrows was related to date with clear seasonal patterns that did not mirror the dawn chorus. Nocturnal singing rates declined seasonally, but peaked earlier for white-throated sparrows than for ovenbirds. Both species sang less often on nights with a full moon or precipitation. Ovenbirds also sang fewer songs on cold and windy nights while white-throated sparrows sang less often on cloudy nights. We show that nocturnal song is shaped by environmental factors and shows a seasonal pattern that may be useful for gaining insights into functions of nocturnal song.
16 citations
TL;DR: First recorded case of rescue behaviour in birds is reported in the cooperatively breeding Seychelles warbler, where individuals were observed displaying behaviour aimed at removing sticky seeds from the feathers of an entangled individual belonging to their group.
Abstract: Rescue behaviour is a special form of cooperation in which a rescuer exhibits behaviours directed towards averting a threat to an endangered individual, thereby potentially putting itself at risk. Although rescue behaviour has been well-documented in experimental studies on rats and ants, published cases in other non-human animals are rare. Here, we report observations of rescue behaviour in the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). In this species, individuals sometimes become entangled in seed clusters of ‘bird-catcher trees’ (Pisonia grandis). Just one or a few of these sticky seeds can prevent Seychelles warblers to fly and may lead to mortality. In four cases, individuals were observed displaying behaviour aimed at removing sticky seeds from the feathers of an entangled individual belonging to their group. Intriguingly, the rescuing individuals engaged in this behaviour despite potentially risking entanglement. To our knowledge, this is the first recorded case of rescue behaviour in birds.
16 citations
TL;DR: In this paper, the authors examined evidence for grooming reciprocity and interchange for tolerance at drinking sources among adult females within a group of rhesus macaques ( Macaca mulatta ) on Cayo Santiago.
Abstract: In group-living animals, allogrooming is a common, heterogeneously distributed affiliative behaviour. Among non-human primates, Barrett et al. (1999) predicted ways in which Biological Markets principles interact with competitive regimes to influence grooming reciprocity and interchange. Most tests of these predictions, done at a group level, have produced inconsistent results. Here we take a novel approach by testing these predictions across individuals within a group. This is based on the premise that in groups facing moderate-to-high within-group-competition, individuals vary in their abilities to access resources based on their competitive abilities, causing them to pursue different grooming exchange strategies. We examine evidence for grooming reciprocity and interchange for tolerance at drinking sources among adult females within a group of rhesus macaques ( Macaca mulatta ) on Cayo Santiago. We test the above premise by assessing hierarchical steepness, and the relationship between individuals’ David’s scores (DS) and access to drinking sources. Finally, we examine the relationship of DS with grooming reciprocity and interchange to see whether they are consistent with the operation of market forces among individuals. Social network comparisons revealed that giving grooming was strongly predicted by both receiving drinking tolerance (interchange) and receiving grooming (reciprocity), despite strong associations with proximity and maternal kinship. The group showed a moderately steep hierarchy, and negative correlations between individuals’ David’s scores and difficulties in accessing drinking stations. Finally, we found partial support for a market-based explanation. Individuals with relatively low David’s scores were more likely to interchange grooming with drinking tolerance. However, grooming reciprocity wasn’t greater among individuals with higher David’s scores. Our findings suggest that multiple explanatory frameworks — reciprocity, market-based interchange, and/or proximity-mediated interchange/social bond investment — may all shape rhesus grooming exchange patterns. Future directions include examining evidence for additional forms of grooming interchange, and the influence of between-group-competition and stress-indicators on grooming reciprocity.
15 citations
TL;DR: In this article, the authors compared the widely used groupmembership method and an alternative time-based method to analyze associations within a population of bottlenose dolphins (Tursiops truncatus ) in Doubtful Sound, New Zealand.
Abstract: Photo-identification is an invaluable method for documenting associations. Based on the assumption that individuals photographed close together in time are physically close in space, the metadata associated with digital photography offers an opportunity to base association analyses on time between images. This was tested via analysis of associations within a population of bottlenose dolphins ( Tursiops truncatus ) in Doubtful Sound, New Zealand. We compared the widely used group-membership method and an alternative time-based method. Overall social structures between methods were similar; high degrees of association among all individuals and little support for sub-groups. Results also indicated an increase in the precision of pairwise indices for the time-based method. This study validated the approach of using time as a basis for analyses of associations. Importantly, this method can be retrospectively applied to any photo-ID data set in which images of uniquely identifiable individuals are time-stamped by the camera.
13 citations
TL;DR: This article examined how personality traits and early experiences predict age of natal emigration and timing of first ascent to alpha status in 169 wild male white-faced capuchins studied at Lomas Barbudal, Costa Rica, 75 of whom emigrated and 23 of whom acquired alpha status.
Abstract: It is rare in studies of long-lived animals to know enough about the personalities and early experiences of individuals to use this information to predict their behaviour during major life transitions in adolescence and adulthood. Here, we examine how personality traits and early experiences predict age of natal emigration and timing of first ascent to alpha status in 169 wild male white-faced capuchins studied at Lomas Barbudal, Costa Rica, 75 of whom emigrated and 23 of whom acquired alpha status. Males were more likely to delay natal emigration if they were more extraverted, more neurotic, if their fathers co-resided longer with them, and if there were fewer alpha male turnovers. More extraverted males attained alpha status sooner.
13 citations
TL;DR: Whether the nursing behaviour of giraffes differs between the zoo and nature reserve is analyzed and which factor (food intake, presence of predators, population density) can explain the difference is discussed.
Abstract: Nursing behaviour is one component of mammalian life history strategy that demonstrates context-dependent flexibility within species. Wild giraffes live in groups and feed themselves over large area. In the zoo, giraffes are kept in enclosures with abundant food resources. We aimed to analyse whether the nursing behaviour of giraffes differs between the zoo and nature reserve and discuss which factor (food intake, presence of predators, population density) can explain the difference. We observed seven and four female–calf pairs in the Bandia reserve, Senegal, and in Prague Zoo, Czech Republic, respectively. Nursing bouts were less frequent and longer and calves were less successful in nursing solicitations in the reserve, as females there seemed to be more selective for nursing times and locations, likely due to presence of predators and differences in food intake. Allonursing occurred more frequently in the zoo which can be attributed to higher population density in captive conditions.
TL;DR: This article showed that New Caledonian crows respond to different tool-using problems by altering the length of the tools that they manufacture; on average, crows made shorter tools for task requiring short tools and longer tools for tasks requiring long tools They continued to do so when they could not simultaneously see the tool-manufacturing material and the apparatus requiring the use of a tool Despite altering their tools, the crows frequently did not make tools short or long enough to reliably extract the bait, though this may have been due to shortcomings in the task presented to them.
Abstract: New Caledonian crows have demonstrated flexible behaviour when using tools and solving novel problems However, we do not know whether this flexibility extends to tool manufacture Here, we show that these crows respond to different tool-using problems by altering the length of the tools that they manufacture; on average, crows made shorter tools for tasks requiring short tools and longer tools for tasks requiring long tools They continued to do so when they could not simultaneously see the tool-manufacturing material and the apparatus requiring the use of a tool Despite altering the length of their tools, the crows frequently did not make tools short or long enough to reliably extract the bait, though this may have been due to shortcomings in the task presented to them Our results demonstrate that these crows have a degree of behavioural flexibility when making tools, which may be used in the wild during foraging
TL;DR: It is shown that the Croatian population is acoustically divergent from the western populations of Sicily and Sardinia, which could be consistent with geographical isolation, and a possible genetic differentiation between populations, and/or an adaptation to the acoustic environment.
Abstract: Whistles are acoustic signals produced particularly during social interactions Here, we compare whistles by bottlenose dolphins from three Mediterranean areas (Croatia, Sicily and Sardinia) to investigate the presence of acoustic divergence and to discuss the possible causes of variability Whistle parameters differ significantly between populations, but PCA highlights that the majority of variability is due to a limited number of frequency parameters Cluster and DFA show that the Croatian population is acoustically divergent from the western populations of Sicily and Sardinia This divergence could be consistent with geographical isolation, and a possible genetic differentiation between populations, and/or an adaptation to the acoustic environment Moreover, in a comparison of whistle parameters of different Mediterranean populations with those of previously published Atlantic populations, it was revealed that the Sicilian population was acoustically closer to Atlantic populations Our results represent a contribution to identifying acoustically differentiated populations of bottlenose dolphins in the Mediterranean
TL;DR: It is demonstrated that yellow warblers use social cues informing successful pairing over other types of social cues to select breeding habitat.
Abstract: Breeding habitat selection strongly affects reproduction and individual fitness. Among birds, using social cues from conspecifics to select habitat is widespread, but how different types of conspecific social cues influence breeding habitat selection remains less understood. We conducted a playback experiment evaluating if the yellow warbler ( Setophaga petechia ), a species with two song categories linked to pairing status, uses categories differently when selecting breeding habitat. We hypothesized that yellow warblers use second-category singing mode, which is mostly sung by paired males, over first-category singing mode for habitat selection, as successfully paired males should indicate higher-quality habitat. We broadcast yellow warbler first-category singing mode, second-category singing mode, and silent controls at sites in Illinois. Yellow warblers were more abundant at sites treated with second-category singing mode compared other sites. Our results demonstrate that yellow warblers use social cues informing successful pairing over other types of social cues to select breeding habitat.
TL;DR: It is shown that after the period of active maternal care, roosting groups became smaller with a significantly higher level of genetic relatedness among adult females in contrast to the pregnancy and lactation stages, providing some evidence that temporal social associations may be positively correlated with Genetic relatedness.
Abstract: Social groups of bats that operate under fission–fusion dynamics tend to establish and maintain non-random associations. We examined the social and genetic structure of the Leisler’s bat ( Nyctalus leisleri ), a species that is typical of tree-dwelling and long-distance migratory species in Europe. We used long-term co-occurrence data (capture-recapture sampling of roosting individuals) in combination with individual genetic relatedness (inferred from a set of microsatellite markers) to assess relationships between structural, temporal and genetic properties of roosting groups. Our results showed that social structure in groups of roosting Leisler’s bat was not random. Social clusters revealed by network analysis were almost identical to demographic cohorts, which indicates that Leisler’s bats are able to maintain social bonds only over a single season. After the period of active maternal care, roosting groups became smaller with a significantly higher level of genetic relatedness among adult females in contrast to the pregnancy and lactation stages. This provides some evidence that temporal social associations may be positively correlated with genetic relatedness. Low recapture rates of bats across seasons in light of natal philopatry indicates a shorter life span of individuals likely due to high mortality during long distance migratory movements. This probably has the most significant effect on the social system of this species.
TL;DR: It is argued that not only are social networks shaping parasite transmission, but parasites in turn shape social networks through their effects on the behaviour of infected individuals.
Abstract: Social network models provide a powerful tool to estimate infection risk for individual hosts and track parasite transmission through host populations. Here, bringing together concepts from social network theory, animal personality, and parasite manipulation of host behaviour, I argue that not only are social networks shaping parasite transmission, but parasites in turn shape social networks through their effects on the behaviour of infected individuals. Firstly, I review five general categories of behaviour (mating behaviour, aggressiveness, activity levels, spatial distribution, and group formation) that are closely tied to social networks, and provide evidence that parasites can affect all of them. Secondly, I describe scenarios in which behaviour-altering parasites can modify either the role or position of individual hosts within their social network, or various structural properties (e.g., connectance, modularity) of the entire network. Experimental approaches allowing comparisons of social networks pre- versus post-infection are a promising avenue to explore the feedback loop between social networks and parasite infections.
TL;DR: The structure of personality traits is described and it is asked if two traits, boldness and exploration, play a role in the strength or pattern of social associations in a wild population of degus, a rodent that often lives communally with unrelated conspecifics.
Abstract: Recent research in behavioural ecology has revealed the structure of animal personality and connections to ecologically and evolutionarily important traits. Personality is hypothesized to influence social interactions through individual behavioural differences or personality-based dyadic interactions. We describe the structure of personality traits and ask if two traits, boldness and exploration, play a role in the strength or pattern of social associations in a wild population of degus, a rodent that often lives communally with unrelated conspecifics. Boldness was repeatable in both adults and juveniles, but exploration was only repeatable in adults. We found evidence for a behavioural syndrome between exploration and boldness in adult degus. We documented negative assortment by exploratory personality type; more exploratory animals shared burrows with less exploratory animals. However, tendency towards boldness and exploration were not predictive of association strength. Our results highlight a potential connection between personality and social structure in a communally nesting species.
TL;DR: The authors found that early infant handling is associated with later social bonds that are stronger than expected based on kinship, rank, sex, and age in rhesus macaques (Macaca mulatta).
Abstract: Throughout the primate order, individuals are highly motivated to handle infants that are not their own. Given the differing and often conflicting interests of the various participants in handling interactions (handler, infant, and mother), most functional hypotheses are specific to particular handling roles. Here we explore one hypothesis that may apply to all participants, but that has received relatively little attention: that handling may facilitate the formation and maintenance of social bonds. Using free-ranging rhesus macaques ( Macaca mulatta ) on Cayo Santiago, we examine the relationship between infant handling in the early weeks and the strength and diversity of infant social bonds months later, when infant relationships were more independent from those of their mothers. Our results largely confirm the influence of several social characteristics (kinship, rank, sex, and age) in governing handling interactions. They also provide the first evidence that early handling is associated with later social bonds that are stronger than expected based on these social characteristics. However, the enhancement of bonds is largely confined to related handlers; frequent unrelated handlers did not generally go on to form strong bonds with infants. This suggests that kinship may be a sort of prerequisite to the enhancement of social bonds via handling. Given the adaptive benefits of strong social bonds among adult primates, future research should investigate whether early infant handling may have longer term fitness effects.
TL;DR: Chemical analysis of the secretions applied during grooming revealed volatile organic compounds that may be involved in chemosensory-mediated communication and/or mate choice in tent-making Indian short-nosed fruit bats.
Abstract: Social grooming is conspicuous in group-living mammals. Bats are gregarious and may groom each other, but the motivation for such social behaviour remains unclear. Here, we describe patterns and infer function of social grooming in tent-making Indian short-nosed fruit bats. Combining field and captivity observations, we found that males and their harem of females mutually groom and apply bodily secretions to one another in tight clusters. Mutual grooming is more commonly initiated by females, before emergence flight at dusk, and during the non-mating season. The within-harem association pattern suggests males may recognize female reproductive status via social grooming. Chemical analysis of the secretions applied during grooming revealed volatile organic compounds that may be involved in chemosensory-mediated communication and/or mate choice. These fruit bat harems were previously seen as simple aggregations, with limited interactions among individuals. Our findings suggest social grooming is multi-functional, with potential implications for the bats’ social lives.
TL;DR: The inter-specific comparative analysis based on quantification of social traits related to the spatial-and-ethological population structure and cooperation allows author to propose a new conceptual approach to the assessment of differences between the species under consideration in terms of the evolution of sociality.
Abstract: There are two types of complex social units — aggregations and family groups — in rodent populations, with an essential difference in their social organization The impact of ecological factors on the evolution of sociality in rodents (the transition from solitary towards family-group lifestyle) is still unclear The inter-specific comparative analysis based on quantification of social traits related to the spatial-and-ethological population structure and cooperation allows author to propose a new conceptual approach to the assessment of differences between the species under consideration in terms of the evolution of sociality A new conceptual model of the evolution of sociality in rodents should incorporate ecological conditions and social factors, including cooperation, operating as a complex of selective forces promoting formation of family groups
TL;DR: It is found that lemurs exhibited strong preferences for the clean water, supported even at low levels of faecal contamination and in species adapted to water-limited habitats, for which choosiness about water quality could present a dehydration risk.
Abstract: Many parasites and pathogens are transmitted via water, including through faecal contamination of water sources. Yet water is essential for survival, and some species gain nutritional and other benefits from coprophagy. We investigated how primates balance the risks of faecal pathogen transmission with potential benefits of faeces ingestion in their selection of water sources by conducting behavioural experiments with five species of lemurs (Family Lemuridae) in captivity. Subjects were given a choice between clean water and water ‘contaminated’ with disinfected faecal material, which contained cues associated with faecally transmitted parasites, but minimal risk. We found that lemurs exhibited strong preferences for the clean water. This pattern was supported even at low levels of faecal contamination and in species adapted to water-limited habitats, for which choosiness about water quality could present a dehydration risk. Our results strongly support the hypothesis that avoiding faecal contamination is important in water selection.
TL;DR: In this article, the authors compare the vocal output among male mountain chickadees living along an urbanization gradient to assess how urbanization affects male signalling, and find that males in more urbanized habitats had greater vocal output.
Abstract: Vocal output during the dawn chorus is often an honest indicator of male quality, where males with greater access to food and in better condition produce more vocalizations. We compare the vocal output among male mountain chickadees living along an urbanization gradient to assess how urbanization affects male signalling. Chickadees forage in the canopy, and because urban habitats are associated with lower canopy volume, we predicted that urban habitats may offer lower food and thus lead to reduced song output. Contrary to our predictions, males in more urbanized habitats had greater vocal output. We suggest that despite decreased canopy cover, urban birds may have greater access to food in both the breeding and pre-breeding seasons due to differences in both supplementary resources and vegetation composition of urban vs rural landscapes in our area. Living in urban habitats may allow males to enter the breeding season in better condition.
TL;DR: It is shown that beyond neighbourhood recognition, residents are able to evaluate the potential threat of stranger intruders in general, thereby extending the evolutionary gains of the dear enemy by saving energy even in the context they are expected to acts with higher costs.
Abstract: A reduction of territory owners’ aggression towards their neighbours in relation to the intrusion of strangers characterises the dear enemy phenomenon Supposedly, the disparity in aggression levels of territory owners is due to a higher threat imposed by strangers compared to the threat imposed by neighbours To evaluate the occurrence of the phenomenon in males of the small-sized lizard Eurolophosaurus nanuzae we performed a field manipulative study We considered three models to run intrusions in males’ territories: neighbour, tailed stranger (unfamiliar) and tailless stranger intruders Our results lend support to the presence of dear enemy for this species as residents acted more aggressively towards strangers than to neighbours In addition, the information we provide supports the relative threat hypothesis as territory owners were more aggressive towards tailed stranger intruders than to tailless stranger intruders In this sense, tail condition can represent a trait that signals the ‘resource holding power’ (RHP) of a lizard Therefore, we show that beyond neighbourhood recognition, residents are able to evaluate the potential threat of stranger intruders in general, thereby extending the evolutionary gains of the dear enemy by saving energy even in the context they are expected to acts with higher costs
TL;DR: In this paper, the effects of physical and social environments on eastern chipmunks' (Tamias striatus) vigilance, by varying the perceived risk through playback experiments of alarm calls and neutral environmental sounds, were investigated.
Abstract: Animals foraging under risk have to trade-off resource acquisition and predator avoidance. Environmental factors can modulate the level of risk and should thus influence the expression of anti-predator behaviours such as vigilance. In this study, we investigated the effects of physical and social environments on eastern chipmunks’ (Tamias striatus) vigilance, by varying the perceived risk through playback experiments of alarm calls and neutral environmental sounds, and by integrating habitat and weather characteristics, as well as neighbour density. Chipmunks showed higher levels of vigilance when foraging in more open habitats, under high wind conditions, when they heard alarm calls and when surrounded by a high neighbour density. The effects of wind intensity and neighbour density on vigilance were also stronger during the broadcast of alarm calls rather than neutral sounds. Our results emphasize how both the physical and social environments can modify risk perception and therefore risk-taking decisions of foraging individuals.
TL;DR: In this article, the authors assessed if measures of road and traffic characteristics serve as indicators of risk, and compared behaviours of different age classes during road-crossing events, finding that immature individuals tended to move ahead of others on the road, suggesting that it is more important for immature individuals to follow adults at the beginning of crossing than to follow along for the entire crossing.
Abstract: Among group-living animals, some members may derive benefit by following the decisions of other members. Free-ranging wild Asian elephants in Mudumalai National Park, southern India, must often cross roads and can be disturbed by vehicles. We assessed if measures of road and traffic characteristics serve as indicators of risk, and compared behaviours of different age classes during road-crossing events. More individuals displayed excitable behaviour on wider roads. A larger number of adults entered the road first, which is considered the most dangerous position, compared with immature elephants. Immature individuals tended to move ahead of others on the road, suggesting that it is more important for immature individuals to follow adults at the beginning of a crossing than to follow along for the entire crossing. These findings may suggest that less experienced group members derive benefit by following the decisions of experienced ones under risky situations.
TL;DR: In this article, self-handicapping was investigated in a captive group of brown capuchin monkeys (Cebus apella ) by recording the duration and sequence of play during focal samples.
Abstract: Play may serve several potential functions, including learning to overcome unexpected circumstances. Self-handicapping, during which individuals do not utilize their full strength, is proposed to provide training for the unexpected. If self-handicapping occurs, then play fight intensity should decrease as partner age discrepancy increases. By playing with reduced intensity, the older partner self-handicaps, exposing itself to situations that it does not fully control. Self-handicapping was investigated in a captive group of brown capuchin monkeys ( Cebus apella ) by recording the duration and sequence of play during focal samples. All instances of play fighting were scored from video for intensity. As the age difference between the partners increased, the intensity of play bouts decreased. Since partners with larger age disparities played less intensely, results provided quantitative evidence for self-handicapping, although additional factors may affect play intensity. We suggest that self-handicapping encourages play and provides support for the training for the unexpected hypothesis.
TL;DR: Subordinates used several types of tactical deception, including concealment and distraction, especially when paired with competitors of much higher social rank, and they obtained the hidden food more frequently when they used a combination of tactics rather than only one.
Abstract: The complex social environments of primates create opportunities for engaging in tactical deception, especially for subordinate individuals. We analysed the behaviour of subordinate Tonkean macaques with dominant conspecifics in an experimental food competition context. The subordinate macaque could see two pieces of food in a test area, but only one piece was visible to the dominant. Both individuals were released into the test area at the same time or with the subordinate given a short head start on the dominant. Here, based on video analysis of the subordinates’ behaviours, we describe and classify functionally deceptive behaviours displayed by subordinates, and report factors that influenced these behaviours. Subordinates used several types of tactical deception, including concealment and distraction, especially when paired with competitors of much higher social rank, and they obtained the hidden food more frequently when they used a combination of tactics rather than only one.
TL;DR: In this paper, a group of 113 men were photographed to obtain their degree of facial symmetry, i.e., the small random deviations in facial bilateral traits, and two saliva samples (pre- and post-stimulus sample) were collected to measure the change in their testosterone levels.
Abstract: An individual’s body odour is a characteristic that is used to obtain information about conspecifics. However, to our knowledge the role of body odour and the degree of facial symmetry on testosterone changes among men as indicators of possible rivals has not been investigated yet. A group of 113 men were photographed to obtain their degree of facial symmetry, i.e., the small random deviations in facial bilateral traits. They smelled and assessed the odour of men with different grades of facial symmetry, and donated two saliva samples (pre- and post-stimulus sample) to measure the change in their testosterone levels. We found that testosterone levels decreased in symmetrical men who perceived the odour of asymmetrical men. Our results suggest that men could perceive characteristics in other men that are highly valued by women through odour to identify possible rivals, and that the observed decrease in testosterone levels could be related to an inhibition of competitive behaviours.
TL;DR: Troupial duets may be especially threatening because they indicate the presence of a mated pair, which likely poses a greater territorial threat than lone, unmated birds.
Abstract: Both females and males of many animals possess elaborate displays, such as solo songs and duets of songbirds. We know little about the function of female song or what selects for duets. To examine their possible functions, we played female solos, duets and a heterospecific control to pairs of troupials (Icterus icterus). Both sexes responded strongly to duets by approaching the playback speaker significantly closer, faster, and more often compared to female solos or the control. Neither sex responded strongly to female solos; troupials approached closer, sang sooner, and duetted more following female solos than the control, but this difference was not significant. Our results indicate that troupial duets pose a greater threat than female solos and female troupial solos are not particularly threatening. Troupial duets may be especially threatening because they indicate the presence of a mated pair, which likely poses a greater territorial threat than lone, unmated birds.
TL;DR: It is shown that the three sister species of the striped mouse genus Rhabdomys had similar spatial memory and cue use, differing only when external cues were initially removed and during the first probe test of spatial memory.
Abstract: Variation in spatial cognition is correlated with differences in the environments where animals originate, such that different environments might select for different cognitive ability. We investigated whether three sister species of the striped mouse genus Rhabdomys differed in their spatial cognition. The species originated from three locations across a rainfall gradient in southern Africa, which vary in habitat complexity. We tested individuals in a modified Barnes maze and asked whether the species had different spatial memory and navigation and whether these differences were related to their geographic location. We showed that the species had similar spatial memory and cue use, differing only when external cues were initially removed and during the first probe test of spatial memory. The similarities suggest that the environment of origin is not associated with spatial cognition in Rhabdomys , and that spatial cognition is phylogenetically constrained or there might be similar selection pressures across the distribution.