Showing papers in "Behaviour in 2007"
TL;DR: The authors reviewed research on intergroup encounters in non-human primates published over the last 20 years, focusing on participation by different classes of individuals and provided testable hypotheses about group-level behaviour based on individual costs and benefits.
Abstract: Summary Group members do not always act cohesively when facing extra-group rivals. When benefits such as group-defence are not monopolizable, it poses an economics problem: who should contribute to public goods and who should freeload? A collective action framework compliments existing theoretical explanations for cooperation, and provides testable hypotheses about group-level behaviour based on individual costs and benefits. Using this approach, we review research on intergroup encounters in non-human primates published over the last 20 years, focusing on participation by different classes of individuals. While food- and matedefence explain much between-sex variation in participation, rank and reproductive access frequently explain within-sex variation. In some species, individuals may use intergroup interactions to survey potential transfer locations and mating options, which might coincidently intimidate rivals. Experimental evidence suggests that when intergroup dominance is based on relative number of fighters, individual participation still varies with sex, rank, companion behaviour and dependent offspring presence. Relatively few studies have examined how factors such as relationships within and between groups or individual temperament mediate aggression. Long-term studies of multiple habituated groups and methodological advances (e.g., playback experiments) will continue to improve our understanding of how complex group-level patterns are predictable when viewed from an individual perspective.
155 citations
TL;DR: It was found that when individuals were tested alone, those that were more active were more likely to resume foraging sooner when subjected to a simulated predator attack in a separate test, and also consumed more prey in foraging competition trials.
Abstract: Summary Boldness refers to the extent to which animals balance risk against benefits when engaging in such behaviors as foraging, exploration or resource competition. Evidence suggests that individuals can behave strategically, acting boldly in situations when doing so is adaptive, whilst avoiding risk when the rewards are correspondingly lower. In this study we sought to determine the effects of social context upon the boldness of threespine sticklebacks (Gasterosteus aculeatus). We found that when individuals were tested alone, those that were more active were more likely to resume foraging sooner when subjected to a simulated predator attack in a separate test, and also consumed more prey in foraging competition trials. We found no effect of group size upon the relative ability of individuals to effectively compete for prey. Group size did affect other behaviours however: focal fish were more active and resumed foraging more rapidly when tested in groups that they did when tested alone. Finally, individual social information use was not correlated with behaviour in other contexts. Two competing hypotheses, the adaptation and the constraint hypotheses have been posited to explain the presence and prevalence of individual variation in boldness; our findings offer partial support for the former of these.
118 citations
TL;DR: This work presents the most systematic inter-troop comparison of this behaviour from an investigation of nine troops of Macaca fuscata fuscATA and one troop of M. f.
Abstract: Summary Stone handling (SH), a form of solitary object play, consists of an individual manipulating stones by performing various behavioural patterns. Previous findings from the Arashiyama population of Japanese macaques suggested that SH is socially transmitted across generations as a behavioural tradition. To further test the hypothesis that SH is a traditional behaviour in this species, we present the most systematic inter-troop comparison of this behaviour from an investigation of nine troops of Macaca fuscata fuscata and one troop of M. f. yakui living at six sites in Japan. We analyzed a total 1280 video-recorded SH bouts and charted the relative frequency of occurrence of 45 SH behavioural patterns across age classes. Many SH patterns showed geographically patchy distributions and were referred to as local variants or SH traditions. In terms of behavioural complexity, we found three levels of SH culture, each level being defined by troop-dependent clusters of SH traditions. We found a positive correlation between geographic proximity and cultural similarity in SH between troops. To explain similarities in the SH repertoires between the free-ranging troops living at the same site, we discussed the phenomenon of cultural zones. We interpreted intra-group variability in the performance of SH patterns from the viewpoint of developmental factors. We found no major difference between the two subspecies in the occurrence and form of SH.
106 citations
TL;DR: In this paper, the authors examined data from the Kanyawara chimpanzee community, Kibale National Park, Uganda to test for evidence of two strategies: travelling in larger subgroups (parties) and travelling silently.
Abstract: Summary Chimpanzees have hostile intergroup relations and are reported to use two strategies to reduce risk in the territory periphery: travelling in larger subgroups (‘parties’), and travelling silently. We examined data from the Kanyawara chimpanzee community, Kibale National Park, Uganda to test for evidence of these strategies. We compared behaviour in the territory core with two potentially dangerous contexts: the periphery and croplands. Parties that visited the periphery had over twice as many adult males as parties that remained in the core. Analysis of vocal production rate of 249 parties revealed that, controlling for time of day and party composition, chimpanzees produced fewer pant-hoot calls in croplands than in the core. Pant-hoot production varied in different sectors of the periphery, being reduced in three sectors, unchanged in one, and increased in one. Focal follows of 12 males found results similar to party follows, but with rank-related individual variation. Overall, these results indicate that chimpanzees have the ability to modify grouping and vocal behaviour to reduce risk in areas with a high risk of detection. However, rather than consistently remaining silent in the periphery, chimpanzees in this population sometimes increased their vocalization rate, perhaps to advertise territory ownership and coalition strength.
104 citations
TL;DR: Data used to test the hypothesis that overlap zones are smaller or used less in species that are subject to a higher risk of lethal aggression in intergroup encounters conform to previous reports suggesting that primate groups tend to have large overlap zones, regardless of the risk of violence.
Abstract: Summary Overlap zones between home ranges of neighboring groups of primates are routinely reported to be under-used. However, little is known about how the size of overlap zones varies, or what factors influence their size. Here we use ranging data on three species of group-living primates to test the hypothesis that overlap zones are smaller or used less in species that are subject to a higher risk of lethal aggression in intergroup encounters. Redtail monkeys (Cercopithecus ascanius) have a low risk of violence; white-faced capuchins (Cebus capucinus )h ave an intermediate risk; chimpanzees (Pan troglodytes) face a high risk of violent encounters with their neighbors. We calculated two indices of use of the overlap zone. First, we assessed the opportunity for groups to meet each other as the range overlap, i.e., the diameter of the home range in relation to the distance between neighboring ranges. Second, we compared the intensity with which groups used the overlap zone by calculating utilization curves that described how space-use patterns change with distance from a group’s center of activity. Neither the overlap potentials nor utilization curves supported the risk hypothesis. There was little evidence of differences among the three species, all of which showed substantial underuse of overlap zones. Our data, which provide the first systematic comparison of overlap zones among primates, thus conform to previous reports suggesting that primate groups tend to have large overlap zones, regardless of the risk of violence. Since such zones are potentially responsible for carrying capacity being lower than expected by an ideal-free distribution, it is an important problem to understand why they are apparently widespread.
86 citations
TL;DR: This article found that juvenile jackdaws exhibit high levels of active giving outside parental care and courtship in the 3 months following nest dispersal and proposed a new functional explanation for active giving in this species to facilitate the formation of social bonds.
Abstract: Food sharing in birds occurs largely in the context of parental care and courtship. Previous studies found that juvenile jackdaws demonstrate high levels of active giving outside these contexts in the 3 months following nest dispersal. The function of this behaviour is not understood, although it seemed compatible with hypotheses of mutualism (both participants benefit), reciprocity and harassment avoidance. We propose a new functional explanation for active giving in this species, namely facilitating the formation of social bonds. Captive juvenile jackdaws actively gave 2.5% of temporarily available food items and objects to peers, irrespective of sex and kinship. Active giving accounted for 43.7% of all food transfers. Donors advertised food and objects through a distinctive display and initiated active giving more than recipients. The direction of giving was initially unfocused, but became selective until each donor predominantly gave to one recipient and affiliative relationships were formed. We conclude that food-sharing may be an integral part of jackdaw ontogeny which allows juveniles to explore their social environment and facilitates the formation of affiliative relationships when family bonds dissolve. We also suggest that the ritualised food offer display may signal the 'collaborative intent' of the donor and serve to attract potential partners/mates.
84 citations
TL;DR: The consequences of dominance for resource use in crayfish do not follow the current understanding of resource holding potential and feeding and mating was unaffected by social status in populations, a surprising result given current views on the role of dominance and aggression.
Abstract: [Our study examined the effect of dominance on feeding, mating behaviour, and shelter use in the crayfish, Orconectes rusticus In three different experiments, dominance and resource use were recorded in male populations, mixed-sex populations, and when crayfish were alone Crayfish established dominance status in populations or through status conditioning and had access to variable resources (food, mates, and/or shelters) in each experiment Subsequent resource use was quantified and compared to dominance rank Our results did not match conventional predictions that dominance would confer increased access to resources Top ranked dominant crayfish occupied shelter significantly less than lower ranks This differential shelter use may be due to dominant motivation to reinforce status, as dominants also participated in the most agonistic interactions When dominant crayfish had access to resources in the absence of conspecifics, dominant crayfish occupied shelter significantly more than subordinate and naive crayfish This result illustrates that present social context has a significant impact on behavioural decisions in crayfish Social history and social context interact to determine shelter occupancy in this case Feeding and mating was unaffected by social status in our populations This is a surprising result given current views on the role of dominance and aggression in many animal systems The consequences of dominance for resource use in crayfish do not follow our current understanding of resource holding potential We hypothesize that these consequences vary due to changing behavioural motivations in different social contexts Future studies should examine under which conditions dominance may impact feeding and mating and whether differential resource use results in differential reproductive success, Our study examined the effect of dominance on feeding, mating behaviour, and shelter use in the crayfish, Orconectes rusticus In three different experiments, dominance and resource use were recorded in male populations, mixed-sex populations, and when crayfish were alone Crayfish established dominance status in populations or through status conditioning and had access to variable resources (food, mates, and/or shelters) in each experiment Subsequent resource use was quantified and compared to dominance rank Our results did not match conventional predictions that dominance would confer increased access to resources Top ranked dominant crayfish occupied shelter significantly less than lower ranks This differential shelter use may be due to dominant motivation to reinforce status, as dominants also participated in the most agonistic interactions When dominant crayfish had access to resources in the absence of conspecifics, dominant crayfish occupied shelter significantly more than subordinate and naive crayfish This result illustrates that present social context has a significant impact on behavioural decisions in crayfish Social history and social context interact to determine shelter occupancy in this case Feeding and mating was unaffected by social status in our populations This is a surprising result given current views on the role of dominance and aggression in many animal systems The consequences of dominance for resource use in crayfish do not follow our current understanding of resource holding potential We hypothesize that these consequences vary due to changing behavioural motivations in different social contexts Future studies should examine under which conditions dominance may impact feeding and mating and whether differential resource use results in differential reproductive success]
72 citations
TL;DR: In this article, the authors found that animals use ratio to determine differences in group sizes when making decisions about group membership, and that the ease of any numerical comparison is based on the ratio between the stimuli compared; as the ratio becomes smaller the comparison becomes more difficult.
Abstract: Summary Little is known about the mechanisms individuals might use to compare group sizes when making decisions about group membership. One possibility is that animals use ratio to determine differences in group sizes. Weber’s Law states that the ease of any numerical comparison is based on the ratio between the stimuli compared; as the ratio becomes smaller the comparison becomes more difficult. We set out to test this prediction by offering female green swordtails, Xiphophorus helleri, dichotomous choices between different shoal sizes, varying both in ratios and absolute numbers of fish. Swordtails attended to the ratio of group size between stimulus shoals, rather than the numerical difference between shoals, when making shoaling decisions. Where group size ratio was 2:1, subjects showed a significant preference for the larger shoal, independent of the numerical difference between the shoals. When the ratio was 1.5:1, subjects showed no preference. The ratio between group sizes may, thus, be an important factor in shoaling decisions. More broadly, ratio could prove to be a widespread mechanism for animals to make numerical comparisons in group assessments.
65 citations
TL;DR: FID increased as distance to refuge increased and temperature decreased, supporting the hypothesis that individual differences in boldness are consistent among encounter phases, and DF increased as FID increased, supportingThe hypothesis thatindividual differences inboldness are consistency among encounter phase is supported.
Abstract: Escape studies often focus on one variable, but tactics and refuge use vary with microhabitats, exposure, distance to refuge, and temperature. We studied these effects and effects of microhabitats and risk factors (distance from refuge, temperature) on flight initiation distance (FID, distance between predator and prey when escape begins) and distance fled (DF) in the lizard Sceloporus virgatus . FID increased as distance to refuge increased and temperature decreased. DF increased as FID increased, supporting the hypothesis that individual differences in boldness are consistent among encounter phases. Refuges were rock crevices, trees, logs, and grass clumps. Interhabitat differences in FID and DF matched those in distance to refuge. FID was longer for lizards on rocks and ground than trees due to proximity to and use of refuge. Lizards on trees rarely changed microhabitats, moving to the far side and unpredictably up or down. Lizards on slopes fled long distances up slopes. Most lizards on rocks entered crevices or switched microhabitats. Lizards on ground usually changed microhabitats. Optimal escape theory accurately predicted effects of risk on FID, but initial microhabitats and final microhabitats and refuges affected tactics, FID and DF. DF was affected by risk, being longer when lizards remained visible.
62 citations
TL;DR: It was shown that egg survival was greatest in gravel, suggesting an adaptive explanation for zebrafish oviposition decisions, and a field-based mesocosm study in Bangladesh found the same substrate preference, although it failed to detect a significant effect of the presence of vegetation.
Abstract: In oviparous species a female's choice of oviposition site can have a significant impact on off-spring survival and thereby on reproductive fitness. Here we compare the spawning behaviour of domesticated zebrafish, Danio rerio, in the laboratory with wild fish in a field-based mesocosm study in Bangladesh. We manipulated spawning site characteristics in order to examine oviposition decisions by females. In the laboratory experiment zebrafish were provided with a choice of four discrete spawning sites containing gravel or silt, with or without vegetation. We observed the behaviour of females and territorial males during spawning and recorded the number of eggs deposited in each spawning site. A gravel substrate was preferred by both males and females and vegetation was preferred over non-vegetated substrates. We repeated the experiment in Bangladesh and found the same substrate preference, although we failed to detect a significant effect of the presence of vegetation. When eggs were incubated under all four treatments, it was shown that egg survival was greatest in gravel, suggesting an adaptive explanation for zebrafish oviposition decisions.
61 citations
TL;DR: Activity patterns, behavioural repertoires, and agonistic encounters of rusty crayfish during the summer months are explored using continuous, 24-hour, underwater video recording at a series of representative field sites.
Abstract: Summary Agonistic behaviour of crayfish has been studied extensively in laboratory settings where pairs or groups of individuals are allowed to interact within an experimental arena. Crayfish agonistic behaviour within its natural context, however, has received little attention to date. The present, non-manipulative field study explored activity patterns, behavioural repertoires, and agonistic encounters of rusty crayfish (Orconectes rusticus) during the summer months using continuous, 24-hour, underwater video recording at a series of representative field sites. Following the filming, crayfish within the vicinity of the camera site were captured and measured. Individual densities were high, reaching a maximum of 68 individuals/m 2 at some sites. Large crayfish predominantly inhabited deeper sections of the river and were mostly active at night, whereas small crayfish generally utilized the shallows and were active outside their burrows during day and dusk. Time outside their shelter was mainly used for feeding. Individuals frequently returned to the same shelter they had emerged from. Agonistic encounters were common events and generally occurred in the context of shelter acquisition or defense. Dyadic fighting progressed with escalating sequences of stereotyped aggressive acts. Furthermore, high intensities with unrestrained use of claws were seen in encounters between size-matched opponents. The results of this study allow us to root laboratory findings of crayfish aggression within a comprehensive, ethological framework and to consider ultimate consequences for individual fighting decisions and strategies.
TL;DR: It is found that olfactory cues can be more important than visual cues in determining foraging performance in this species, potentially influencing how they cope with naturally occurring periods of turbidity, and how they adapt to human-induced eutrophication.
Abstract: In aquatic habitats turbidity can affect the foraging efficiency of visual predators, directly influencing their capacity to detect prey. In a laboratory study we tested the effect of different loads of suspended sediment upon the foraging rates of threespine sticklebacks (Gasterosteus aculeatus). We compared the foraging rates of fish under a series of different turbidity treatments, testing fish originating from four habitats within a single drainage basin that differed in a number of environmental parameters including turbidity. Although we found habitat specific differences in foraging rates, these did not correspond to local turbidity levels. The findings of a follow up experiment revealed habitat-specific variation in boldness, which may be indirecly linked to the observed differences in foraging rate. The main finding of our study was that turbidity alone had no impact upon their prey capture rates, but that high turbidity in combination with saturation with prey odour extract caused prey capture rates to fall significantly. This suggests that olfactory cues can be more important than visual cues in determining foraging performance in this species, potentially influencing how they cope with naturally occurring periods of turbidity, and how they adapt to human-induced eutrophication.
TL;DR: Findings are not consistent with male mating competition and, in conjunction with overlapping home ranges, high interaction rate, and a positive relationship between IGA rate and both food availability and fruit patch size, they indicate that intergroup feeding competition may be important for capuchins.
Abstract: I investigate the ecological context of intergroup agonism (IGA) in white-faced capuchins ( Cebus capucinus ) to elucidate the roles of feeding and mating competition, explicitly exploring both long- and short-term competitive strategies. Short-term mating competition is not a major function of IGA in C. capucinus . Males were the primary participants in IGA, but did not attempt to prevent extra-group copulations by herding females, and there was no relationship between IGA rate and conception rate. Long-term mating competition, on the other hand, may be important: 41% of interactions were low intensity, as would be expected if males were assessing the composition of neighboring groups in anticipation of a takeover. However, 59% of intergroup interactions escalated to chases or physical contact and females were frequent participants in IGA, directing aggression at adults of both sexes and at juveniles. These findings are not consistent with male mating competition and, in conjunction with overlapping home ranges, high interaction rate, and a positive relationship between IGA rate and both food availability and fruit patch size, they indicate that intergroup feeding competition may be important for capuchins. However, interactions do not preferentially occur at food sources, suggesting that capuchins may gain long-term, rather than short-term, benefits from IGA.
TL;DR: In this paper, the authors investigated variation in the acoustic properties of the long-distance vocalizations emitted by free-living spotted hyenas, Crocuta crocuta, and found that the minimum fundamental frequency of a whoop provides reliable information about the caller's general age and, for adult callers, information about sex.
Abstract: It has long been recognized that vocal signals communicate information about the age, sex and affective state of callers. However, the mechanisms by which these types of information are communicated are less well understood. Here we investigated variation in the acoustic properties of the long-distance vocalizations, called 'whoops', emitted by free-living spotted hyenas, Crocuta crocuta. Specifically we investigated whether the fundamental frequency, length and rate of whoops provide information about the caller's age, sex and/or level of arousal. We determined the latter by contrasting whoops emitted spontaneously with whoops emitted during periods of social excitement, when callers typically also exhibited visual signals associated with heightened arousal. We found that the minimum fundamental frequency of a whoop provides reliable information about the caller's general age and, for adult callers, information about sex as well. The vast majority of adult male whoop bouts were emitted spontaneously, but juveniles and adult females produced many of their bouts during periods of social excitement. Although context did not significantly affect the whoop bouts of adult females, juvenile bouts emitted during social excitement had higher maximum fundamental frequencies, greater proportions of asymmetric whoop subtypes, and reduced inter-whoop intervals. By reducing the inter-whoop intervals of bouts, juvenile hyenas significantly increased the likelihood that conspecifics would respond to whoops by approaching the caller or its social companion. Peak fundamental frequency and the relative abundance of whoop subtypes did not appreciably affect response. We discuss the potential functions of whooping by juvenile and adult hyenas in light of these findings.
TL;DR: While the sensory mechanisms allowing round gobies to selectively respond to conspecific vocalizations remain unknown, it is clear that they show highly directional responses to acoustic cues in both laboratory and field settings.
Abstract: Summary Many species of fish use auditory cues as part of their reproductive repertoire but intended receivers must be able to localize sounds to make full use of this information. Specialized couplings between the ear and swim bladder are thought to be critical for acoustic localization, yet species without specialized connections use acoustic cues in reproductive displays. In an attempt to better understand mechanisms of acoustic localization, we used the round goby (Neogobius melanostomus), a hearing generalist, to assess responses to calls in the lab and field. The call used for playback was recorded in the field from an actively displaying male round goby and consisted of a series of low frequency pulses. In the field, playback of the call resulted in a significant enhancement of approaches toward, and entries into, an experimental arena as compared to when the sound was off. There was no effect on the amount of time spent near the speaker however. In the lab, males and females responded actively when calls were played and females showed a significant attraction to the playing speaker. Responses were highly directional with little angular deviation, suggesting true localization to the sound source. While the sensory mechanisms allowing round gobies to selectively respond to conspecific vocalizations remain unknown, it is clear that they do show highly directional responses to acoustic cues in both laboratory and field settings.
TL;DR: In this article, the authors used data spanning 5 years and 5 wild groups to address factors that might explain variable participation, both across age-sex classes and among individual adult females.
Abstract: While blue monkey groups often defend feeding territories against their neighbours, group members do not participate equally. Data spanning 5 years and 5 wild groups were used to address factors that might explain variable participation, both across age-sex classes and among individual adult females. Adult females participated most, although there was a 9-fold difference between those individuals who participated most and least. Juvenile participation increased with age, but female juveniles participated more than males in each cohort. Male juveniles reduced participation as they approached the age of natal emigration. In general, it seems that adult participation patterns are acquired gradually during ontogeny. Among adult females, those with infants participated less than those without infants, and higher-ranking females participated more than lower-rankers. The presence of matrilineal kin in the group did not generally affect participation by adult females. Age-sex class differences and the effect of infant presence can be explained in terms of relative costs and benefits to participation. The lack of a kinship effect was unexpected. The rank effect was also unanticipated, given that rank does not predict reproductive success in this species. High-ranking females may face lower costs, offer staying incentives to lower-ranked females, or trade services with them.
TL;DR: The mode of acquisition and the developmental process of stone handling, a form of solitary object play, in a capti ve troop of Japanesemacaques housed in an outdoor enclosure at the K yoto U niversity PrimateResearch Institute, Japan is investigated.
Abstract: (Section of E cology ,D epartment of E cology and S ocial B eha vior,Primate R esearchInstitute, K yoto U niversity,41-2 K anrin, Inuyama, A ichi 484-8506, Japan)(Accepted: 5 July 2007)SummaryIn this study we systematically investigate the mode of acquisition and the developmentalprocess of stone handling, a form of solitary object play , in a capti ve troop of Japanesemacaques (Macaca fuscata ) housed in an outdoor enclosure at the K yoto U niversity PrimateResearch Institute, Japan. T his study w as conducted to evaluate tw o alternati ve hypothesesregarding the mode of acquisition of stone handling in infants: (1) en vironmental stimuli(availability of and exposure to stones) and (2) social stimuli (exposure to stone handlingindi viduals). Early exposure to stones in the en vironment had no signiÞcant effect on wheninfants acquired the beha vior . N o signiÞcant correlations were recognized between the ageof stone handling acquisition and number of stones encountered per hour from birth to ac-quisition, or the time spent in a speciÞc area of the enclosure as a function of the number ofavailable stones therein. H ow ever, being exposed to a stone handling m odel(s) w as a socialstimulus that had an effect on the age of acquisition, with a signiÞcant negative correlationbetween a m otherO s stone handling frequenc y and the age of acquisition by her infant. Infantsof non-stone handling m others acquired the beha vior much later than others. Inf ant peerswho acquired stone handling earlier played no signiÞcant role as stone handling m odels. O fthe factors tested here, the timing of acquisition depended m ainly on the level of proximityto a demonstrator and the frequenc y at w hich those available demonstrators performed thebeha vior .K eywor ds : solitary object play, proximity , beha vioral m odel, stimulus enhancement, trans-mission.
TL;DR: In this article, the applicability of a maximum likelihood estimation method (MLM) for identifying dive bouts was investigated and compared with a recently proposed sequential differences analysis (SDA).
Abstract: Foraging behaviour frequently occurs in bouts, and considerable efforts to properly define those bouts have been made because they partly reflect different scales of environmental variation. Methods traditionally used to identify such bouts are diverse, include some level of subjectivity, and their accuracy and precision is rarely compared. Therefore, the applicability of a maximum likelihood estimation method (MLM) for identifying dive bouts was investigated and compared with a recently proposed sequential differences analysis (SDA). Using real data on interdive durations from Antarctic fur seals (Arctocephalus gazella Peters, 1875), the MLM-based model produced briefer bout ending criterion (BEC) and more precise parameter estimates than the SDA approach. The MLM-based model was also in better agreement with real data, as it predicted the cumulative frequency of differences in interdive duration more accurately. Using both methods on simulated data showed that the MLM-based approach produced less biased estimates of the given model parameters than the SDA approach. Different choices of histogram bin widths involved in SDA had a systematic effect on the estimated BEC, such that larger bin widths resulted in longer BECs. These results suggest that using the MLM-based procedure with the sequential differences in interdive durations, and possibly other dive characteristics, may be an accurate, precise, and objective tool for identifying dive bouts.
TL;DR: It is suggested that high ranking males discourage revolutionary alliances by using two strategies: They primarily rely on conservative alliances, but also offer tolerance in cases in which conservative coalitions are less effective.
Abstract: Tibetan macaque males at Huangshan ( Macaca thibetana huangshanensis ) display highly skewed mating success and highly asymmetric patterns of aggression, but also high levels of tolerance. We examined affiliation, tolerance and agonistic support to test the hypothesis that increased tolerance in otherwise despotic males may occur when high-ranking males require support from other males to prevent (1) potentially destabilizing revolutionary coalitions against them, or (2) young adult males from usurping the alpha position. Several predictions of the first hypothesis were supported: Support was unrelated to kinship or affiliation and was generally conservative, serving to reinforce the current hierarchy. Nevertheless revolutionary coalitions posed a threat, particularly to alpha males. High-ranking males displayed tolerance in the form of co-feeding toward lower ranking males that supported them, and alpha males showed the most cooperation with the males that targeted them in revolutionary coalitions. Predictions of the second hypothesis were not consistently supported; male coalitions targeted young potential usurpers of the alpha position during only one of two periods of hierarchical stability. We suggest that high ranking males discourage revolutionary alliances by using two strategies. They primarily rely on conservative alliances, but also offer tolerance in cases in which conservative coalitions are less effective.
TL;DR: To answer this question, individual virgin female guppies were exposed to different combinations of males: just one male; three males, one at a time; and three males presented simultaneously, revealing that male harassment causes a direct reduction in female short-term fitness.
Abstract: [Males can maximise their fitness by copulating with as many females as possible. Although this behaviour may have negative consequences for the females involved, females can also benefit from multiple mating. For example, multiple mated female guppies produce more, larger and fitter offspring. It is not clear if these fitness benefits are a direct result of multiple mating, or the product of female choice — either pre or post copulatory — for better quality males. To answer this question, individual virgin female guppies were exposed to different combinations of males: just one male; three males, one at a time; and three males presented simultaneously. Mating activity was more intense in the three-at-a-time treatment but did not differ between the other two. This increased attention did not affect gestation time nor offspring size, but significantly reduced the number of offspring produced. This reveals that male harassment causes a direct reduction in female short-term fitness., Males can maximise their fitness by copulating with as many females as possible. Although this behaviour may have negative consequences for the females involved, females can also benefit from multiple mating. For example, multiple mated female guppies produce more, larger and fitter offspring. It is not clear if these fitness benefits are a direct result of multiple mating, or the product of female choice — either pre or post copulatory — for better quality males. To answer this question, individual virgin female guppies were exposed to different combinations of males: just one male; three males, one at a time; and three males presented simultaneously. Mating activity was more intense in the three-at-a-time treatment but did not differ between the other two. This increased attention did not affect gestation time nor offspring size, but significantly reduced the number of offspring produced. This reveals that male harassment causes a direct reduction in female short-term fitness.]
TL;DR: The association of start time and song rate with population fertility, continuation of dawn song after territory establishment, and depressed song rate when mates were fertile, are all consistent with the hypothesis that the availability of extra-pair females is the primary factor selecting for male participation in dawn song.
Abstract: We quantify the singing behaviour of eastern kingbirds ( Tyrannus tyrannus ) in the 'dawn song' period to describe variation in performance, identify sources of variation, and identify the main recipient(s) of the information conveyed in the display. All males ( N = 87) participated in dawn song, but the probability that a male did not sing increased if he was relatively isolated, and it was late in the season. The earliest and longest song bouts were made by males with many neighbours and when population level female fertility was high. High song rates were typical of males in dense nesting assemblages, early in the season and nest cycle, and when social mates were infertile. However, among males with active nests, song rates varied only with neighbour density and either date or population level female fertility. Given the strong inverse correlation between population fertility and date, we suspect that population fertility drove the relationships. The association of start time and song rate with population fertility, continuation of dawn song after territory establishment, and depressed song rate when mates were fertile, are all consistent with the hypothesis that the availability of extra-pair females is the primary factor selecting for male participation in dawn song.
TL;DR: The authors examined the influence of frugivory and social factors on behaviour during intergroup encounters in the mountain gorillas of Bwindi Impenetrable National Park, Uganda.
Abstract: The aim of this study was to examine the influence of frugivory and social factors on behaviour during intergroup encounters in the mountain gorillas of Bwindi Impenetrable National Park, Uganda Frugivory was associated with an increase in the frequency of intergroup encounters, but had no impact on the length of the encounter, or on the type of behaviour exhibited, suggesting that while neighbouring groups may be attracted to limited fruit patches, there was no indication of between group feeding competition Encounters with solitary males were more likely to elicit more avoidance, less tolerance, more herding behaviour, and a trend towards more aggression than encounters with groups The number of potential migrant females and the number of silverbacks had no impact on the type of behaviour exhibited However, an older dominant male was less likely to be aggressive towards the opposing group when a subordinate male was present, suggesting a collective action problem rather than cooperation in multi-male groups Combined these results suggest that between group competition is linked more to mate defence and acquisition than resource defence This study contributes to our understanding of the relationship among intergroup encounters, feeding ecology, reproductive strategies and social structure in gorillas
TL;DR: In this article, the authors examined duets of the yellow-naped amazon (Amazona auropalliata) at two sites in Costa Rica to determine the syntactical rules underlying duet variation.
Abstract: Summary Pair duets are acoustically complex communication signals formed jointly by members of a mated pair. Duets may serve multiple communication functions; quantitative studies of the acoustic structure and organization of notes (or ‘syntax’) within duets are an important step in identifying these functions. This study examined duets of the yellow-naped amazon (Amazona auropalliata) at two sites in Costa Rica to determine the syntactical rules underlying duet variation. Duets were composed of contact calls and three other note types found only in duets. These latter note types were sex-specific, with one type performed by females and the other two types by males. Sex-specific notes were delivered antiphonally and in distinct pairs, with the male note following and often overlapping that of the female. Note types appeared in a strict sequential order in which each note could be repeated a variable number of times or omitted entirely, a pattern previously termed ‘combinatorial syntax’. Additionally, there was considerable variation in acoustic parameters of notes within types. Many of these parameters varied significantly with note order within a duet. These syntactical features suggest a preliminary hypothesis that males and females encode different, and possibly multiple, messages in their respective contributions to duets.
TL;DR: While Anolis sleeping site choice is strongly influenced by diurnal behavior (including territorial defense and microhabitat choice), differential diurnal and nocturnal microhabITat use may result from differing pressures during day and night.
Abstract: Summary Where animals sleep may be an important component of their behavioral ecology, as sleeping renders animals immobile and hypothetically vulnerable for long periods. Yet, sleep is rarely studied outside of the laboratory. To investigate factors that influence natural sleeping behavior, we examined sleeping locations of three sympatric species of territorial Anolis lizards (Anolis lineatopus, A. grahami and A. valencienni) that have evolved adaptations to different microhabitats. Results indicate that sleeping perch differences among these species are consistent with their diurnal specializations, and sleeping perches are generally higher, narrower, and more horizontal than diurnal perches. We find only limited evidence for sleeping site fidelity; although individuals of one species have apparent sleeping areas within their home ranges, few lizards repeatedly sleep on perches within 0.5 m of previous sleep perches. In a closer examination of the sleeping sites of A. lineatopus, we find that male nocturnal ranges are more dispersed from conspecific males than their diurnal ranges, and they typically sleep near their territory boundaries. We conclude that while Anolis sleeping site choice is strongly influenced by diurnal behavior (including territorial defense and microhabitat choice), differential diurnal and nocturnal microhabitat use may result from differing pressures during day and night.
TL;DR: Seasonal variation in song activity paralleled seasonal changes in T levels and song activity and the proportion of time spent incubating was significantly negatively correlated with T levels in individual males, suggesting this negative correlation between T and incubation behaviour may be partly explained by T increases in males responding to the presence of prospecting females with additional nestbox occupation and mate attraction song.
Abstract: In temperate-zone birds, seasonal testosterone (T) profiles often vary among species with different mating systems. The trade-off hypothesis suggests that T levels in male birds represent a trade-off between additional mating effort, stimulated by high T, and paternal effort, inhibited by high T. To study the role of T in mediating the trade-off between paternal and mating effort in the facultatively polygynous European starling (Sturnus vulgaris), we monitored seasonal fluctuations in T levels and song activity, which functions mainly in mate attraction, and we investigated natural covariation between plasma T levels and male parental and song behaviour during the parental phase. T concentrations peaked during nest building, remained high during the fertile period, and then decreased gradually during the period of paternal care. This resembles the profile typically found in polygynous species with biparental care. Seasonal variation in song activity paralleled seasonal changes in T. The proportion of time spent incubating was significantly negatively correlated with T levels in individual males. There was a positive, but non-significant, correlation between song activity at an additional nest box and T levels during incubation. We suggest that this negative correlation between T and incubation behaviour may be partly explained by T increases in males responding to the presence of prospecting females with additional nestbox occupation and mate attraction song, rather than that high T levels stimulate mate attraction song. During the feeding period, characterized by a very low availability of unmated females, variation in T levels was low and there was no covariation between T and feeding. T levels during the parental phase reflect, but do not seem to directly regulate, the trade-off between parental and additional mating effort and other factors such as opportunities for additional matings may influence the resolution of this reproductive trade-off.
TL;DR: The hypothesis that female mate preferences for carotenoid-based coloration of males have evolved via indirect benefits such as the high foraging ability of their offspring has been supported.
Abstract: In the guppy Poecilia reticulata, females often choose their mates on the basis of the orange spot coloration of males. It is known that the colour saturation of orange spots in males is determined by the amount of intake of algae, a natural source of carotenoids. In this study, we examined the relationship between sexually selected traits in wild-caught males and their algal-searching ability in a laboratory experiment. Neither the body size nor the orange spot size of males correlated significantly with the algal-searching ability. However, males that possessed orange spots with a high colour saturation in the wild exhibited a high searching ability in the laboratory. This result suggests that the algal-searching score of males in the laboratory experiment indicated their algal-foraging ability in the natural environment. In a previous study, the algal-searching ability of guppies in a laboratory experiment was demonstrated to be a heritable trait. The result of this study further supported the hypothesis that female mate preferences for carotenoid-based coloration of males have evolved via indirect benefits such as the high foraging ability of their offspring.
TL;DR: The results directly suggest greater volitional control of vocal production in gibbons than previously considered and implies the possibility of upper level volitionalControl in this species, which involves differentiation of several call types in response to specific arbitrary stimuli over the motivational state.
Abstract: Volitional control of vocal production is an essential ability for vocal usage learning in animal calls Operant conditioning of vocal production is one of the most direct experimental approaches for assessing volitional vocal control in animals In this case study, we attempted operant conditioning of the vocalizations of an immature female white-handed gibbon ( Hylobates lar ) For the operant conditioning of vocal production, the gibbon was required to immediately vocalize in response to a V-sign cue by the human experimenter's hand During the 2-month period of intensive training for conditioning, the gibbon successfully learned to produce the contingent response of vocalizations We again tested the conditioning with a 30-day interval after the completion of conditioning and were able to immediately show memorization of vocal conditioning These results directly suggest greater volitional control of vocal production in gibbons than previously considered Our study implies the possibility of upper level volitional control in this species, which involves differentiation of several call types in response to specific arbitrary stimuli over the motivational state
TL;DR: Information is presented on the annual cycle of song activity in female European Starlings housed in a large outdoor aviary in a single-sex situation and social and environmental factors motivating singing behaviour are examined.
Abstract: Nearly all studies on seasonal changes in song behaviour have focused on male songbirds and detailed studies on seasonal patterns of song activity in females are lacking. Here, we present information on the annual cycle of song activity in female European Starlings ( Sturnus vulgaris ) housed in a large outdoor aviary in a single-sex situation (except for the breeding season when males were introduced) and examine social and environmental factors motivating singing behaviour. Female song activity varied significantly throughout the year and was highest during December-mid April. Little or no song was produced when males were present (mid April-June) and in July. With these exceptions, females produced song in every month of the year. A high proportion of females occupied a nestbox throughout the year. Females occupying a nestbox sang significantly more than females without a nestbox, independently of the period. During March and early April females owning a nestbox sang significantly more in their nestbox and/or defended it more often, suggesting that song in that period is produced in the context of intrasexual competition. There was a large individual variation in song rates among females. Furthermore, song rates of individual females were repeatable across the year.
TL;DR: In this paper, the authors present the results of analyses of between-group encounter intensity variation in Thomas langurs while controlling for threat when evaluating familiarity and vice versa, showing that both familiarity and threat influence encounter intensity.
Abstract: During between-group encounters in primates, males often defend mates, food or infants against other males. Males, however, show variation in contests between opponents. In other taxa, such variation has been attributed to variation in familiarity with or threat of opponents. Here we present the results of analyses of between-group encounter intensity variation in Thomas langurs while controlling for threat when evaluating familiarity and vice versa. Encounter intensity was measured by the proportion of encounters with chases and the number of loud calls per minute during the encounter given by the focal male. The results indicate that both familiarity and threat influence encounter intensity. Less familiar opponents had more intense encounters and opponents that differed in the threat level to each other also had more intense encounters. Thus, Thomas langur males seem to incorporate information on both the level of threat and familiarity of other males to make a decision on how to react during a between-group encounter.
TL;DR: It is shown that Mexican jays use PS roles and that these roles were consistent through many trials, but might have changed between trial sets, and dominance influenced joining in that joining was more likely to occur between birds with a larger difference in their dominance rank.
Abstract: Summary While foraging, animals often exploit group members to obtain food. One way to describe this behaviour is with the producer-scrounger (PS) model, where scroungers use social interaction to obtain food discovered by producers. Mexican jays (Aphelocoma ultramarina) are a groupforaging species with a linear dominance hierarchy. We studied interactions in a free-living foraging group to determine (1) if foraging interactions can be explained with the PS model, (2) if these roles are consistent and (3) if dominance or relatedness affects joining frequency. We recorded board-flipping, eating, and joining events during sets of feeding trials. We show that Mexican jays use PS roles and that these roles were consistent through many trials, but might have changed between trial sets. Relatedness and frequency of joining were not correlated. Dominance influenced joining in that joining was more likely to occur between birds with a larger difference in their dominance rank. In contrast to other studies, our results suggest that this effect is mediated through joiner preference. Scroungers preferentially joined birds of lower dominance rank and high search activity. Producers with these qualities had fewer eating events with full access to seeds, suggesting that scrounging exacts a cost on producers.