Showing papers in "Behaviour in 2004"
TL;DR: The hypothesis that agonistic behavior and interference competition induce species replacements in freshwater decapods is tested and resources influenced fighting and dominance translated into a differential capability to compete.
Abstract: We tested the hypothesis that agonistic behavior and interference competition induce species replacements in freshwater decapods. Our model organisms were two crayfish (the indigenous Austropotamobius italicus and the non-indigenous and invasive Procambarus clarkii ) and the indigenous river crab Potamon fluviatile . A first experiment was aimed at analyzing the agonistic behavior of similarly-sized males in pairs of the three species combinations. Records were taken for an hour per day during five consecutive days of combats. Results showed that P. fluviatile was dominant over the two crayfish species and P. clarkii over A. italicus , as confirmed by their field distribution. In nature, the non-indigenous species might even reach higher levels of dominance over A. italicus . In fact, both the larger body size and the 'stronger' chelae of P. clarkii can induce asymmetries in fighting ability. Pairs composed of the non-indigenous crayfish and either A. italicus or P. fluviatile did not form stable hierarchies, possibly due to the failure of status recognition. In a second set of experiments, the agonistic behavior of the three species combinations was studied in the presence of either food (earthworms) or an artificial shelter (a 10 cm-long piece of a PVC pipe). As expected, resources influenced fighting and dominance translated into a differential capability to compete. In a third experiment, in which we measured shelter use by each species in a non-competitive context, shelters were more extensively occupied by A. italicus (which is dependent on natural crevices as hiding places) than by the other two species (which usually dig burrows). We expected that Potamon and Procambarus would gain less from occupying the offered shelter than Austropotamobius , and therefore their defense should be less vigorous. To the contrary, the presence of a rival strengthened the attraction to the shelter of these two species, in particular when river crabs were opposed to A. italicus .
117 citations
TL;DR: Male mate choice was affected by male reproductive status: while virgin males strongly preferred penultimate and virgin females to mated females, mated males were apparently indifferent to females of different mating status.
Abstract: In theory, male mate choice should occur when the costs of copulation, in terms of future mating opportunities, are high. The criteria males use to choose mates may change depending upon male mating history and the potential for future matings. We examine male mate choice in the St. Andrew's Cross Spider (Argiope keyserlingi Araneae: Araneidae). Laboratory experiments revealed that death and injury caused by female sexual cannibalism limits males to a maximum of two copulations. We assessed the mate choices of virgin and mated males for females of different reproductive status. We used field and laboratory choice bioassays involving airborne and web-based pheromones. In field experiments, wild males were strongly attracted to webs built by laboratory-raised virgin females. Webs from mated females did not attract males. Male mate choice was affected by male reproductive status: while virgin males strongly preferred penultimate and virgin females to mated females, mated males were apparently indifferent to females of different mating status. Such post-copulatory changes in male mate choice have not been previously documented, and may reflect a decreased potential for future mating.
110 citations
TL;DR: Behavioural responses to simulated avian predation in three-spined sticklebacks: the effect of experimental Schistocephalus infections.
Abstract: Barber, I., Walker, P., Svensson, P. A. (2004). Behavioural responses to simulated avian predation in three-spined sticklebacks: the effect of experimental Schistocephalus infections. Behaviour, 141,(11-12),1425-1440.
98 citations
TL;DR: Results supported the hypothesis that male behavior functions to prevent extra-group males from gaining access to sexually receptive females in chacma baboons in the Okavango Delta, Botswana.
Abstract: Summary Inter-group encounters among baboons range from peaceful to aggressive. During 23 months we observed 110 inter-group interactions involving four groups of chacma baboons in the Okavango Delta, Botswana. Results supported the hypothesis that male behavior functions to prevent extra-group males from gaining access to sexually receptive females. Males were more likely to chase females in their own group when estrous females were present, and their chases targeted estrous females more often than expected. Males also chased members of the opposing group more when estrous females were present. When estrous females were absent, male displays were shorter in duration, involved fewer participants, were less intense, and were more likely to result in peaceful mingling between groups. The alpha male was the individual most actively involved in inter-group chases and displays, but males of all ranks participated, especially when they were in consort with a female. However, males did not cooperate in group defense. While behavior during encounters was affected by the presence of
94 citations
TL;DR: The presence of foliage greatly affects the potential for vocal information transfer in great tits and requires behavioural and/or perceptual adjustment of the communicating individuals to counteract or reduce the impact of foliage on signal degradation.
Abstract: Songbirds living in temperate forests experience great seasonal changes in habitat acoustics during the part of the breeding season when singing activity is high. These changes, which are brought about by accelerated vegetation growth and leaf burst in spring, affect sound propagation and potentially render vocal communication more difficult as the total number of scattering and absorbing obstacles increases. We investigated this in a sound transmission experiment in which representative great tit ( Parus major ) songs were broadcast in a typical forest habitat before and after foliation. Speaker and microphone were placed at natural separation distances and in typical sender and receiver positions. For each song note we quantified several aspects of sound degradation and found that they all increased considerably when leaves were present. Before foliation the same amount of degradation would only be obtained by doubling the transmission distance, i.e. foliage shortens the active space of great tit song. This inevitably alters distance information, provided that distance-dependent, structural changes of received songs are used as ranging cues. Moreover, sender and receiver positions within the canopy become unfavourable compared to heights just below the canopy when the aim is to maximise song propagation distances. Altogether, the presence of foliage greatly affects the potential for vocal information transfer in great tits and requires behavioural and/or perceptual adjustment of the communicating individuals to counteract or reduce the impact of foliage on signal degradation.
93 citations
TL;DR: It was found that both sexes initiated group movements, but females did so more often, lead groups further and enlisted more followers than males, and sifakas did not use a particular call or other signals to initiate or control group movements.
Abstract: Summary Maintenance of group cohesion is of vital importance for group-living species. Individuals therefore need to coordinate their potentially divergent interests to maintain group cohesion. We studied behavioural aspects and mechanisms of coordinated group movements in Verreaux’s sifakas (Propithecus verreauxi), an arboreal Malagasy primate living in small groups. During a field study in Kirindy forest, western Madagascar, we studied the initiation and course of group movements, as well as vocalisations used in this context, in three social groups. We found that both sexes initiated group movements, but females did so more often, lead groups further and enlisted more followers than males. Sex of the leader had no effect on the probability that a group would feed or rest after a successful movement, however. Grumble vocalisations were emitted by both leaders and followers at high rates, both before and during group progressions, but Grumbles uttered just before an individual moved were characterised by a significantly steeper frequency modulation at the beginning of the call and higher call frequencies in both females and males. The results of this study indicated that sifakas, which evolved group-living independently from other primates, converge with many other group-living primates in several fundamental proximate aspects of group coordination and cohesion. In contrast to many other primates, however, sifakas did not use a particular call or other signals to initiate or control group movements.
90 citations
TL;DR: A role for B rather than T in the regulation of territorial defence in male great tits is suggested, which does not agree with the predictions of the 'challenge hypothesis' that males exposed to a territorial challenge while having breeding baseline T levels will respond with an increase in T or that T correlates with the intensity of aggression during a challenge.
Abstract: The apparent ability of plasma testosterone (T) and corticosterone (B) levels to fluctuate rapidly in response to agonistic interactions, suggests that these hormones may play an important role in an animal's acute behavioural response during such interactions. In the present study, free-living male great tits, Parus major, were subjected to a simulated territorial intrusion (STI) during the egg laying, incubation and nestling stage of first broods. Plasma T and B levels of challenged males were compared to those of control males matched for breeding stage, day in breeding stage, and time of day. Plasma B levels were significantly higher in challenged males compared to control males during the egg laying and incubation stage but not during the nestling stage. On the other hand, challenged males had significantly lower plasma T levels than control males throughout the breeding cycle. While having low plasma T and elevated plasma B levels, challenged males showed a vigorous and unrelenting territorial response to the STI. Plasma T and B levels of challenged males did not correlate with the intensity of the behavioural response to the STI. These findings do not agree with the predictions of the 'challenge hypothesis' that males exposed to a territorial challenge while having breeding baseline T levels will respond with an increase in T or that T correlates with the intensity of aggression during a challenge. Together, our findings suggest a role for B rather than T in the regulation of territorial defence in male great tits.
90 citations
TL;DR: In this article, the authors examined whether variation in the strength of territory defense corresponds to differences in intrinsic factors such as the age or experience of the territory owner, the extrinsic factor of the level of aggression shown by neighbours, or both.
Abstract: In many species, the ability to defend a territory is essential for a male to obtain any reproductive success at all, and even among territorial individuals, variation in the strength of territory defense could have a significant impact on how much reproductive success is obtained. Previous studies have documented consistent individual differences in the vigor with which male song sparrows (Melospiza melodia) defend their territories, as measured by the strength of their reactions to territorial intrusions simulated through song playback. Variation in the strength of defense could reflect intrinsic differences among individuals in their resource holding potential (RHP), or variation in extrinsic factors. In this study, we examined whether variation in the strength of territory defense corresponds to differences in intrinsic factors such as the age or experience of the territory owner, the extrinsic factor of the level of aggression shown by neighbours, or both. Results indicate that males that previously held territories on the study site, regardless of whether they were holding the same territory as the previous year, show higher levels of territory defense than males that are new to the study site, and, assuming that returning males are older males, suggest that age is more important than experience on a specific territory in determining strength of territory defense. In addition, we found evidence that males with high levels of territorial aggression tend to be spatially clustered. The pattern observed suggests that a combination of intrinsic and extrinsic factors contribute to the expression of individual differences in territorial aggression.
89 citations
TL;DR: A number of genomic and genetic tools should make it possible to identify the molecular basis of many different evolutionary traits in stickleback, and to begin to answer longstanding questions about the numbers and types of mutations that control the appearance of new morphological, physiological, and behavioral traits during vertebrate evolution.
Abstract: The dramatic radiation of sticklebacks in different post-glacial environments provides a unique opportunity to study the molecular mechanisms that underlie rapid evolutionary change in vertebrates. We have developed a number of genomic and genetic tools to facilitate further study of a wide range of morphological, physiological and behavioral traits in sticklebacks. A large collection of microsatellite markers has previously been developed for use in genome-wide linkage mapping of interesting traits in crosses between different stickleback forms. cDNA libraries have been generated and EST sequencing projects have begun to isolate stickleback homologs of developmental control genes. Large insert BAC libraries have been built to compare chromosome regions of interest from both anadromous and freshwater stickleback populations. Large scale fingerprinting of one of these libraries has been used to assemble overlapping contigs of BAC clones for chromosome walking and positional cloning. Together with recent development of methods to make transgenic sticklebacks, these tools should make it possible to identify the molecular basis of many different evolutionary traits in stickleback, and to begin to answer longstanding questions about the numbers and types of mutations that control the appearance of new morphological, physiological, and behavioral traits during vertebrate evolution.
80 citations
TL;DR: In this paper, the authors present data on inter-group encounters and male incursions (where one or several males encounter a reproductive unit) in Colobus vellerosus at the Boabeng Fiema Monkey Sanctuary in Ghana to assess whether they are compatible with three functions, and in the case of the limiting resource defense hypothesis, to assess the resource competed for.
Abstract: [Inter-group encounters can 1 — reflect between-group contest competition for access to limiting, defensible resources, 2 — allow individuals to gather information on the surrounding groups to assess mating or dispersal opportunities or to assess resistance to a possible transfer or takeover, 3 — allow individuals to convey information to the other group about one's quality/status. We present data on inter-group encounters and male incursions (where one or several males encounter a reproductive unit) in Colobus vellerosus at the Boabeng Fiema Monkey Sanctuary in Ghana to assess whether they are compatible with these three functions, and in the case of the limiting resource defense hypothesis, to assess the resource competed for. Our study group was observed for 343 hours over 61 days between June and November 2001, and interacted with three neighboring groups in 47 encounters. Inter-group encounters were more frequent than male incursions (34 vs 13) and lasted longer (median: 45 vs 9 minutes). Most encounters included aggression towards individuals in the opposing group (39/47). Males were aggressors as well as targets of male aggression in a majority of encounters. Females were targets of male aggression in over half of encounters, while being aggressive in only a few of them. We describe three cases of male aggression towards immatures during male incursions, and one case of female transfer following one of these male, Inter-group encounters can 1 — reflect between-group contest competition for access to limiting, defensible resources, 2 — allow individuals to gather information on the surrounding groups to assess mating or dispersal opportunities or to assess resistance to a possible transfer or takeover, 3 — allow individuals to convey information to the other group about one's quality/status. We present data on inter-group encounters and male incursions (where one or several males encounter a reproductive unit) in Colobus vellerosus at the Boabeng Fiema Monkey Sanctuary in Ghana to assess whether they are compatible with these three functions, and in the case of the limiting resource defense hypothesis, to assess the resource competed for. Our study group was observed for 343 hours over 61 days between June and November 2001, and interacted with three neighboring groups in 47 encounters. Inter-group encounters were more frequent than male incursions (34 vs 13) and lasted longer (median: 45 vs 9 minutes). Most encounters included aggression towards individuals in the opposing group (39/47). Males were aggressors as well as targets of male aggression in a majority of encounters. Females were targets of male aggression in over half of encounters, while being aggressive in only a few of them. We describe three cases of male aggression towards immatures during male incursions, and one case of female transfer following one of these male]
76 citations
TL;DR: This paper used a three-speaker playback design to evaluate whether male black-capped chickadees (Poecile atricapillus) respond differently to two simulated countersinging intruders who differ only in relative features of their singing performance.
Abstract: Within a network of communicating individuals, animals may gather information about the relative quality of conspecifics by eavesdropping on their signalling interactions. For territorial male songbirds, eavesdropping may be a low-cost, low-risk method for assessing the relative quality of the males around them. We used a three-speaker playback design to evaluate whether male black-capped chickadees (Poecile atricapillus) respond differently to two simulated countersinging intruders who differ only in relative features of their singing performance. We arranged three loudspeakers in an equilateral triangle at the center of playback subjects' territories. After luring males to the first loudspeaker by broadcasting non-song vocalizations, we played songs from the remaining loudspeakers to simulate a countersinging interaction between two male intruders. During the interactions, one simulated intruder consistently overlapped the songs of the other, a behaviour thought to be a signal of directed aggression in songbirds. Territorial male chickadees discriminated between the simulated intruders by preferentially approaching the loudspeaker broadcasting the overlapping signal, suggesting that males eavesdrop on other males' countersinging interactions. Male responses to playback support the idea that overlapping is a more threatening signal than being overlapped. Responses varied with the dominance status of the subject. High-ranking males approached the overlapping loudspeaker in 15 of 16 cases whereas low-ranking males approached the overlapping speaker in only 5 of 10 cases, suggesting that males of different quality may use different tactics for territorial defense.
TL;DR: The long-term persistence of individual song characteristics suggests that they are not related to dynamically changing individual attributes, but may reflect long- term storage of information during song acquisition as juveniles.
Abstract: Common nightingales (Luscinia megarhynchos) are among those bird species that possess an extremely large repertoire and perform it in a versatile singing style. Thereby, repertoire size, composition, and performance differs considerably among individuals. In this longitudinal field study, we investigated the long-term stability of these differences in the song characteristics of free-ranging nightingales. We determined the repertoire characteristics for nine adult male individuals in two successive years (three of these individuals were investigated over the course of three years) and compared these to similar measurements obtained from comparisons of song samples of different birds. Comparisons revealed remarkable differences among males, but we did not find systematic differences in the song performance of birds in successive years. Instead, song characteristics were remarkably stable within successive years. The long-term persistence of individual song characteristics suggests that they are not related to dynamically changing individual attributes, but may reflect long-term storage of information during song acquisition as juveniles. In addition, we found that the repertoire performance of adult nightingales allows fine-tuned vocal interactions among several neighbouring males.
TL;DR: It is concluded that adult males need coalition partners not only to gain entry to a group but also to maintain their membership within it, and that aggressive takeovers are more likely to happen when the group is vulnerable because it has a lower proportion of adult males.
Abstract: Male primates may immigrate into groups by peacefully joining the residents and taking up low-ranking positions in the hierarchy, or they may enter by force, challenging the resident males and attempting to drive them from high rank or from the group. Here we address the questions of how, when, and why immigrating male white-faced capuchins (C. capucinus) at Santa Rosa replace the former resident males of our groups, rather than simply joining them. We present data on 15 male replacements in 6 study groups tracked from 1984 through March 2004. During 11 aggressive takeovers, resident males were nearly always outnumbered by coalitions of invading males; lone resident males were particularly vulnerable. Both residents and invaders were wounded and infants often perished during or soon after takeovers. Male replacements also occur when resident males abandon their groups and males from neighboring groups 'waltz in' to become resident. Three such 'waltz in' replacements occurred during the study period. If we combine takeovers with 'waltz in' cases, replacements occur about every 4 years in our study groups, almost invariably during the dry season months of January to April, about 3-6 months before the annual peak in conceptions. In the years that groups are subject to takeovers, group composition includes significantly lower proportions of adult males than in no-takeover years. We conclude that: (1) the mechanism of male replacement is usually aggressive takeover, but sometimes abandonment of the group by prior resident males occurs; and (2) aggressive takeovers are more likely to happen when the group is vulnerable because it has a lower proportion of adult males, particularly when all co-resident males have emigrated, leaving only the alpha male in residence. Our long-term study shows that adult males need coalition partners not only to gain entry to a group but also to maintain their membership within it.
TL;DR: Data from this study favour the assumption from van Schaik and Sterck et al. that contest and scramble competition within and between groups can vary independently; and also favour the formulation from Isbell & Van Vuren (1996) on female dispersal.
Abstract: Theoretical models about female relationships within primate social groups hypothesise that food abundance and distribution are important factors determining the variation of patterns observed among species and populations. Despite some common premises, models formulated by van Schaik (1989) and Sterck et al. (1997) and by Isbell (1991) differ with respect to the importance of predation risk, the co-variation of contest and scramble competition and causes of female dispersal. In this study, data from a population of Cebus apella nigritus from Brazilian Atlantic Forest are analysed using predictions from these models. Competition among females, both within and between groups, is strong and related to food abundance and distribution. Females can transfer between groups, as well as males. Female dispersal is related to a significant reduction in per capita energy intake by group foragers during fruit scarcity periods. The data from this study are not conclusive about the importance of predation in causing variation of female relationships but favour the assumption from van Schaik and Sterck et al. that contest and scramble competition within and between groups can vary independently; and also favour the formulation from Isbell & Van Vuren (1996) on female dispersal. The exact pattern of female social relationships is not sufficiently explained by ecological causes alone. Social benefits provided by the dominant male also seem to be important.
TL;DR: Investigation of whether newly hatched Atlantic salmon fry (alevins) exhibit innate predator recognition and whether this recognition could be improved by prior exposure to combined conspecific and predator (pike) odours showed that the response to p Pike odour was not affected by previous exposure to pike odour and conspespecific tissue extract but was consistent with innate recognition of pike as predators.
Abstract: It is well established that fish can learn to associate odours from potential predators with risk and alter their behaviour accordingly. However, newly-hatched individuals have few opportunities for acquired predator recognition and may depend on unlearnt (innate) responses. We therefore considered whether newly hatched Atlantic salmon fry (alevins) exhibit innate predator recognition and whether this recognition could be improved by prior exposure to combined conspecific and predator (pike) odours. Our investigation showed that the response to pike odour was not affected by previous exposure to pike odour and conspecific tissue extract but was consistent with innate recognition of pike as predators. Trials conducted using odour from a non-piscivorous species confirmed that the fish were not simply reacting to a novel stimulus.
TL;DR: Red-backed shrikes high aggression against cuckoo dummies also showed a highly developed antiparasite adaptation, suggesting that red- backed shrikes won the arms race leaving no chance for cuckoos to develop better mimicry for their eggs.
Abstract: The red-backed shrike Lanius collurio once was parasitised by the common cuckoo Cuculus canorus in low frequency until the late 1960s in Hungary, but no case of parasitism is known from the last three or four decades. The cuckoo most probably abandoned this host species because its arms race had defeated, which may be indicated by the high level egg recognition and rejection ability of shrikes. However, mimicry of the cuckoo eggs in the last known cases of parasitism was significantly lower than between cuckoo eggs and host eggs collected from great reed warbler Acrocephalus arundinaceus nests within the same period. This suggests that red-backed shrikes won the arms race leaving no chance for cuckoos to develop better mimicry for their eggs. We tested these findings with experimentally induced parasitism using two types of real eggs: red-backed shrikes rejected 57.6% of the foreign conspecific eggs, but rejected 93.3% of the real cuckoo eggs transferred form nests of great reed warblers. This high level of rejection against real cuckoo eggs shows that there is no chance for presently occurring cuckoos to reparasitise red-backed shrikes in Hungary. Experimental eggs rejected by shrikes had lower mimicry than the eggs which were accepted, but intraclutch variation did not differ between accepters and rejecters. Hosts' aggression was significantly higher against the stuffed cuckoo than against the control species, the collared dove Streptopelia decaocto, and it was the least against female red-backed shrikes. Red-backed shrikes high aggression against cuckoo dummies also showed a highly developed antiparasite adaptation.
TL;DR: Intraspecific visual communication was studied quantitatively by testing the behavior of Sepia officinalis, the common cuttlefish, as senders and receivers of body pattern signals, suggesting that both males and females advertise their species, sex, location, and size to conspecific receivers.
Abstract: Intraspecific visual communication was studied quantitatively by testing the behavior of Sepia officinalis, the common cuttlefish, as senders and receivers of body pattern signals. These signals can be achromatic and/or linearly polarized and are produced by specialized dermal cells. Experiment 1 addressed whether the presence of conspecifics affected the visible, achromatic body patterns of males. These patterns tended to vary among conditions, suggesting limited sensitivity to audience. One set of body patterns varied with the number of conspecifics viewed while an uncorrelated set of body patterns varied with the sex of conspecifics viewed. Males showed high-contrast zebra banding when viewing another male, supporting previous studies of body patterns in male-male agonistic behavior. Experiment 2 addressed the relationship of polarized light patterns with visible body patterns of males and females, and tested whether senders modified their polarization patterns in response to conspecifics. Polarization patterning was only weakly associated with visible body patterns. Females showed more polarized body patterns than did males, but polarized patterns did not differ among conditions; thus, no sensitivity to audience by senders was found. Experiment 3 addressed whether conspecific receivers used information from polarized body patterns. Limited evidence was found for changes in the behavior of female but not male observers, suggesting that female receivers may use polarized patterns as a source of information about conspecifics. The information contained in polarization patterning may complement that contained in zebra patterning such that both males and females advertise their species, sex, location, and size to conspecific receivers.
TL;DR: The structure of dawn chorus songs could function across large distances to signal the identity of familiar singing males whose relative quality is known to the listener from other interactions (such as encounters within winter flocks).
Abstract: The two-note fee-bee song of male black-capped chickadees functions during the dawn chorus, in part, as a sexual signal across large distances. How song structure might encode information about male quality, however, remains unclear. We studied the availability of cues to male social rank (a proxy indicator of male quality), within the acoustic structure of dawn chorus songs of male chickadees whose flock dominance status we determined the previous winter. We used analysis of variance and discriminant function analysis to demonstrate that five temporal, frequency or relative amplitude features of song can predict individual identity but not the category of social rank (dominant versus subordinate) to which individuals belong. After transmitting chickadee songs through the forest and re-recording them at four broadcast distances, we found that song structure continued to effectively predict singer identity by our statistical methods despite significant acoustic degradation for as long as songs remained audible (up to 80 m). In particular, the relative frequency interval between the two notes is both the most invariant between-male measure and among the most individually distinctive. We conclude the structure of dawn chorus songs could function across large distances to signal the identity of familiar singing males whose relative quality is known to the listener from other interactions (such as encounters within winter flocks).
TL;DR: Results showed that hornbills consistently distinguished between eagle- and leopard-related stimuli, suggesting that birds attended to the predator class associated with the various stimuli.
Abstract: Black-casqued hornbills ( Ceratogymna atrata ) forage in small flocks in the tropical forests of West Africa, often in the vicinity of primate groups, including Diana and Campbell's monkeys ( Cercopithecus diana , C. campbelli ). Previous work has shown that these monkey species produce acoustically distinct alarm calls to crowned eagles ( Stephanoaetus coronatus ) and leopards ( Panthera pardus ), two of their main predators. Black-casqued hornbills are highly vulnerable to crowned eagles, but not leopards, suggesting that individuals may respond differently to these two predators. We analysed the vocal response of these birds to field playbacks conducted on different monkey species in Tai National Park, Ivory Coast. We tested six stimuli, three of which related to the presence of a crowned eagle (eagle shrieks, Diana and Campbell's eagle alarm calls) and three to the presence of a leopard (leopard growls, Diana and Campbell's leopard alarm calls). Results showed that hornbills consistently distinguished between eagle- and leopard-related stimuli, suggesting that birds attended to the predator class associated with the various stimuli. Second, within eagle-related stimuli, hornbills responded more strongly to the actual predator vocalizations than the associated alarm calls. One interpretation of these data is that birds were sensitive to the precision of information concerning the location of the eagle. We discuss these results in light of previous data on hornbill behaviour and cognitive capacities.
TL;DR: In this article, the authors examined whether alpha-subordinate relationships, number of intruders, or age affected subordinate contest participation in black howler monkeys (Alouatta pigra) and found that subordinate males in long-term alpha submissive associations had stronger howling and approach responses than males in short-term associations.
Abstract: When assessing a group's overall fighting ability, functional group size (i. e. the number of cooperative members willing to confront opponents) may be more important than actual group size. Despite obvious benefits, group members do not always act in a collective manner. For example, participation by subordinate male black howler monkeys (Alouatta pigra) in natural group-level contests is highly variable. Using playback experiments, we examined whether alpha-subordinate relationships, number of intruders, or age affected subordinate contest participation. Long-term census data were used to estimate the nature and duration of intra-group male associations. Some subordinate males had long-term relationships with the alpha that existed prior to residence in the current group or they were the alpha male's grown sons. Other subordinate males were in more recent associations with the alpha that formed under seemingly antagonistic circumstances (e. g. the deposed alpha or his grown sons). We found that subordinate males in long-term alpha-subordinate associations had stronger howling and approach responses than males in short-term associations. Younger long-term associates had the strongest reactions to simulated intruders, similarly aged shortterm associates rarely responded, and older males in both association categories responded at intermediate levels. We discuss the variable strategies of subordinate male black howlers and suggest that males who were more likely to participate in group-defence might be gaining direct or indirect fitness benefits by group living.
TL;DR: It is shown that, depending on the boundary conditions, in principle, all coal tits experience EPP: When analysing three or more broods of the same individual, there were no completely 'faithful' females and also nearly no males, which were not cuckolded at least once.
Abstract: In the majority of socially monogamous bird species, extra-pair paternity (EPP) has been shown to be common, while its frequency varies considerably among as well as within species. Our knowledge of factors affecting this variation, however, still remains comparatively poor. A thorough analysis of EPP patterns on an individual level may lead to a better understanding of the general diversity in EPP. Here, we analyse intra- and inter-annual as well as individual variation in the occurrence of EPP in first and second broods of coal tits (Parus ater) in three successive years. Based on a sample of 483 broods with 3559 offspring genotyped, we show that EPP was extraordinarily frequent in the study population, surpassing the values observed in other species of the genus Parus by far. On the population level, the rates of EPP were found to be remarkably similar between years, while there was pronounced intra-annual variation such that EPP rates increased significantly from first to second broods. Considering consecutive broods of individual females and males, the general occurrence of EPP was 'inconsistent' (i.e. EPP often affected only one of two broods), but the proportion of extra-pair young (EPY) per brood showed significant repeatability for both sexes in case of mate retention. When mate change occurred, repeatability collapsed, indicating that pair identity was more important in determining the repeatability of EPP than female or male identity alone. This was further supported by the fact that, besides female and male age, also their interaction (reflecting pair age combination) significantly predicted the proportion of EPY, though not in all breeding periods surveyed. Hence, the identity of the breeding pair (reflecting possible interactions of male and female characteristics) should be explicitly considered and accounted for in future studies investigating patterns of EPP on an individual level. Finally, we show that, depending on the boundary conditions, in principle, all coal tits experience EPP: When analysing three or more broods of the same individual, there were no completely 'faithful' females and also nearly no males, which were not cuckolded at least once.
TL;DR: Although colonial breeding facilitates CBP, it is less frequent in this eider population than in several other diving ducks, and possible contributing reasons are the relatively small clutch size and start of incubation after egg 2 or 3, limiting the time window for successful parasitism.
Abstract: The common eider differs from many other ducks in being a colonial 'capital' breeder, producing eggs from stored resources. These traits are expected to influence the occurrence of conspecific brood parasitism (CBP), which is particularly common in waterfowl. We analysed CBP in an eider population in the central Baltic Sea 2001-2002, using non-destructive egg albumen sampling combined with protein fingerprinting. This technique greatly increases the detection of parasitic eggs compared to more traditional methods. Parasitic eggs occurred in 20-22% of 164 nests studied, 6% of 754 eggs being laid by other than the host female. Parasitism increased with nest density, was rather evenly distributed over the laying season, and occurred both early and late in the laying sequence of the host. Protein fingerprinting showed that host females laid up to seven eggs, more than previously reported. Among 33 parasitised nests 22 had one parasitic egg, nine had two and two had three. In all but one case all parasitic eggs within a nest were laid by the same female. Although colonial breeding facilitates CBP, it is less frequent in this eider population than in several other diving ducks. Possible contributing reasons are the relatively small clutch size and start of incubation after egg 2 or 3, limiting the time window for successful parasitism.
TL;DR: Characteristics of the group such as measured by body mass, standard length, and body condition of its members did not significantly explain the shoaling preference for familiar kin, and it was indicated that adult, reproductively non-active sticklebacks prefer to shoal with familiar relatives.
Abstract: Theory predicts several advantages for animals to shoal with kin or familiars such as the evolution of altruistic behaviour or the reduction of competition because of more stable dominance hierarchies. In three-spined sticklebacks, Gasterosteus aculeatus, the influence of kinship and familiarity on shoaling decisions is ambiguous. We tested the potential for kin recognition of laboratory-bred adult, reproductively non-active sticklebacks in an experimental design in which a testfish was given the choice between two different shoals. One shoal consisted of its familiar full sibs while the other one was composed of fish unfamiliar and unrelated to the testfish. The time that testfish joined each group indicated that adult, reproductively non-active sticklebacks prefer to shoal with familiar relatives. Characteristics of the group such as measured by body mass, standard length, and body condition of its members did not significantly explain the shoaling preference for familiar kin.
TL;DR: A field playback experiment to male and female white-crowned sparrows on their territories to see if they made similar distinctions between songs, which found that females are more selective in responding to song than are males.
Abstract: Bird song varies both between species and across geographic areas, and there is abundant evidence from playback experiments that both male and female birds are sensitive to these differences in song structure. Comparisons between the sexes are complicated by differences in the behavioral assays used for each sex: males are often tested in the field, i.e. in a natural setting, and females usually in the laboratory with hormone treatment. We performed a field playback experiment to male and female white-crowned sparrows on their territories to see if they made similar distinctions between songs. After we temporarily removed the females' mates from their territories, females approached and called significantly more in response to playback of conspecific song than to heterospecific song. Females gave the same responses to the local dialect as they did to songs containing phrases from a foreign dialect. In contrast, males gave significantly weaker responses to songs containing a phrase from a foreign dialect than they did to the local dialect. We discuss reasons why our results conflict with previous studies that found that females are more selective in responding to song than are males.
TL;DR: These field observation and playback results suggest that monkeys might be able to modify the acoustic properties of vocalizations according to the preceding context so as to elicit a more effective vocal response from other group members.
Abstract: This study investigated the extent to which vocal production in wild Japanese macaques, Macaca fuscata yakui, is flexible. Japanese macaques frequently exchange coo calls with other group members to maintain auditory contact. When a coo call is emitted but no other members respond within a short interval, the same monkey often emits another call repeatedly. This study focused on these two successive coo call sequences. First, the sequences of eleven females in a free-ranging group were recorded and analyzed. Comparisons of the acoustic properties between the initial and repeated coo calls revealed that the repeated call was higher in fundamental frequency and longer in duration than the initial call. Next, playback experiments were conducted to examine the efficiency of the exaggerated acoustic features of these repeated coo calls. Eight pairs of initial and repeated coo calls were prepared from eight female monkeys as the playback stimuli, and played back to the eight subject females. Comparisons of subject responses to the initial and repeated coo call stimuli revealed that the repeated call stimuli elicited more frequent vocal responses. These field observation and playback results suggest that monkeys might be able to modify the acoustic properties of vocalizations according to the preceding context so as to elicit a more effective vocal response from other group members. The pattern of vocal interactions among wild Japanese macaques is therefore likely to be flexible and to some extent context-sensitive.
TL;DR: Results are similar to those found for all-male groups of mountain gorillas in the wild and demonstrate that all- male groups can be a cohesive social unit in this species, and raise the questions of why all-Male groups have rarely been observed in wild populations and how social, ecological and anthropogenic factors influence male sociality.
Abstract: Male mammals show considerable variation in their association (e.g. single-male, multi-male, all-male groups) and relationship (e.g. affiliative versus intolerant) patterns. Although a number of primates have been observed to form all-male groups, studies of the social dynamics of these groups are limited. This study examined the social interactions of 25 male western lowland gorillas living in nine captive all-male groups. Over 1,300 hours of data were collected using group scan and all-occurrence sampling methodologies. Groups were cohesive, with males spending approximately one-third of their time within 5 meters of another individual. Although complete linear dominance hierarchies within a group were not observed, dominance relationships between individuals were evident for the majority (66%) of dyads. Social interactions varied as a function of age, with subadults engaging in more affiliative behavior and less non-contact aggression than either blackbacks or silverbacks. Visual/olfactory access to females increased non-contact aggression between males. Such results are similar to those found for all-male groups of mountain gorillas in the wild and demonstrate that all-male groups can be a cohesive social unit in this species. They also raise the questions of why all-male groups have rarely been observed in wild populations and how social, ecological and anthropogenic factors influence male sociality.
TL;DR: It is shown that the density of breeding males is higher in habitats with a denser growth of filamentous algae, but the variation in egg number among nests is lower, which is the most likely explanation for reduced variation among males in mating success.
Abstract: Summary The intensity of sexual selection depends on environmental conditions; factors such as predation risk and energy limitation determine the strength of mate choice and the intensity of sexual displays. Eutrophication of shallow coastal areas is changing the breeding habitats of the three-spined stickleback Gasterosteus aculeateus by increasing the growth of filamentous algae. Here I show that the density of breeding males is higher in habitats with a denser growth of filamentous algae, but the variation in egg number among nests is lower. This more equal distribution of eggs in densely vegetated habitats could be due to a lower variation among males in mating success, or to habitat-dependent frequencies of egg consumption, egg stealing or sneak fertilisation homogenising the distribution of eggs among nests in densely vegetated habitats. Of these possibilities, reduced variation among males in mating success is the most likely explanation, because increased vegetation reduces the opportunity for mate choice by reducing visibility and mate encounter rate. Variation in egg stealing and sneak fertilisation are less likely to explain the result because of their generally low frequency. Further experimental work is required to determine the causes and consequences of the habitatdependent distribution of eggs among nests.
TL;DR: Although plasma melatonin levels are high at night and low during the day, experiments using melatonin administration via the water indicate that melatonin is of no or little importance for the photoperiodic response.
Abstract: In sticklebacks, sexual maturation is stimulated by long photoperiods but not by short photoperiods, even at high temperatures. Extra-retinal photoreception can mediate this response, and appears to be more important thanretinal photoreception. Although plasma melatonin levels are high at night and low during the day, experiments using melatonin administration via the water indicate that melatonin is of no or little importance for the photoperiodic response. Androgens can be aromatised to estrogens in the stickleback brain. Treatment with aromatase inhibitors stimulates maturation of males also under short photoperiod, suggesting that aromatase is involved in the suppressive actions of short photoperiod. Expression of both follicle stimulating hormone (FSH)-β and luteinizing hormone (LH)-β is higher under long than under short photoperiod. FSH-β is controlled by a negative steroid feedback on the brain-pituitary-gonad axis under short photoperiod and by a positive steroid feedback under long photoperiod. It is suggested that the former can suppress reproduction under short photoperiod and the latter can stimulate breeding under long photoperiod.
TL;DR: Since algae-intake enhanced not only male orange coloration but also growth and reproduction, female guppies may obtain benefits through mate preference for males having brighter coloration and, hence, greater foraging ability for algae.
Abstract: Carotenoids often influence male coloration, and the carotenoid-based coloration is used for female mate choice in some animals. The positive influence of carotenoids on a variety of physiological systems in animals is also known. Because animals have to obtain carotenoids from their food, the conspicuousness of carotenoid-based coloration may indicate the male's foraging ability for carotenoid-rich food. It is possible, therefore, that females can obtain benefits of the high-foraging ability and, thus, health or vigor of their offspring through their mate preference for the male coloration. In order to test this prediction, we examined the influence of algae-intake (carotenoid-resource in nature) on guppies. By algae-supplement, not only male orange coloration but also growth of both sexes and female reproduction were enhanced compared with fish in control groups, although they got the same amount of energy from their food. However, carotenoid-supplementation did not show the positive influence on growth and reproduction, though male orange coloration became conspicuous. It is possible to explain the difference of the influence on growth and reproduction between algae- and carotenoid-supplement groups in two ways. First, some kinds of carotenoids within algae other than carotenoids used for carotenoid-supplementation play an important role for enhancement of growth and reproduction. Second, other substances (e.g. non-digestible carbohydrates) within algae influenced growth and reproduction through the positive effect on digestive system. Since algae-intake enhanced not only male orange coloration but also growth and reproduction, female guppies may obtain benefits through mate preference for males having brighter coloration and, hence, greater foraging ability for algae.
TL;DR: It is suggested that the ability to detect the indirect cues of a potential predator may be an important factor determining the anti-predator responses of insects towards spiders.
Abstract: Summary In many species, prey detect predators using chemical cues, which may be based on the predator’s previous diet. Furthermore, the predator’s previous hunting strategy and diet may affect the prey’s behavioural strategies to avoid predation. Juvenile Gryllid field crickets face predation by spiders, but the responses of juvenile crickets to spiders are unknown. We studied whether naive juvenile field crickets can detect a predatory spider, Hololena nedra, using chemotactile cues (silk, secretions and excreta). We also studied the effect of the predator’s diet on the juvenile field cricket’s anti-predator behaviour. Cricket nymphs avoided the chemotactile spider cues when the spiders were previously fed with crickets, but not when spiders were not fed crickets. Our study suggests that the ability to detect the indirect cues of a potential predator may be an important factor determining the anti-predator responses of insects towards spiders.