The role of body size and fighting experience in predicting contest behaviour in the black field cricket, <Emphasis Type="Italic">Teleogryllus commodus</Emphasis>

Body size strongly predicts fighting behaviour and outcome in many species, with the larger opponent usually winning contests. However, recent fighting experience can have a strong influence on the establishment of dominance hierarchies, with recent winners being more likely to win subsequent contests, while recent losers are more likely to lose. Recent fighting experience therefore has the potential to modify the effect of body size in determining contest behaviour and outcome. Here, we investigate whether recent fighting experience weakens the role of body size in predicting contest behaviour in the black field cricket, Teleogryllus commodus. We compared the role of body size in determining contest outcome during initial non-physical encounters and escalated aggressive physical encounters (grapples), as well as the probability of escalation occurring, in contests involving either a naïve or experienced smaller male against a naïve larger male. We found that recent fighting experience only affected contest outcome during non-physical encounters. Once a contest had escalated into grappling, the effect of previous wins and losses was no longer apparent and body size strongly predicted contest outcome. Thus, once males can directly assess their opponent's fighting ability, recent fighting experience did not alter the effect of body size on contest behaviour and outcome.     

Loud calls as indicators of dominance in male baboons (Papio cynocephalus ursinus)

Adult male baboons (Papio cynocephalus) give loud two-syllable 'wahoo' calls during dawn choruses, interactions between groups, when chasing females, and in aggressive interactions with other males. These 'contest' wahoos are acoustically different from 'alarm' wahoos given to predators. In a study of free-ranging baboons in the Okavango Delta, Botswana, we found no significant correlations between the acoustic features of wahoos and adult male size; however, acoustic features were correlated with male dominance rank, age, and calling bout length. Here we show that other measures of calling behavior also appear to function as honest indicators of stamina and competitive ability. High-ranking males were more likely than middle- or low-ranking males to participate in wahoo bouts. They called at significantly higher rates, and their bouts were longer and contained more calls. All males were significantly more likely to participate in wahoo bouts with another male if their opponent's rank was similar to their own. Bouts involving males of similar ranks were longer, contained more wahoos, and involved calling at higher rates, than other bouts. In contests between males of similar ranks, the subordinate and dominant were equally likely to end the bout, whereas in contests involving males of disparate ranks, subordinates were significantly more likely to end the bout. Bouts involving males of similar rank were significantly more likely than others to escalate and result in physical fighting.     

Shouting the odds: vocalization signals status in a lizard

Many species possess multiple sexually dimorphic traits, which incorporate different sensory modalities (e.g., acoustic, olfactory and visual), although their relative roles in sexual selection and in determining reproductive success are still poorly understood for most taxa. We assessed the role of multiple male traits, including one acoustic (dominant call frequency) and one visual (yellow throat patch) trait, in residency advertisement, contest behavior, and breeding success in barking geckos (Ptenopus garrulus garrulus). We show that male barking geckos maintain largely exclusive home ranges, with a trend for larger males to maintain larger home ranges. We also show that larger males have a lower dominant calling frequency. When aggressive behavior was elicited in the field using a recorded call of average frequency, resident males with low frequency calls were more likely to respond aggressively and charge the speaker compared to males with high frequency calls. However, body size and small relative throat patch size, rather than call frequency, were the best predictors of overall aggressiveness. Body size was also the best predictor of whether males bred. We suggest that call frequency in this crepuscular species constitutes an effective long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries in low-light environments.     

Female mate choice in the gray treefrog (Hyla versicolor) in three experimental environments

We studied female mate choice by Hyla versicolor in three venues to examine how acoustic and spatial complexity, background noise, and the calling behavior of males might influence preferences manifest in previous laboratory two-stimulus choice tests. Our laboratory-based two-stimulus choice tests with and without broadcasts of chorus noise demonstrated that females prefer long calls relative to short calls when calling efforts of alternatives are equivalent. Background noise impaired the ability of females to discriminate in favor of longer over shorter calls, but the magnitude of the effect was small. Captures of females at eight speakers broadcasting 6- to 27-pulse calls at the edge of a pond revealed strong discrimination against only the shortest call variant. In natural choruses, females may only rarely encounter males using such unattractive vocalizations. Female phonotaxis at an artificial pond with caged and electronically monitored calling males also indicated that consequences of female preferences for temporal aspects of calling observed in two-stimulus choice tests are much attenuated in choruses and explain only small portions (<10%) of the variation in male mating success. Nevertheless, relatively high call duration and calling effort increased male attractiveness. Acoustic interference emerged as another significant factor influencing male mating success and possibly the differences in female choice observed in laboratory and chorus settings. We suggest that the bias of females against both overlapped and very short calls may help explain why males lengthen their calls but lower their rate of delivery in response to increases in chorus size.     

Fighting,assessment, and frequency alteration in Blanchard's cricket frog

Summary This study examines the use of dominant frequency for assessment of fighting ability in Blanchard's cricket frog Acris crepitans blanchardi. Like most anurans, the dominant frequency of the call is negatively correlated with size. However, unlike many anurans, dominant frequency varies within individual males, providing a less reliable signal of size. Wrestling contests between male cricket frogs were differentially won by larger males. I thus tested the hypothesis that males use dominant frequency for assessment of an opponent's fighting ability. Males retreated from, or became satellites of, broadcasts of synthetic low frequency calls, simulating the calls of a large male. In contrast, males attacked broadcasts of synthetic high frequency calls, simulating the calls of a small male. The dominant frequency of the call therefore appears to contain information about size which males use to assess the fighting ability of opponents, despite the lower degree of reliability resulting from individual variation in the signal. Individual variation in dominant frequency arises partially as a consequence of active alteration of the signal in response to social competition. Males differentially lowered their dominant frequencies in response to lower frequency broadcasts, thus in response to larger opponents. Furthermore, the higher a male's dominant frequency relative to that of an opponent, the greater was the decrease in dominant frequency. These results suggest that smaller males may conditionally lower their dominant frequencies in order to sound larger to larger opponents, thereby inflating their apparent fighting ability. Two alternative hypotheses are discussed.     

Size assessment in simulated territorial encounters between male green frogs (Rana clamitans)

We examined the ability of male green frogs to assess the size of an opponent based on the dominant frequency of their advertisement call, which is negatively correlated with size, using synthetic stimuli to simulate intruders of different sizes. In one field playback experiment, we broadcast a pair of stimuli representing a small and a large male; in a second experiment, we broadcast calls of a medium and a large male. In both experiments, males produced calls with significantly lower dominant frequencies in response to each stimulus. Contrast analyses revealed that males lowered the dominant frequency of their calls more in response to the large-male stimulus than in responses to the small- and medium-male stimuli. In the second experiment, males also responded to the large-male stimulus by calling at higher rates. There were no differences in mean note duration or the number of moves made toward or around the playback speaker in response to any stimulus. Thus, the frequency of an opponent's calls elicits a differential modification of calling behavior, primarily in the form of differential dominant frequency alteration, suggesting that males use dominant frequency to assess the size of opponents during aggressive encounters. Received: 17 April 1998 / Accepted after revision: 7 October 1998     

A lover, not a fighter: mating causes male crickets to lose fights

Both resource-holding potential (RHP) and experience in aggressive contests are known to affect future aggressive behaviour. However, few studies have examined the effects of mating experience on agonistic behaviour, despite the fact that dominant males usually acquire more matings. We investigated the effect of mating experience on male aggressive behaviour including the relationship between RHP and fighting success in the fall field cricket, Gryllus pennsylvanicus. We formed pairs of size- and age-matched males that varied in RHP (relative weapon size) and conducted two experiments. In the first, we varied male mating experience by allowing one male in a pair to either be (a) ‘mated’: court, be mounted and copulate with a virgin female or (b) ‘experienced’: court, be mounted, but prevented from copulating. The second experiment varied postcopulatory experience where the male was allowed (‘contact’) or prevented from (‘no-contact’) continued contact with his recent mate. Following treatment, experimental males engaged in an aggressive contest with the naïve size- and age-matched male. In our first experiment, we found that mated and experienced males were equally likely to escalate contests to combat with a naïve opponent, but mated males were less likely than experienced males to win. There was no effect of mating on the relationship between RHP and fighting success. In our second experiment, we found no effect of maintaining contact with the female on the tendency to escalate or the probability of winning. As in the first experiment, males with relatively larger heads again won more fights and this relationship was unaffected by male experience. These results suggest that mating is itself detrimental to male success in aggressive contests, but that this effect is not sufficient to eliminate the effect of RHP on fighting success.     

Aggressive thresholds in Dendropsophus ebraccatus: habituation and sensitization to different call types

Males in many chorusing anuran species use aggressive calls during defense of calling spaces from other males. The minimal intensity of another male’s vocalizations that elicits an aggressive call response has been termed the aggressive threshold. Previous studies of aggressive thresholds have shown that they are plastic: males habituated (increased their aggressive thresholds) in response to repeated presentation of stimuli above initial threshold levels. Habituation likely contributes to the stable chorus structure of these species, in which aggressive calling is rare compared to advertisement calls. I have observed high levels of aggressive calling in the treefrog Dendropsophus ebraccatus, suggesting that males of this species do not habituate. In this study, I investigated the plasticity of aggressive thresholds in D. ebraccatus. I measured the aggressive thresholds of males before and after suprathreshold stimulation by both advertisement and aggressive calls. I found that the different call types had different effects: males habituated to advertisement calls but lowered their aggressive thresholds in response to aggressive calls. I consider the latter response to be an example of sensitization, a behavior that has been documented infrequently in vocalizing anurans. Sensitization is a plausible mechanism responsible for the high levels of aggressive calling observed in this species. Given the high costs of aggressive calling, however, it is unclear why a mechanism that increases aggressive call output would be maintained.     

The effect of social interactions on calling energetics in the gray treefrog (Hyla versicolor)

Summary The vocal behavior of Hyla versicolor was studied in the field by means of behavioral observations and playback experiments, and these data were coupled with measurements of oxygen consumption in calling frogs to estimate the effect of social interactions on calling energetics. Male gray treefrogs have intense calls (median peak SPL=109 dB, fast RMS SPL=100 dB at 50 cm). At an air temperature of 23° C, males produced an average of 1,200–1,300 calls/h for 2–4 h per night. Calling rates and call durations differed among individuals, but were relatively constant for each male during periods of sustained calling. Males in dense choruses gave calls about twice as long as isolated males, but produced calls at about half the rate. Consequently, total calling effort and estimated aerobic costs were largely independent of chorus density. Playbacks of recorded calls to males in the field elicited increases in call duration and decreases in calling rate, regardless of the rate or duration of the stimulus. Males gave longer calls in response to long calls or to stimuli presented at high rates, but they did not precisely match either stimulus rate or duration. Calling effort and estimated oxygen consumption changed only slightly during stimulus playbacks. These results indicate that male-male competition elicits pro-found changes in the vocal behavior of calling males, but these changes have little effect on energy expenditure. We estimated that most calling males had metabolic rates of about 1.7–1.8 ml O₂/(g\h), or about 280 J/h for an average size (8.6 g) male at 20° C. Although changes in call duration and calling rate did not affect aerobic costs of calling, males producing long calls at slow rates called for fewer hours per night than males producing shorter calls at higher rates. This suggests that calling time may be limited by the rate at which muscle glycogen reserves are depleted.     

Twilight fighting in the evening brown butterfly,<Emphasis Type="Italic"> Melanitis leda</Emphasis> (L.) (Nymphalidae): age and residency effects

Butterflies are conspicuous among animals that fight for mating opportunities because it is not clear how contest costs could accrue. Nevertheless, the bulk of research in this group suggests that contests are settled on the basis of asymmetries in fighting ability (the superior competitor hypothesis). There is also a consistent effect on contest escalation due to apparent 'confusion' over residency, which could result from resident butterflies playing different tactics than non-residents, or from a causal link between residency and fighting ability. I addressed these hypotheses by studying contest behavior in the crepuscular species Melanitis leda (L.) (Nymphalidae) over a 5-month period in tropical Australia. Males competed via conspicuous two-stage maneuvers of a form unique among butterflies. Prior residents won 77% of all contests. Non-resident males arrived and perched in occupied sites until challenged by incumbent residents, and the aggressiveness of these interlopers increased as a function of the time before they were detected. Contest winners also tended to be younger than losers, and contest escalation was negatively related to both the age of the losing male and the magnitude of the between-combatant age asymmetry. These results are consistent with the superior competitor hypothesis based upon age as a determinant (or correlate) of fighting ability, but also suggest residency has a unique influence on contest behavior. Further research is clearly required to unravel the effects of age, residency and other potential biophysical determinants of fighting ability in this species.     

The effect of perceived intruder proximity and resident body size on the aggressive responses of male green frogs, Rana clamitans (Anura: Ranidae)

We examined variation in aggressive responses within and among individuals in the green frog, Rana clamitans. We tested the hypothesis that resident males respond in a graded fashion to changes in perceived intruder proximity (stimulus intensity). We also investigated how response level varied with responder body size. We found that green frogs differentially alter aggressive responses (increasing movement and calling rates while decreasing the duration and dominant frequency of their calls) with an increase in stimulus intensity. Body size did not appear to be a significant influence on most response levels. We suggest that aggressive responses are graded, and advertisement and aggressive calls represent opposite ends of a continuum. Green frogs do not exhibit clearly defined thresholds for responses like those reported for some other frogs. By using graded responses rather than discrete all-or-nothing responses, males may reduce the potential costs of aggressive encounters.     

Signaling effort does not predict aggressiveness in male spring field crickets

The relationship between signaling and aggression is still unclear despite several decades of research. However, there is a growing interest in studying signals that predict aggressive behavior or fighting ability. The goals of our study were threefold: we investigated the relationship between signaling effort and aggression, the relationship between body condition and aggression, and the effect of fighting experience on subsequent signaling behavior in wild-caught and laboratory-reared male spring field crickets (Gryllus veletis). We found that aggressive behavior was not related to signaling effort, body size, or body condition. For contest winners, wild-captured males were more aggressive than laboratory-reared males. Signaling effort was highly repeatable within individuals, but aggressive behavior had low repeatability. We found no evidence for a winner or loser effect on signaling; there was no change in signaling effort when we compared contest winners and losers before and after they participated in aggressive contests. Long-distance acoustic signaling and aggressive behavior appear to be independent of one another in spring field crickets, perhaps serving different functions in female attraction and male–male competition, respectively.     

How do fighting ability and nest value influence usurpation contests in <Emphasis Type="Italic">Polistes</Emphasis> wasps?

Most research on animal contests has focused on the factors that influence the intensity and outcome of aggressive contests within nonsocial species, while relatively little is known about contests in social taxa. Here, we examine contests among queens of the social paper wasp, Polistes dominulus. Queens use multiple reproductive strategies, including nesting alone, usurping established colonies, and cooperatively joining other queens. We stage contests between a nesting queen and a challenger to test how resource value (RV) and resource holding potential (RHP) influence (a) who occupies the nest at the end of the contest and (b) the extent of conflict between the queen and challenger. We found that RHP, as measured by individuals’ facial patterns and body size, influenced the outcome of the contest. Challengers with high RHP were more likely to successfully usurp the nest than challengers with low RHP. Interestingly, queens with relatively high RHP were more likely to form a cooperative association with the challenger than queens with lower RHP, suggesting that queens may evict individuals that are an aggressive threat. RV influenced the intensity of conflict. There was more aggressive conflict over large nests than over small nests. Overall, social taxa have complex contest dynamics with important parallels to contests in nonsocial taxa. Studying contests in social taxa provides an important perspective on the factors that influence individual decisions about conflict versus cooperation.     

Female preferences for spectral call properties in the western genetic lineage of Cope's gray treefrog (Hyla chrysoscelis)

Female frogs discriminate among potential mates based on individual variation in male advertisement calls. While considerable data have accumulated allowing comparisons of female preference functions among species, we still lack fundamental knowledge about how and why the shapes of preference functions for particular call properties vary among populations within all but a few species. Here, we report results from a study aimed at describing female preference functions for spectral call properties in Cope's gray treefrog (Hyla chrysoscelis). Widespread throughout the eastern half of North America, Cope's gray treefrog is the diploid member of the cryptic diploid–tetraploid Hyla versicolor species complex, and its populations are divided into two distinct genetic lineages (eastern and western). In this study of a western lineage population, we recorded and analyzed the spectral properties of 1,000 advertisement calls from 50 males and conducted two-stimulus phonotaxis experiments to estimate a population-level preference function. Females preferred calls with average frequencies over calls with frequencies that were 2 or 3 semitones (1.4 or 2.1 standard deviations, respectively) lower than the population mean. We observed no behavioral discrimination between calls with average and higher-than-average frequencies. Preferences discriminating against low-frequency calls were weak and were abolished by attenuating the preferred average call by 3?dB. We discuss these results in light of previous studies of eastern lineage populations, geographic variation in female preference functions, and the potential adaptive value of discriminating against calls with low frequencies.     

Sequential analysis of aggressive interactions in the stalk-eyed fly Teleopsis dalmanni

Understanding the mechanisms and determinants of conflict resolution is of great theoretical and practical importance because the outcome of contests between males over limited resources such as mates, territories, and food has profound fitness consequences. Despite the large literature on the theory of conflict resolution, relatively few empirical studies explicitly test predictions related to contest structure for these models. In sexually dimorphic species of stalk-eyed flies (Diopsidae), males engage in characteristic aggressive interactions over both females and food resources. We used sequential analysis of aggressive interactions between dyads of male stalk-eyed flies to investigate patterns of escalation, behavioral matching, and physical contact in order to distinguish between three common models of conflict resolution: the sequential assessment model, the cumulative assessment model, and the energetic war of attrition. Stalk-eyed flies were shown to engage in both low- and high-intensity behaviors during interactions with patterns of escalation and no de-escalation. Aggressive interactions did not demonstrate behavioral matching between winners and losers. Stalk-eyed flies also escalated to behaviors that included physical contact without injuries. Our results provide support for the sequential assessment model based on patterns of escalation with no de-escalation, behavioral mismatching, and behaviors which include physical contact but no injuries.     

Initiation and resolution of jumping spider contests: roles for size, proximity, and early detection of rivals

Animals are commonly expected to assess each other during contests in order to economically identify relative status. Escalated or long contests are expected to arise mainly when rivals have difficulty discriminating small differences. Results of the present study of male-male contests in Plexippus paykulli, a jumping spider (Salticidae) with acute vision, are not in accord with this widely held view. Despite the typical finding that size-advantaged rivals are more likely to win contests and that this tendency increases with size disparity, contest dynamics suggest that these tendencies are achieved in the absence of direct size assessment. In contests between different-sized spiders, maximum escalation and overall duration were predicted by the absolute size of the size-disadvantaged spider (usually the loser) rather than the size difference between the rivals. This result suggests that spiders base decisions of persistence on their own size, such that size-disadvantaged rivals usually reach their limits first, and then retreat. This interpretation is further supported by findings that maximum escalation and total duration were both positively related to size in contests between size-matched spiders. Spiders were more likely to win if they oriented and displayed first, and longer, more escalated, contests ensued if the size-disadvantaged spider was the first to orient and display. Proximity of rivals at contest outset also influenced contest dynamics, but not outcome.     

Fighting without weaponry: a review of male-male contest competition in butterflies

The males of many butterfly species compete via pair-wise intrasexual contests, yet lack any obvious morphological traits conventionally associated with animal aggression. The evolution of contest behavior in this group is therefore interesting because the means by which individuals are able to inflict costs upon each other during combat are unclear. Here we review the relevant empirical information within a game-theoretical context in order to analyze contest-related costs and mechanisms of dispute settlement. Territorial butterfly contests carry obvious role asymmetries, and individuals in the 'resident' role are more likely to win across all studied species. We use this phenomenon as a framework for gaining further insight into the evolution of contest settlement in this group. Four principal hypotheses are evaluated: (1) that residency is used as an arbitrary convention, (2) that residents stand to gain a greater payoff if successful, (3) that residency bestows higher resource-holding potential (RHP) on males in that role, and (4) that residents are males of intrinsically higher RHP. We found most support for the latter explanation (the 'superior-competitor' hypothesis), partly because the alternatives require a restrictive set of ecological conditions, but also due to positive support for the idea of intrinsic RHP. The strongest evidence is provided by species in which repeated interactions (between the same individuals) always have the same outcome, regardless of changes in residency status. However, we also found a consistent effect on contest duration due to apparent 'confusion over residency,' which suggests a conventional element to contest behavior. Although butterfly contests must be costly in some way, the literature provides limited insight into how costs accrue, and hence the determinants of contest RHP remain obscure. We suggest that careful experimentation, using 'natural' manipulations where possible, should prove most beneficial in identifying costs and exploring schedules of contest settlement in this group. Moreover, future investigations should be sensitive to the fact that butterfly territoriality and associated male-male interactions are seated within a broader ecological and life-historical context.     

Male calling behavior,female discrimination and acoustic interference in the Neotropical treefrog Hyla microcephala under realistic acoustic conditions

Summary Anuran choruses are acoustically complex assemblages of calling males. Little is known about the behavior of males or females in such natural sound environments. I studied calling behavior of males of Hyla microcephala in nature by using an interactive computer-based system that allowed me to simulate call interruptions by a number of males. I also monitored the calling behavior of groups of four to six males. When a male is interrupted by the call of another frog, he increases the spacing between the notes of his call. Responses of this kind are strongest to the loudest neighbor, and some males may ignore interruptions by all but a single close male. Interruptions using synthetic calls with silent gaps indicated that males respond vocally to reductions in sound intensity as brief as 20 ms. This ability helps to explain how males can rapidly alternate notes during pairwise interactions. Amounts of acoustic overlap between pairs of males in the choruses were usually below 10% of an individual's total calling time during bouts. The time a male spent calling that was free of acoustic interference by any other male ranged from 34–92% of his total calling time. When group size was decreased, this unobstructed calling time increased. Previous research showed that females of H. microcephala discriminate against calls that overlap so that the call pulse-train structure is degraded. Here I show that a 6 dB difference in intensity between the overlapped calls is sufficient to reduce the degradative effect of call interference. Females were also given a choice between interfering calls broadcast from two adjacent and two widely separated speakers. An angular separation between speakers of 120° was insufficient to elicit a preference for the separated sources. Together, data on behavior of males and females indicated that males actively reduce acoustic interference with those loud individuals most likely to degrade seriously the temporal structure of their calls.     

Causes and consequences of contest outcome: aggressiveness, dominance and growth in the sheepshead swordtail, Xiphophorus birchmanni

Although our understanding of how animal personality affects fitness is incomplete, one general hypothesis is that personality traits (e.g. boldness and aggressiveness) contribute to competitive ability. If so, then under resource limitation, personality differences will generate variation in life history traits crucial to fitness, like growth. Here, we test this idea using data from same-sex dyadic interaction trials of sheepshead swordtails (Xiphophorus birchmanni). In males, there was evidence of repeatable variation across a suite of agonistic contest behaviours, while repeatable opponent effects on focal behaviour were also detected. A single vector explains 80 % of the among-individual variance in multivariate phenotype and can be viewed as aggressiveness. We also find that aggressiveness predicts dominance—the repeatable tendency to win food in competition—and dominant individuals show faster post-trial weight gain (independently of initial size). In females, a dominance hierarchy predictive of weight gain was also found, but there was no evidence of variation in aggressiveness. While size often predicts contest outcome, our results show that individuals may sometimes grow larger because they are behaviourally dominant rather than vice versa. When resources are limited, personality traits such as aggression can influence growth, life history, and fitness through impacts on resource acquisition.     

Habitat preference increases territorial defence in brown trout (Salmo trutta)

The striking ability of territory owners to repel intruders has generated a number of theoretical explanations as well as experimental studies in many animal species. However, effects of individual habitat preferences on territorial defence have rarely been studied. From the territory value hypothesis, we predicted that owners of preferred habitats should invest more resources in defence than owners of non-preferred habitats. We tested this prediction with young territorial brown trout in a two-stage experiment. First, trout were allowed to choose individually between gravel and a uniform bright substrate. As expected, they showed a significant (79%) preference for gravel. However, there was considerable variation between individuals in substrate preference, with a few fish preferring the bright substrate. Half of the tested fish were then transferred to a gravel substrate and the rest to a bright substrate, manipulating habitat type in relation to preference. Territory owners were then staged against size-matched intruders whereupon contest aggression was observed and the winner of each contest determined. Overall, owners won most of the contests. Satisfied owners won 86% and owners of less preferred territories, 74% of the contests. Furthermore, more satisfied owners attacked sooner and were more aggressive relative to the intruders. We conclude that brown trout show individual variation in habitat preference, which appears to be linked with their investment in territorial defence. These results suggest that understanding and modelling of animal contests could benefit from considering how territorial defence is influenced by individual habitat preference and specialisation. Received: 25 February 2000 / Revised: 22 May 2000 / Accepted: 25 June 2000