Showing papers in "Behaviour in 1988"
TL;DR: The study shows that, while the behavioral repertoires of the two Pan species are fundamentally similar, interesting differences exist in their vocal repertoires, sexual behavior, and agonistic behavior.
Abstract: Ten bonobos (Pan paniscus), housed in three separate subgroups at the San Diego Zoological Garden, were observed for 288 hours over a four-month period. The colony included one adult male, two adult females, two adolescent males, four juveniles, and one infant. Data on 5,135 sequences of social behavior were collected either as spoken accounts or as video recordings. In addition, high-quality sound recordings were obtained for spectrographic analysis. The data were subjected to a quantitative analysis of probabilities of association between 44 communicative behavior patterns and 40 different context types. The paper treats each communicative behavior pattern separately, providing a) its frequency, b) the most common inter-individual directions of performance, c) characteristic contexts, d) a description, e) a commentary on its possible functions, and 1) a comparison with the behavior of chimpanzees (Pan troglodytes). The study shows that, while the behavioral repertoires of the two Pan species are fundamentally similar, interesting differences exist in their vocal repertoires, sexual behavior, and agonistic behavior. The bonobo's voice has a higher pitch, and many of its vocalizations are structurally different from homologous chimpanzee vocalizations. The greatest difference concerns the long-distance hooting calls of the two species. The bonobo's sexual behavior is much more elaborate than the chimpanzee's, including ventro-ventral copulation, and "GG-rubbing" between adult females. Sexual forms of contact seem to serve many of the reassurance and reconciliation functions fulfilled by nongenital contact forms in the chimpanzee. Finally, the bonobo's agonistic behavior is less elaborate and appears more controlled than the chimpanzee's.
327 citations
TL;DR: The development and the reproductive output of 26 Bombus terrestris colonies were investigated and the loss of dominance by the queen was expressed by the beginning of aggression on the part of queen and workers, worker oviposition, oophagy and the functional elimination of the queen.
Abstract: The development and the reproductive output of 26 Bombus terrestris colonies were investigated. Four important points in colony development are distinguished. These are: a) the start of egg laying by the queen, leading to the beginning of the eusocial phase, the emergence of the first workers; b) the moment which we term the switch point, at which the queen switches from laying diploid eggs (producing workers or queens) to the laying of haploid eggs (producing males); c) the onset of queen production reared from diploid eggs; d) the loss of dominance by the queen, expressed by the beginning of aggression on the part of queen and workers, worker oviposition, oophagy and the functional elimination of the queen. This we call the competition point. The onset of queen production is highly correlated with the competition point but not correlated with the switch point. The pattern in time of the egg laying by a queen differed from the rate of increase of worker numbers published by previous authors. After an initial and slow phase, in which two broods of egg cells are produced, the rate of egg laying of a queen becomes constant, whether or not the eggs are fertilized. The transformation from this rate of egg laying to the earlier descriptions of increase in number is only possible if one neglects differences between colonies in time spent in the production of the two broods as well as the highly variable time needed for development into adults. The time at which the competition point occurs is much more predictable (at day 30.8 ± 4.9 after the emergence of the first worker) than the switch point. The latter ranges from day 6 to day 32. In our colonies two groups can be discerned, one of early switching colonies (at day 9.8 ± 2.4), the other of late switching colonies (at day 23.4 ± 4.6). The occurrence of the switch cannot be predicted from preceding behavioural or demographic data. As a consequence of the early switch such colonies produce mainly males. Partly due to the unfavourable larva/worker ratio only a few queens were reared from the last laid diploid eggs. In contradiction the late switching colonies produce on average sexuals at a 1.3:1 sex ratio (1:1.7 investment ratio). Remarkable however, biomass of sexuals is equal in both types of colonies. Males are about half the weight of queens. Certain colonies invest in males only ("3 males : 0 queens"). Since the two types of colonies occurred in about equal numbers, our local population is characterized by a 4:1 1(♂:♀) sex ratio. This male biased sex ratio, also observed for other bumblebees species (B. terricola and B. melanopygus, OWEN et al., 1980; OWEN & PLOWRIGHT, 1982), contrasts with existing theoretical models based on kin selection (TRIVERS & HARE, 1976) or local mate competition (ALEXANDER & SHERMAN, 1977) arguments. A model is proposed in which the males of the early switching colonies monopolize the matings due to their early appearance in the field. In fact, the early switching colonies, by investing mainly in males, parasitize on the reproductive strategy of the late switching colonies, which are characterized by a 1:1 sex ratio. At population level the two reproductive strategies are in equilibrium at a 1:1 frequency.
312 citations
284 citations
TL;DR: Extra-pair copulation behaviour was observed in three resident, colour-banded populations of black-capped chickadees and it was found that lower-ranked males may suffer temporary losses through the EPCs of their mates, while each male has some chance of attaining alpha rank if he lives long enough.
Abstract: Extra-pair copulation (EPC) behaviour was observed in three resident, colour-banded populations of black-capped chickadees. Because these populations were nonmigratory, I was able to determine the relative winter rank of all individuals involved (the females, their mates, and the other males) in the months prior to each breeding season. Over 14 years, a total of 13 EPCs, involving 12 females and 10 'other' males, were seen. Every one of the 13 EPCs was with a male ranked higher than the female's own mate. No female that was paired with an alpha male was ever seen engaging in an EPC. Only 4 observed EPCs occurred in the female's own territory; the other 9 all took place in the territory of the other male. Hence these females had apparently entered those territories to copulate with those resident males. All but one of the EPCs occurred within an hour of dawn, although WPCs are about equally likely to occur at any time of day. At least 4 of the observed EPCs occurred during the female's fertile period. No forced EPC attempts were seen. In resident species like chickadees, where females have the opportunity to learn the relative rank of all neighbouring males with respect to her own mate, females may regularly pursue the strategy of seeking out EPCs with superior partners. While lower-ranked males may suffer temporary losses through the EPCs of their mates, each male has some chance of attaining alpha rank if he lives long enough. Once at alpha rank, a male will likely engage in more EPCs, while having a mate that will no longer seek EPCs elsewhere.
223 citations
TL;DR: The importance of dispersed ground foods for each species of chimpanzee was compared and, although the results are not conclusive, they indicate that this type of food was equally important in the diets of both populations.
Abstract: The relative importance of feeding competition in Pan paniscus and Pan troglodytes schweinfurthii is examined in an attempt to understand the major differences in social organization of the two species. P. paniscus at Lomako is characterized by a stronger tendency for association among females than among female P. troglodytes at Gombe. Party size in P. paniscus is dependent on patch size. Feeding competition was more important in small patches than in large patches. The total amount of feeding time by a party in a patch (chimp-minutes) was a measure of patch size that was available for both chimpanzee species. P. paniscus was found to have larger party sizes and to use larger food patches than P. troglodytes. The importance of dispersed ground foods for each species of chimpanzee was compared and, although the results are not conclusive, they indicate that this type of food was equally important in the diets of both populations. Two hypotheses of the ecological basis for differences in social structure are compared in light of this evidence.
213 citations
TL;DR: It is suggested that the upper limit to group size is set by the daylength available for foraging in large groups, which is substantially greater than the 4% gain in mean food intake that large groups achieve by displacing smaller groups from fruit trees.
Abstract: The effects of group size and fruit availability in tree crowns on per-capita food intake was examined for wild brown capuchin monkeys living in groups of 3-12 individuals. Per-capita feeding time was nearly exactly inversely proportional to group size in small-crowned trees with little fruit, but was essentially independent of group size in large-crowned trees with abundant fruit. Despite the use of such productive trees, per-capita feeding time in the average tree visited decreased by 50% over a 4-fold range of group sizes. This cost of indirect food competition in large groups was not compensated by increased rates of ingestion, preferential use of large trees, of a higher rate of fruit tree encounter per distance travelled. Instead, foraging effort (distance travelled, number of minutes devoted to foraging, total activity minutes per day) increased at large group sizes. Estimates of total energy intake and expenditure suggest that net energy gain is constant for individuals in group sizes of 5-12. I suggest that the upper limit to group size is set by the daylength available for foraging in large groups. Aggression in food trees increased in frequency in larger groups, but the relative feeding rates of dominants and subordinates of a given rank did not appear to depend on group size. Observed decreases in per-capita food intake due to either indirect or aggressive food competition within large groups are substantially greater than the 4% gain in mean food intake that large groups achieve by displacing smaller groups from fruit trees.
202 citations
TL;DR: It is concluded that both components of feeding competition exist in long-tailed macaques, but that contest for food is often transferred into contest for safety and a framework is proposed to relate interspecific variation in contest effects to food distribution and group cohesion.
Abstract: Most previous studies of feeding competition in gregarious primates compared some average or group-level characteristic over a range of group sizes. Here an attempt is made to separate the effects of within-group scramble (the "group size" effect) and of within-group contest (the "dominance" effect) on energy expenditure and food intake in female long-tailed macaques (Macaca fascicularis). Significant or consistent scramble and contest components were demonstrated for locomotion and energy expenditure, for the presence in the main party of the group, and for birth rate. The intake of fruit or animal matter was not increased in compensation, but the intake of dispersed vegetable matter probably was. It is concluded that both components of feeding competition exist in long-tailed macaques, but that contest for food is often transferred into contest for safety. A framework is proposed to relate interspecific variation in contest effects to food distribution and group cohesion.
164 citations
TL;DR: The results demonstrated male competition was not the cause of assortative mating as has previously been suggested and male choice was dependent on male size as has been demonstrated within kokanee, but appeared to also involve a form component.
Abstract: Assortative mating between the anadromous (sockeye salmon) and non-anadromous (kokanee) forms of Oncorhynchus nerka was documented in Pierre Creek, Babine Lake, British Columbia. Sockeye males of all sizes mated almost exclusively with sockeye females. Only a small proportion of the smallest sockeye males (acks) were observed courting kokanee females. Kokanee males either courted kokanee females or acted as sneaks to sockeye pairs. We experimentally tested the hypotheses that assortative mating occurred because of: a) male intrasexual competition for the largest (sockeye) females; b) male choice dependent on male size; and c) male choice dependent on form. Our results demonstrated male competition was not the cause of assortative mating as has previously been suggested. Kokanee males only preferred sockeye over kokanee females when direct access to kokanee females was denied. Male choice was dependent on male size as has previously been demonstrated within kokanee, but appeared to also involve a form component. Kokanee males preferred kokanec females over the much larger and fecund sockeye females. The evolution of assortative mating between sockeye and kokanee fits models of sympatric speciation. An initial degree of assortative mating between forms is predicted by their environmentally induced great size difference. This promotes genetic divergence between the forms, which has been documented, accompanied by the evolution of premating isolating mechanisms. However, behavioural divergence is not complete in Pierre Creek. Kokanec males restricted from direct access to kokanee females prefer to sneak on sockeye pairs over kokanee pairs.
162 citations
TL;DR: Food competition is expected to be highest in species using small and scarce food sources, subject to a high risk of predation, and with large satiation levels.
Abstract: The results of the various studies in this volume lead to a series of predictions about the relationships of group size to various components of food intake. Individuals in larger groups should generally encounter fewer new food sources per unit foraging effort than they would alone (prediction 1); an exception may occur when large groups defend areas of high food density against small groups. In addition, individuals in larger groups generally will suffer reduced intake per food source encountered because of increased sharing with other group members, at least for food sources that supply little total nutrient relative to an individual's satiation level for the nutrient (prediction 3) or are scarce relative to the spacing between individuals in the group (prediction 5). Individuals in larger groups may compensate for such reductions in foraging efficiency by increasing rates of food encounter (prediction 2), using food sources with greater amounts of nutrient (prediction 4), or increasing total foraging effort per day (prediction 6). Reduced foraging efficiency for a particular nutrient may not affect total intake of that nutrient if other nutrients require greater daily foraging effort (prediction 7). Food competition is expected to be highest in species using small and scarce food sources, subject to a high risk of predation, and with large satiation levels. An appendix on statistical problems describes some of the pitfalls inherent in studies of the kind presented in this volume.
146 citations
TL;DR: It is proposed that within-troop feeding competition is generally not a critical factor in the feeding ecology of this mixed species tamarin troop, and the formation of such a troop enables each resident species to more effectively exploit and defend a set of productive feeding trees.
Abstract: In the Amazon Basin of northeastern Peru, moustached (Saguinus mystax) and saddle-back (S. fuscicollis) tamarins form stable mixed species assemblages in which groups of each species feed, forage, rest, travel and cooperatively defend a territory throughout the entire year. Data presented indicate that despite extreme overlap in feeding and ranging behavior, a change in troop size did not have a significant affect on dietary preferences, activity budgets, day range, foraging effort, and the number and length of daily feeding bouts of either resident species. The larger troop, however, was more successful at defending major feeding trees than the smaller troop. Unsuccessful resource defense resulted in a decrease in time spent feeding and foraging, and an increase in the distance traveled to the next major feeding site. It is proposed that within-troop feeding competition is generally not a critical factor in the feeding ecology of this mixed species tamarin troop. Rather, the formation of such a troop enables each resident species to more effectively exploit and defend a set of productive feeding trees.
137 citations
TL;DR: For instance, this article found that field sparrows are sensitive to changes in song frequency, number and order of phrases, trill-note duration, note "shape", and internote interval.
Abstract: Computer-modified songs were presented to wild territorial male field sparows to assess the relative importance of different acoustic features in species-song recognition. The features tested exhibited differing degrees of relative variability within field sparrow song. The experiments demonstrate that field sparrows arc sensitive to changes in song frequency, number and order of phrases, trill-note duration, note 'shape', and internote interval. Field sparrows appear to be 'tuned' to the normal range of varition in song features. Responses decreased significantly when features in the experimental songs were changed by two to three standard deviations relative to a control song. These results contrast with previous conclusions that birds only use 'invariant' features in species-song recognition. However, manipulations of invariant features, frequency and number of phrases, interfered with recognition more than did an equally-noticeable change to a variable feature, inter-note interval. The number of phrases in a song and the duration of trill notes appear to be equally important recognition cues. Thus, field sparrows integrate information from at least five different features in species song recognition, but give more weight to information from an invariant feature, song frequency, than they do to information from variable features.
TL;DR: The evidence presented here suggests that the spider and howling monkeys of Santa Rosa National Park, Costa Rica use food resources that occur in patches and generally deplete the patches they use.
Abstract: Patch depletion is an assumption that underlies many behavioural ecological models, yet it has rarely been examined. The evidence presented here suggests that the spider and howling monkeys of Santa Rosa National Park, Costa Rica use food resources that occur in patches and generally deplete the patches they use. However, some types of patches (e.g. large fruiting trees for spider monkeys, and trees used as sources of leaves for howlers) are not depleted by the feeding activity of primates. An examination of which types of patches are depleted and the manner in which depletion likely occurs, allows an assessment of possible factors underlying the different types of social organizations in these species.
TL;DR: Differences in behaviour between Otaria and males of other sea lion species are evident in harem size, time away from females, the high percentage of males breeding, and the low variance in mating success among breeding males.
Abstract: The reproductive behaviour of individually marked southern sea lions, Otaria byronia, was studied from 1981 to 1986, at Punta Norte, Peninsula Valdes, Argentina Males defended territories along the high water mark early in the breeding season but switched to female defence as they were joined by females Males defended females from neighbours and intruders, and forcefully held pre-oestrous females near them Males defended territories and females against neighbours and intruders with threat displays and by fighting Males never strayed far from females The frequency of aggressive interactions among males was positively correlated with the number of females in oestrus A mean of 28 females was associated with each male in the central breeding area at peak season, with some males being associated with 8-16 females for a few hours Ninety four percent of the males that held a territory for five or more days copulated Copulations were not observed away from territories in the central breeding area Mating success was positively correlated with tenure on territory The first males to arrive had the longest tenures and achieved the most copulations Mean tenure on territory was 24 days (range = 15-57 days) The mean number of observed copulations per marked adult male was 387 ± 331 Variance among breeding males was low; the most successful male achieved only 7% of the copulations observed Females gave birth a mean of 33 days after arrival, copulated once six days later and then went to sea to feed 76 days after parturition Thereafter, females alternated periods of feeding at sea (X = 28 days) with periods of nursing their pups (X = 23 days) Males sequester pre-oestrous females This mating strategy leads to differences in behaviour between Otaria and males of other sea lion species These differences are evident in harem size, time away from females (as manifested by brief and infrequent fighting), the high percentage of males breeding, and the low variance in mating success among breeding males
TL;DR: In this article, the authors examined the limitations on the registration and computation of directional cues which originate from an active or a passive outgoing trip, and found that the greater the number of rotations, the less precise the homing performance.
Abstract: When hoarding food in an experimental arena (o = 2.20 m), golden hamsters tend to return along a direct path from the food source at the centre of the arena to their peripherally located nest. Under infra-red light the animals' homing behaviour is exclusively controlled by 'internal' cues which have been generated during the outward journey to the feeding place. The paper examines the limitations on the registration and computation of directional cues which originate from an active or a passive outgoing trip. The compensation of the angular component of the outward journey was examined by inducing the subjects to walk (actively) around the centre of the arena, or by rotating the animals (passively) on a platform which contained the food source. The greater the number of rotations, the less precise the homing performance. After three to five active rotations, and after two to three passive rotations of 360°, the animals ceased to yield significant homing vectors. Unidirectional rotations induced a systematic ipsidirectional bias, an indication of undercornpensation; no bias was observed after rotations which occurred in equal extents in both directions. Special importance was given to the compensation for passive translations. The experiments involved either the shift of the subjects from their nest exit to an unfamiliar, adjacent arena, or the combination of an active and a passive outward leg during the outward journey to the centre of the animals' own arena. During their return to the nest, either the hamsters did not take into account at all the direction of the passive translation, or if they did, the compensation was only limited. These results are discussed in relation to the animals' capacity to assess 1) an active outward journey through the availability of different categories of self generated cues, and 2) a passive outward journey predominantly on the basis of vestibular signals. A final series of experiments showed that under certain conditions, the hamsters commit systematic homing errors which can be attributed to their failure to initiate the registration and computation of path dependent cues at the right instant in time and space.
TL;DR: In this paper, natural observations and field playback experiments were conducted on five groups of free-ranging vervet monkeys to determine when infants recognize the alarm calls of starlings as general alerting signals.
Abstract: Natural observations and field playback experiments were conducted on five groups of free-ranging vervet monkeys to determine when infants recognize the alarm calls of starlings as general alerting signals. Results show that infants do not recognize starling alarm calls at birth. Recognition of starling calls emerges gradually and age at recognition is affected by differences in auditory environment. Infants who have heard starling alarm calls at high rates respond at an earlier age than infants who hear calls at low rates. More importantly, in those groups where infants respond at an earlier age, starlings give alarm calls to vervet predators more often than to non-vervet predators. Thus in the former groups, when adults respond to starling alarm calls, their behavior is more positively reinforcing than in the other groups where starling alarm calls are commonly given to non-vervet predators.
TL;DR: In this paper, the authors investigated the capability of monkeys to assess special characteristics in conspecifics and found that high ranking animals began to hold back their initial chasing of the specialist from the food site in course of the trials and were soon tolerated to sit near the subordinate food producer.
Abstract: The aim of this study was to investigate the capability of monkeys to assess special characteristics in conspecifics. In a first phase I ascertained that all members of a colony of longtailed macaques (Macaca fascicularis) were able to attain food by manipulating a one lever apparatus, thus introducing the "tradition" of lever pulling. Then, experiments were carried out on subgroups of the colony where only one of the lower ranking subgroup members was trained to succeed in a more complex task where three levers had to be pulled in a correct sequence. Eight specialists were established in sequence. These specialists became food producers for themselves and for the other group members. Each trial of a specialist's series was carried out in two phases. In the first, the food phase, the food dispensing apparatus was active and responses of other subgroup members to the food producing specialist were observed. In the second, the social phase, the apparatus remained inactive and observations focused on social interactions of the subgroup. As expected, primarily high ranking subgroup members attempted to participate in the food rewards gained by the specialist. It is shown that high ranking animals began to hold back their initial chasing of the specialist from the food site in course of the trials and were soon tolerated to sit near the subordinate food producer. Furthermore, some of the non-specialists began to follow or even to pass the specialist when he was approaching the apparatus to manipulate the levers. These non-specialists thus indicated that they were able to anticipate later actions. In seven out of 55 specialist-non-specialist relationships all predicted changes in social interactions occurred. In the majority of the dyads in which a change in social affiliation was registered an increase of grooming or spatial proximity was positively correlated with the amount of benefit gained from the specialist. In the social phase of the trials the non-specialists gave more grooming to the food producers and maintained spatial proximity even in this second phase. To conclude: At least some of the group members became aware of the skills of the specialists and adapted their behaviour accordingly as if to maximize benefits from their skills. Previous studies had already suggested that monkeys know about social position, social relationships and kinship of group members. This study adds a new aspect of knowledge, namely knowledge on capabilities and skills of others. Differential knowledge allows monkeys to select partners optimally according to their skills and social position.
TL;DR: It is confirmed that under certain food regimes male and female fecundity are increased by sexual cannibalism, but the observations indicate that males do not sacrifice themselves at mating, but attempt to avoid being eaten, suggesting that whileSexual cannibalism may be adaptive for females it is unlikely to be so for male H. membranacea.
Abstract: We tested the idea that sexual cannibalism increases male and female fecundity in the mantid Hierodula membranacea. Two experiments were performed, in the first we maintained females on one of three nutritional planes; high medium or low. Food intake was positively and significantly associated with: maximum mass attained, the mass of first and subsequent oothecae, and the rate at which oothecae were produced. Ootheca mass was positively correlated with maximum female mass, and the number of young hatching from oothecae was positively correlated with ootheca mass. In the second experiment we maintained females on low diets and allowed some to eat the male during mating and prevented others from doing so. Females which ate the male produced significantly heavier oothecae than those which did not. The female's nutritional state influenced her likelihood of eating the male; well fed females rarely ate males. These results confirm that under certain food regimes male and female fecundity are increased by sexual cannibalism. However, our observations indicate that males do not sacrifice themselves at mating, but attempt to avoid being eaten, suggesting that while sexual cannibalism may be adaptive for females it is unlikely to be so for male H. membranacea.
TL;DR: Non-anadromous sockeye salmon males (kokanee), Oncorhynchus nerka, were tested to determine if they select mates according to their absolute size (fork length) or if male mate choice was governed by the size of the male, and the results demonstrated male choice is dependent on male size and not solely on the absolute size of females.
Abstract: [Non-anadromous sockeye salmon males (kokanee), Oncorhynchus nerka, were tested to determine if they select mates according to their absolute size (fork length) or if male mate choice was governed by the size of the male. In a series of four experiments, involving three size groups of mâles and females, the size of females presented and males tested were systematically varied. The results demonstrated male choice is dependent on male size and not solely on the absolute size of females as previously suggested in salmon and other fishes. Males of all sizes discriminated against females smaller than themselves, but did not discriminate between females of their own size and those larger. Thus, male selectivity increases with male size in salmon. The smallest males are the least selective of mates whereas the largest males arc the most selective, preferring the largest females. This varying selectivity corresponds to the availability of females on the spawning grounds. Small males have the most limited range of potential mates (because of the effects of size in intrasexual competition and female choice) whereas large males have the widest range in potential mates. The experimental results presented are consistent with two observed patterns of association of male and female salmonids on the spawning grounds: a) the number of males aggregated around females increases with increasing female size; and b) pairing between the sexes is assortative by size. Assortative mating by size was demonstrated to be further increased by male intrasexual competition. These results suggest that intrasexual competition and mate choice by the opposite sex can lead to the evolution of varying strategies of mate choice within sexes, just as it can lead to the evolution of varying strategies of seeking mates., Non-anadromous sockeye salmon males (kokanee), Oncorhynchus nerka, were tested to determine if they select mates according to their absolute size (fork length) or if male mate choice was governed by the size of the male. In a series of four experiments, involving three size groups of mâles and females, the size of females presented and males tested were systematically varied. The results demonstrated male choice is dependent on male size and not solely on the absolute size of females as previously suggested in salmon and other fishes. Males of all sizes discriminated against females smaller than themselves, but did not discriminate between females of their own size and those larger. Thus, male selectivity increases with male size in salmon. The smallest males are the least selective of mates whereas the largest males arc the most selective, preferring the largest females. This varying selectivity corresponds to the availability of females on the spawning grounds. Small males have the most limited range of potential mates (because of the effects of size in intrasexual competition and female choice) whereas large males have the widest range in potential mates. The experimental results presented are consistent with two observed patterns of association of male and female salmonids on the spawning grounds: a) the number of males aggregated around females increases with increasing female size; and b) pairing between the sexes is assortative by size. Assortative mating by size was demonstrated to be further increased by male intrasexual competition. These results suggest that intrasexual competition and mate choice by the opposite sex can lead to the evolution of varying strategies of mate choice within sexes, just as it can lead to the evolution of varying strategies of seeking mates.]
TL;DR: The stable age distribution derived from the life table successfully predicted the observed average distribution of age-sex categories in groups, suggesting that the group structure of Cebus olivaceus groups is not a consequence of intragroup social interactions, but results from demographic parameters.
Abstract: The extent to which population demography determines the age and sex composition of primate groups was examined using data from a population of wedge-capped capuchin monkeys Cebus olivaceus in central Venezuela. Demographic parameters were derived from censuses of individually recognized, aged, and sexed individuals living in nine groups over a ten year period. Animals were aged by extrapolation from census data. Animals of both sexes were classed as infants during their first year, and juveniles until they reached six years of age. Females reach sexual maturity at this time, while males were classed as subadults until they reached full adult size at age 12. Adulthood lasts at least 30 years in females, at least 24 years in males. Age-sex class specific mortality and fecundity rates generated a life table which indicated that the population was increasing (r = 0.087) between 1977 and 1986. The age and sex composition of the nine groups was described annually. On average, non-adults made up 60% of a group, with this percentage increasing with group size. There were more females than males in all groups in all years. The strong female-biased adult sex ratio (1:4.4) was a consequence of a biased birth sex ratio (1:1.9), higher female than male survivorship especially between the ages of 3 and 7 when males were dispersing, and a pronounced sexual bimaturism. The stable age distribution derived from the life table successfully predicted the observed average distribution of age-sex categories in groups. This suggests that the group structure of Cebus olivaceus groups is not a consequence of intragroup social interactions, but results from demographic parameters.
TL;DR: One important implication of the determinants of rank maintenance and rank stability in matrilineal dominance systems is that any female, regardless of her age, is dependent on allies to maintain her rank.
Abstract: In many species of cercopithecines characterized by a matrilineal dominance system, a female inherits her mother's rank (genealogical rank) and there is no correlation between a female's genealogical rank and her physical strength. This paper explores the determinants of rank maintenance and rank stability in such systems. Theoretically, a female might be in need of allies to maintain her rank because (1) she could be challenged by single larger females in dyadic agonistic interactions, and/or (2) she could be challenged by smaller or same-size females acting together (rebellious coalitions). A series of experiments designed to test these two possibilities were carried out in a captive group of Japanese macaques (N = 17) comprised of three families with similar age-sex compositions. Experimental subgroups of females were formed to test the capacity of a single female (i. e. with none of her relatives present) to maintain her rank above genealogically subordinate females (G-Subordinate females) in four social situations: (a) with same-age G-Subordinate females; (b) with a single, older G-Subordinate female, (c) with a group of G-Subordinate sisters, and (d) with a complete G-Subordinate family. Sixty seven experimental subgroups were formed, and 45% of these induced genealogical rank reversals. Low-ranking females appeared to be conditional opportunists who competed for rank only in situations where they clearly had more relative power than the single G-Dominant female (minimal risk strategy). In the experimental subgroups where a G-subordinate female was by herself (no kin present: situations a and b above), she challenged a single G-Dominant female only if the latter was younger and smaller than herself, and she did so only if the G-Dominant female was immature ( 3). Thus, single G-subordinate females did not challenge single same-age G-Dominant females nor did they even challenge single younger G-Dominant females if the latter were mature. In contrast, in the experimental subgroups comprised of a G-Subordinate kin group (situations c and d above), G-Subordinate females could challenge collectively, and outrank, single G-Dominant females, regardless of the latter's age (size). One important implication of these findings is that any female, regardless of her age, is dependent on allies (sensu KAWAI, 1965) to maintain her rank. Thus the hierarchy's stability in matrilineal dominance systems would reflect the existence of inter-individual differences in alliance power, such that for any dyad the G-Dominant female has more collective power than the G-Subordinate female. Two categories of mechanisms are discussed in this context. Stability might result from the dynamics of intra-familial alliances (power asymmetry or power equality among kin-based coalitions) and/or from the dynamics of inter-familial alliances (asymmetry of inter-familial dependence).
TL;DR: The present study describes the structure and the organization of warbling song in individuals from varied geographical origins, showing warbling to be an extremely complex song in which there is much contrast.
Abstract: Male starlings sing two very different categories of song: whistles and warbles. The present study describes the structure and the organization of warbling song in individuals from varied geographical origins. In all cases, warbling is shown to be an extremely complex song in which there is much contrast: very different notes follow each other and are even superimposed. Higher levels of organizations are present: notes are grouped in repeating units, the motifs, each of which is sung in bouts of 1 to 12 repetitions, and finally these bouts show a clear sequential organization. A certain amount of variability occurs at each of these levels: slight variations are seen from one rendition of a given motif to the next; the number of repetitions of each motif varies from one song sequence to another and the sequential organization of bouts seems to be able to vary seasonally. All these characteristics were found in all individuals. Nevertheless, warbling appears to be an essentially individual song. Beyond two or three species-specific motifs, the others in the repertoire are individually characteristic. The beginnings and endings of the songs are clearly defined commencing usually with an individual motif whilst ending with a species-specific motif. We observed marked differences between individuals in repertoire size, extending from about 20 to more than 35 different motifs. This is the only measure of the repertoire that we have been able to define for this continuous song.
TL;DR: The importance of the enhanced predator detection ability of fish shoals and the social transmission of alarms within them is discussed in relation to predator avoidance behaviour and other activities of fish in shoals.
Abstract: The relationship between shoal size and group vigilance was investigated in the laboratory using a strongly schooling characin fish, the glowlight tetra (Hemigrammus erythrozonus). Group vigilance, as measured by the probability that at least one fish in the group detected (i.e. exhibited a startle response to) a brief, artificial alarm stimulus, increased curvilinearly at a decelerating rate with increasing shoal size. This would be predicted by the proposed early predator warning function of social groups. The observed relationship between corporate vigilance and shoal size was similar in form to one predicted by a simple signal detection model. However, observed detection probabilities for shoal sizes above 7 fish were lower than expected on the basis of this model, suggesting that an individual's probability of detection was not always independent of shoal size nor of the probabilities of detection of other shoal members. The numbers of tetras in a shoal exhibiting a startle response to an alarm stimulus increased non-linearly with increasing shoal size and exceeded the values predicted by the above mentioned model for the larger shoals, which implies social transmission of the alarm response among shoal members. The importance of the enhanced predator detection ability of fish shoals and the social transmission of alarms within them is discussed in relation to predator avoidance behaviour and other activities of fish in shoals.
TL;DR: Age-based dominance hierarchies may be stable in Polistes because colony members resist larger individuals' attempts to win high dominance rank by fighting, and young non-foragers have the highest rank and replace the queen.
Abstract: In primitively eusocial wasps, dominance hierarchies predict which female will become queen when the original queen is removed. At each of 3 latitudes spanning a range from temperate sites to tropical ones, an older, dominant, worker of the primitively social wasp, P. instabilis, became the replacement queen. Thus, even in the tropics, this species follows a temperate queen replacement pattern rather than the standard tropical pattern in which young non-foragers have the highest rank and replace the queen. Old individuals are dominant even though they are often smaller than their subordinates. These results are surprising because large size increases the chance of winning fights for queenship among Polistes females in other circumstances. Age-based dominance hierarchies may be stable in Polistes because colony members resist larger individuals' attempts to win high dominance rank by fighting.
TL;DR: Competition for fruit within chimpanzee foraging parties was investigated, finding that large food patches supported significantly larger parties than did smaller food patches, and foraging efficiency was apparently higher for small parties than for large ones, although the difference was marginally statistically significant.
Abstract: Competition for fruit within chimpanzee foraging parties was investigated by testing the hypotheses that food patch size was a limiting factor to foraging party size and to foraging efficiency while chimpanzees were foraging in Pseudospondias microcarpa trees for fruit. Large food patches (as measured by phenological score or the product of diameter at breast height and phenological score) supported significantly larger parties than did smaller food patches. In addition, foraging efficiency was apparently higher for small parties than for large ones, although the difference was marginally statistically significant. Per-capita feeding time for individuals in small parties was significantly higher than for those in large parties when chimpanzees had access to both Pseudospondias and Uvariopsis congensis fruit trees. Per-capita feeding time was not significantly correlated with food patch size. When Uvariopsis fruit trees became exhausted in mid-August, some chimpanzees apparently avoided severe competition for fruit by leaving the C.C. area, where they had been feeding on both Uvariopsis and Pseudospondias fruit. Social factors did not significantly affect foraging party size nor per-capita feeding time.
TL;DR: Sexual communication and the mating system of an undescribed genus of zaprochiline katydid is described and it is suggested that females do not prefer calls of large males because only in the early part of the season does male song give information on the size of the male and his spermatophore glands.
Abstract: We describe sexual communication and the mating system of an undescribed genus of zaprochiline katydid. Males produce an ultrasonic calling song described as a series of simple pulses at a carrier frequency near 50 kHz. Zaprochilines contrast with most other katydids in having a narrow diet consisting of pollen. Males in nature exhibited a resource-defence mating system by calling in choruses near flowers which were attractive to females. We determined whether females discriminated among calling males as mates. An early-season sample of male calls showed a correlation between song frequency and both body size and the size of the glands that produce a large, nutritious spermatophore which is eaten by the female. The prediction that larger males would have a mating advantage over small individuals was supported in laboratory experiments. However, examination of paired males in nature failed to reveal any evidence of such a mating advantage. Furthermore, in other laboratory experiments it was found that females preferred high frequency call models, representative of small males, over low frequency calls. It is suggested that females do not prefer calls of large males because only in the early part of the season does male song give information on the size of the male and his spermatophore glands. In addition, spermatophore nutrients may be less important to the nutrition of female zaprochiline than other katydiyds, due to the high-protein pollen diet of this species. Since higher frequencies of calls show relatively greater attenuation with distance, the high frequency calls preferred by females may be perceived as males calling closeby.
TL;DR: The role of song in the social behavior of a cooperatively living songbird, the Australian magpie, Gymnorhina tibicen, is investigated; vocal imitation and improvisation as major processes in vocal learning; song sharing as a possible badge of recognition for groups; and the function ofsong in social cohesion are discussed.
Abstract: In this study we investigate the role of song in the social behavior of a cooperatively living songbird, the Australian magpie, Gymnorhina tibicen (Cracticidae). In this species, kin and nonkin cooperative groups exist in the same population. We sampled the vocal repertoires of 23 magpies in six territorial groups and the nonterritorial flock, and of a tame magpie. Our results include: 1. Description of song. Soft warble syllables and loud carol syllables compose magpie songs, sung in communal choruses in both territorial and nonterritorial contexts. Warble syllables are diverse in physical structure. 2. Song repertoires. Most songs are individual-specific, though some are shared. Song variants could be found within the repertoire of a given individual, produced by various means (e.g., recombining segments). 3. Syllable repertoires. We classified 893 syllable types from our study population; 67% were individual-specific, and few were shared by more than two to five birds. 4. Repertoire sharing in groups. We found the average percentage of the repertoire shared between all pairwise combinations of birds higher (p 0.05, Mann-Whitney rank sum test). 5. Syllable sharing and vocal imitation in a tame magpie. A handreared bird had a repertoire consisting in whistles: some were perfect copies of human whistles, and some were improvisations on the same themes. She learned a new whistle from one of her human "group mates", the senior author. We discuss vocal imitation and improvisation as major processes in vocal learning; song sharing as a possible badge of recognition for groups; and the function of song in social cohesion.
TL;DR: It is suggested that dominant-subordinate relationships during the wintering phase are not based on differential aggression of plumage types and that they are not maintained by elevated plasma levels of androgens in high-ranking birds.
Abstract: We measured plasma levels of luteinizing hormone (LH), testosterone (T), 5α-dihydrotestosterone (DHT) and corticosterone (B) in flocks of wintering white-throated sparrows This species occurs in two colour morphs that are distinguishable by white or tan colour of the median crown stripe and differ in frequency of agonistic behaviour during the reproductive season During winter, white-throated sparrows form flocks that are characterized by dominance hierarchies, in which social rank was correlated with sex and age, but not with crown colour Plasma levels of LH and androgens (T and DHT) were basal in most free-living and captive birds and not correlated with sex, age, morph or social rank Plasma levels of testosterone did not increase in captive groups, when aggressive interactions increased due to experimental manipulation of distribution and amount of food These results suggest (1) that dominant-subordinate relationships during the wintering phase are not based on differential aggression of plumage types and (2) that they are not maintained by elevated plasma levels of androgens in high-ranking birds Plasma concentrations of B increased rapidly with duration of capture stress in females and first-year males, but not in adult males Since adult males were of highest rank it appears that high social status may restrain acute adrenal response to stress Further, baseline levels of B were highest in low-ranking first-year females and lowest in high-ranking adult males In captive groups, amount and distribution of food resources altered levels of B Levels appeared to be most variable and very high in some birds of intermediate rank, when agonistic interactions in competition for food were most frequent This suggests greater impact of change in food distribution on those birds, whose social status is less clear than that of high or low ranking birds
TL;DR: Group raids consist of a collective revolt against the status quo, similar in form to troop takeovers by groups of male hanuman langurs, and can achieve proximity to oestrous females with less risk of injury by raiding in a group rather than by attempting to seize a female by themselves.
Abstract: [Southern sea lions, Otaria byronia, breed in a narrow zone along the high tide mark where males sequester females, defending them against competitors that congregate on the periphery. During four breeding seasons, 15 December to 10 February, 1983-1986, we observed marked animals at Punta Norte, Peninsula Valdes, Argentina, and recorded the form, frequency and consequences of an unusual mating strategy: groups of males raid the breeding area attempting to seize females from resident, territorial males. Raids were often triggered by one male rushing into the breeding area. Females fled from the point of attack and were separated from their pups and were redistributed within the breeding area. Some resident males gained females, others were deposed and lost females, while some raiders gained females and residency in the breeding area. A mean of 144 (sd = 22) raids were observed per breeding season, with 57% of them occurring at peak season, 14-26 January. During this period, raids occurred at a rate of one every two hours of observation. Raids occurred at all hours of the day and at night, the rate, time and site of occurrence being associated with the location and number of females in oestrus, and with tide. The mean size of the raiding party was 10 males (sd = 8, range = 2-40 males); 66 % of the males were subadults. In 36% of 355 raids, at least one female was seized and held for at least a few minutes; in the remainder, all raiders were repelled. There were three outcomes when a raider seized a female: 1) In 53% of the seizures, the male lost the female in less than one hour and was driven out; 2) in 8% of the seizures, the raider could not withstand the attacks of resident males and herded the females a few metres to the periphery of the breeding area, and 3) in 39% of the seizures, the raider remained in the breeding area with one or more females. Subadult raiders were not successful in securing females but in 18% of 484 raids, they seized a pup. Fifty seven percent of the time, pups were abducted from the breeding area and held forcibly likc adult females. At least five of them were killed. Raiders that secured a female during a raid remained in residency a mean of 13 days (sd = 9), a significantly shorter tenure than that of males that set up residence in the breeding area at the start of the season (X = 24 days, sd = 5). Group raids were an effective mating strategy for some participants. The probability of copulating was higher when a male raided the breeding area in a group than when alone. Raiders that seized females and became residents copulated 1.5 times per 100 hrs in the breeding area, achieving a mean of 2.2 copulations per male (variance = 6.0). Founder residents copulated at a similar rate, but were more successful than raider-residents due to longer tenures, achieving a mean of 5.3 copulations per male (variance = 12.3). The incidence and success of raids as a mating strategy was partially dependent on topography. At Puerto Piramide, where males defended territories containing tidepools and access to the breeding area was limited to a few sites at high tide, raids were infrequent and ineffective. Raiders synchronized their rush into the breeding area, keying on the first male to move. However, no alliances or coalitions, suggesting cooperation, were formed. Group raids consist of a collective revolt against the status quo, similar in form to troop takeovers by groups of male hanuman langurs. Outside males can achieve proximity to oestrous females with less risk of injury by raiding in a group rather than by attempting to seize a female by themselves., Southern sea lions, Otaria byronia, breed in a narrow zone along the high tide mark where males sequester females, defending them against competitors that congregate on the periphery. During four breeding seasons, 15 December to 10 February, 1983-1986, we observed marked animals at Punta Norte, Peninsula Valdes, Argentina, and recorded the form, frequency and consequences of an unusual mating strategy: groups of males raid the breeding area attempting to seize females from resident, territorial males. Raids were often triggered by one male rushing into the breeding area. Females fled from the point of attack and were separated from their pups and were redistributed within the breeding area. Some resident males gained females, others were deposed and lost females, while some raiders gained females and residency in the breeding area. A mean of 144 (sd = 22) raids were observed per breeding season, with 57% of them occurring at peak season, 14-26 January. During this period, raids occurred at a rate of one every two hours of observation. Raids occurred at all hours of the day and at night, the rate, time and site of occurrence being associated with the location and number of females in oestrus, and with tide. The mean size of the raiding party was 10 males (sd = 8, range = 2-40 males); 66 % of the males were subadults. In 36% of 355 raids, at least one female was seized and held for at least a few minutes; in the remainder, all raiders were repelled. There were three outcomes when a raider seized a female: 1) In 53% of the seizures, the male lost the female in less than one hour and was driven out; 2) in 8% of the seizures, the raider could not withstand the attacks of resident males and herded the females a few metres to the periphery of the breeding area, and 3) in 39% of the seizures, the raider remained in the breeding area with one or more females. Subadult raiders were not successful in securing females but in 18% of 484 raids, they seized a pup. Fifty seven percent of the time, pups were abducted from the breeding area and held forcibly likc adult females. At least five of them were killed. Raiders that secured a female during a raid remained in residency a mean of 13 days (sd = 9), a significantly shorter tenure than that of males that set up residence in the breeding area at the start of the season (X = 24 days, sd = 5). Group raids were an effective mating strategy for some participants. The probability of copulating was higher when a male raided the breeding area in a group than when alone. Raiders that seized females and became residents copulated 1.5 times per 100 hrs in the breeding area, achieving a mean of 2.2 copulations per male (variance = 6.0). Founder residents copulated at a similar rate, but were more successful than raider-residents due to longer tenures, achieving a mean of 5.3 copulations per male (variance = 12.3). The incidence and success of raids as a mating strategy was partially dependent on topography. At Puerto Piramide, where males defended territories containing tidepools and access to the breeding area was limited to a few sites at high tide, raids were infrequent and ineffective. Raiders synchronized their rush into the breeding area, keying on the first male to move. However, no alliances or coalitions, suggesting cooperation, were formed. Group raids consist of a collective revolt against the status quo, similar in form to troop takeovers by groups of male hanuman langurs. Outside males can achieve proximity to oestrous females with less risk of injury by raiding in a group rather than by attempting to seize a female by themselves.]
TL;DR: The relationship between variation in a cultural trait, the songs of male swamp sparrows Melospiza georgiana, and genetic variation at nine polymorphic enzyme loci was examined using seven geographic locations covering a major portion of the breeding range of this species as mentioned in this paper.
Abstract: The relationship between variation in a cultural trait, the songs of male swamp sparrows Melospiza georgiana, and genetic variation at nine polymorphic enzyme loci was examined using seven geographic locations covering a major portion of the breeding range of this species. Swamp sparrow songs exhibit geographical variation, and song populations at a location can remain relatively stable over a ten year period. Three measures of song syllable variation were used to examine the similarities between the song populations. Electrophoretic analysis suggested at least 3 groups of locations based on allelic frequency differences. Two of these groups are geographically extensive. The mean proportion of songs two locations share is related independently to the distance between the locations and to the similarity of their allele frequencies. The allele frequency similarity between two locations is not related to the geographic distance between them. A descriptive analysis of the relationship between song and genetic variation yielded two conclusions. First, two of the three population subdivisions exhibited a pattern of correlation between song syllable variation and genetic variation that may resemble character displacement. The similarity of song syllables at two locations may depend on the position of the two locations relative to the region where different allele-frequency groups come into contact. Second, this pattern of correlation did not hold for comparisons involving the third subdivision, and thus was not species universal in swamp sparrows. Song syllable variation may have different biological relevance in different geographical areas.
TL;DR: In this paper, a three-year study of two rookeries at Peninsula Valdes, Argentina, from 1985 to 1987 revealed major differences in mating behavior and mating success of males, associated with temperature, solar radiation and rookery topography.
Abstract: [Southern sea lions, Otaria byronia, breed during the Austral summer on flat rocky shelves containing tidepools and boulders, or on wide, uniform pebble beaches lacking tidepools and shade. The first substrate provides breeding animals with relief from heat stress, the second does not. A three-year study of two rookeries at Peninsula Valdes, Argentina, from 1985 to 1987 revealed major differences in mating behaviour and mating success of males, associated with temperature, solar radiation and rookery topography. At Puerto Piramide, males defended territories containing tidepools throughout the breeding season. Thermoregulatory requirements caused females to concentrate in tidepool areas, and males completed aggressively for these recources. Seven males that defended territories with large, water-renewable tidepools copulated a mean of 11.6 ± 4.2 times during three weeks, versus a mean of 1.4 ± 1.4 times for ten males that defended territories without tidepools. The latter lost their females and went to sea when air temperature rose over 30°C. At Punta Norte, the homogeneous pebble substrate forced animals to breed in a narrowly confined area along the high tide mark, where the substrate remained wet. Only those males holding females in this narrow zone copulated. All of 32 marked males that associated with females near the high tide mark copulated. Males breeding outside of this narrow strip of beach deserted and lost females after 1-3 hrs of air temperatures 30°C, and solar radiations 1 .2 cal/cm2/min. Rookery topography and associated thermoregulatory constraints are critical variables shaping breeding behaviour in southern sea lions. The thermal and physical environment is a determinant of the social behaviour of otariids and has been important in shaping their social system., Southern sea lions, Otaria byronia, breed during the Austral summer on flat rocky shelves containing tidepools and boulders, or on wide, uniform pebble beaches lacking tidepools and shade. The first substrate provides breeding animals with relief from heat stress, the second does not. A three-year study of two rookeries at Peninsula Valdes, Argentina, from 1985 to 1987 revealed major differences in mating behaviour and mating success of males, associated with temperature, solar radiation and rookery topography. At Puerto Piramide, males defended territories containing tidepools throughout the breeding season. Thermoregulatory requirements caused females to concentrate in tidepool areas, and males completed aggressively for these recources. Seven males that defended territories with large, water-renewable tidepools copulated a mean of 11.6 ± 4.2 times during three weeks, versus a mean of 1.4 ± 1.4 times for ten males that defended territories without tidepools. The latter lost their females and went to sea when air temperature rose over 30°C. At Punta Norte, the homogeneous pebble substrate forced animals to breed in a narrowly confined area along the high tide mark, where the substrate remained wet. Only those males holding females in this narrow zone copulated. All of 32 marked males that associated with females near the high tide mark copulated. Males breeding outside of this narrow strip of beach deserted and lost females after 1-3 hrs of air temperatures 30°C, and solar radiations 1 .2 cal/cm2/min. Rookery topography and associated thermoregulatory constraints are critical variables shaping breeding behaviour in southern sea lions. The thermal and physical environment is a determinant of the social behaviour of otariids and has been important in shaping their social system.]