Showing papers in "Behaviour in 1999"

Behavioral development in wild bottlenose dolphin newborns (tursiops sp.)

Abstract: Newborn characteristics, patterns of motoric and social behavioural development, and mother-infant relationships in free-ranging and semi-provisioned bottlenose dolphins (Tursiops sp.) are examined. Nine newborns were observed for 189 hours over the first 10 weeks of life. Newborn infants breathe more often than their mothers, and synchronize their breathing and swimming with her soon after birth, but show a gradual decline in synchrony as they age. Virtually all patterns of infant behaviour, mother-infant proximity, and spatial relationships with the mother changed as a function of infant age. Maternal activity, however, does not change over time, except that mothers decrease their role in maintaining proximity to their infants from the first month to the second month of infant life. Infants spend less time close to their mothers, less time echelon swimming (close, alongside the mother), and more time infant-position swimming (in contact under the mother) as they age. Infants spend more time traveling and socializing independently over time. They also separate from their mothers more often and for longer periods of time. Infants do not forage during the newborn period, but are observed 'practice foraging' by the end of the first month. Rubbing, petting, chasing, and displaying with other animals (including the mother) were common forms of socializing. Infants frequently initiate rubbing with their mothers, with particular focus on her head region. Infants typically associate with young females, adult females and other infants, but not with adult or subadult males. Developmental shifts and overall patterns are discussed in the context of the bottlenose dolphin's fission-fusion social organization and ecology. The effects of provisioning on dolphin behaviour are addressed.

Fission, fusion and nonrandom associations in female bechstein's bats (myotis bechsteinii)

Abstract: Maternity colonies of the Bechstein's bat (Myotis bechsteinii) are socially closed units that frequently split into subgroups which occupy different roosts. We analysed the social structure of one colony over three years in the field and quantified associations among pairs of females by using three association indices. Colony members exhibited marked mixing, although individual composition of subgroups was not completely random. Females associated according to the reproductive status, with lactating females preferentially roosting together. Relatedness, determined from 5 nuclear and 1 mitochondrial microsatellite, had no consistent influence on the degree of association. In combination, the indices allowed for the interpretation that nonrandom associations occur even in the absence of shared roost and group size preferences. High individual associations among reproducing female Bechstein's bats might reflect the importance of cooperation in maternity colonies. The frequent fission and fusion of subgroups suggests a flexible reaction of Bechstein's bats according to enviromental conditions.

The structure of social relationships among female savanna baboons in moremi reserve, botswana

Abstract: Here we examine the effects of maternal kinship, reciprocity, and dominance rank on the social relationships of female baboons (Papio cynocephalus ursinus) in a well-habituated, free-ranging group in the Okavango Delta of Botswana. These data are useful for testing comparative hypotheses about the ecological and demographic factors that shape the evolution of social organization in primates and other animals. In this group, adult females had well-differentiated grooming relationships with one another, and limited their grooming to a relatively small subset of available partners. Although there were 19 adult females in the group, the average female groomed only 8 other females, and devoted at least 5% of her grooming to only four other females. Females groomed maternal kin at significantly higher rates and for significantly longer periods than they groomed other females. The bias in favor of maternal kin was not an artifact of a general attraction toward females of adjacent rank. However, members of high-ranking lineages did devote a relatively greater fraction of grooming to maternal kin than members of low-ranking lineages did. Females most often groomed the females from whom they received the most grooming and grooming was very evenly balanced within the majority of dyads. Female rank had little impact upon grooming patterns and there was no evidence that females competed overtly over access to high-ranking partners.

Individual behavioural characteristics and dominance in aviary groups of great tits

Abstract: In previous work we have shown that juvenile male great tits Parus major show consistent behavioural differences in exploratory and aggressive behaviour. Fast and superficial explorers (FE) won from slow and thorough explorers (SE) during controlled pair-wise confrontations in small cages. The present study assesses the relationship between early exploratory behaviour and later dominance in aviary groups of juvenile male great tits; such groups might approach natural conditions better than 'simple' pair-wise confrontations. Observations of nine aviary groups showed that a stable hierarchy is only established after a first dynamic phase of several days with many dominance shifts and a peak in number of interactions. In seven other aviary groups we determined the dominance relationships between FE and SE. In a stable hierarchy, SE had on average a significantly higher dominance score than FE. This finding contrasts our previous results in pair-wise confrontations. However, on the first day in the aviary, FE had on average a higher dominance score and initiated more fights than SE. This agrees with our previous results and indicates a gradual development of the situation in the stable hierarchy. Behavioural observations indicate that during this development, FE took more risks in their fighting behaviour and had more difficulty to cope with defeat than SE. In the stable hierarchy they either won or lost from all SE. SE were more cautious and had intermediate dominance scores in the stable hierarchy. These differences in fighting behaviour and the role of individual differences in exploratory behaviour and in coping with defeat are discussed as possible causes for the unexpected results of this study.

Male wing pigmentation may affect reproductive success via female choice in a calopterygid damselfly (zygoptera)

Abstract: Male calopterygid damselflies show striking morphological and behavioural secondary sexual traits which are known to function in intrasexual contests. The distribution of pigment in the sexually dimorphic wing 'spot' is prominently displayed to the female during courtship, yet there is little empirical evidence that this trait functions in an epigamic context. Observations of marked field populations revealed (a) there was variation in wing pigment distribution in males, (b) the pigmentation was fixed in reproductively active males, (c) resource holding males had less heterogeneity in the distribution of the wing pigment than males that were never observed to hold a resource and (d) that females frequently (60.3%) rejected males after courtship. An experiment was conducted in which the frequency of key reproductive behaviours (female inspection flights, courtships, copulations, and oviposition) was measured for the same male utilising the same territory before and after treatment or control manipulation of wing pigment parameters. Increasing the heterogeneity (and decreasing the area) of the wing pigmentation by removing small areas of pigmented cuticle from their wings resulted in a decrease in the measured reproductive behaviours (control males that had non-pigmented areas removed from their wings showed no decreases). Since females cannot be coerced into these behaviours, the experimentally induced decrease suggests females avoided males with higher levels of wing pigment heterogeneity. The results are discussed in the context of the benefits females might receive as a consequence of their reproductive decisions.

To synchronise or not to synchronise: a dilemma for young bighorn males?

Abstract: Bighorn sheep (Ovis canadensis) are sexually dimorphic and live in nursery groups, bachelor or mixed groups. To remain in a group, individuals have to synchronise their activity according to the type of group they are in, which may incur a cost for individuals of different body size from the other group members. To test this hypothesis, I calculated the degree of synchrony of activities for each individual within a group. Animals in nursery or bachelor groups were highly synchronised with each other while mixed-age-sex groups had the lowest group synchronisation index. Two and three-year old bighorn males are intermediate in body size between the two adult sexes. Two-year-old males always adjusted their behaviour independent of group type, while three-year-old males synchronised their behaviour when with bachelor, but less so when in nursery groups. I suggest that two- and three-year-old males may face a conflict between synchronising their behaviour to stay in a group and the need to forage according to their own time budgets. I conclude that intermediate-sized young male ungulates of sexually dimorphic species may be better off forming same-sex-age groups.

Social bonds and genetic ties: Kinship association and affiliation in a community of bonobos (Pan paniscus)

Abstract: Studies of captive populations of bonobos suggest that females are more gregarious than males. This seems to contradict assumed sex-differences in kinship deriving from a species-typical dispersal pattern of female exogamy and male philopatry. Here we present data on spatial associations and affiliative relations among members of one wild community (Eyengo) for which genetic relationships were identified by analysing mitochondrial and nuclear DNA. Our data from Lomako confirm the existence of spatial associations among resident females. In addition, they reveal strong social bonds between males and females. While most female-female associations did not last longer than one field season, long-term associations occurred predominantly between mixed-sex dyads and involved both close kin and unrelated individuals. Differences in social grooming appeared to be related to patterns of spatial association rather than to kinship. It is suggested that under natural conditions social organisation of bonobos is characterised by strong inter-sexual bonds. Males may benefit from bonding with females by increased reproductive success via rank acquisition. For females benefits may derive from inclusive fitness and reduced food competition. Preliminary evidence suggests that females also may benefit from protection by resident males against male intruders.

Duet songs of the siamang, hylobates syndactylus: ii. testing the pair-bonding hypothesis during a partner exchange

Abstract: It has repeatedly been suggested for several duetting bird and primate species that duetting might act as a reinforcement of the pair bond. Until now, it has apparently not been demonstrated that the premises underlying the pair-bonding hypothesis are met by any duetting species. Siamangs (Hylobates syndactylus) are monogamous apes which produce long and complex duet songs. This study analyses the changes in duet structure in two pairs of siamangs during a forced partner exchange. The duet songs of the siamangs underwent many notable changes during partner exchange. Of 33 different variants of the great call sequence, 29% in one pair and 21% in the other were restricted to the first stage just after the partner exchange. Some of these changes were certainly due to individualistic traits of the new partner, and for some other changes, this possibility cannot be reliably excluded. At least two changes, however, can only be interpreted in terms of a learning effort by which one partner adapts its duetting behaviour to that of its new mate. The two newly formed pairs of this report appear to be the first documented cases to fulfil the requirements underlying Wickler's (1980) pair-bonding hypothesis: The animals under study were showing a stable song pattern with pair-specific traits. After the partner exchange, new pair-specific traits occurred, some of them obviously achieved through a partner-directed effort of one or both individual(s). Moreover, the pair-bonding hypothesis appears to be one of the few biological functions suggested so far which could explain a high degree of duet-complexity as adaptive. However, the loudness of the siamang song alone suggests that other functions are also involved. These are most probably related to territorial advertisement, pair bond advertisement and (possibly) mate attraction.

Tenure related changes in wild Thomas's Langurs. I : Between-group interactions

Abstract: Between-group conflicts are believed to serve two major functions: mate defence and resource defence In addition, in species where females can disperse, both female choice and male coercion may play a role in between-group interactions In this paper, I evaluate the resource vs mate defence hypotheses and investigate male and female strategies in between-group interactions in wild Thomas's langurs (Presbytis thomasi) This species lends itself well to study the intertwining of male and female strategies Thomas's langurs live in one-male multifemale groups; both males and females disperse from their natal groups; female secondary dispersal is also common, and infanticide occurs The life-span of a group is, as a rule, restricted to the tenure of its reproductive male (median tenure length is 72 months) Male tenure in bisexual groups was divided into three phases: the early phase (no infants yet), the stable middle phase, and the late phase (last year) Because AMBs remained after all females had left a male, they were treated as a fourth phase I analysed interactions of group members with individuals outside the group using data from a four year field study (1093 observation days) of 15 bisexual and eight all-male groups of Thomas's langurs at Ketambe, Indonesia Two types of interactions could be distinguished: (1) group encounters: whole groups meet each other, and (2) male provocations: a male silently approaches a group and suddenly attacks the individuals This study involves 329 group encounters and 265 male provocations The results support the mate defence hypothesis, but are ambiguous about the role of resource competition: Group encounters during the middle and late tenure phase took place more often in the context 'food patch', than was expected, and they mostly took place in fruit patches, which were a preferred food item However, the proportion of group encounters that involved aggression did not depend on feeding context or tenure, and fruit availability did not influence group encounter rates Male aggression during between-group conflicts reflected mate defence, rather than resource defence, although females had the possibility of obtaining resource defence through a male's mate defence This study suggests that females use the outcome of group encounters and male provocations to assess the relative strength of males, and thus 'chose' a male who is able to defend future offspring It also suggests that males can use coercion (infanticide and aggression against females) to show the relative weakness of a female's current male and encourage her to transfer: Aggressive behaviour during group encounters was primarily between males Females only reacted aggressively to extra-group males when their infant was under attack Male infanticide only occurred during provocations by males from neighbouring groups or AMBs The intensity of male competition for mates, as measured by male-male aggression and extra-group male interest in a groups' females, was higher during the early and late phases, than during the middle phase of the tenure It was also higher during the AMB than during the late phase of male tenure The relative strength of males, as measured by a male's provoking behaviour and his ability to protect his females from aggression by extra-group males, was lower during the late than during the middle tenure phase Male strength seemed lowest during the subsequent AMB phase Females avoided extra-group males least during the early tenure phase, before infants were born

Association by male chimpanzees: a social tactic?

Abstract: Whether and with whom to associate are possibly some of the most fundamental of choices faced by a chimpanzee, choices constrained by and dependent upon similar decisions made by potential association partners. Although much work has focused on the impact of ecological factors on the size of the temporary associations, or parties, it seems that chimpanzees, especially the males, form parties to gain social benefits, and that these benefits are dependent the particular composition of these parties. This paper examines the social determinates of the association patterns of male chimpanzees, members of the Sonso community in the Budongo Forest Reserve, western Uganda. Male chimpanzees showed clear preferences for association partners, and these partners had a strong tendency to associate in small parties. Strength of association within dyads accounted for a significant fraction of the variance in party size [all parties containing males: r2 = 0.30; male parties only: r2 = 0.24 (all dyads), r2 = 0 . 50 (dyads with positive associations only)]. These results supported the hypothesis that association was the result of tactical decisions, and refuted predictions of alternate hypotheses: random and passive (independent attraction to the same locations, such as fruiting trees) association. Further support for the tactical association hypothesis was provided by observations that association between males was flexible and that association patterns resolved into alternative association strategies, with some males shifting between strategies over time. The presence of cycling females influenced party size, which increased with the number present. The number of adult males in a party was also greater when cycling females were present, although remained similar whether one, two, three or four such females were in the party. Samples sizes for parties containing more than two cycling females were low, however. It is suggested that, for a Machiavellian primate in fission-fusion social system, the need to make decisions concerning association partners is cognitively demanding and may be an important, frequently used, function of the intelligence demonstrated by captive chimpanzees.

Responses to multiple chemical cues by the crayfish orconectes virilis

Abstract: To investigate how organisms respond to multiple cues, the responses of the crayfish Orconectes virilis to natural chemical stimuli presented both one at a time and in combinations were recorded in the laboratory. Following the introduction of predator (snapping turtle) odours, individuals decreased the rate of non-locomotory movements compared to control levels. The addition of food odour resulted in an increase in movement as well as postural changes. When both signals were presented simultaneously, the level of food-elicited movements was reduced and the extent of inhibition of food-related responses depended upon the relative intensity of the two types of input. The behavioural effect of predator odour introduction lasted about two hours. When alarm odour and food odour were presented simultaneously, movements were reduced even more strongly than with the predator odour-food odour combination. Presentation of two signals associated with danger (alarm and predator odours) resulted in a significantly greater reduction of food odour-induced movement than for either danger signal by itself.

Alarm calling in three species of marmots

Abstract: Many species produce alarm calls that vary according to situation. Theoretically, alarm call structure could covary with predator type and could communicate potentially ''referential information, or calls could covary with the degree of risk a caller experienced when it emitted a call. Using similar methods, I studied the ways in which Olympic (Marmota olympus), hoary (M. caligata), and Vancouver Island marmots (M. vancouverensis) communicated situational variation. I observed both natural alarm calling, and I artificially elicited alarm calls with simulated terrestrial and aerial predators. I used playback experiments to study marmots' responses to different alarm call variants. All three species produced four roughly similar but distinctive loud alarm vocalizations that could be categorized by their relative shape, duration, and whether calls were quickly repeated to create multi-note vocalizations. In addition, the Vancouver Island marmot produced a fifth loud alarm call-the kee-aw. Call micro-structure varied as a function of the distance the caller was from an alarming stimulus and the type of alarming stimulus. Two lines of evidence suggest that all three species had alarm calls associated with the caller's risk (i.e. they were not referential). First, marmots often changed call types within a calling bout: there were no unique stimulus-class specific vocalizations. Second, marmot responses to alarm calls were graded: marmots did not have unique responses to different call types. These three close taxonomic relatives with superficially similar calls, communicated risk differently.

Extra-pair paternity in great tits (parus major)-a long term study

Abstract: Extra-pair paternity is known to be common in many socially monogamous avian species. One question to which much attention has been paid is which benefits females might gain from copulations outside the pair bond. The 'good genes' hypothesis suggests that females obtain indirect benefits (i.e. good genes for at least part of their offspring). To test predictions from this hypothesis we analysed paternity in a study on great tits (Parus major) over 5 years. Each year 27.8-44.2% of broods contained at least one nestling that derived from a male other than its social father. 5.4-8.6% of all nestlings investigated were extra-pair sired. Males that were cuckolded survived with the same probability to the next year's breeding season as males whose broods did not contain extra-pair young. In addition there were no differences in local recruitment rates of offspring whether they were extra-pair sired or not. Our results do not fit the predictions of the 'good genes' hypothesis. Moreover, patterns of extra-pair paternity in successive years were highly inconsistent, suggesting that factors other than the genetic quality of males play an important role in determining if a particular female or male has extra-pair young in its brood.

Extra-harem paternity in the white-lined bat saccopteryx bilineata (emballonuridae)

Abstract: We studied the paternity in a colony of the harem-polygynous white-lined bat Saccopteryx bilineata by microsatellite typing and compared the data with group composition and stability. Although we recorded a high stability for harem groups, neither spatial proximity of males to harem females nor harem ownership allowed us to predict the paternity of the next year's harem offspring. Eight out of 28 juveniles were fathered by holders of the harem in which they were born, while the other 20 represent Extra-Harem-Young (EHY). 50% of EHY were fathered by males from outside the colony and 50% by other harem holders or peripheral males of the colony. On average, reproductive success of harem holders (1.2 offspring/year) was higher compared with peripheral males (0.4 offspring/year). Harem size seemed not to influence reproductive success of harem holders. Although maintaining of a territory seems to be costly for a harem male, his ability to control the females of his harem may be restricted; instead female Saccopteryx bilineata appear to have a high potential for female choice.

The study of intersexual selection using quantitative genetics

Abstract: In this review, I stress the importance of incorporating Quantitative Genetics (QG) in the study of sexual selection through female mate choice. A short overview of QG principles and methods of estimating genetic variance and covariance is given. The state of knowledge is summarized as to two QG assumptions (genetic variance in female mating preferences and male sexual traits) and one QG prediction (genetic covariance between preferences and preferred traits) of models of sexual selection. A review is given of studies of repeatability of mating preferences because of recent accumulation of data. The general conclusion is that sexual traits and mating preferences show large genetic variation and are genetically correlated. The extensive genetic variation asks for an explanation that goes beyond the ususal explanations of the maintenance of genetic variation in fitness traits. Two models that explain the high genetic variance in sexual traits are treated in detail: modifier selection and condition dependence. There are many unexplored areas of QG research that could stimulate further research in sexual selection like the study of genetic covariance between mating preferences and good genes, of genetic variances and covariances of multiple male traits and multiple females preferences, of genetic variance in condition, and of condition dependence of mating preferences.

Lack of worker policing in the cape honeybee (apis mellifera capensis)

Abstract: In honeybees (Apis mellifera) laying worker offspring is rare. One mechanism to suppress worker reproduction is through worker policing, i.e. workers remove unfertilised eggs laid by other workers. This behaviour has been shown to be adaptive as soon as the queen performs polyandrous matings. The average relatedness to the queen's drones is higher than to the worker laid offspring. In the Cape honeybee (A. m. capensis) reproductive workers lay fertilised eggs which develop into females. In this case the average worker relatedness to sexual reproductives reared from worker or queen offspring is identical. Worker policing has been predicted by evolutionary theory to be less expressed in A. m. capensis colonies than in other honeybees. We found genetic evidence that worker policing is not common in the Cape honeybee. Laying worker offspring was identified in queen right colonies using microsatellite DNA analysis.

Within-colony relatedness in a termite species: genetic roads to eusociality?

Abstract: Hamilton's theory predicts that relatedness asymmetries, with higher relatedness between alloparents and brood than between parents and brood, favour the evolution of eusociality. The haplodiploid reproductive system of the social Hymenoptera does indeed produce relatedness asymmetries, but the diplodiploid system of the eusocial Isoptera does not automatically do so. Three mechanisms that might favour relatedness asymmetries, and therefore eusociality, in termites have been extensively debated: First, substantial inbreeding generates the background for effective kin-selection. Second, inbreeding-outbreeding cycles within and between colonies cause a higher relatedness between individuals of the same generation than between them and their potential offspring. This would be analogous to the haplodiploid system. Third, translocation complexes of sex-linked chromosomes may generate higher relatedness within sexes than between sexes, again analogous to the haplodiploid system. We tested these three hypotheses for the African termite Schedorhinotermes lamanianus (Isoptera, Rhinotermitidae) using estimates of within-colony relatedness derived by multilocus DNA fingerprinting with a synthetic oligonucleotide probe. We found little support for any of the three hypotheses. We observed inbreeding to occur only during one or a few generations within colonies, which is unlikely to be an operational basis for ongoing kin-selection. Overall, we conclude that ecological factors and constraints must be considered a major selective force.

The benefits of dear enemy recognition in three-contender convict cichlid (cichlasoma nigrofasciatum) contests

Abstract: We staged eight types of contests using adult male convict cichlids (Cichlasoma nigrofasciatum) to study the effects of dear enemy recognition on the defensive decisions of territorial residents when confronted by two opponents. Our observations supported the hypothesis that residents faced with two intruders simultaneously would divide the overall response shown to a single intruder between the two intruders with respect to their relative threats (i.e. sizes). Consequently, in comparison to a single-intruder circumstance, the residents' attacks against any given intruder were reduced. The relative threat of competitors was dramatically altered when one of the residents' opponents was a dear enemy neighbour. When faced with a dear enemy neighbour and an unfamiliar intruder simultaneously, residents preferentially confronted the unfamiliar opponent. That is, the establishment of dear enemy recognition between a resident and a neighbour allowed the resident to direct his aggression to the greater competitive threat, i.e. the intruder. In this case, the amount of aggression residents exhibited toward the intruder was similar to the amount of aggression against a single nonterritorial intruder. Therefore, having a dear enemy neighbour freed a resident to defend its territory against an intruder with similar efficiency compared to when the intruder had been the resident's only opponent.

Mating behaviour and male mate choice in Tribolium castaneum (Coleoptera, tenebrionidae)

Abstract: Mate choice by males has received less attention than female choice, despite the recognition that males can incur non-trivial reproductive costs through mating. In this study we investigate male mate choice in the red flour beetle, Tribolium castaneum. We determine whether male beetles have evolved sensitivity that enables them to discriminate between females and we then examine how males discriminate between females that present different reproductive potentials. Recently-emerged adult females are immature, and we investigate when egg-laying maturity develops, and whether male mating attempts with immature females provide reproductive pay-offs. We show that males are the sex most likely to initiate mating attempts (more than 85% of male-female contacts are male-initiated). Therefore, we test male mating initiations when presented with choices between: (i) immature and mature virgin females; (ii) mature virgin females and previously mated mature females; and (iii) mature females previously mated either with different male or with the test males. Last male sperm precedence exists in T. castaneum and females are polyandrous. Matings with immature females are therefore likely to generate lower fertilization successes than matings with mature females. Furthermore, males are likely to achieve higher total fertilization success when they mate if they precede a rival male's sperm than if they precede their own sperm. Accordingly, we find that: (i) males copulate more frequently with mature, than with immature females; (ii) males do differentiate between virgin and mated females; and (iii) males prefer females that have been inseminated by a different male to those previously inseminated by the test males themselves. The results demonstrate that male T. castaneum recognise female status, display mate choice, and prefer to inseminate females which provide greater reproductive potential.

Sperm Competition in a Nuptial Feeding Spider, Pisaura Mirabilis

Abstract: The paper tests two hypotheses about sperm priority in the spider Pisaura mirabilis. A 'phylogenetic constraints hypothesis' states that since the females have conduit spermathecae, first male priority should prevail. On the other hand, males offer nuptial prey to the females and females mate with multiple males. The evolution of these traits is most easily understood if late mating males also have a substantial fertilization success. The results indicate a compromise solution. Sterile-male technique with double-mated females indicated a first male priority pattern (P1 = ca 70%, after adjusting for sterilization damage and experimental mortality). However, the success of the fourth male of quadroublemated females was unexpectedly high (adjusted P4 = ca 24%, not different from P of 2 two-male matings). This lends support to a supplementary hypothesis of constant last male success, which may turn an initial first-male advantage into a last-male advantage, when the number of males mating with a female raises above a certain number. Independent of mating order, males may increase their share of fertilizations by long copulation times. It was tested whether female choice for symmetric males might account for differential male success. However, fluctuating asymmetry (FA) in male leg length showed no relationships with fertilization success or copulation duration.

Offspring-parent communication in a subsocial treehopper (hemiptera: membracidae: umbonia crassicornis)

Abstract: Parental care of post-hatching offspring is widespread in insects, but the role of communication in parent-offspring interactions remains largely unknown. I have found that, in the subsocial treehopper Umbonia crassicornis, aggregated nymphal offspring produce substrate-borne, vibrational signals in synchronized bursts that elicit the mother's antipredator behavior. In this study I describe the signals used by nymphs and explore their role in mother-offspring interactions and within-brood communication. Nymphs were stimulated to signal in the laboratory in response to light contact, simulating the approach of a predator. Signals of nymphs at the site of disturbance triggered a rapid wave of signaling by many individuals within the aggregation. This coordinated signaling was associated with the mother's defensive behavior. Signaling was limited to the vibrational channel: when transmission of vibrations was blocked between signaling nymphs and the mother, the mothers' response was abolished. Nymphs signaled not only in response to contact, but also in response to playback of signals from their siblings. Nymphs in otherwise undisturbed aggregations signaled only in response to signals coordinated into synchronized, group displays, and not to signals in random temporal patterns. However, nymphal signaling thresholds were lowered after a recent experience of simulated predation. After a period in which nymphs were stimulated to signal (by light contact simulating a predator's approach), playback of one individual signal could trigger a coordinated burst within the aggregation. It remains unknown if coordination among siblings to produce synchronized, group signals is completely cooperative, or if siblings compete for the mother's proximity. But it is clear that a complex system of communication among siblings, and between siblings and their parent, is an important feature of maternal care in these subsocial insects.

Behavioural strategies, testis size, and reproductive success in two caviomorph rodents with different mating systems

Abstract: We summarize our studies on the social and mating systems of Cavia aperea and Galea musteloides , two closely related South-American rodents. In Cavia an extremely high incompatibility exists among adult males. As a consequence, only a single male can be kept together with several females even in richly structured enclosures of 20 m2. From this, a polygynous mating system emerges. In contrast, under similar housing conditions male Galea are much more tolerant and large groups can be established consisting of several adult males and several adult females. The mating system of Galea is promiscuous because of the female's soliciting behaviour when receptive that makes it impossible for a single male to monopolize her. The diverging mating systems correspond well with functional variations in testis size and sexual dimorphism: the polygynous Cavia show low testis masses (weight of both testes = 0.58% of body weight) and body weights are 11% higher in males than in nonpregnant females. The promiscuous Galea have extremely high relative testis masses (1.86% of body weight) and non-pregnant females are 15% heavier than males. In the latter species promiscuous mating results in a high percentage of multiple paternities (> 80% in groups of 4 males and 6-7 females) as revealed by multi-locus DNA fingerprinting. Nevertheless dominant males achieve a significantly higher reproductive success than subordinates. The high frequency of overt aggression directed from dominant to subordinate males, therefore, may be a mechanism to lower the fertilizing capacity of the lower ranking males. Concerning the females' reproductive success we demonstrated in a mating experiment that Galea which were paired with four males and became pregnant, weaned significantly more offspring than females which were paired with a single male. Thus, for the first time a reproductive benefit from promiscuous mating is shown for a female mammal. Field studies in the natural habitats of Cavia aperea and Galea musteloides are now performed to elucidate whether the differences in social and mating systems can be related to differences in ecological conditions.

Vocal communication and individual variation in breeding south american sea lions

Abstract: The purpose of this study was to analyse the structure, social contexts, and individual variation of South American sea lion (Otaria flavescens) airborne vocal communication during the breeding season. This is the first comprehensive analysis of the vocal repertoire of this species. Since breeding colonies are complex acoustic environments, we expect that male, female, and pup vocalizations would show individuality, and that individual variation would rely on several acoustic traits. We identified four calls for adult males: high pitched call or HPC (aggressive interactions, such as attack and retreat displays, and fights), bark (aggressive interactions, territory establishment, and usually combined with growls), growl (male-female interactions), and exhalation (after agonistic encounters); and two for adult females: mother primary call or MPC (female-pup interactions, such as after birth, during pup separation, and pup development), and grunt (agonistic interactions between females). Juveniles vocalized yearling primary calls or YPC (searching for their mothers or after being threatened by females), pups gave pup primary calls or PPC (in response to MPCs, when hungry, searching for their mothers, if nursing was interrupted, or when trying to nurse). Our results suggest that male's HPC and bark, female's MPC, and pup's PPC have acoustic features that support individuality. These calls are associated with contexts in which recognition of neighbours (HPC and bark) or relatives (MPC and PPC) may confer a relative advantage in reproductive performance. Individual variation depended on frequency, temporal, and intensity traits; such multi-trait individuality could be regarded as an adaptation to colonial life to overcome the high noise levels within pinniped breeding colonies.

Finding One's Mate in a King Penguin Colony: Efficiency of Acoustic Communication

Abstract: In the king penguin, during the three months of incubation and the brooding stage, members of a pair alternate care duties on land with foraging trips. Contrary to most of the species of birds that nest at a fixed location, the king penguin carries its egg on its feet during incubation. This allows the incubating parents to move in the colony. Brooding or incubating parents moved on average 4.4 meters between egg-laying and the end of the brooding stage. This movement in a group of thousands of other birds reduced the reliability of visual cues for recovering the pair mate during the change-over. We showed that the difficulty in relocating the mate was more important during the brooding stage than during incubating. We confirmed earlier findings that acoustic communication was the main mode of communication during a change-over, and showed that the omnidirectional properties of sound allowed birds to reach more than five hundred other birds with each emitted call. Our experiments proved that the communication system is performed at short or medium range. On average, the birds identified their mate at a distance of 8.8 m. Seventy percent of the birds started the acoustic search of their mate when the distance was shorter or equal to this discrimination range, and so acoustic communication is a particularly efficient strategy in the king penguin.

Does the behaviour of the neonate influence the expression of maternal behaviour in sheep

Abstract: Maternal care is provided in response to cues from the offspring. The role of offspring stimuli in determining the quality of maternal care was assessed using the sheep (Ovis aries) as a model. The effects of variation in lamb behaviour on the expression of maternal behaviour in a hill (Scottish Blackface) and a lowland (Suffolk) breed of ewe was examined by embryo transfer of single embryos between the two breeds to give the four possible combinations of ewe and lamb. Labour was significantly shorter for both breeds of ewe when delivering Blackface lambs than Suffolk lambs. Blackface lambs were also significantly more active than the Suffolk lambs in the first 3 days after birth; there was no effect of maternal breed. Despite these differences in both length of labour and lamb activity at birth with lamb breed, the behaviours of the ewe associated with the onset of maternal care (e.g. licking the lamb, allowing the lamb to the udder, absence of aggressive behaviours) were unaffected by the breed of lamb. Suffolk ewes, however, were more likely to show an aversive reaction to their lamb, spent less time licking the lamb and were more likely to move as the lamb approached the udder. There was a significant influence of ewe breed on lamb sucking behaviour. Suffolk ewes received significantly more sucking attempts than Blackface ewes from both breeds of lamb. A higher sucking rate on Suffolk ewes continued over the first 3 days after birth. Other behaviours, such as playing, were specific to lamb breed and not affected by ewe behaviour at this time. These data suggest that offspring behaviour had no effect on the onset of bonding behaviours of the ewe. Neonatal lamb activity was also largely independent of the behaviour of their dam. However, sucking behaviour of the lamb was modified by ewe behaviour and this may affect the strength of the bond between ewe and lamb.

Female-female conflict in the harem of a snail cichlid (lamprologus ocellatus): behavioural interactions and fitness consequences

Abstract: Female intra-sexual competition plays an important role in the settlement process during pair or harem formation and in established harems of Lamprologus ocellatus , a small snail shell inhabiting cichlid from Lake Tanganyika. Larger females settle first and this could partly be due to male preference for larger females as shown in simultaneous choice tests but is also due to dominance of the larger female. Smaller females were unable to settle close to a larger one. Even when snail shells were not limiting the smaller was either unable to settle or had to settle at a considerable distance. This effect was independent of prior residence. Intense female-female aggression suggests that close settlement is disadvantageous to females. Genetic analyses of maternity using microsatellite length polymorphism at five loci showed a reproductive skew between females in a harem. Additionally, it proved brood mixing in aquaria as well as in the field. Brood mixing can be detrimental to female breeding success through interbrood cannibalism if size difference of juveniles amounts to 5 mm. Territoriality of juveniles, shown even between same-sized siblings, may cause indirect mortality through earlier dispersal of young. Females rejected experimentally added larger juveniles but accepted young smaller than their own fry. Acceptance of smaller juveniles could be advantageous through a dilution of predator attacks but it also appears to induce costs since females with young at the shell do not rear another brood. Large median distances of 91 cm maintained aggressively between breeding females in the field may serve to minimize the adverse effects of breeding in a harem.

The risk of cannibalism and male mating behavior in the mediterranean praying mantid, iris oratoria

Abstract: This study examined male behavior in response to the risk of cannibalism in the Mediterranean praying mantid, Iris oratoria (Mantodea: Mantidae). The risk of cannibalism was manipulated by placing males in one of two positions at the start of a mating trial: Frontal, where the males faced the females' fronts (high risk of cannibalism), or Rear, where the males were behind the females, facing their posteriors (lower risk). Three male behaviors were examined in terms of risk-reduction: whether the male attempted to mount the female, the direction of his first mount attempt, and the time taken for him to attempt to mount. Initial position did not have a significant effect on whether males attempted to mount the females. Males showed a preference for non-frontal mount attempts, and males placed Frontally were less likely to mount from their initial direction than were males placed in the Rear. Males placed in the Rear attempted to mount sooner than males placed Frontally, especially if the males could approach and mount while remaining behind the females. While the males approached the females, movements by both sexes resulted in changes in how the males faced the females,

Contrafreeloading in starlings : Testing the information hypothesis

Abstract: Contrafreeloading (CFL) behaviour, in which animals forage persistently in patches that require effort to exploit when patches containing ad lib. food are easily available, seems to contradict the predictions of optimal foraging theory. However, it has been proposed that contrafreeloaders are in fact exploiting a hidden resource, namely information about patches that may be useful in future foraging attempts. We performed two experiments on starlings Sturnus vulgaris to test this hypothesis by determining the circumstances in which CFL occurs and assessing whether any useful information is acquired by animals performing the behaviour. In accordance with previous results we found that CFL is reduced when foragers are previously deprived of food and also when there are means of gathering information aside from sampling (namely when patches that require effort to exploit can be visually inspected). We also found that useful information is acquired by birds that perform CFL, in that when subsequently tested in extinction with the best patch removed they reliably chose the patch that had been the second best. These results are consistent with the information gain hypothesis. However, birds with low levels of CFL did not perform discernably worse in this test of patch knowledge and experimental reductions in CFL achieved through deprivation treatments did not produce apparent reductions in useful information possessed.

The 'whinny' of spider monkeys: individual recognition before situational meaning

Abstract: When spider monkeys (Ateles geoffroyi) are dispersed and moving through wooded areas in the dry forest of Santa Rosa National Park in Costa Rica, they give loud calls, whinnies, that can be heard over long distances and appear to be answered with the same call from other monkeys. We examined the circumstances in which this vocalization was emitted and the responses elicited from other group members. A total of 105 h of continuous recordings on emission of whinnies, 113 h of individual focal samples and 291 spectrograms were analyzed from a study group with 15 identified subjects. Whinnies emitted in different circumstances caused different reactions. Whinnies provoked by the sight of an observer were never responded to in any particular way, while those given during resting or feeding sometimes caused an active response of approach or calling. Most strikingly, whinnies given during group movement provoked hearers to approach or call significantly more often than either those given while feeding or resting. Playback experiments found one response, 'scan', to differ according to the original circumstances of emission of the broadcast call: monkeys scanned more in the direction of the sound when hearing feeding rather than group movement whinnies.

The importance of being larger: intraspecific competition for prime web sites in orb-web spiders (araneae, araneidae)

Abstract: The effects of two contrasting habitats on the distribution and the body condition of Larinioides sclopetarius (Clerck, 1757) were studied in an urban area. Throughout the season, significantly more spiders of all size classes were found in the prime habitat, which was characterised by the presence of artificial light and, consequently, a superabundance of prey. The higher food intake in the prime habitat also resulted in a better body condition of immature spiders. During periods of high spider density, small immatures were found more frequently than expected in the lower ranked habitat, which contained no artificial light and significantly less prey, while larger conspecifics exclusively foraged in the prime habitat. High females density in the prime habitat coincided with decreasing density and decreasing territory sizes of smaller immatures.