bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Foraging in Peromyscus Polionotus: the Influence of Item-Size and Predation Risk
Authors: Phelan John P. , Baker Richard H.
Published: April 2008

Predictions of optimal foraging theory were tested for Peromyscus polionotus in the laboratory and in two field experiments in which seed item-size was manipulated. In the laboratory, handling times for millet, sunflower seeds, and peanuts were determined. Additionally, energy/handling (E/h) time values were calculated and seed preference experiments were conducted. Mice showed a clear preference for the seeds more profitable in terms of E/h. Seed preference experiments were also conducted in the field to determine the relative influence of optimal foraging and predation risk in diet choice. In the first of the two field experiments, behavioral strategies to reduce predation vulnerability could not influence differential seed selection. As predicted, the mice again showed a preference for the more profitable seed type. In the second experiment, animals were presented with conflicting demands because foraging on a more abundant, but less preferred, seed type afforded the animal an increased ability to avoid predators. Presented with this opportunity to reduce the risk of predation, the animals shifted their preference to the safer, but less profitable food. This shift in seed preference was accompanied by predation-risk-reducing changes in spatial foraging patterns.
Perception of Distress Call Harmonic Structure By the Starling (Sturnus Vulgaris)
Authors: Aubin T. , Bremond J.C.
Published: April 2008

To examine the ethological role of signal composition in the distress calls of starlings (Sturnus vulgaris), we conducted a series of playback experiments in the field. Earlier researches revealed that frequency modulations are important features of distress calls for triggering the responses of starlings. Another feature, the harmonic structure, was thought to play a role in the coding/decoding process of the call. The aim of this work was to investigate the role of this structure. Four points emerge from these experiments: 1) Ethological message is effectively encoded in the harmonic structure. 2) Wide-band frequency spectra are preferred to narrow-band spectra. 3) Starlings examine the width of the spectrum but not the interval between frequency bands. 4) Spectra with a high intensity upper part produce a stronger response than other types of spectra. Such a coding/decoding process is discussed regarding transmission of information at long range, the ability to appreciate distance, to locate the caller and the possibility of grading the information.
Habitat Shift After Experimental Removal of the Bigger Species in Sympatric Ctenomys Talarum and Ctenomys Australis (Rodentia: Octodontidae)
Authors: Vassallo Aldo I.
Published: April 2008

A removal trapping experiment was conducted in the field to investigate if microhabitat choice and population characteristics of Ctenomys talarum are affected by the bigger, dominant Ctenomys australis, in a zone where these subterranean rodent species are geographically sympatric. As reported previously by other authors, the species were distributed in a habitat segregation pattern which characterized the initial state, prior to C. australis removal. I detected a significant habitat shift-that is, changes in microhabitat choice by C. talarum individuals- in response to C. australis removal. However, it is remarkable that this only occurred after one year of continuous removal of C. australis, and was restricted to a very small expansion by C. talarum into the fringe of the area previously occupied by the dominant species. In addition, a slight increase of the C. talarum population density took place which was possibly due to the absence of the other species. It is suggested that the microhabitat typical of C. australis (with deeper, more friable soil and less vegetation) could be suboptimal and thus unpreferred for C. talarum. If the pre-experimental C. talarum population was satiated to its carrying capacity, it is possible that the small number of C. talarum individuals-mostly subadults-had invaded areas previously occupied by C. australis because they had no other choice than a suboptimal habitat. No substantial changes were detected in other population characteristics (sex ratio, age structure, distance between individuals) which were very similar to that in a control area. Interspecific interactions and displacement by the bigger C. australis could be significant but nonetheless marginal in sustaining the pattern of microhabitat segregation between the species. Difference in habitat preference, linked with species differences in body size and colour, are probably of much greater importance.
The Interaction of External and Internal Factors in the Courtship of Parasitic Wasps (Hym., Pteromalidae)
Authors: Jachmann F. , VAN DEN ASSEM J.
Published: April 2008

Our topic of interest is the causal organization of courtship and mating behaviour of parasitic wasps (Hymenoptera, Pteromalidae), more especially that of Nasonia vitripennis. Males pursue newly emerged females over a short distance, mount on top, and take up a position at the front, the fore tarsi placed on the female's head. Courtship displays consist of characteristic combinations of motor patterns, which are repeated a variable number of times in so-called courtship cycles. Movements with the wings, head, mouthparts, and antennae are conspicuous components. This applies in particular to head-nodding movements, which occur in series. A female may become sexually receptive while being courted; she signals the onset of this condition with a movement of her antennae. The male will react promptly: he stops courting and backs up into the copulatory position. The signal coincides almost invariably with the first nod of a series; signalling at other times led to a postponement of the backing-up reaction. Because Nasonia males readily court on dummy females, we used a dummy with moveable antennae to investigate the temporal relationship of signal and reaction. We observed two types of postponed backing-up reactions: simple backing up, and backing up after performance of one or more display movements. At the same time, we found a quantitative relationship between durations of the latencies, and the timing of the signal relative to the display. Our investigations produced evidence for endogenous, periodic changes, which take place during the succession of courtship cyles. The postponed backing-up reactions of different types could be explained in terms of interactions between the effects of signalling and the endogenous dynamics of courting males.
Differences in Site Fidelity Among Territorial Males of the Carpenter Bee Xylocopa Varipuncta (Hymenoptera: Anthophoridae)
Authors: Alcock John
Published: April 2008

Lekking males of the carpenter bee Xylocopa (Neoxylocopa) varipuncta compete for landmark territories, where they are occasionally visited by receptive females. In a study conducted over three flight seasons, less than 10% of marked males qualified as long-term residents (i.e. bees that held the same hovering station for 90 min or more on at least two afternoons). However, among the small minority of long-term residents were some bees that returned to the same landmark for up to 3 hr every afternoon for several weeks. These males defeated many intruders in aerial combat during each afternoon. The hypothesis that site-faithful males were individuals of unusual resource-holding power is not supported. Long-term residents were not larger on average than short-term territory holders. Moreover, the frequency of mating by long-term residents was very similar to that of males in the general population, suggesting that long-term residents did not hold territories that were exceptionally attractive to females. Thus, the basis for site fidelity in this species remains elusive. The rarity of site-faithful males in this species may be related to great daily fluctuations in the numbers of potentially receptive females visiting the landmark territories, which may make the timing of male mate-attracting behavior far more important than regularly returning to defend any one site.
Risk-Taking By Juvenile Vervet Monkeys
Authors: Fairbanks Lynn A.
Published: April 2008

Because of their greater vulnerability to mortality, juveniles might be expected to be more conservative than adults in response to novel and potentially threatening situations. Results from research on vervet monkeys (Cercopithecus aethiops sabaeus) in the field and in captivity suggest that the opposite is true. Juveniles in the field were more likely to approach a human observer, and in captivity they had shorter latencies to enter a new area, approach a novel food container, and come within a meter of a strange adult male when compared to younger and older animals. In all four test conditions, risk-taking was an inverted U-shaped function of age. Latency to approach in unfamiliar and potentially dangerous situations declined from birth to two years of age, then increased with age to adulthood.
Polyandry and Incest Avoidance in the Cooperative Stripe-Backed Wren of Venezuela
Authors: Piper Walter H. , Slater Gary
Published: April 2008

We made behavioral observations in 37 social groups of the communal stripe-backed wren during 1990 and 1991 to investigate the recently-discovered shared paternity between dominant and subordinate males (or "SMs"). We found two distinct kinds of social groups that differed in terms of social behavior: "mother" groups, which contained only subordinate males that were sons of the dominant female (termed "DF-sons"), and "stepmother" groups, which contained at least one subordinate male unrelated to the dominant female (termed "DF-stepsons"). In mother groups only dominant males courted dominant females, mate-guarding was infrequent and aggression by dominant males toward other males was absent. On the other hand, stepmother groups were characterized by frequent association with and courtship of dominant females ("DFs") by both dominant males ("DMs") and DF-stepsons and relatively frequent aggression by dominant males toward DF-stepsons. DF-stepsons, moreover, sired 15% of all young in stepmother groups. Thus, incest avoidance dictated the behavior of subordinate males, and the mating system in wren groups was either monogamous or polyandrous, depending upon the relatedness between subordinate males and the dominant female.
Aggressive Performance as a Behavioral Correlate of Plumage Polymorphism in the White-Throated Sparrow (Zonotrichia Albicollis)
Authors: Kopachena Jeffrey G. , Falls J. Bruce
Published: April 2008

Morph and sex-specific differences in aggressive performance were examined in the white-throated sparrow. Among the four morph/sex classes, white-striped males had the strongest response to white-striped models and were the most likely to approach and attend song playbacks independently. The slightly weaker responses of tan-striped males and white-striped females were similar to each other. Tan-striped females were the least aggressive. Aggression by white-striped females enabled tan-striped male x white-striped female pairs to perform as well, or better, than white-striped male x tan-striped female pairs. Tan-striped males paired earlier than white-striped males. An increased prevalence of territorial tan-striped males corresponded to the arrival of females on the breeding grounds. The data are consistent with the hypothesis that negative assortative mating benefits tan-striped males through the supplemental aggression of white-striped females. However, the apparent preference of white-striped females for tan-striped males suggests that there are benefits to negative asortative mating other than those that might arise from differences in aggressive performance.
Sexual Preferences of Female Zebra Finches: Imprinting On Beak Colour
Authors: Weisman R. , Shackleton S. , Ratcliffe L. , Weary D. , Boag P.
Published: April 2008

Sexual preferences of adult zebra finches are influenced by early learning of parental characteristics. We studied how imprinting affects the preference of female zebra finches for male beak colour. The beaks of male and female parents were painted, 2-3 days before hatch and thereafter until the young were fledged, as follows: male red, female orange (R-O group); male orange, female red (O-R group); both male and female red (R-R group); or both male and female orange (O-O group). Females were raised by painted parents until 35 days, then visually isolated from other birds until test at 100 days. In 4-way choice tests using red- and orange-painted stimulus males, females from Groups O-R and R-O chose males with beaks painted the same colour as their father's beak, whereas females from Groups R-R and O-O did not. We conclude that preference for male beak colour was acquired only by females reared by parents with unlike, discriminative, beak colours. The results suggest an associative learning basis for sexual imprinting.
Repertoire Turnover and the Timing of Song Acquisition in European Starlings
Authors: Chaiken Marthaleah , BÖHNER JÖRG , Marler Peter
Published: April 2008

In order to establish unambiguously whether a reputed open-ended learner, the European starling, could memorize new songs in adulthood, we exposed hand-reared male starlings to a series of either live conspecific tutors or tape recordings of conspecific song over a period of 18 months, and isolated them from any other exposure to conspecific song. The song motifs produced by the birds were compared with those of their tutors or training tapes to infer the time of motif memorization. We found that the starlings continued to memorize and produce new song motifs, both within and between breeding seasons, up to the age of at least 18 months. Not all the new motifs in the repertoires had been recently memorized; in some cases there was an apparent lag of a year and a half between memorization and production. There were no significant differences between live-tutored and tape-tutored groups in the timing of learning or in the rate of repertoire turnover (55-92% new motifs in each repertoire sample), although, as we have reported previously, live-tutored birds imitated a greater number of motifs and developed larger repertoires.
Predator Inspection Behaviour Covaries With Schooling Tendency Amongst Wild Guppy, Poecilia Reticulata, Populations in Trinidad
Authors: Magurran Anne E. , Seghers Benoni H.
Published: April 2008

When fish inspect a predator they incur risk. One way of reducing the cost of inspection is to approach predators in groups large enough to benefit from the safety in numbers advantages of schooling. In a survey of nine populations of guppies, Poecilia reticulata, in their native streams in Trinidad, we observed marked variation in schooling behaviour. Guppies from sites also inhabited by a major predator, the pike cichlid, Crenicichla alta, devoted more time to schooling than those from less dangerous locations where the cyprinodont Rivulus hartii was present. We found a strong correlation between schooling tendency and the group sizes adopted by guppies inspecting a realistic model predator. Since guppies in dangerous localities approached a potential predator in large groups it seems unlikely that many of these fish were caught in a Prisoner's Dilemma. Inspections by singleton fish were rare in high-risk locations but predominated in those populations where risk from fish predators was reduced.
Age, Sex and Prior Site Experience Have Independent Effects On the Foraging Success of Wintering Snow Buntings
Authors: Smith Richard D. , Metcalfe Neil B.
Published: April 2008

Intraspecific variation in foraging success amongst birds is often associated with differences between individuals in competitive ability or experience. However, it is usually difficult to separate the importance of experience per se from that of age. Here we examined the feeding rates of wintering snow buntings (Plectrophenax nivalis) at Cairn Gorm, North-east Scotland in both competitive and non-competitive situations. Although flock-size/density and stage of the feeding bout accounted for most of the explainable variation in peck-rates, there remained significant and additive residual effects of both age and prior experience of the site (older/more experienced birds achieving higher feeding rates) and these effects were very similar for birds feeding alone or in flocks. Sex differences in feeding rates were only apparent in large flocks, where males (the dominant sex) had faster peck-rates than females. Birds without previous experience (whether age or site-related) showed increases in relative feeding rate during the course of the winter, whereas experienced birds did not. This suggests that the differences between experienced and inexperienced birds were due to learning rather than the disproportionate loss of poor foragers.
Affiliation Patterns Among Male Costa Rican Squirrel Monkeys
Authors: Boinski Sue
Published: April 2008

Remarkably close male bonding exists among Costa Rican squirrel monkeys, Saimiri oerstedi. In this population males were philopatric, exhibited no male-male within-troop aggression, and only very slight evidence for a dominance hierarchy. Juvenile, young and full adult males were spatially clumped in same-age male cohorts. A less intense, secondary association was also shown between the young and full adult male cohorts. These associations were most dense over a spatial scale of 5 m or less, but can also be detected in a 5-10 m distance from a focal male. Males also cooperated in 1) sexual investigation of females during the mating season, 2) aggressive interactions with males of neighboring troops, and 3) valiant defense of infants and subadults from potential predators. In contrast, the spatial association among adult females never exceeded random expectations and only a transitory period of cooperation was observed among mothers during the birth season. Furthermore, there was little evidence of bonds between the sexes. Seasonal variation in affiliation patterns was best explained by fluctuations in food availability and, secondarily, reproductive activity. These results are surprising both from the perspective of the general pattern of male affiliation among primates and the often marked aggression and dominance relationships among males documented in captive and wild populations of South American squirrel monkeys. The ultimate explanation is suggested to be the disparate distribution of fruit resources exploited by South and Central American squirrel monkeys, mediated by effects on female affiliation and dispersal patterns.
Use of Two Singing Modes By Hooded Warblers as Adaptations for Signalling
Authors: Haven Wiley R. , Godard Renée , Thompson Andrew D.
Published: April 2008

Hooded warblers Wilsonia citrina use two modes of singing, repeat mode (one pattern sung repeatedly) and mixed mode (2-4 other patterns sung in irregular sequence). Intensive focal-individual sampling of 14 males documented the use of these modes of singing throughout the nesting cycle. Males of different ages (first breeding season or later) did not differ in use of the two modes. Time spent singing in repeat mode decreased markedly after acquiring a mate, but time spent singing mixed mode did not change significantly across stages of the nesting cycle. Males sang more when their neighbors sang at a distance of 25 m or more. Repeat mode increased in this situation before a male acquired a mate, while mixed mode increased afterwards. Near a neighbor (within 25 m), males avoided use of repeat mode. Nearby females before the onset of incubation evoked increased use of repeat mode. More distant, calling females elicited little response before incubation, but thereafter calling females tended to suppress all singing. Males used mixed mode proportionately more in locations nearer neighbors. There were no indications that variation in singing influenced the dates on which males acquired mates. Unmated males late in the breeding season sang persistently in repeat mode, even more than eventually mated males had early in the season before they acquired mates. These results provide support, with some reservations, for three hypotheses for the evolution of distinct modes of singing: (1) specializations for male and female listeners; (2) specializations for indicating conditional behavioral tendencies; and (3) specializations for communication in low- and high-noise situations. These hypotheses are not mutually exclusive, and all three in combination might offer the strongest explanation for the evolution of distinct singing modes in this species and other paruline warblers.
Sex-Role Reversal in the Black-Chinned Tilapia, Sarotherodon Melanotheron (RÜPpel) (Cichlidae)
Authors: Balshine-Earn Sigal , Mcandrew Brendan J.
Published: April 2008

In the animal kingdom most species follow standard sex roles: males compete more intensely for mates and females exert greater mate choice. Recent theory suggests that the direction of sexual selection is the outcome of sexual differences in potential reproductive rates (PRRs): the sex with the higher PRR will compete for mates and the sex with the lower PRR will be most selective. This study tests the theory experimentally by examining competition for mates and mate choice in the black-chinned tilapia, Sarotherodon melanotheron, a paternal mouth brooding cichlid. In this species, the PRR of males is lower than that of females. In laboratory competition trials, females were more aggressive: they bit, chased and initiated mouth fights more often than males. Dominant females were also much better at monopolising potential mates compared to dominant males. A second experiment confirmed that males were choosy for size, preferring large partners over small ones, while females did not discriminate for size. Therefore, the prediction of sex role reversal (competitive females and discriminating males) is confirmed.
Parent-Offspring Feeding Relationship of Coots (Fulica Atra) in a Varying Environment
Authors: Amat Juan A.
Published: April 2008

Predictions derived from parental investment theory indicate that when the reproductive value of offspring decreases, parental investment should also decrease. If so, it should be expected that in adverse years, parental investment should be lower, given the lower survival prospects of chicks, than in more favourable years. I tested this by recording the frequency with which coots (Fulica atra) fed their chicks during a ten years period in a set of lakes that experienced considerable interannual variations in water levels. Contrary to the prediction, I found that during drier years, chicks were fed more frequently than during wetter years, in which self-feeding by chicks was more frequent. The reason for this could be that for coots the crucial factor for improving reproductive success is the quality rather than the quantity of chicks, and by increasing parental effort during more adverse years, the lower survival prospects of chicks could be attenuated. However, late in the breeding season, when fledging success is lower, chicks were fed by their parents less frequently than in the early breeding season. This could be related to a change in the cost/benefit ratio, itself independent of offspring quality, that parents experience when rearing chicks late in the season due to the start of plumage moult.
More Is Not Always Better: Male Incubation in Two Acrocephalus Warblers
Authors: Kleindorfer Sonia , Fessl Birgit , Hoi Herbert
Published: April 2008

This study investigates male and female incubation ability in two monogamous Acrocephalus warblers with overlapping, equally sized territories and similar prey abundance. Given the longer breeding time window of the moustached warbler (A. melanopogon) compared with the reed warbler (A. scirpaceus), the trade-off between the need for biparental care and the cost of inefficient incubation is discussed. Hourly protocols and egg temperature measurements were analyzed with regard to four primary questions: male and female incubation ability, the role of environmental parameters, hatching success and the influence of male incubation on female time allocation. In both species, males increase egg temperature per minute at a slower rate than do females. There is no species difference in the percentage of incubation per hour for males (20%) or females (50%). Ambient temperature influences male incubation only in the moustached warbler during the early season (April) when male incubation correlates with hatching success. The male reed warbler shows daily temporal selectivity throughout the breeding season, increased incubation during rainfall, and no correlation with hatching success. In both species, females receive direct benefits of increased foraging time through male incubation. However, only the female reed warbler adjusts her incubation duration to previous male incubation. Thus, female reed warblers maximise the male component and thereby reduce the total incubation phase with high male effort whereas the incubation phase is increased with above average male effort in the moustached warbler.
The Effect of Hunger On the Learning of New Food Preferences in the Mongolian Gerbil
Authors: Forkman Björn
Published: April 2008

A new and more profitable food type was introduced to three groups of Mongolian gerbils (Meriones unguiculatus). When first presented with the new food one group was sated, another was hungry and the third group was hungry and expected a food shortage. In addition to the new food all groups had access to familiar food during the experimental sessions. The group that expected a food shortage had a lower intake of new food than either of the other groups, both in absolute and relative numbers. Both the sated and the hungry group ate the same absolute amount of new food during the first presentation, but since the sated animals had a lower total intake, the new food represented a higher proportion of the intake for these animals. The animals were then tested during the subsequent days (all groups now hungry). Thc group that had been sated showed a stronger preference for the new and profitable food than the hungry group, which in turn showed a stronger preference than the expected food shortage group. This means that in a semi-natural situation a strong need may actually decrease the rate of learning. The results can be explained in terms of risk prone/risk aversive behaviour along the lines of previous studies of risk sensitivity in optimal foraging. In an additional experiment it was shown that sated individuals will decrease their total intake of food when presented with both new and familiar food, in comparison with when only familiar food is present. This may have the effect of enhancing learning about the new food.
Avoidance Response By Adult Newts (Cynops Pyrrhogaster and Notophthalmus Viridescens) To Chemical Alarm Cues
Authors: Marvin Glenn A. , Hutchison Victor H.
Published: April 2008

Many fishes and aquatic invertebrates use chemical alarm cues to avoid predation, however relatively little is known about the occurrence of chemical alarm cues in amphibians. We tested the response of adult fire-bellied newts (Cynops pyrrhogaster) and red-spotted newts (Notophthalmus viridescens) to chemical cues from damaged tissues of newts and other salamanders. Both species avoided chemical cues from a conspecific skin extract. Notophthalmus viridescens also avoided chemical cues from C. pyrrhogaster skin extract, but the converse was not true. Neither species avoided chemical cues from a conspecific viscera extract, plethodontid salamander (Desmognathus and Plethodon) skin extracts, or a conspecific skin extract which had been heated. These results indicate that the avoidance behaviour is an alarm response to chemical cues released from damaged newt skin and is not a general response to chemical cues from damaged salamander tissue. This study provides the best evidence to date for an avoidance response by caudate amphibians to chemical alarm cues.
Intertidal Breeding and Aerial Development of Embryos of a Stickleback Fish (Gasterosteus)
Authors: Macdonald J.F. , Bekkers J. , Macisaac S.M. , Blouw D.M.
Published: April 2008

Males of the newly discovered 'white' stickleback disperse their embryos over the filamentous algae in which they nest and, unlike any other stickleback, they provide no subsequent parental care. Previously known populations of white sticklebacks nest only in shallow subtidal waters where filamentous algae are abundant. Our purpose in this paper is to describe highly divergent populations at Spry Bay, Nova Scotia, Canada, in which males build nests on bare rock in the subtidal and intertidal zones, and disperse their embryos over bare rock. Intertidal embryos are exposed to air and are vulnerable to desiccation at low tide. Field studies reveal that nests are built from locally available materials directly on the rock substrate. They are constructed very quickly and tend to be less substantial than subtidal nests. Internest distances are shorter in the intertidal zone than in adjacent subtidal areas. Dispersed intertidal embryos tend to settle into crevices between stones where the microenvironment remains moist and temperate between tides due to the presence of organic detritus and shade. Such embryos survive, develop, and hatch. Similar behaviours occur at other sites in Nova Scotia, and we know that it has persisted for at least four years at Spry Bay. We conclude that breeding and dispersing embryos over bare rock substrate, and intertidal breeding, are novel but stable breeding repertoires. We hypothesize that they have evolved secondarily to the evolution of emancipation from parental care in the white stickleback.
Temporal Structure in Stickleback Behaviour
Authors: Sevenster P. , FEUTH-DE BRUIJN E. , Huisman J.J.
Published: April 2008

Research was started into a possible circadian periodicity in the behaviour of the threespined stickleback. The behaviour of solitary males in the sexual phase of their breeding cycle was studied under constant conditions, including illumination of constant brightness (LL). No, 'free-running', circadian rhythm was found. Both the frequency of nest-visits and the rate of creeping-through (which shows an ultradian periodicity) were remarkably constant over long periods. Also, operant conditioning experiments, in which the male could switch the lights on or off, did not reveal any circadian fluctuation in the preference for light or dark. In the course of the long-term recordings 'rest-periods' were found, lasting some 10 to 50 minutes, in which the fish was surprisingly inactive, and did not visit the nest. Although some characteristics of these 'rest-periods' seem to point to a 'sleep-like' nature, others seem to argue against this.
Attachment and Social Withdrawal in Autism: Hypotheses and Findings
Authors: Buitelaar J.K.
Published: April 2008

Autism is characterized by an impaired development in social interaction and communication and a markedly restricted repertoire of activities and interests. This paper summarizes the research into the social abnormalities in autism, and reviews the empirical support for two behavioural hypotheses on autism, i.e. that autism results from impaired attachment, or from intense and prolonged approach-avoidance conflicts. The core social impairment of autistic subjects seems to be a deficit in attunement and timing of actions and reactions rather than a difference in frequencies of behaviours. Attachment behaviour of most, if not all autistic children tends to be disorganized; nevertheless, they do form attachment relationships in terms of preferential proximity seeking or reunion behaviour in the Strange Situation Test. Attachment studies performed sofar however have methodological limitations ; particularly the study of maternal-infant attunement and reciprocity has been neglected. Empirical evidence fails to support the presence of approach-avoidance conflicts in autistic subjects, and is further at variance with the predicted consequences of such conflicts. Insufficient attention has hitherto been paid to the clinical heterogeneity of autism in behavioural studies. A promising approach to deepen our understanding of the development of the autistic symptomatology is the early detection and subsequent behavioural study of 1-2 year old children at high-risk for autism. Finally, behaviour observation studies in autistic subjects are likely to benefit from the concurrent assessment of physiological indices of arousal, and from the integrated measurement of social-cognitive processes.
Absence of 'Youngest Ascendancy' in the Dominance Relations of Sisters in Wild Japanese Macaques (Macaca Fuscata Yakui)
Authors: Hill David A. , Okayasu Naobi
Published: April 2008

Dominance relations among females were studied in a small, well-habituated troop of Yakushima macaques (Macaca fuscata yakuz) in southernjapan. Data were collected using focal animal sampling over a 20-month period. Although the frequency of aggression was much lower than that reported for provisioned groups, and support in agonistic interactions was rare, a clear linear dominance hierarchy was apparent. In each of the four pairs of sisters in the troop the older was dominant to the younger. This is contrary to the pattern commonly reported for provisioned groups of Japanese and rhesus macaques, in which dominance among sexually mature sisters tends to be inversely correlated with age. For each pair of sisters in the study troop the mother was alive and healthy when the younger daughter became sexually active, but no cases were seen of a mother aiding one daughter against another. We therefore conclude a) that the absence of youngest ascendancy was due to a lack of support, rather than a lack of potential allies, and b) that both frequent agonistic support and youngest ascendancy are most likely to occur under conditions where concentrated food resources result in frequent and intense aggression.
Induction and Development of a Filial Predisposition in the Chick
Authors: Hampton Neil G. , Bolhuis Johan J. , Horn Gabriel
Published: April 2008

Filial preferences in young domestic chicks, Gallus gallus domesticus, are influenced by at least two systems: one involved in learning about stimuli to which the animals are exposed, and the other a predisposition to approach stimuli resembling conspecifics. The predisposition is manifest in dark-reared chicks as an emerging preference for a rotating, stuffed jungle fowl over a rotating red box. In previous studies, 24 h-old visually naive chicks were placed in running wheels for 2 h. Throughout this time the chicks were in darkness. A significant preference for the stuffed fowl was found 24 h, but not 2 h later. In the present study it was shown that the predisposition becomes manifest at 10 h (Experiment la) and 5 h (Experiment 1 b) after either placement in running wheels, or after the chicks had been trained by exposure to a rotating red box. In Experiment 2 it was shown that placement in running wheels was not necessary for the predisposition to emerge. However, handling the birds was sufficient for the induction of a significant preference, expressed 5 h later. Exposure to a maternal call for 2 h (Experiment 3) was also sufficient to induce the development of the visual predisposition 24 h later. These results show that a visual predisposition to approach certain stimuli becomes manifest in dark-reared chicks between 2 and 5 h after the experience of handling, and that exposure to a maternal call is also sufficient to induce this predisposition.
Escape Behaviour of Juvenile Psammodromus Algirus Lizards: Constraint of or Compensation for Limitations in Body Size?
Authors: Martín José , López Pilar
Published: April 2008

We compared the escape behaviour of juvenile and adult Psammodromus algirus lizards, by using data of escape performance in the laboratory and field observations of escape behaviour. We specifically examined whether a differential escape response is a constraint of body size, or whether juveniles behave differently in order to maximize their escape possibilities taking into account their size-related speed limitations. In the laboratory, juvenile lizards were slower than adult lizards, and escaped during less time and to shorter distances, even when removing the effect of body size. In the field, juveniles allowed closer approaches and after a short flight usually did not hide immediately, but did so after successive short runs if the attack persists. Approach distance of juveniles was not affected by habitat, but initial and total flight distances were shorter in covered microhabitats. There was no significant effect of environmental temperature on approach and initial flight distances of juveniles. However, the total flight distances were significantly correlated with air temperatures.
Ranging of Conspecific Songs By Kentucky Warblers and Its Implications for Interactions of Territorial Males
Authors: Haven Wiley R. , Godard Renée
Published: April 2008

Kentucky warblers (Oporornis formosus) each sing a single song pattern. To determine whether males could range (estimate the distance to) conspecific songs, we presented clean and reverberated versions of strangers' songs to 12 males in a factorial design. To assess differences between the playbacks and the subjects' own songs or neighbors' songs, we measured differences in minimal repetition periods between repeated acoustic elements in songs, features that could contribute to assessment of reverberation. Results indicated that Kentucky warblers can range conspecific songs and that similarity between playback songs and established neighbors' songs or a subject's own songs did not enhance this ability. Direct evidence that males misjudged the distance to reverberated playbacks excluded other interpretations of the results based on differences in the detectability or habituation of clean and reverberated songs. These results suggest further that assessment of reverberation is sufficient for ranging and that perceptual analysis of song is not necessarily linked to overt production. As a consequence, repertoires of songs do not necessarily promote interference between territorial neighbors.
Responses To Songs With Altered Tonal Quality By Adult Song Sparrows (Melospiza Melodia)
Authors: Strote Jared , Nowicki Stephen
Published: April 2008

Pure-tone sounds are a common and distinctive feature of many birdsongs. We used field playback experiments to test whether this tonal quality is perceptually salient to adult male song sparrows in the context of song recognition, by comparing responses to playback of normal songs with responses elicited by songs that had harmonics added. This species was chosen for study based on the recent finding that young song sparrows do not show a preference for songs with pure tones over songs with harmonics when choosing model songs to copy during their sensitive phase for learning. We found adult song sparrows to be significantly more responsive to normal song than to harmonic song, consistent with results from adult birds of other species. We conclude that the perceptual salience of the tonal quality of song changes during ontogeny or is context-dependent.
Behavior of Male and Female Zebra Finches Treated With an Estrogen Synthesis Inhibitor as Nestlings
Authors: Adkins-Regan E. , Yang S. , Mansukhani V.
Published: April 2008

In order to test hypotheses about the organizational role of early estrogen in
the sexual differentiation of behavior in zebra finches (Taeniopygia guttata),
newly hatched birds were given one of three treatments: (1) daily injection with
an aromatase inhibitor (fadrozole hydrochloride) for the first week; (2) the
same treatment for the first two weeks; (3) daily injection of the vehicle for
one or two weeks. As adults, birds were implanted with testosterone propionate
and underwent a three-phase testing procedure designed to measure singing,
dancing, copulation, and preferences for male vs female partners. Males were
completely unaffected by fadrozole hydrochloride treatment; they sang, danced,
and mounted at control levels, and like control males they preferred female
partners. Females were similarly unaffected, with one important exception: those
treated with fadrozole hydrochloride during the first week preferred to be spend
time near females instead of males in choice tests, unlike control females.
These results suggest that a model of zebra finch sexual differentiation in
which estrogen organizes male-typical behavior is unlikely to be correct. At the
same time, they provide evidence that a key dimorphic feature of mate choice,
preference for opposite-sex birds (sexual orientation), may result from
organizational hormone actions during the early post-hatching period in this
pair-bonding species.
Silk Investment in Gifts By Males of the Nuptial Feeding Spider Pisaura Mirabilis (Araneae: Pisauridae)
Authors: Lang Andreas
Published: April 2008

Adult males of the hunting spider Pisaura mirabilis wrap up prey with silk and pass these nuptial gifts to females prior to copulation. The females digest the nuptial gifts, including the silk, during mating. Laboratory experiments were carried out to determine the amount of silk males of P. mirabilis invest in nuptial gifts, and its possible role in sexual reproduction. The amount of silk was always small, indicating that the silk of the nuptial gift has little nutritional value for females. Males that had more time to wrap up the prey produced a larger amount of silk. Starved males required more time than satiated males to produce a given amount of silk. A larger male body size had a positive effect on the amount of silk. In general, the size of the prey used for nuptial gifts had no influence on the amount of silk. However, due to handling problem, smaller males produced no silk for very large flies. Females took more time to digest a nuptial gift with a larger amount of silk than a nuptial gift with a smaller amount of silk. A possible interpretation of the adaptive significance of wrapping is that males use silk to prolong the copulation time during mating.
Pair Bonds in Monogamous Apes: a Comparison of the Siamang Hylobates Syndactylus and the White-Handed Gibbon Hylobates Lar
Authors: Palombit Ryne A.
Published: April 2008

Descriptions of the social systems of gibbons (Hylobates, Hylobatidae) have typically emphasized generically uniform attributes such as 'monogamy' and 'territoriality'. This has prevented testing of the hypothesis that pair bonds differ in the siamang (Hylobates syndactylus) and the white-handed gibbon (Hylobates lar) (Chivers, 1972). I replace a description of sociality based on mating system and group size/composition with quantitative measurement of social interactions and spatial relations between wild adult males and females in three heterosexual pairs of siamang and two pairs of white-handed gibbons studied for 2.5 years at the Ketambe Research Station (Sumatra, Indonesia). Siamang pair bonds show greater heterosexual cohesion than those of white-handed gibbon as reflected in higher rates of affinitive interactions such as close proximity, relaxed physical contact, embraces, and communal use of sleep trees. Although males are more responsible than females for the maintenance of close proximity in both species, sex differences in intra-pair allogrooming suggest divergent mechanisms maintaining pair bonds in the two species. In white-handed gibbons, the female rarely initiates grooming and grooms her mate significantly less than he grooms her, partly because she solicits grooming from him at higher rates while simultaneously ignoring more of his 'presents' for grooming. In siamang, the contributions of the sexes to grooming are more equivalent and reciprocal. Taken together, these results suggest that investment of the sexes in maintaining the pair bond is more asymmetrical in white-handed gibbons (i.e. males contribute relatively more than females) and more mutual in siamang. Although mate guarding may have been the selective force behind the origin of pair bonds in both species, greater intra-group feeding competition in the gibbon and substantial paternal care in the siamang may account for the evolution of more reciprocal and stronger pair bonds in the latter. Future research on more groups is necessary to clarify the proposed species differences in light of existing intraspecific variation in social behavior.
The Proximate Mechanisms of Natal Dispersal in Female Horses
Authors: Monard Anne-Marie , Duncan Patrick , Boy Vincent
Published: April 2008

The aim of this study was to investigate proximate mechanisms of natal dispersal by female horses, Equus caballus (i.e. proximate causes and the factors influencing the timing), and to test predictions from two functional hypotheses: the intrasexual competition hypothesis, and inbreeding avoidance. The data concerned 40 individuals born between 1974-1985 in a closely monitored herd which developed a natural social structure during this period. All the females dispersed from their natal groups; none became solitary; 80% transferred to existing harems, the others formed new groups with bachelor stallions. Abduction by stallions affected only a quarter of the females whose transfers were observed. The results of this study do not support the hypothesis that a function of natal dispersal is to reduce intrasexual competition. The young females were not expelled by resident females of their natal groups, and did not, as a rule, experience increased aggression from these females before emigration. Their social bonds with members of their natal groups showed no progressive weakening prior to departure, and there was no gradual strengthening of bonds with individuals in the groups to which they transferred. There was no evidence for reproductive competition between the young females and resident mares of their natal groups, since the young females always refused the sexual approaches by males of these groups. Finally, age at dispersal did not decrease with the number of resident females in the groups they left. In contrast, as predicted by the inbreeding avoidance hypothesis, the primary cause of dispersal appeared to be sexual attraction to unfamiliar males. When in oestrus and before dispersing, the young females accepted matings only with males of other groups in spite of frequent sexual approaches by males of their natal groups (normally close relatives). In addition, none dispersed before first oestrus, and most did so during an oestrous period, at or before the conception of their first foal. The mothers of most young females interposed themselves when close kin males of the natal group approached their daughters sexually; this could contribute to the avoidance of close inbreeding. Among the other factors examined, some did not influence dispersal of the young females : they experienced low levels of aggression by adult stallions of their natal groups, particularly at the time of departure; their weight and body condition had no significant effects on leaving age nor did their mother's rank, the number of siblings, or the birth of another. In contrast, as the number of groups and the breeding sex ratio increased, dispersal age declined, occurring at a median age of 23 months (range 12-42 months) in the later years, when the herd had developed a natural social system.