Showing papers in "Behaviour in 1998"

Vigilance Behaviour in African Ungulates: The Role of Predation Pressure

Abstract: Impala Aepyceros melampus and wildebeest Connochaetes taurinus vigilance behaviour was concurrently monitored in two adjacent sites where re-introduction of large felids at one site gave rise to increased predation pressure. In the high predation site, rate of looking and proportion of time spent looking by both species was significantly greater than in the low predation site. Vigilance behaviour also showed an increase over time following feIid re-introduction: there was no increase where re-introduced feIids were absent. The relationship between vigilance and herd size, position in herd and presence of juveniles was compared for high and low predation conditions. Herd size and vigilance behaviour showed a negative correlation for both species regardless of predation conditions. Mothers with juveniles were always the most vigilant members of the herd and central animals were always the least watchful in both predation conditions. The interplay between vigilance behaviour and predation pressure, herd size, position in herd and presence of juveniles is discussed. It is suggested that predation pressure is the principal influence on vigilance behaviour in ungulates and even very low risk of predation appears to contribute to vigilance. Impalas and wildebeest spared the risk of predation devoted very little time to vigilance, suggesting it played a minor role in intraspecific interactions and finding food.

An evaluation of the roles of predation rate and predation risk as selective pressures on primate grouping behaviour

Abstract: Summary Establishing the importance of predation pressure in determining primate social structure has generated a great deal of discussion. However, the substantive issues in this debate have been obscured by a conflation of the respective roles of predation risk and predation rate as selective forces. In addition, the reported relationships between predation rate and both group size and body weight are likely to be confounded by the effects of reproductive rate and activity period. We propose that the level of sustainable predation rate for a species is determined by the rate at which it is able to reproduce, and that, within this constraint, a species adjusts its body weight and a population its group size so as to reduce predation rate to some tolerable level. In effect, the observed predation rate is the excess mortality from predation that animals are unable to control by adjusting their behaviour. This implies that there should be no relationship between predation rate and either group size or body weight, once the effects of reproductive rate and activity period are removed. We analyse data from the primate literature and show that reproductive rate is indeed the best predictor of a species' predation rate, and that the reported relationships with group size are entirely attributable to a combination of the inclusion of nocturnal species which do not use group size as an antipredator response and the confounding effects of reproductive rate. We discuss these findings in the light of current investigations on predation risk, and conclude that an understanding of the role of predation as a selective pressure on primates will only

Chorusing and Call Convergence in Chimpanzees: Tests of Three Hypotheses

Abstract: Male chimpanzees produce a species-typical long distance call known as the pant hoot. Males give acoustically similar pant hoots when calling together during choruses, but the process by which this vocal convergence takes place is unclear. Three potential mechanisms might account for call matching. First, vocal convergence could represent the passive effect of male chimpanzees sharing a common affective state during choruses. Second, matching could result through the active modification of calls. Such modification might occur if males modeled their calls after those produced by their current chorusing partner. Alternatively, actively mediated convergence would result if males mimicked the calls given by high-ranking males. We examined acoustic variation in calls given during choruses and while alone to test these three hypotheses. Results showed that a similar call type is not given repeatedly during successive choruses. In addition, low-ranking individuals did not produce calls that matched those of the alpha male. Chorused calls produced by two dyadic pairs were more similar to each other than they were to calls delivered during other choruses. The higher ranking, yet dependent, member of one of these dyads appeared to give calls that converged on those produced by the other individual. These data are consistent with the hypothesis that male chimpanzees accomodate each other vocally through the active alteration of their calls during choruses. We suggest that a similar form of accomodation takes place in animals from a wide range of other taxa and that the process serves to maintain and strengthen social bonds between individuals.

Geograpmc Variation in South Pacific Humpback Whale Songs

Abstract: Every winter, (male) humpback whales (Megaptera novaeangliae) produce long complex songs. Song content is dynamic and singers incorporate changes as they occur, thus song is shared through cultural transmission. We compared songs recorded in winter migratory termini in Tonga, New Caledonia, Eastern Australia, and on migration paths off Eastern Australia and New Zealand, in the winter of 1994. Seven themes were shared by all regions, with an additional two themes shared by all but Tonga. Differences in regional variants were most pronounced between Tongan and Eastern Australian song. New Caledonian and Kaikouran song were more similar to songs from Eastern Australia rather than Tonga. These regional differences were stable across the season. The results suggest some migratory exchange among widely separate wintering regions of Area V, consistent with tag recovery data, but the time and location at which song sharing occurs remains speculative.

Feeding innovations and forebrain size in Australasian birds

Abstract: Many authors have proposed that behavioural flexibility in the field is associated with learning ability in captivity, relative forebrain size and rate of structural evolution. In birds, the frequency of feeding innovations reported in the short notes sections of ornithology journals may be a good way to operationalize flexibility. In this paper, we examine in the birds of Australia and New Zealand the relationship between forebrain size and innovation frequency found in a previous study covering North America and the British Isles. From a methodological point of view, the two variables are highly reliable: innovation frequency per taxonomic group is similar when different readers judge innovation reports and when different editorial styles govern journals; relative forebrain size yields very similar estimates whether mean residuals from a log-log regression are used or ratios of forebrain to brainstem mass. Innovation frequency per taxon is correlated between the two Australasian zones and between these zones and the more northerly ones studied previously. Innovation frequency is also associated with relative forebrain size in Australia and, to a lesser extent, in New-Zealand; in Australia, parrots show the high frequency of innovations predicted by their large forebrain, but yield no innovations in the New Zealand sample. The forebrain/innovation trend is independent of juvenile development mode, but phylogeny appears to be an important intervening variable in Australasia, as evidenced by non-significant independent contrasts.

Olfactory Recognition of Urine Signals in Dominance Fights Between Male Lobster, Homarus Americanus

Abstract: The maintenance of dominance hierarchies in the American lobster (Homarus americanus) is based on recognition of the dominant animal by the loser of a recent fight. It is hypothesized that chemical signals are the basis of this recognition. Adult male lobsters were paired for initial boxing matches between unfamiliar animals. The same pairs were re-matched for 3 more consecutive fights. In the first experiment, treatment animals had their primary olfactory receptor cells of the lateral and medial antennules lesioned before fights 2-4 and control animals received sham lesions. The durations of fights 2-4 for control pairs were significantly shorter than the durations of fights between lesioned animals. In the second experiment, male pairs were again allowed to establish a dominance relationship in a first fight. During second fights, urine release by both animals was prevented by the use of catheters in treatment animals while control pairs wore sham catheters. Again, durations of the second fights of control animals were significantly shorter than those of treatment animals. Together, these experiments indicate that urine-carried chemical signals, perceived by the antennules, reduce the duration and aggression of male dominance fights on subsequent days because the loser of the first fight backs off almost immediately when he smells the urine of the known dominant.

Neocortex Size, Social Skills and Mating Success in Primates

Abstract: The social brain hypothesis predicts that species with relatively larger neocortices should exhibit more complex social strategies than those with smaller neocortices. We test this prediction using data on the correlation between male rank and mating success for polygamous primates. This correlation is negatively related to neocortex size, as would be predicted if males of species with large neocortices are more effective at exploiting social opportunities to undermine the dominant male's power-based monopolisation of peri-ovulatory females than are those with smaller neocortices. This effect is shown to be independent of the influence of male cohort size.

Spatial and breeding relationships of the lizard, Anolis carolinensis : Evidence of intrasexual selection

Abstract: 1. We used continuous 8-day monitoring to document the spatial and mating relationships of free-ranging Anolis carolinensis lizards at each of seven habitat-delineated study sites. 2. We found a polygynous social structure, consisting of a male and 2-6 resident females (x = 3.3), on each site. 3. Spatially, both sexes utilized all available perch heights and diameters on the study sites (habitat generalists), though females tended to perch slightly higher and on significantly thinner substrata (x = 2.4 m, 3.4 em, respectively) than males (x = 2.3 m, 5.3 em, respectively). 4. Mean home range volume was eight fold greater for males (69 m3) than females (8 m3). Male home ranges were exclusive of other males (0% overlap), while neighboring female home range volumes overlapped an average of 18%. 5. Male snout-vent length (SVL) was positively correlated with male home range size (area, volume) and with number of resident females, but not with resident female SVL or resident female home range size. 6. Half of 397 male-female encounters led to close contacts in which males influenced courtship outcomes by: recognizing receptive and non-receptive females (differential display rate); bypassing 69% (85/123) of mating opportunities with receptive females; and copulating only when courtship was male-initiated. 7. Larger males (who also had larger territories and more females) courted less per female, but with longer duration, and had longer copulatory durations than smaller males. 8. Male frequency of copulation (x = once/1.4 days), however, had no correlates with measured variables; females were mated without bias to male or female attributes. 9. Male potential reproductive rate (PRR), estimated from the number of copulations with different females, positively correlated with male SVL. Female PRR, estimated from the inter-mating interval (i.e. the single-egg clutch interval), did not correlate with any measured male or female trait. 10. Our data, in concert with other field studies and A. carolinensis life history traits, document a polygynous mating system in which females seem to fit a 'no cost, neutral-mate-choice' model, and males (in response to sedentary, contiguously distributed females who clutch at weekly intervals over a 4-month period) employ territorial contests within an endurance rivalry as a prime mechanism for mate assortment.

Reconciliation in domestic goats

Abstract: The aim of this study was to test whether domestic goats (Capra hircus) reconciled after experimentally induced conflicts. After conflicts, goats showed a higher frequency of affiliative contacts (muzzle-muzzle and muzzle-body contacts, allogrooming) and of lying in proximity than in control observations. Besides, renewed aggression was more frequent after conflicts, and both the victim and the aggressor showed a higher frequency of displacement activities (scratching and selfgrooming), possibly indicating an anxious emotional state. Post-conflict friendly reunions reduced the frequency of displacement activities in the victim, but not in the aggressor. These results provide evidence of post-conflict reconciliation in domestic goats and suggest that one of the functions of reconciliation is to reduce the victim's arousal or anxiety.

Positioning Behaviour in Roach Shoals: The Role of Body Length and Nutritional State

Abstract: This study investigated the positioning behaviour of individual fish in small shoals of 2 and 10 roach, Rutilus rutilus. In pairs consisting of one small and one large fish with an average length difference of 10 mm, no difference was observed in the number of initiations of shoal movement between small and large fish. However, once both fish were moving, large fish took up the front position more frequently than small ones. A subsequent experiment showed that body length was positively correlated with swimming speed which could explain the leading position of large fish. In a second experiment, using pairs of size-matched fish we found that in moving shoals fish which had been deprived of food for 7 days were more likely to take up front positions than well-fed conspecifics. No difference, however, was observed in the frequency of initiations of shoal movement. A final experiment with pairs and shoals of 10 fish showed that fish in the front position (and in the front half of the shoal for shoals of 10 fish) were much more likely to obtain food particles than fish in other shoal positions when resources were limited. This could provide a functional explanation for the occurrence of food-deprived fish in front positions. Our results suggest that the initiation of new swimming directions in stationary shoals does not follow the same principles as positioning behaviour in shoals that are already on the move.

Testing the Predation Hypothesis for Vertebrate Sociality: Prospects and Pitfalls

Abstract: Primates are in some ways excellent subjects for studying the impact of predation on prey. They are generally easy to watch and identify as individuals, so that long-term tracking of both death rates and anti-predator behaviors is possible, as amply shown by many of the studies in this volume. On the flip side, their low predation rates and large group sizes require very large total sample sizes for statistically powerful tests of the direct effects of sociality on predation rates. To study the indirect effects of predation On primate behavior requires defining the intrinsic predation risk they experience, that is the expected rate of predation they would suffer under standardized levels of anti-predator behavior (possibly none — see Hill & Dunbar, this volume). This abstract variable can be assessed qualitatively across different conditions by reference to modeling or common sense, or quantitatively by analyzing the hunting success of the predator independent of the prey's behavior (Cowlishaw, 1997). Great care must be taken in interpreting the behavioral responses of animals to different levels of predation risk when a given behavior can serve multiple functions, such as is the case with vigilance. Furthermore, most anti-predator behaviors carry fitness costs, not only from the lost opportunity to perform other fitness-enhancing activities, but even in terms of predation itself — apparently some primate species benefit from living in small groups which are very difficult for predators to detect instead of using a large-group early-warning defense as postulated in many theoretical models. Such costs will limit the extent to which primates are able to reduce their intrinsic predation risk (Fig. 1).

Impact of Predation Risk on the Behaviour of Propithecus Diadema Edwardsi in the Rain Forest of Madagascar

Abstract: The main predators on large-bodied primates in rain forest are birds of prey and mammalian carnivores, which may require distinct strategies by prey for successful detection and defense. In the three dimensional rain forest environment with diminishing light at lower levels, downward visibility is difficult, and keen eyesight may not be as effective for detecting in-forest predators as soaring ones. It is therefore predicted that cryptic behaviours, where the problems of detection are shifted to the predator, may be used in these conditions. In Madagascar there is debate on whether extant eagles are a threat to the largest primate species, while there is mounting evidence that a mammalian carnivore, the fossa, impacts heavily on lemur populations. In a new approach to understanding the differential impact of raptor and carnivore hunting styles on lemur anti-predator behaviours, I analyzed ten years of behavioural data on Milne-Edwards' sifakas in the rain forest of Madagascar. I show that Propithecus diadema edwardsi responds to aerial predators by giving loud alarms calls with responsive avoidance behaviour, and by choosing daytime rest sites lower than feeding sites. In response to the mammal predator, Propithecus gave a distinct ground predator call, used higher nighttime sleep sites than daytime rest sites, and males were in most dangerous spatial positions during travel and feeding. The combination of protective travel order, high sleeping sites and small sleeping parties suggested behaviours against fossa predation. However, the dramatic 'alarm call and drop low in the canopy' response to birds of prey is an indication that avian predators are feared.

The influence of group size and neighbors on vigilance in two species of arboreal monkeys

Abstract: (Acc. 5-VIII-1997) Summary In theory, one of the main benefits of group-living is the sharing of vigilance among groupmates. However, data on scanning in redtail and red colobus monkeys indicate that only one class of individuals in each species derives clear benefits from shared vigilance. Moreover, the expected negative relationship between individual scanning and social group size was not met in these monkeys. Nor was time spent scanning influenced by the sex or species composition of groups. Shared vigilance was observed only among red colobus adult males and redtail adult females and only when they had neighbors within 2 m. Red colobus adult males saved 10% of their scanning time when they had one neighbor within 2 m, while redtail adult females saved 16% of their time under the same conditions. No other age-sex class demonstrated a significant decrease. The role of near neighbors has been underemphasized in previous work on grouping and vigilance, an oversight made more serious because of the often confounded relationship between spatial cohesion and group size. In redtails, but not in red colobus, the number of neighbors within 2 m was significantly positively correlated with group size. This prompts the hypothesis that the inconsistency and poor explanatory power of group size in studies

The Role of Vigilance in the Survival and Reproductive Strategies of Desert Baboons

Abstract: This study investigates the relative importance of vigilance in the survival strategies (detection of predators) and reproductive strategies (detection of mates and competitors) of adult baboons Papio cynocephalus ursinus among four groups in a desert population. The proportion of time spent vigilant under a variety of conditions was quantified through instantaneous sampling of focal individuals. Matched comparisons were then conducted to test six predictions for each functional explanation (survival or reproduction). These relate vigilance to (1) sex, (2) group size, (3) activity, (4) habitat, (5) refuge use and (6) spacing behaviour. Vigilance levels do not differ between sexes or groups. However, females are more vigilant when engaged in high-risk activities, when distant from refuges and when distant from neighbours. Male vigilance similarly covaries with refuge use and spacing behaviour, but males are not always more vigilant in dangerous activities and show greater vigilance in open rather than closed habitats. According to the predictions tested, the results provide partial support for the proposal that vigilance plays a role in predator detection for both sexes, although in males the detection of potential mates and competitors appears to be of greater importance. There was no evidence that males provide a vigilance service for females. Vigilance patterns are complicated by activity constraints and the multifactorial nature of anti-predator strategies.

Do Female Zebra Finches Vary Primary Reproductive Effort in Relation to Mate Attractiveness

Abstract: Female choice and mate preference have been shown to affect female reproductive effort both prior to copulation (e.g. females seeking extra-pair copulation) and during parental care ('secondary' reproductive effort) in relation to mate quality. Here we show that female zebra finches, Taeniopygia guttata, vary their 'primary' reproductive effort in egg production in relation to the attractiveness of their male partner, for some components of reproduction but not others. Females were allowed to choose 'preferred' and 'non-preferred' males in standard mate choice trials, and were then paired sequentially with each male. Preferred males had significantly higher song duration and song frequency than non-preferred males confirming that females preferred attractive, higher quality males. Male attractiveness had a positive, but weak, effect on clutch size: in breeding experiments individual females laid on average 0.5 eggs more when paired with their preferred male compared to the non-preferred male. However, there was no significant difference in breeding propensity (whether females laid eggs or not), number of days between pairing and laying, mean egg size or egg quality (protein and lipid composition) in relation to male type. These results suggest that components of primary reproductive effort in individual female zebra finches are relatively non-plastic traits.

The Territory Defense Function of Song in Song Sparrows: A Test with the Speaker Occupation Design

Abstract: Territory defense is considered one of the primary functions of bird song, but this hypothesis has been directly tested in only a few cases. We used the speaker replacement method to ask whether song functions as a 'keep out' signal in song sparrows, a species for which there is considerable evidence supporting a mate attraction and stimulation function of song, but only indirect evidence that song functions as a signal to other males. We removed 11 matched pairs of male song sparrows from their territories, replacing one male of each matched pair with loudspeakers broadcasting that male's song (the 'experimental' territory) while leaving the other male's territory silent (the 'control' territory). In all cases in which encroachments or takeovers occurred, these occurred first (or solely) on the control territory of a matched pair, supporting the hypothesis that song functions in territory defense in this species. The incidence of intrusions on control territories was very low, however, posing difficulties for the interpretation of speaker replacement experiments designed to ask more specific questions about how song functions in male-male aggressive competition.

Infant 'Babbling' in a Nonhuman Primate: Complex Vocal Sequences with Repeated Call Types

Abstract: The pygmy marmoset is a small South American primate with a complex social system based on cooperative breeding. Infant pygmy marmosets are extremely vocal; most of their calling is a repetitive pattern of mixed call types that is babbling-like. In a longitudinal study of vocal development in 8 infant pygmy marmosets, we recorded more than 750 calling bouts which occurred in a wide range of behavioural contexts. The infants used 16 different call types that we grouped into three categories: Adult-Like (acoustic structure consistent with that of adult calls), Adult-Variant (acoustic structure with some adult features and some variable features), and Infant (absent from the adult repertoire). The calling bouts were highly conspicuous in their duration (ranging up to more than 6.5 min/bout), complexity (up to 10 different call types/bout), and call rate with nearly 3 calls/s. When the infants were older, their call rate slowed and they shifted to using several of the Adult-Like calls with greater frequency, and used fewer Adult-Variant types. The infants did not use the Adult-Like call types appropriately when compared to the typical adult usage of those types. Caregivers were significantly more likely to respond to an infant when it was vocalizing than when it was not.

Individual Recognition in a Cooperatively Breeding Cichlid: Evidence from Video Playback Experiments

Abstract: Summary Most theories of social behaviour and cooperation assume that animals can recognise other individuals, but this is rarely tested. Using Neolamprologus brichardi, a cooperatively breeding cichlid fish, we monitored behavioural responses to (1) real fish versus video images of fish; (2) mate versus neighbour and (3) video images of mate versus video image of neighbour. All tests were controlled for size and sex. Fish reacted appropriately to the playbacks, although responses to videos were not as strong as to real fish. Both males and females fought against the images of stranger and neighbour fish and they courted images of mates. These results confirm that the cooperatively breeding fish, Neolamprologus brichardi, recognises individuals based on vision and that video playbacks contain sufficient information to facilitate recognition.

Conspecific recognition in pigeons (columba livia) using dynamic video images

Abstract: Video images of pigeons were used to examine the degree to which these images are equivalent to real live conspecifics by analyzing the natural behaviors of pigeons in the presence of each stimulus. Three aspects of courtship display (i.e. bowing, tail-dragging, and vocalizations) were selected and the display duration for each was measured. When videotaped images of female pigeons were presented as stimuli, the display duration by male pigeons was not significantly different from that for the live birds. In contrast, the subjects showed much shorter, or no, displays to the video images of a non-pigeon bird (cockatoo) and an empty chamber. The results suggest that the video images of pigeons contained necessary information to trigger the courtship behaviors. Furthermore, the present study examined which features of the video images were critical for triggering the displays by manipulating the images. Thus, the subjects' behaviors were more vigorous (1) when video images were in motion rather than still, and (2) when the head-only region was visible rather than the body-only region. These results suggest that motion and facial/head characteristics are important features. Collectively, the results indicate that the use of video images as stimuli and courtship displays as measures provide a useful method to study the visual recognition of conspecifics in birds.

Direction of Predator Turning, a Neglected Cue to Predation Risk

Abstract: Assessed risk for prey should depend not only on distance from a predator, but also on probability that it has been detected. If an indirectly approaching predator close enough to pose a threat suddenly turns toward prey, risk increases because the joint probability that the predator has detected and will attack is raised abruptly. I conducted field experiments on the effect of a predator turning toward prey on escape behaviour by simulating a predator, slowly approaching adult keeled earless lizards, Holbrookia propinqua, on linear paths that did not lead directly toward them, but bypassed them by various distances. At the minimum bypass distance for a path, I stopped and turned directly toward a lizard or directly away. The effect of turning varied dramatically with bypass distance. Regardless of tum direction, almost all lizards fled for very close approaches and no lizards fled for sufficiently large bypass distances. At intermediate distances a greater proportion of prey fled when I turned toward them than away from them. Possible cues used by lizards to assess risk are direction of turning per se and increased visibility of eye and facial features or other morphological correlates of orientation. Ydenberg & Dill's (1986) optimality model of escape behaviour can account for the results if prey can continually assess rapidly changing risk. By turning toward prey, an indirectly approaching predator may suddenly shift from outside to within the break-even point for risk and cost of escape, thereby eliciting flight.

Effects of Experimental Forager Removals on Division of Labour in the Primitively Eusocial Wasp Polistes Instabilis (Hymenoptera: Vespidae)

Abstract: Experimental forager removals were performed to assess the mechanisms by which Polistes instabilis colonies regulate their intake of nectar and water. Most foragers gathered nectar, while water was collected by a small number of fixated foragers. Removal of the most active water foragers led to decreases in water foraging, followed by recruitment of a single replacement water forager. Replacement water foragers were usually recruited from among the workers that had previously collected water at low rates. Water forager removals showed that some workers specialized on water collection, but these workers differed in their thresholds of response to colony need for nest cooling. Removal of the most active nectar foragers led to longer-lasting (one to three days) decreases in colony nectar collection rates, and resulted in replacement nectar foragers being recruited away from other foraging tasks or from nest tasks. Nectar forager removals were followed by increases in rates of dominance interactions among nest wasps; this response was not observed after water forager removals. Dominance interactions among workers appear to regulate nectar foraging in P. instabilis. The mechanisms of regulation of foraging differ among materials, and correspond to their maximum rates of collection, predictability of resources, and on the costs of short-term changes in supply to the colony.

Risk factors and emergence from refuge in the lizard eumeces laticeps

Abstract: I studied effects of three risk factors, predator proximity, persistence in attacking, and speed, on latency to emerge after entering a refuge in the scincid lizard Eumeces laticeps. I simulated a predator by directly approaching a lizard until it took refuge, usually a tree hole. Costs per unit time of lost opportunities to forage or engage in other activities enhancing fitness did not vary with risk factors. Skinks remained in refuges longer when I stayed near the refuges than when I withdrew to a greater distance. At both distances, skinks monitored my presence visually from positions at or near refuge entrances. Skinks remained in refuges longer after the second of two successive similar approaches at the same speed than after the first, suggesting that they perceived increased risk due to persistence by an individual predator, but the assessment might have been based on attack rate without individual recognition. Latency to emergence increased with predator approach speed, giving another indication of response to higher risk. If lizards were approached twice in succession, latency to emergence was much greater when predator speed was faster during the second approach. When the second approach was slower, there was no significant difference in latency between trials. Risks associated with speed and persistence thus simultaneously affect risk assessment. A recent model (Sih, 1992) of emergence from refuge supposes that decisions affecting latency to emerge are based on a balance of costs of remaining in refuge (often predominantly costs of lost opportunities for feeding or mating) against risk of predation. All data are consistent with a generalized view of Sih's (1992) model, but studies are needed to assess effects of cost and limited information about predator presence.

Courtship Communication in Meadow Katydids: Female Preference for Large Male Vibrations

Abstract: Males of the katydid Conocephalus nigropleurum (Orthoptera: Tettigoniidae) shake their body to produce a substrate-borne vibratory signal in the context of courtship and mate attraction. We measured the physical parameters of this tremulation signal and then tested its effectiveness in eliciting taxis by virgin females. We also investigated the role of these vibrations in the choices made by females of larger males as mates. A search for correlations between male weight and vibratory signal parameters revealed a strong negative relationship to inter-pulse interval (ipi). In two-choice playback experiments females oriented towards tremulation vibration when it was the only vibration stimulus provided. In further playback experiments females also distinguished conspecific tremulation from a control vibration. When offered simultaneous presentations of tremulation signals that differed in ipi, females moved toward the stimulus with the shorter ipi indicative of a larger male. This is the first study to demonstrate that tremulation signalling by male katydids encodes critical information on body size, and that females discriminate among different vibratory signals in favour of those indicating a larger male.

Intragroup Variation in Conciliatory Tendencies in Captive Japanese Macaques

Abstract: Nonhuman primates have been observed to exchange friendly gestures soon after an agonistic episode, a behaviour labelled reconciliation. Frequency of reconciliation has been shown to vary both within and between primate groups. This study used both univariate and multivariate analyses to investigate intragroup variation in the frequency of reconciliation in captive Japanese macaques (Macaca fuscata). Frequency of reconciliation was lower during the mating season, and was also affected by the intensity of aggression and by the sex and age combination of the opponents. On the contrary, outcome of aggression and number of aggressors did not influence the frequency of reconciliation. Kin reconciled more than nonkin, and individuals with a good social relationship reconciled more than those with a bad or weak relationship. The effects of kinship and relationship quality appeared to be independent since among individuals with a good relationship, kin reconciled more than nonkin, while among nonkin, individuals with a good relationship reconciled more than those with a bad or weak relationship. Our results show that Japanese macaques are highly flexible in their conciliatory behaviour, and highlight a possible role of reconciliation in the negotiation and management of primate social relationships.

Food Abundance, Intruder Pressure, and Body Size as Determinants of Territory Size in Juvenile Steelhead Trout (Oncorhynchus Mykiss)

Abstract: We observed the behaviour of juvenile steelhead trout (Oncorhynchus mykiss) in two rivers in British Columbia, Canada, to determine the importance of invertebrate drift abundance, intruder pressure, and body size of territory holders as correlates of territory size. Territory size increased with increasing fish size, but fish smaller than 5 cm had relatively large territories for their body size, in comparison to fish that were larger than 5 cm in length. After statistically controlling for the effect of body size, territory size was inversely related to the abundance of drifting invertebrates. Territory size was not related to the number of intrusions observed on a territory per hour, but was inversely related to local fish density, a second measure of intruder pressure. Steelhead trout appear to defend territory areas that are most similar in size to juvenile Atlantic salmon. This study provides evidence that stream-dwelling salmonids scale territory size to body size in a manner that allows them to capture a maximum daily ration of food on their territories.

Alternative Tactics in the Breeding Behaviour of Male Coho Salmon

Abstract: 1. The movements and breeding behaviour of male coho salmon in Kanaka Creek, British Columbia, Canada, were studied by means of radio-telemetry and detailed observations of males in breeding groups. 2. Males were of three morphological types, large, three year old males (which we term alpha males), small, three year old males (which we term satellite males) and small, two year old 'jack' males (which we term sneak males). All three types of male were common in the population. 3. Males associated with females in breeding groups that included one alpha male and one or more of the two smaller male types. Alpha males dominated in breeding groups. Their movements tended to be restricted to a small section of the spawning stream where they had primary access to redd building females. 4. The majority of aggressive interactions were between resident alpha males and intruding large males, which the resident attempted to drive away. Alpha males would not tolerate another large male nearby and would attack until the intruder left the area. Aggressive interactions between alpha and satellite males or between alpha and sneak males were much less frequent. The alpha males moved from female to female within their section of stream, often returning several times to the same female over the space of a few days. 5. Satellite males adopted positions downstream from a breeding pair. Satellite males were highly mobile within the stream and were observed to join breeding groups at widely spaced locations without significant aggressive interaction with the alpha male. An established satellite male would oppose but not drive away other satellite males attempting to join the breeding group, allowing them to adopt subordinate positions further downstream. The first satellite male in a breeding group would also defend and court the female during periods when the alpha male was absent. 6. Sneak males were most often observed in the spawning redd with the alpha male and female. Sneak males were also found hiding outside the redd early in redd construction, when the cavity of the redd was still shallow, or if the sneak was larger than 30 cm. Sneak males were subject to little aggression from the alpha male or satellite males and displayed the lowest frequency of aggressive interactions of the three types of male. Sneak males would defend their position against other sneak males. Like alpha males, sneak males restricted their movements to a small section of the spawning stream. 7. Overall levels of aggression were lowest in breeding groups consisting of two or three males and much higher in groups consisting of just the alpha male or of four or more males. Intrusion by a large male that challenged the alpha increased the rate of aggressive interaction among all members of the group. 8. Our results suggest three unique breeding tactics among coho males, here termed alpha, satellite and sneak. On the basis of the information currently available, it cannot be determined whether the choice of tactic by a particular male is genetically determined, environmentally determined, or both.

Isolated Spider Web Stabillmentum Attracts Insects

Abstract: The insect-attraction function of silk stabilimenta spun by Argiope spiders was directly tested by examining if isolated stabilimenta will increase insect interception in artificial webs. Artificial webs were made from basswood frames and fine monofilaments coated with a sticky substance and were divided into two groups, experimental and control. In the experimental group, silk stabilimenta isolated from stabilimentum-decorated webs spun by Argiope aurantia were introduced. In the control group, corresponding areas collected from the undecorated webs of A. trifasciata were introduced. A general linear model was used to examine the effect of stabilimenta, web location, and date of data collection on insect interception in artificial webs. When the effects of location and date were simultaneously considered, artificial webs containing isolated stabilimenta intercepted significantly more flying insects (41.6% more) than those in the control group. However, there was no difference in orthopteran interception rates between experimental and control groups. These results indicate that silk stabilimenta of Argiope spiders do attract insects, although not all insects exhibit a strong orientation response to them.

Computer Animations as a Tool in the Study of Mating Preferences

Abstract: The study of multiple female mating preferences and multiple male signals requires correct and precise measurement of preferences. A review is given of existing preference test paradigms. Non-interactive preference tests using computer animations perfectly fulfil the demands for the study of multiple preferences for visual traits: exclusion of confounding variables, exclusion of variation within and between male pairs, great potential of experimental manipulation of single and combinations of visual traits including behaviour. We give a detailed description for the production of computer animation movies based on commercial software. Finally, we show how computer animations can be properly applied to the testing of mating preferences. In sticklebacks, female mating preferences that were tested in this way agreed with preferences that were measured with other test paradigms.

Mate selection by male winter moths operophtera brumata (lepidoptera, geometridae): adaptive male choice or female control?

Abstract: Mate choice is an important component of sexual selection. It is expected to evolve if the benefits of choice outweigh the costs. Yet, the relative importance of costs and benefits in the evolution of mate choice remain poorly understood. In this study we present experimental evidence for adaptive mate choice by males, but not females, in the winter moth. In a series of experiments we show that: (a) males have a higher probability of attempting to copulate, and consequently also a higher probability to copulate with a larger, more fecund female; (b) if males are given the choice between two females they are more likely to copulate with the larger female; and (c) females do not seem to show any mate discrimination. A sample of winter moths collected in copula in the field did not show any assortative mating for body size. This is the first demonstration of male choice in a moth species with chemical communication. This choice is possibly based on variation in female pheromone quality and/or quantity. We argue that the relatively higher variation in female quality and the limited number of male matings probably have led to male choosiness despite a strongly male biased operational sex ratio. This is consistent with recent studies indicating that choice and competition may occur more frequently in the same sex than previously thought.

Dominance Styles of Female and Male Barbary Macaques (Macaca Sylvanus)

Abstract: Dominance styles can be understood as consequences of different competition regimes imposed by socio-ecological conditions. As vital resources differ for males and females of the same species, one might expect different competitive tactics, hence differential dominance styles in both sexes. This was investigated on the basis of dyadic competition over a food resource (peanut) or mating partner (estrous female) in the semifree ranging colony of Barbary macaques at 'Affenberg Salem'. Both, females and males competed over nuts. The dominant typically won the nut by eliciting the retreat of the subordinate with a ritualised assertive signal, the 'rounded-mouth threat face'. The competitive style in adult male dyads (AM-AM) differed from that of all other age-sex class combinations, including adult versus subadult males, and did not change with the kind of incentive: Use of threat faces and retreat was replaced by ignoring, tension, or recruitment behaviour, and in 115of AM-AM dyads at least one nut was taken by a third party. In the few cases where a male did perform a threat face his rival responded by counter aggression, recruitment or appeasement/affiliation, or by taking the nut nevertheless. It is concluded that (1) dominance relations among adult females are stricter than those between males, indicating different dominance styles for the two sexes; (2) the 'egalitarian' competitive style of adult males was compatible with an absence of formalisation of dominance-subordination relations and did not indicate an absence of competition among them; (3) Adult males behaved as dominance oriented as females if the risk of injury was small (as in AM-SM dyads). The 'egalitarian' behaviour in AM-AM dyads is best understood as the result of a stalemate where the risks of escalation are high relative to the value of the resource. In sum, the results suggest that variance in power asymmetries and differential cost-benefit ratios of escalated competition may produce different dominance styles even within the same species.