Ethology

Published by Wiley
Online ISSN: 1439-0310
Publications
Article
Social foragers may be regarded as being engaged in a producer-scrounger game in which they can search for food independently or join others who have discovered food. Research on the producer-scrounger game has focused mainly on the different factors influencing its ESS solution, but very little is known about the actual mechanisms that shape players' decisions. Recent work has shown that early experience can affect producer-scrounger foraging tendencies in young house sparrows, and that in nutmeg mannikins learning is involved in reaching the ESS. Here we show that direct manipulation of the success rate experienced by adult sparrows when following others can change their strategy choice on the following day. We presented to live sparrows an experimental regime, where stuffed adult house sparrows in a feeding position were positioned on a foraging grid that included two reward regimes: a positive one, in which the stuffed models were placed near food, and a negative one, in which the models were placed away from food. There was a significant increase in joining behavior after the positive treatment (exhibited by 84% of the birds), but no change after the negative treatment. Further analysis demonstrated that sparrows more frequently used the strategy with which they were more successful (usually joining), and that differences in strategy use were correlated with differences in success. These results suggest that adult birds can monitor their success and learn to choose among social foraging strategies in the producer-scrounger game.
 
Article
Ethologist Konrad Lorenz proposed that baby schema ('Kindchenschema') is a set of infantile physical features such as the large head, round face and big eyes that is perceived as cute and motivates caretaking behavior in other individuals, with the evolutionary function of enhancing offspring survival. Previous work on this fundamental concept was restricted to schematic baby representations or correlative approaches. Here, we experimentally tested the effects of baby schema on the perception of cuteness and the motivation for caretaking using photographs of infant faces. Employing quantitative techniques, we parametrically manipulated the baby schema content to produce infant faces with high (e.g. round face and high forehead), and low (e. g. narrow face and low forehead) baby schema features that retained all the characteristics of a photographic portrait. Undergraduate students (n = 122) rated these infants' cuteness and their motivation to take care of them. The high baby schema infants were rated as more cute and elicited stronger motivation for caretaking than the unmanipulated and the low baby schema infants. This is the first experimental proof of the baby schema effects in actual infant faces. Our findings indicate that the baby schema response is a critical function of human social cognition that may be the basis of caregiving and have implications for infant-caretaker interactions.
 
Article
In many species of small mammals, including meadow voles, Microtus pennsylvanicus, females come into postpartum estrus (PPE) within 12-24 h of giving birth, allowing them to mate and become pregnant while raising the current litter. PPE females show increases in attractivity, proceptivity, and receptivity, the three components of sexual behavior, relative to females not in PPE. Several studies have shown that food deprivation and restriction reduce attractivity, proceptivity, and receptivity of females not in PPE. We tested the hypothesis that food deprivation and restriction during late gestation causes deficits and decreases the attractivity, proceptivity, and receptivity of females when they enter PPE. Our data support the hypothesis. On day 1 of lactation, females that were food deprived and food restricted produced scent marks that were significantly less attractive as those produced by control PPE females. Food deprivation but not food restriction caused females to no longer display significant preferences for the scent marks of males over those of females (proceptivity). Food deprivation and food restriction were sufficient to induce females to become significantly less sexually receptive than control females. Eleven of 12 control PPE females mated, 4 of 12 food-restricted females mated, and 3 of 12 food-deprived females mated. Dams facing food deprivation or restriction during late gestation may have to balance the benefits of mating during PPE with the increased costs associated with getting pregnant while they are lactating.
 
Article
Models of age-related effects on behavior predict that among short-lived species younger adults are more attractive and attracted to opposite-sex conspecifics than are older adults, whereas the converse is predicted for long-lived species. Although most studies of age-related effects on behavior support these predictions, they are not supported by many studies of scent marking, a behavior used in mate attraction. Over-marking, a form of scent marking, is a tactic used by many terrestrial mammals to convey information about themselves to opposite-sex conspecifics. The present study tested the hypothesis that the age of meadow voles, Microtus pennsylvanicus; a microtine rodent, affects their over- and scent marking behaviors when they encounter the marks of opposite-sex conspecifics. Sex differences existed in the over-marking behavior of adult voles among the three different age groups that were tested. Male voles that were 5-7 mo-old and 10-12 mo-old over-marked a higher proportion of the marks of females than did 2-3 mo-old male voles. Female voles that were 2-3 mo-old, 5-7 mo-old, and 10-12 mo-old over-marked a similar number of marks deposited by male voles. Overall, the data were not consistent with models predicting the behavior of short-lived animals such as rodents when they encounter the opposite sex. The differences in over-marking displayed by older and younger adult male voles may be associated with life history tradeoffs, the likelihood that they will encounter sexually receptive females, and being selected as mates.
 
Article
Scent marking and over-marking are important forms of communication between the sexes for many terrestrial mammals. Over the course of three experiments, we determined whether the amount of time individuals investigate the scent marks of opposite-sex conspecifics is affected by 4 d of olfactory experience with those conspecifics. In Experiment 1, female meadow voles, Microtus pennsylvanicus, spent more time investigating the scent mark of the novel male conspecific than that of the familiar male donor, whereas male voles spent similar amounts of time investigating the scent mark of the familiar female and a novel female conspecific. In Experiment 2, voles were exposed to a mixed-sex overmark in which subjects did not have 4 d of olfactory experience with either the top-scent donor or the bottom-scent donor. During the test phase, male and female voles spent more time investigating the scent mark of the opposite-sex conspecific that provided the top-scent mark than that of a novel, opposite-sex conspecific. Male and female voles spent similar amounts of time investigating the scent mark of the bottom-scent donor and that of a novel opposite-sex conspecific. In Experiment 3, voles were exposed to a mixed-sex over-mark that contained the scent mark of an opposite-sex conspecific with which they had 4 d of olfactory experience. During the test phase, male voles spent more time investigating the mark of the familiar, top-scent female than the scent mark of a novel female donor but spent similar amounts of time investigating the mark of the familiar, bottom-scent female and that of a novel female donor. In contrast, female voles spent more time investigating the mark of a novel male donor than that of either the familiar, top-scent male or that of the familiar, bottom-scent male. The sex differences in the responses of voles to scent marks and mixed-sex over-marks are discussed in relation to the natural history and nonmonogamous mating system of meadow voles.
 
Article
An individual's nutritional status affects the manner in which same- and opposite-sex conspecifics respond to that individual, which may affect their fitness. Male meadow voles, Microtus pennsylvanicus, increase their sperm allocation if they encounter the scent mark of an unfamiliar male that is not nutritionally challenged. If, however, the scent mark comes from a male that has been food deprived for 24 hours, stud male voles do not increase their sperm allocation. Food deprived males may be viewed as being lower quality and a reduced risk of sperm competition by rival males. We hypothesized that stud males in promiscuous mating systems tailor their sperm allocations depending on whether rival males have been food deprived and then re-fed. We predicted that newly re-fed males will be considered a strong risk of sperm competition because of the potentially high fitness and survival costs associated with food deprivation in males, and that they will cause stud males to increase their sperm allocation. Our results, however, showed that the recovery period from 24 hours of food deprivation was a relatively slow process. It took between 96 hours and 336 hours of re-feeding male scent donors that were food deprived for 24 hours to induce stud males to increase their sperm allocation to levels comparable to when scent donors were not food deprived. Stud male voles may be conserving the amount of sperm allocated until the male scent donors have recovered from food deprivation and subsequent re-feeding.
 
Article
Different forms of aggression have traditionally been treated separately according to function or context (e.g. aggression towards a conspecific versus a predator). However, recent work on individual consistency in behavior predicts that different forms of aggression may be correlated across contexts, suggesting a lack of independence. For nesting birds, aggression towards both conspecifics and nest predators can affect reproductive success, yet the relationship between these behaviors, especially in females, is not known. Here we examine free-living female dark-eyed juncos (Junco hyemalis) and compare their aggressive responses towards three types of simulated intruders near the nest: a same-sex conspecific, an opposite-sex conspecific, and a nest predator. We also examine differences in the strength of response that might relate to the immediacy of the perceived threat the intruder poses for the female or her offspring. We found greater aggression directed towards a predator than a same-sex intruder, and towards a same-sex than an opposite-sex intruder, consistent with a predator being a more immediate threat than a same-sex intruder, followed by an opposite-sex intruder. We also found positive relationships across individuals between responses to a same-sex intruder and a simulated predator, and between responses to a same-sex and an opposite-sex intruder, indicating that individual females are consistent in their relative level of aggression across contexts. If correlated behaviors are mediated by related mechanisms, then different forms of aggression may be expressions of the same behavioral tendency and constrained from evolving independently.
 
Article
We report here on the interrelationship of aggressive behaviour and thermoregulation in honeybees. Body temperature measurements were carried out without behavioural disturbance by infrared thermography. Guard bees, foragers, drones, and queens involved in aggressive interactions were always endothermic, i.e. had their flight muscles activated. Guards made differential use of their endothermic capacity. Mean thorax temperature was 34.2-35.1°C during examination of bees but higher during fights with wasps (37°C) or attack of humans (38.6°C). They usually cooled down when examining bees whereas examinees often heated up during prolonged interceptions (maximum >47°C). Guards neither adjusted their thorax temperature (and thus flight muscle function and agility) to that of examined workers, nor to that of drones, which were 2-7°C warmer. Guards examined cool bees (<33°C) longer than warmer ones, supporting the hypothesis that heating of examinees facilitates odour identification by guards, probably because of vapour pressure increase of semiochemicals with temperature. Guards in the core of aggressive balls clinged to the attacked insects to fix them and kill them by heat (maximum 46.5°C). Bees in the outer cluster layers resembled normal guards behaviourally and thermally. They served as active core insulators by heating up to 43.9°C. While balled wasps were cooler (maximum 42.5°C) than clinging guards balled bees behaved like examinees with maximum temperatures of 46.6°C, which further supports the hypothesis that the examinees heat up to facilitate odour identification.
 
Article
Alarm calling is common in many species. A prevalent assumption is that calling puts the vocalizing individual at increased risk of predation. If calling is indeed costly, we need special explanations for its evolution and maintenance. In some, but not all species, callers vocalize away from safety and thus may be exposed to an increased risk of predation. However, for species that emit bouts with one or a few calls, it is often difficult to identify the caller and find the precise location where a call was produced. We analyzed the spatial dynamics of yellow-bellied marmot (Marmota flaviventris) alarm calling using an acoustic localization system to determine the location from which calls were emitted. Marmots almost always called from positions close to the safety of their burrows, and, if they produced more than one alarm call, tended to end their calling bouts closer to safety than they started them. These results suggest that for this species, potential increased predation risk from alarm calling is greatly mitigated and indeed calling may have limited predation costs.
 
Article
Introduced species can exert outsized impacts on native biota through both direct (predation) and indirect (competition) effects. Ants frequently become established in new areas after being transported by humans across traditional biological or geographical barriers, and a prime example of such establishment is the red imported fire ant (Solenopsis invicta). Introduced to North America in the 1930's, red imported fire ants are now firmly established throughout the southeastern United States. Although these invasive predators can dramatically impact native arthropods, their effect on vertebrates through resource competition is essentially unknown. Using a paired experimental design, we compared patterns of foraging and rates of provisioning for breeding eastern bluebirds (Sialia sialis) in unmanipulated (control) territories to those in adjacent (treated) territories where fire ants were experimentally reduced. Bluebirds inhabiting treated territories foraged nearer their nests and provisioned offspring more frequently than bluebirds inhabiting control territories with unmanipulated fire ant levels. Additionally, nestlings from treated territories were in better condition than those from control territories, though these differences were largely confined to early development. The elimination of significant differences in body condition towards the end of the nestling period suggests that bluebird parents in control territories were able to make up the food deficit caused by fire ants, potentially by working harder to adequately provision their offspring. The relationship between fire ant abundance and bluebird behavior hints at the complexity of ecological communities and suggests negative effects of invasive species are not limited to taxa with which they have direct contact.
 
Article
The question of why animals participate in duets is an intriguing one, as many such displays appear to be more costly to produce than individual signals. Mated pairs of yellow-naped amazons, Amazona auropalliata, give duets on their nesting territories. We investigated the function of those duets with a playback experiment. We tested two hypotheses for the function of those duets: the joint territory defense hypothesis and the mate-guarding hypothesis, by presenting territorial pairs with three types of playback treatments: duets, male solos, and female solos. The joint territory defense hypothesis suggests that individuals engage in duets because they appear more threatening than solos and are thus more effective for the establishment, maintenance and/or defense of territories. It predicts that pairs will be coordinated in their response (pair members approach speakers and vocalize together) and will either respond more strongly (more calls and/or more movement) to duet treatments than to solo treatments, or respond equally to all treatments. Alternatively, the mate-guarding hypothesis suggests that individuals participate in duets because they allow them to acoustically guard their mate, and predicts uncoordinated responses by pairs, with weak responses to duet treatments and stronger responses by individuals to solos produced by the same sex. Yellow-naped amazon pairs responded to all treatments in an equivalently aggressive and coordinated manner by rapidly approaching speakers and vocalizing more. These responses generally support the joint territory defense hypothesis and further suggest that all intruders are viewed as a threat by resident pairs.
 
Article
Yawning appears to be involved in arousal, state change, and activity across vertebrates. Recent research suggests that yawning may support effective changes in mental state or vigilance through cerebral cooling. To further investigate the relationship between yawning, state change, and thermoregulation, 12 Sprague-Dawley rats (Rattus norvegicus) were exposed to a total of two hours of ambient temperature manipulation over a period of 48 hours. Using a repeated measures design, each rat experienced a range of increasing (22→32°C), decreasing (32→22°C), and constant temperatures (22°C; 32°C). Yawning and locomotor activity occurred most frequently during initial changes in temperature, irrespective of direction, compared to more extended periods of temperature manipulation. The rate of yawning also diminished during constant high temperatures (32°C) compared to low temperatures (22°C). Unlike yawning, however, stretching was unaffected by ambient temperature variation. These findings are compared to recent work on budgerigars (Melopsittacus undulatus), and the ecological selective pressures for yawning in challenging thermal environments are discussed. The results support previous comparative research connecting yawning with arousal and state change, and contribute to refining the predictions of the thermoregulatory hypothesis across vertebrates.
 
Article
The South American weakly-electric knifefish (Apteronotidae) produce highly diverse and readily quantifiable electrocommunication signals. The electric organ discharge frequency (EODf), and EOD modulations (chirps and gradual frequency rises (GFRs)), vary dramatically across sexes and species, presenting an ideal opportunity to examine the proximate and ultimate bases of sexually dimorphic behavior. We complemented previous studies on the sexual dimorphism of apteronotid communication signals by investigating electric signal features and their hormonal correlates in Apteronotus bonapartii, a species which exhibits strong sexual dimorphism in snout morphology. Electrocommunication signals were evoked and recorded using a playback paradigm, and were analyzed for signal features including EOD frequency and the structure of EOD modulations. To investigate the androgenic correlates of sexually dimorphic EOD signals, we measured plasma concentrations of testosterone and 11-ketotestosterone. A. bonapartii responded robustly to stimulus playbacks. EODf was sexually monomorphic, and males and females produced chirps with similar durations and amounts of frequency modulation. However, males were more likely than females to produce chirps with multiple frequency peaks. Sexual dimorphism in apteronotid electrocommunication signals appears to be highly evolutionarily labile. Extensive interspecific variation in the magnitude and direction of sex differences in EODf and in different aspects of chirp structure suggest that chirp signals may be an important locus of evolutionary change within the clade. The weakly-electric fish represent a rich source of data for understanding the selective pressures that shape, and the neuroendocrine mechanisms that underlie, diversity in the sexual dimorphism of behavior.
 
Article
Extreme asymmetric morphologies are hypothesized to serve an adaptive function that counteracts sexual selection for symmetry. However direct tests of function for asymmetries are lacking, particularly in the context of animal weapons. The weapon of the maritime earwig, Anisolabis maritima, exhibits sizeable variation in the extent of directional asymmetry within and across body sizes, making it an ideal candidate for investigating the function of asymmetry. In this study, we characterized the extent of weapon asymmetry, characterized the manner in which asymmetric weapons are used in contests, staged dyadic contests between males of different size classes and analyzed the correlates of fighting success. In contests between large males, larger individuals won more fights and emerged as the dominant male. In contests between small males, however, weapon asymmetry was more influential in predicting overall fighting success than body size. This result reveals an advantage of asymmetric weaponry among males that are below the mean size in the population. A forceps manipulation experiment suggests that asymmetry may be an indirect, correlate of a morphologically independent factor that affects fighting ability.
 
Article
PIP This study of reproductive decisions in human mate selection used data from "lonely hearts" advertisements to examine a series of predictions based on the mate preferences of male and females relating to age; physical appearance; financial condition and socioeconomic status; family commitment and personal traits; short- and long-term mating; and marital status and preexisting children. The sample consisted of 1000 personal advertisements (500 male) placed in two daily, national papers between February and October 1994 in Hungary. The research procedure included a pilot study of 150 advertisers (75 male) to refine the categories examined. Analysis was performed using 1) a matrix with one axis referring to offers and the other to demands of males and females separately; 2) a matrix of offers only to derive correlated traits of claims by males and females; and 3) a matrix with columns describing sex, offers, demands, advertiser's age, and required age and a row for each of the 1000 samples. It was found that men preferred younger mates, while women preferred older ones. Men were more likely to seek physical attractiveness, while women were more likely to seek financial resources (ranked 7th) and high status (ranked 6th). Women strongly preferred male domestic virtue and family commitment, and twice as many women as men demanded long-term relationships. Women more frequently declared preexisting children, and men exhibited a reluctance to accept these children. Both males and females employed "trade-off" strategies, making greater demands if they felt they had attractive offers.
 
Article
Aquatic organisms often detect predators via water-borne chemical cues, and respond by showing reduced activity. Prey responses may be correlated with the concentration of predation cues, which would result in graded antipredator behavioral responses that adjust potentially costly behavioral changes to levels that are commensurate with the risk of predation. Larvae of the predatory mosquito Toxorhynchites rutilus prey upon other container-dwelling insects, including larvae of the mosquito Ochlerotatus triseriatus. Previous work has established that O. triseriatus reduce movement, foraging, and time below the surface, and increase the frequency of resting at the surface, in the presence of water-borne cues from predation by T. rutilus. We tested whether these responses by O. triseriatus are threat sensitive by recording behavior of fourth instar larvae in two runs of an experiment in which we created a series of concentrations (100, 10, 1, 0.1, and 0.01% and 100, 70, 40, 20, and 10%) of water that had held either O. triseriatus larvae alone (control) or a T. rutilus larva feeding on O. triseriatus (predation). We also tested whether associated effects on time spent feeding are threat sensitive by determining whether frequencies of filtering or browsing are also related to concentration of cues. The frequencies of resting and surface declined, whereas frequency of filtering (but not browsing) increased more rapidly with a decrease in concentration of predation cues compared with control cues. Thus, O. triseriatus shows a threat sensitive behavioral response to water-borne cues from this predator, adjusting its degree of behavioral response to the apparent risk of predation.
 
List of predictions derived from female defence (FDH) and resource defence (RDH) hypotheses
Hinde index for proximity calculated from the male's perspective
Home ranges of eight Lepilemur ruficaudatus pairs in 2002–2004 plotted on a sketch of the grid system of the study area. Shown are Kernel 95% probability home ranges (KHR). Home ranges of females are located within home ranges of the respective male pair partners.
Interindividual distances between pair partners during pre-mating/mating and non-mating season (n = 8 pairs).
Mean percentage of time females and males spent in certain distance categories to the centre of their respective home range during mating (m) and non-mating (nm) season (females n = 8; males n = 8).
Article
Pair-living and a monogamous mating strategy are rare and theoretically unexpected among mammals. Nevertheless, about 10% of primate species exhibit such a social system, which is difficult to explain in the absence of paternal care. In this study, we investigated the two major hypotheses proposed to explain the evolution of monogamy in mammals, the female defence hypothesis (FDH) and the resource defence hypothesis (RDH), in red-tailed sportive lemurs (Lepilemur ruficaudatus), a nocturnal primate from Madagascar. We analysed behavioural data from eight male-female pairs collected during a 24-mo field study to illuminate the determinants of pair-living in this species. Male and female L. ruficaudatus were found to live in dispersed pairs, which are characterised by low cohesion and low encounter rates within a common home range. Social interactions between pair partners were mainly agonistic and characterised by a complete absence of affiliative interactions - body contact was only observed during mating. During the short annual mating season, males exhibited elevated levels of aggression towards mates, as well as extensive mate guarding and increased locomotor activity. In addition, males were exclusively responsible for the maintenance of proximity between pair partners during this period, and they defended their territories against neighbouring males but not against females. Together, these results point towards the importance of female defence in explaining pair-living in L. ruficaudatus. We discuss the spatial and temporal distribution of receptive females in relation to the female defence strategies of males and suggest possible costs that prevent male red-tailed sportive lemurs from defending more than one female.
 
Article
The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non-human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale-multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non-functional by-product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free-ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower-ranking males mated less and tended to masturbate more frequently than higher-ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.
 
Article
Quantifying signal repertoire size is a critical first step towards understanding the evolution of signal complexity. However, counting signal types can be so complicated and time consuming when repertoire size is large, that this trait is often estimated rather than measured directly. We studied how three common methods for repertoire size quantification (i.e., simple enumeration, curve-fitting and capture-recapture analysis) are affected by sample size and presentation style using simulated repertoires of known sizes. As expected, estimation error decreased with increasing sample size and varied among presentation styles. More surprisingly, for all but one of the presentation styles studied, curve-fitting and capture-recapture analysis yielded errors of similar or greater magnitude than the errors researchers would make by simply assuming that the number of types in an incomplete sample is the true repertoire size. Our results also indicate that studies based on incomplete samples are likely to yield incorrect ranking of individuals and spurious correlations with other parameters regardless of the technique of choice. Finally, we argue that biological receivers face similar difficulties in quantifying repertoire size than human observers and we explore some of the biological implications of this hypothesis.
 
Sex ratio (proportion of males among developing embryos or earliest developmental stage for which data were available) and (b) nearest neighbour distance (distance between adult females) for six Anelosimus species of various levels of sociality, respectively, plotted against their estimated sociality score. Filled symbols denote subsocial species, and unfilled symbols denote social species.
Anelosimus spp. of Ecuador and their sociality index scores
Anelosimus eximius scores from different localities and Anelosimus guacamayos scores from different years
African mole-rat social data and sociality scores
Article
Species are often classified in discrete categories, such as solitary, subsocial, social and eusocial based on broad qualitative features of their social systems. Often, however, species fall between categories or species within a category may differ from one another in ways that beg for a quantitative measure of their sociality level. Here, we propose such a quantitative measure in the form of an index that is based on three fundamental features of a social system: (1) the fraction of the life cycle that individuals remain in their social group, (2) the proportion of nests in a population that contain multiple vs. solitary individuals and (3) the proportion of adult members of a group that do not reproduce, but contribute to communal activities. These are measures that should be quantifiable in most social systems, with the first two reflecting the tendencies of individuals to live in groups as a result of philopatry, grouping tendencies and intraspecific tolerance, and the third potentially reflecting the tendencies of individuals to exhibit reproductive altruism. We argue that this index can serve not only as a way of ranking species along a sociality scale, but also as a means of determining how level of sociality correlates with other aspects of the biology of a group of organisms. We illustrate the calculation of this index for the cooperative social spiders and the African mole-rats and use it to analyse how sex ratios and interfemale spacing correlate with level of sociality in spider species in the genus Anelosimus.
 
Article
Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response.
 
Article
Zusammenfassung1Mehrere Gruppen junger und ausgewachsener Segelflosser wurden über rund 12 Monate hin im Aquarium beobachtet. Ihre Verhaltensweisen werden beschrieben und mit denen anderer Cichliden verglichen.2Im Färbungsmuster dominiert die Querbänderung. Der auf dem Kiemendeckel gelegene Augenfleck entwickelt sich unabhängig vom Bändermuster, gewinnt aber später Anschluß an das über den Kopf hin laufende Vertikalband. Er stellt auch weiterhin ein unabhängig variables Musterelement dar, dessen Ausfärbung einen bestimmten Zusammenhang mit dem Kampfverhalten aufweist. Er ist bei aggressiven Fischen dunkel, bleicht aber während des Angriffs aus. Die Querbänderung hingegen wird und bleibt während des Kampfes tiefschwarz.3Unter den Bewegungen der Augen werden Fixierbewegungen und Stellreflexe unterschieden.4Die wesentlichen Bewegungsweisen der Lokomotion werden beschrieben.5Im Funktionskreis der Nahrung zeigen junge wie alte Fische ein heftiges Ruckschwimmen mit scharfen Wendungen, wenn sie eine große Beute geschnappt haben. Sitzt Beute einer bestimmten Größe (z. B. Tubifex) am Substrat fest, so sieht man bei jungen Fischen ein Sichherumwerfen, bei adulten nur Kopfrucken. Die Postlarven haben vor dem Schnappen eine lauernde Beugestellung, aus der heraus sie sich vorwärtsschnellen. Diese fehlt älteren Stadien.6Im Komfortverhalten findet man neben zwei Streckbewegungen mindestens 9 verschiedene Koordinationen, die häufig in einem Syndrom gemeinsam auftreten. Sichscheuern ist bei älteren Fischen immer gegen vertikale Unterlagen gerichtet, in einem frühen Jugendstadium kurze Zeit gegen den Boden. Die letztere Form stellt bei vielen anderen Cichliden den Normalfall dar. Daneben wird ein soziales Komfortverhalten beschrieben: Ein Fisch vollführt schnappende, anscheinend putzende Bewegungen mit dem Maul an der Flanke oder den Flossen des Partners.7Im Kampfverhalten findet man frontales und laterales Imponieren, außerdem direkten Angriff mit Rammstoß und Maulkampf. Im Frontalimponieren spreizen Segelflosser die Bauchflossen, während die meisten anderen Buntbarsche die Kiemendeckel abspreizen. Hinzu kommt eine kennzeichnende, oft wiederholte Kopf- und Flossenruckbewegung. Im Breitseitsimponieren wird die Rückenflosse niedergelegt, die Bauchflossen liegen ventral unter dem Körper aneinander, können in der Intensivform auch gegeneinander verschoben werden. Im Maulkampf drehen sich beide Gegner langsam um ihre Längsachse.8Segelflosser sind typische Offenbrüter. Die Paarbildung entspricht dem Hemichromis-bimaculatus-Typ. Während das Graben weitgehend zu fehlen scheint, sind Putzen und Rüttelputzen charakteristisch. Es wird an vertikalen Substraten wie Vallisneriablättern abgelaicht. Die Brutpflege ist intensiv und lang anhaltend.9Innerhalb der Jugendentwicklung können verschiedene soziale Organisationstypen auftreten: Schwärm, Territorialität, Hierarchie. Adulte Fische sind territorial mit Neigung zum Schwarmverhalten unter bestimmten Außenbedingungen.10Ein Teil der vom Cichlidentypus abweichenden Verhaltensmerkmale der untersuchten Fische lassen sich als primäre oder sekundäre Anpassungserscheinungen auffassen, die mit der ökologischen bzw. morphologischen Spezialisierung im Zusammenhang stehen.
 
Article
Many species find themselves isolated from the predators with which they evolved. Isolation often leads to the loss of costly antipredator behavior, which may have adverse consequences if the population should later come into contact with predators. An understanding of both the mechanism (i.e. the degree to which antipredator behavior depends on experience), and of the time course of loss is important to be able to predict how a population will respond to future contact. We studied ‘group-size effects’– the way in which animals change the time they allocate to antipredator vigilance as a function of group size – and visual and acoustic predator recognition in a population of tammar wallabies (Macropus eugenii), a cat-sized (6–10 kg) macropodid marsupial. To study group size effects we observed wallabies foraging in four populations – three with some sort of predator and a New Zealand population that was isolated from all predators for about 130 yr. To study predator recognition, we observed the response of New Zealand wallabies to the presentation of a model or taxidermic mount of mammalian predators, and to the broadcast sounds of mammalian and avian predators. We compare these predator recognition experiments with results from a previous study of Kangaroo Island (South Australia) tammars. Complete isolation from all predators for as few as 130 yr led to the loss of group size effects and a rapid breakdown in visual predator recognition abilities. Our results are consistent with a key prediction of the multi-predator hypothesis – namely, that the isolation from all predators may lead to a rapid loss of antipredator behavior.
 
Article
Young females were implanted with testosterone propionate (TP) and estradiol benzoate (E2B) during several ontogenetic stages in an attempt to mimic the temporal scheme of the sexually dimorphic developmental steroid pattern of canaries. In males, higher estrogen levels are found during several ontogenetic stages as well as individually elongated periods of androgen secretion (Weichel et al. 1986). The steroid concentration of testosterone (T), dihydrotestosterone (DHT), and estradiol-17β (E2) during implantation and afterwards were analyzed by RIA. Songs were recorded to assess the hormonal influence on song organization of females. Parameters such as duration and frequency of tours were taken as behavioral indicators for song quality improvement. Besides observations of song organization, long-term monitoring of song activity was undertaken. The following results were obtained: Possible neural mechanisms underlying the behavioral responses to steroid treatment are discussed.
 
Article
Microcebus murinus is a photoperiod-dependent polyoestrous seasonal prosimian. In captivity, ♀♀ kept isolated or paired with a ♂ undergo 3 oestruses (April, June, August) during the breeding season. When 2, 3 or 4 pairs are kept together, a 25 % decrease in occurrence of the 2nd and 3rd seasonal oestrus is noticed. Life in social groups induces: — resorption or abortion in about 50 % of grouped ♀♀, — a high infant mortality (50 % of newborn young), — a significant modification of sex ratio (excess of ♂♂). Finally, the body weight gain is significantly reduced during the first two months of life in offspring of grouped ♀♀.
 
Article
Comparative studies were made on different heterosexual groups of Microcebus murinus during the period of sexual activation, which is determined by the photoperiod. In pairs (1 ♂ — 1 ♀), the sexual activation of the ♂ occurs during January. This is accompanied by a loss in body weight and by an increase in basal oxygen consumption. The testes are maximal in size by the beginning of March. In groups of 8 individuals (4 ♂ ♂ — 4 ♀ ♀) only one ♂ exhibits normal sexual activity. He is the heaviest and mates with ♀♀ The 3 other ♂ ♂ of the group show delayed activation and their testes are reduced in size. Two subordinate ♂ ♂ died under the social pressure of severe diseases (e. g. renal failure) normally associated with overcrowding.
 
Article
Oribi were seen marking with the antorbital gland in Murchison falls National Park, Uganda. In 46 observations, males bit off the distal parts of grass stems before marking. Biting resulted in the removal of a long portion from a previously intact stem or removal of the marked tip of stems which had already been bitten and marked. In the first case a stem of relatively constant height, which was possibly optimum for marking, was produced. The function of biting may be to produce suitable marking sites. The function of biting before stems were remarked is unknown.
 
Article
Echidna untersucht ihre Umgebung hauptsächlich mit der Nase und dem Gehör. Der Gesichtssinn ist sehr schwach. Artfremde können von Artgenossen nach dem Geruch unterschieden werden; riecht der Fremde nach Echidna, wird er als Artgenosse anerkannt. Die drei aufeinanderfolgenden Phasen des Paarungsspieles (Abb. 3) werden beschrieben. Die Begattung kann in zweierlei Lagen erfolgen. Echidna setzt mit der ausgestülpten Kloake Duftmarken ab.
 
Article
This paper reports the social behavior of two groups of captive Lemur variegates. An intensive three-month study provided baseline data. This was supplemented by two years of follow-up observations. Various components of the captive behavioral repertoire are described. Data on feeding behavior, vocalizations, grooming, agonistic interactions, sexual behavior and infant development were collected.
 
Article
Hornets (Vespa affinis) flying in a drone congregation area attracted drones of Apis cerana. The drones followed the hornet and were ‘manoeuvred’ towards a leaf or a tree. The hornet then rushed at one of the drones. Many attempts by the hornet to catch a drone were unsuccessful and all drones fled. After failing, the hornet returned to centre of the drone congregation area and repeated the behaviour. Only after successfully seizing of a drone did the hornet leave the drone congregation area carrying its prey. In a two-choice test in the centre of the drone congregation area, free-flying A. cerana drones preferred a hornet model to a live A. cerana queen. V. affinis apparently ‘exploits’ the intraspecific communication between queen and drones of A. cerana. Hunting of drones in the drone congregation area by V. affinis may be an example of predatory mimicry.
 
Article
We investigated whether the piscivorous wolf-fish, Hoplias malabaricus (Bloch, 1794), showed preferences for attacking a ‘straggler’ or a shoal using guppies, Poecilia reticulata (Peters, 1860), as prey. Predators should show a preference to attack single prey items rather than grouped prey to overcome the confusion effect, which has been shown to negatively affect their capture success. However, they may attack groups more frequently because they are more likely to detect them because of their greater conspicuousness. In our study we looked at predator choice for grouped or single prey and whether this was affected by larger shoals being more conspicuous. We offered Hoplias binary choices of a single guppy (straggler) and shoals of 2, 6 and 10 fish. Hoplias preferred to attack the shoal over the straggler with regards to both frequency of attacks (initial and subsequent) and attack duration. The implications for predator–prey interactions of such a preference are discussed.
 
Article
Zusammenfassung1960/62 wurden im August 3 ostafrikanische Elefanten (♂ 1, ♂ 2, ♀), heute zehnjhrig, insgesamt 438 Std. beobachtet, davon nachts 191 Std. Die in einem großen Gehege frei herumlaufenden Elefanten (Kühme 1961) schliefen liegend vor und nach Mitternacht jeweils 1 1/2-2 Std. (Abb. 1). Dabei atmeten sie 6,7 mal/Min.; im wrmeren Stall liegende Zirkuselefanten nur 3,8 mal/Min.Der aggressive -Bulle konnte von Jahr zu Jahr immer besser gezielt mit seinem Rüssel Gegenstnde auf Menschen schleudern (Abb. 2). Auf diese Weise deckte er in einem halbstündigen Versuch einen vor ihm liegenden Menschen ein (Abb. 3). Die auslösende Reizsituation wird mit der “Begrabehandlung” wilder Elefanten verglichen. Im Widerstreit von Angriff und Flucht vor Artgenossen und Menschen schlug sich der Elefant am Futterplatz Gras gegen die Kopfseite, je nher sie kamen, desto hufiger (Tab. 1).Die Ohrenbewegungen waren von der Außentemperatur und der sozialen Stellung abhngig; in Nhe des -Bullen unterdrückten die anderen sie (Tab. 2). Elefanten können also die temperaturregelnde Ohrenbewegung nicht von der drohenden unterscheiden.Es konnten 2 Paarungsvorspiele mit anschließender Kopula beobachtet werden (Abb. 4). Auf die kmpferische Frontalstellung folgte die ritualisierte Flucht der Kuh als Paarungslauf und darauf die Begattung.Beim frontalen Kampfspiel wurde ein Platz verteidigt. Der Schwchere löste sich rückwrtsgehend und drohte mit erhobenem Rüssel (Abb. 7i), wenn er wieder vorging. Diese Rüsselhaltung und vorgestellte Ohren sind Ausdrucksbewegungen, die der Artgenosse versteht.Es wurde versucht, eine vorlufige Motivationsanalyse der im Konflikt zwischen Flucht und Angriff auftretenden Bewegungsweisen des Rüssels aufzustellen.SummaryIn August of 1960/62, 3 East African elephants (♂ 1, ♂ 2, ♀) now 10 years old, were observed for a total of 438 hours, including 191 hours during the night. The elephants, which roam freely in a large enclosure (Kühme 1961), slept lying down for periods of 1 1/2-2 hours, before and after midnight (Fig. 1). During sleep their breathing rate was 6,7 times per minute; circus elephants, lying in a warmer stall, breathed only 3,8 times per minute.The aggressive -bull used his trunk to throw objects at people (Fig. 2), improving in accuracy from year to year. In a half-hour test, he covered over a man lying down in front of him (Fig. 3). The releasing stimulus situation is compared with the “burial behaviour” of wild elephants. In conflict between attack and escape from conspecifics and from humans at the feeding place, this elephant struck the sides of his head with grass, the more often, the closer the enemy came (Table 1).The ear movements were dependent on the external situation and on the external temperature; in the vicinity of the -bull, the other animals suppressed them (Table 2). Evidently elephants cannot distinguish the temperature-regulating from the threatening ear movements.Pairing behaviour ending in copulation was observed in two instances (Fig. 4). The aggressive frontal posture was followed by ritualised fleeing of the cow as a pairing promenade, and then by copulation.In the frontal fight ceremonies a place was defended. The weaker bull disengaged himself by moving backward and threatened with raised trunk (Fig. 7i) when he advanced again. This trunk posture and the spread ears are expression movements understood by the other conspecifics.It was attempted to construct a provisional motivation analysis of the trunk movements appearing in the conflict between flight and attack.
 
Article
ZusammenfassungAn 4 Tenreciden-Arten (insgesamt 41 Exemplaren) wurde bei unspezifischer Erregung, bei starken Fremdgerüchen, bei Abwehr, Angst, Zorn, beim Paarungsverhalten und knapp vor dem Tod eine auffällige Sekretion bestimmter Liddrüsen festgestellt. Das Sekret ist zumeist leuchtend weiß und verdeckt bisweilen ein oder beide Augen; manchmal tritt es auch aus der Nase aus. Die Sekretion findet jedoch durchaus nicht nach jedem Reiz statt, auch kann sie in der Stärke völlig unterschiedlich sein oder nur einseitig sichtbar werden. Entgegen den wenigen bisherigen Meldungen ist sie beiden Geschlechtern gemeinsam.An 26 Beispielen wird die Reaktion auf bestimmte Reize beschrieben, deren Erklärung versucht wird. Eine morphologische Untersuchung der Augenlider zeigt die anatomischen Voraussetzungen für die Sekretion und beschreibt die Histologie der verschiedenen Drüsengruppen.Da sich die Reaktionen auf ähnliche Reize und sogar biologisch sinnlos gewordene Bewegungen teilweise noch beim Menschen erhalten haben, scheint es sich bei der Augendrüsensekretion um ein phylogenetisch altes Geschehen zu handeln. Es hat sich bei höher evoluierten Säugern abgewandelt, bei vielen ist die Sekretion verloren gegangen, bei den basalen Tenreciden ist dieses Verhalten jedoch mit zwei voneinander verschiedenen Drüsengruppen noch vollständig erhalten.
 
Article
In a 3½ year field study the social system of the 2000 white rhinoceros in Umfolozi Game Reserve, Zululand, was investigated in a 30 km5 area and four supplementary areas. Direct observation, individual recognition, tagging and attachment of radio transmitters gave copious information on spacing, grouping, movement, confrontation, territory occupation, rank order. Behaviour patterns are compared with those of the black and Indian rhinoceros, processes underlying their evolution are considered, weighing the influences of phylogeny, ecology, morphology, nutrition. Territorial structure was found to be a strong influence. Selective consequences for survival, reproductive success and progeny viability are discussed.
 
Article
Observations on six free ranging adult brown hyaenas (Hyaena brunnea) fitted with radio collars and beta lights were supplemented by observations on three untagged large cubs and by tracking spoor. Brown hyaenas are predominantly nocturnal and cover large distances alone each night searching for vertebrate remains and other food. Carrion is mainly located by olfactory sense, although auditory cues are also used. Excess food is often stored for short periods. Wild fruits and birds' eggs are eaten and hunting behaviour is directed towards small vertebrates and insects. Some adaptations of the brown hyaena to its environment are discussed.
 
Article
Dans une population de Platycnemis pennipes (Pallas, 1771) du midi de la France, l'auteur a observé pour la première fois que les ♀♀ étaient capables de procéder à la ponte sans être accompagnées du ♂ et, qu'en outre la ponte se faisait principalement dans des substrats verticaux. Ces divergences dans le comportement de ponte sont comparées à des observations semblables faites chez d'autres espèces du sous-ordre Zygoptera. Les Platycnemididae présentent un comportement de ponte nettement ambivalent. On peut supposer que les formes stéréotypées de la ponte en compagnie du ♂ (par exemple ”type Agrion„) sont phylogénétiquement beaucoup plus anciennes que le comportement fortement ritualisé, caractérisé par des schèmes déclencheurs trés complexes, des Calopterygidae. Par conséquent, il semble que les Platycnemididae occupent une place phylogénétique intéressante dans l'évolution du comportement de ponte des Zygoptères. In einer südfranzösischen Population von Platycnemis pennipes (Pallas, 1771) konnte zum erstenmal nachgewiesen werden, daß die ♀♀ auch ohne Begleitung des ♂ zur Eiablage schreiten. Außerdem legten sie die Eier vorwiegend in vertikale statt in horizontale Substrate. Diese Abweichungen vom normalen Eiablageverhalten werden mit ähnlichen bei anderen Arten der Unterordnung Zygoptera verglichen. Die Platycnemididen zeigen ein sehr ambivalentes Eiablageverhalten. Es wird angenommen, daß die stereotypen Formen der Eiablage mit angekoppeltem ♂ (z. B. Agrion-Typ) stammesgeschichtlich viel älter sind als das stark spezialisierte Verhalten mit hochkomplizierten Auslöseschemata der Calopterygiden. Die Platycnemidien hätten somit einen phylogenetisch interessanten Platz in der Evolution des Eiablageverhaltens der Zygopteren.
 
Article
ZusammenfassungNach Aufnahmen der Filme “Afrikanische Tierwelt heimlich belauscht” von W. Schack, Südafrika, und “Serengeti darf nicht sterben” von M. und B. Grzimek werden für das Steppen-Zebra beschrieben die Begegnung, das Imponieren (Abb. 1), das Drohen (Abb. 2), der Zahnkampf (Abb. 3), das Kampfkreiseln (Abb. 6), eine Andeutung des Halskampfes (Abb. 4), der Schlagkampf (Abb. 7) und der Kampfabbruch mit einer Gebrde sozialer Unterwürfigkeit (Abb. 8).
 
Article
and Summary1Action patterns performed by juvenile Dungeness crabs (Cancer magister) do not visibly differ from those performed by adults, although some action patterns are not used during the same situations by all instars.2Juvenile instars one and two are less aggressive than other instars, which correlates with their tendency to be found in dense groups in bays.3Juvenile instars three to six exhibit increased aggression correlating with increased cannibalism in the laboratory and spacing of crabs in the field.4Less aggression between juveniles of instars seven to adult correlates with crowding during their migration out of bays.5Juvenile instars, overall, use more forceful and more variable aggressive behavior than adults, although interactions between adults of the same sex typically contain more action patterns.6Adult male-male interactions involve controlled force and consistently contain the same action patterns.7Adult female-female interactions are more forceful but are still less variable than interactions between juveniles.8Females submit to males, and males perform a more diverse set of behavior when interacting with females which indicates recognition of sex and relates to pairing before copulation.9Crabs that are moving prior to an aggressive interaction or which do not perform the first action pattern typically lose the interaction, i. e., they leave the site of the interaction first.10These results indicate that Cancer magister crab instars do not alter the form of their action patterns with experience, but they do alter in the course of their development the way these action patterns are used in sequences of behavior during interactions.Zusammenfassung1Das Verhalten der juvenilen Krabben ist nicht offensichtlich verscheden von dem der erwachsenen, obwohl einige Verhaltensweisen nicht von allen Jugendstadien in denselben Situationen gezeigt werden.2Die ersten zwei Jugendstadien sind weniger aggressiv als die späteren und sind oft in dichten Gruppen zu finden.3Die Jugendstadien drei bis sechs zeigen erhöhte Aggression und erhöhten Kannibalismus im Labor. Im Freien lösen sich zu dieser Zeit die Grup-pierungen auf.4Die geringere Aggression späterer Stadien paßt zu den erhöhten Dichten während der Auswanderung von den Buchten.5Jugendstadien zeigen insgesamt stärkeres und variableres aggressives Verhalten als erwachsene Krabben.6Interaktionen erwachsener Männchen sind stereotyp.7Interaktionen erwachsener Weibchen sind heftiger, aber weniger variabel als von Juvenilen.8Weibchen unterwerfen sich den Männchen, und diese zeigen eine größere Zahl Verhaltensweisen in Interaktionen mit Weibchen. Das deutet auf Geschlecht-Erkennen hin und hängt mit der Paarbildung vor der Begattung zusammen.9Krabben, die vor einer aggressiven Interaktion in Bewegung sind oder nicht die Interaktion beginnen, verlieren zumeist den Kampf, d. h. sie verlassen zuerst den Platz.10Diese Ergebnisse deuten darauf hin, daß die verschiedenen Wachstumsstufen von Cancer magister ihr Verhalten nicht durch Erfahrung ändern. Wohl aber verändern sie die Verwendung dieser Verhaltensweisen in den sozialen Interaktionen.
 
Top-cited authors
Daniel T Blumstein
  • University of California, Los Angeles
Wolfgang Wickler
  • Max Planck Institute for Ornithology
Jean-Guy J Godin
  • Carleton University
William E. Cooper
  • Indiana University-Purdue University Fort Wayne
Robert R. Provine
  • University of Maryland, Baltimore County