Hierarchies of intensity preference aggregations.

This paper deals with aggregation of fuzz; individual opinions into a single group opinion, based upon hierarchical intensity aggregation rules. Characterization theorems are given, and it is also shown that Montero's rationality and standard ethical conditions propagate under hierarchical aggregations

Structural complexity and social cohesion in gregarious animals: from conflict to cooperation

A social lifestyle is abundant in nature. The social interactions between animals form the basis for complex, highly dynamic structures and may determine group-level processes such as group cohesion. Social behavior is influenced by local environmental conditions, varies over time and has diverse, context-dependent functions. In my thesis I have investigated the spatial, temporal, contextual and structural aspects of social complexity in three model species. First, I explored effects of increasing population density on aggression and contact behavior within and between sexes in water striders (Aquarius paludum). The current, local density regime affected male mating behavior as males sought more frequent contacts to available mates in denser groups. Frequencies of male-to-male conflicts and the duration of male harassment behavior were unaffected by local density, however. Overall, males in high-density groups may experience intense scramble competition over reproductively active females. Current environmental conditions crucially affect the species’ mating system; yet, also the previously experienced environment should be considered. Second, in a flock of free-flying jackdaws (Corvus monedula) I studied seasonal variation in patterns of positive interactions between pair mates and linked the pair bond to group level dynamics. Jackdaw groups are dynamic social units into which mutualistic pair bonds are embedded. Both sexes invested into the bond with different social behaviors and at different times of the year; yet, these are likely the proximate mechanisms employed by males and females to perpetuate a successful bond and secure annual reproductive output. Third, I determined the factors regulating dyadic and polyadic conflict resolution in jackdaws and investigated patterns of social support between the sexes. Conflict aggressors receiving active, aggressive support had high chances of winning encounters and were probably at low risk of receiving counter-aggression. Females cooperated very closely with their mates during conflicts. In doing so, they likely secured male investment into offspring provisioning and care, whereas males might seek conflicts strategically to maintain or improve their social status. Conflicts and interventions hence constitute a vital aspect of jackdaws’ social system. Finally, I used a captive house sparrow (Passer domesticus) flock to determine the destabilizing effects of perturbations of group composition on social structure and behavior. The group’s dominance hierarchy destabilized after a second perturbation and did not re-establish itself quickly. Yet, irrespective of experimental treatment, birds fed regularly and interacted based on their initially determined dominance rank. Only females joined, rather than supplanted, feeding conspecifics more frequently following the second perturbation treatment, thereby shifting to a non-aggressive social foraging strategy. Thus, sparrows in this study might have tolerated and compensated for structural instability to some degree. In conclusion, environmental factors, like population density, may alter the social structure of animal groups, creating a potential for both conflict and cooperation. Cooperation is constantly threatened by the selfish interests of individuals, leading to intra-group conflicts, and group members must resolve these conflicts efficiently. Enduring social stability is likely required for maintaining higher-order structures, such as social alliances or linear hierarchies, but relatively simple mechanisms for mitigating conflicts may exist in fluctuating fission-fusion groups.Sosiaalinen elämäntapa on luonnossa yleinen. Eläinyksilöiden väliset sosiaaliset vuorovaikutukset ovat perusta monimutkaisille ja hyvin dynaamisille sosiaalisille rakenteille. Sosiaalinen käyttäytyminen riippuu vallitsevista ympäristön olosuhteista. Esimerkiksi sosiaalista yhteenkuuluvuutta edistävä käyttäytyminen vahvistaa sosiaalisia siteitä, kun taas vihamielinen käyttäytyminen liittyy ryhmänsisäisiin ja ryhmien välisiin ristiriitoihin. Nämä sosiaalisen käyttäytymisen kaksi ääripäätä ovat sosiaalisten rakenteiden peruspilareita, ja vaikuttavat yhdessä ryhmän toimintaan ja tiiveyteen. Sosiaaliset järjestelmät vaihtelevat tilassa ja ajallisesti sekä ovat rakenteellisesti hyvin monimutkaisia. Väitöskirjatyössäni olen tutkinut kolmella mallilajilla näitä sosiaalisen kompleksisuuden eri ilmenemismuotoja. Tutkin vesimittareilla (Aquarius paludum) populaatiotiheyden kasvun vaikutuksia sukupuolten sisäiseen ja sukupuolten väliseen aggressioon ja pariutumiskäyttäytymiseen. Populaatiotiheys vaikutti koiraiden pariutumiskäyttäytymiseen niiden etsiessä saatavilla olevia kumppaneita. Paikallinen populaatiotiheys ei kuitenkaan vaikuttanut koiraiden välisten häirintäkäyttäytymisten lukumäärään tai kestoon. Kaiken kaikkiaan koiraat saattavat kuitenkin tiheissä populaatioissa kokea voimakasta kilpailua aktiivisesti lisääntyvistä naaraista. Sekä vallitsevat että aiemmissa elämänvaiheissa koetut ympäristön olosuhteet vaikuttavat merkittävästi pariutumisjärjestelmään. Tutkin vapaana elävässä naakkaparvessa (Corvus monedula) parinsisäisten positiivisten vuorovaikutusten esiintyvyyttä eri vuodenaikoina sekä parisiteen vaikutusta parven toimintaan. Naakkaparvessa kummallakin sukupuolella parisidettä ylläpitävät sosiaalisen käyttäytymisen muodot vaihtelivat vuodenajoittain. Kyseessä lienevät proksimaattiset mekanismit, joita naaraat ja koiraat käyttävät varmistaakseen lisääntymisensä onnistumisen vuosittain. Tutkin naakoilla myös kahden- ja monenkeskisiin konfliktinratkaisutapoihin vaikuttavia tekijöitä sekä niitä tapoja, joilla naakkapuolisot tukivat toisiaan ristiriitaisissa tilanteissa. Ristiriitatilanteissa hyökkäävät osapuolet, jotka saivat muilta yksilöiltä aktiivista sosiaalista tukea, voittivat useimmin ja yleensä välttyivät uusilta ristiriidoilta. Naaraat tukivat puolisoitaan ristiriitatilanteissa. Tämä todennäköisesti auttoi niitä varmistamaan koiraan osallistumisen jälkeläisten ruokintaan ja hoitoon. Koiraat puolestaan hakeutuivat ristiriitatilanteisiin joko ylläpitääkseen tai parantaakseen omaa sosiaalista asemaansa. Ristiriitatilanteet ja niiden ratkaiseminen ovat tärkeä osa naakkojen sosiaalista järjestelmää. Lopuksi tutkin tarhaoloissa pidetyillä varpusilla (Passer domesticus) parvirakenteen hajoamisen ja yhdistymisen vaikutusta sen sosiaaliseen rakenteeseen ja yksilöiden käyttäytymiseen. Parven valtajärjestys hajosi häirinnän jälkeen, eikä enää palautunut ennalleen. Tästä huolimatta parven jäsenet ruokailivat säännöllisesti, ja yksilöiden väliset suhteet noudattivat kokeen alussa vakiintunutta valtajärjestystä. Parven häirintäkerran jälkeen naaraat olivat ruokaillessaan vähemmän aggressiivisia. Tutkimukseni siis osoitti, että varpuset pystyvät palauttamaan valtajärjestelmän sen hajottua ja uudelleen yhdistyessä. Yhteenvetona voidaan todeta ympäristötekijöiden kuten populaatiotiheyden voivan vaikuttaa eläinryhmien sosiaaliseen rakenteeseen, mikä luo paitsi ristiriitatilanteita myös yhteistyötä. Yksilöiden itsekkäät vaikuttimet vaarantavat jatkuvasti yhteistyön mahdollisuuksia, mikä johtaa ryhmänsisäisiin ristiriitoihin, joita ryhmän jäsenten tulisi voida tehokkaasti ratkoa. Sosiaaliset rakenteet kuten yksilöiden yhteenliittymät tai lineaariset valtajärjestykset edellyttävät pitkäkestoista sosiaalisten suhteiden vakautta. Alati koostumukseltaan muuttuvissa, toistuvasti hajoavissa ja uudelleen muodostuvissa eläinryhmissä voivat kuitenkin toimia melko yksinkertaiset ristiriitoja lieventävät toimintamallit.Siirretty Doriast

Habitat selection

Habitat selection is the behavioural process determining the distribution of individuals among habitats varying in quality, thus affecting individual fitness and population growth. Models of population dynamics often assume that individuals have perfect knowledge about habitat qualities and settle accordingly in the best habitats available. Many studies of dispersal have focused on the movements of individuals away from a site, but knowledge on settlement decisions is still scarce. I investigated settlement and departure decisions in a long-distant migrant, the northern wheatear (Oenanthe oenanthe), breeding in a heterogeneous agricultural landscape. First, I investigated the settlement of wheatears choosing a new territory at the time of territory establishment in spring. I show that territory selection is non-ideal as wheatears did not prefer territories with characteristics most closely predicting individual fitness. Second, I studied the territory selection of experienced breeders which may use many potential cues as they have been breeding in the same area before. The results show that information gathering of experienced breeders is constrained, and that they cannot always settle at a preferred site probably because of the earlier establishment by other individuals. Third, I show that such a priority constraint in territory site selection may be a proximate cause for female-biased dispersal in wheatears and possibly in many other bird species. Fourth, as a first step to link habitat selection behaviour and population dynamics, I investigated habitat-specific population growth. Overall, I show that constraints acting on individual habitat selection result in a greater proportion of individuals breeding in poorer habitats than would be expected from ideal selection, which has consequences for population persistence

Aspects of the winter behavioral ecology of Anolis carolinensis at the northern limit of its range

In the population used for this study, A carolinensis shift habitats prior to the winter season to a south-facing rocky bluff where they seek refuge in crevices at night and during cloudy days (Gatten et al 1988,personal observations). In part II of this Thesis, I describe the thermal properties of the crevices and the behavior of the lizards in relationship to the crevices. Body Temperatures of lizards were recorded prior to emergence from the crevices to determine if there were temperature differences between lizards with different masses and to see if lizards could maintain body temperatures independent of crevice temperatures. The emergence order of the lizards from several crevices was observed to determine if an individual\u27s position in the emergence sequence was random, and if it was not,what factors influenced emergence position. Also, light intensity, and air, crevice,and rock face temperatures were recorded to identify the major physical cues that trigger emergence from the crevices. Finally, the last section of Part II describes the winter and seasonal movements of the lizards. Movements were monitored to determine if lizards remain at the same crevice throughout the entire winter season and to see if individuals return to the same crevices the following winter season. Part III describes the winter sex ratio, size distribution, and growth of the lizards found on the bluff to see if individuals return to the same crevices the following winter season

Crayfish Recognize the Faces of Fight Opponents

The capacity to associate stimuli underlies many cognitive abilities, including recognition, in humans and other animals. Vertebrates process different categories of information separately and then reassemble the distilled information for unique identification, storage and recall. Invertebrates have fewer neural networks and fewer neural processing options so study of their behavior may reveal underlying mechanisms still not fully understood for any animal. Some invertebrates form complex social colonies and are capable of visual memory–bees and wasps, for example. This ability would not be predicted in species that interact in random pairs without strong social cohesion; for example, crayfish. They have chemical memory but the extent to which they remember visual features is unknown. Here we demonstrate that the crayfish Cherax destructor is capable of visual recognition of individuals. The simplicity of their interactions allowed us to examine the behavior and some characteristics of the visual features involved. We showed that facial features are learned during face-to-face fights, that highly variable cues are used, that the type of variability is important, and that the learning is context-dependent. We also tested whether it is possible to engineer false identifications and for animals to distinguish between twin opponents

Selection of Overwintering Microclimate by Migratory Western Monarch Butterflies

Migratory species are expected to demonstrate habitat selection that occurs at multiple spatial and temporal scales. Western monarch butterflies migrate seasonally to overwinter in groves at geographically predictable locations along the California coast. To date, overwintering habitat selection by western monarch butterflies has been studied assuming that habitat selection occurs where overwintering aggregations form, meaning at the spatial scale where monarchs form dense overwintering aggregations within overwintering groves. We argue that since western monarch butterflies are migratory, studies of habitat selection could have commingled selection at different scales into a single spatial scale. This likely leads to ignoring some levels of habitat selection, confounding the scale of habitat selection itself, and potentially misidentifying the habitat attributes under selection. Therefore, we explore monarch overwintering habitat selection to determine whether an explicit spatial framework is necessary.We studied nine groves on the coast of California and at each grove we collected temperature, humidity, and light data from grove edges, grove interiors, and aggregation locations over several weeks of the overwintering season. We tested the hypothesis that monarchs aggregate in locations within groves that have consistent attributes across groves. We find that locations on the outer edges of groves differed significantly in particular attributes of daily temperature and light from the interior of groves. Yet we find neither evidence supporting the hypothesis that the aggregation locations have a unique microclimate that differs significantly from other locations inside the grove nor that aggregation locations are uniform in their microclimatic attributes across overwintering groves. Rather, we find that the microclimatic attributes at the aggregation locations vary spatially with latitude. Thus, the overwintering climatic attributes that appear to be under selection varied spatially based on locations within groves and based on latitude of each particular grove. We conclude it will be necessary to consider spatial effects when studying western monarch butterfly overwintering habitat selection and that interpretations of habitat selection to date have commingled habitat selection at multiple spatial scales

No behavioural response to kin competition in a lekking species

The processes of kin selection and competition may occur simultaneously if limited individual dispersal i.e. population viscosity, is the only cause of the interactions between kin. Therefore, the net indirect benefits of a specific behaviour may largely depend on the existence of mechanisms dampening the fitness costs of competing with kin. In lekking species, males may increase the mating success of their close relatives (and hence gain indirect fitness benefits) because female prefer large leks. At the same time, kin selection may also lead to the evolution of mechanisms that dampen the costs of kin competition. As this mechanism has largely been ignored to date, we used detailed behavioural and genetic data collected in the black grouse Lyrurus tetrix to test whether males mitigate the costs of kin competition through the modulation of their fighting behaviours according to kinship and the avoidance of close relatives when establishing a lek territory. We found that neighbouring males’ fighting behaviour was unrelated to kinship and males did not avoid settling down with close relatives on leks. As males’ current and future mating success are strongly related to their behaviour on the lek (including fighting behaviour and territory position), the costs of kin competition may be negligible relative to the direct benefits of successful male-male contests. As we previously showed that the indirect fitness benefits of group membership were very limited in this black grouse population, these behavioural data support the idea that direct fitness benefits gained by successful male-male encounters likely outbalance any indirect fitness benefits

The effects of environmental complexity upon the aggressive behaviour and growth of juvenile brown trout (Salmo trutta L.) and the carrying capacity of the environment

Experiments were performed in stream tanks and aquaris to investigate the effects of environmental complexity upon the aggressive behaviour and growth of juvenile brown trout (Salmo trutta L.) and the carrying capacity of the environment. Natural materials and various structures were used to provide environmental complexity. Aggressive interactions were found to be significantly more frequent in simple environments than in complex ones. The different types of structures used to modify the complexity of the experimental environments had different effects upon the observed levels of aggressive behavioral structures providing overhead cover were associated with the lowest levels of aggression. Increasing fish density resulted in relatively greater increase in aggression in simple environment. The wigwag display of the fish was analysed and found to be a highly ritualised, defensive manoeuvre, the efficiency of which was determined by the social ranks of the fish involved. Carrying capacity of complex environments was significantly greater then that of simple environments. There was a significant inverse correlation between aggression and resident population size in the environment types used. In the growth experiment, different relationships between individual fish's specific growth rates and their size rank position were found in populations of fish kept in simple and complex environments. The differences were probably associated with the different levels of aggression observed in the two environment types and the effect of environmental complexity upon feeding behaviour

Differential female sociality is linked with the fine-scale structure of sexual interactions in replicate groups of red junglefowl, Gallus gallus

Recent work indicates that social structure has extensive implications for patterns of sexual selection and sexual conflict. However, little is known about the individual variation in social behaviours linking social structure to sexual interactions. Here, we use network analysis of replicate polygynandrous groups of red junglefowl (Gallus gallus) to show that the association between social structure and sexual interactions is underpinned by differential female sociality. Sexual dynamics are largely explained by a core group of highly social, younger females, which are more fecund and more polyandrous, and thus associated with more intense postcopulatory competition for males. By contrast, less fecund females from older cohorts, which tend to be socially dominant, avoid male sexual attention by clustering together and perching on branches, and preferentially reproduce with dominant males by more exclusively associating and mating with them. Collectively, these results indicate that individual females occupy subtly different social niches and demonstrate that female sociality can be an important factor underpinning the landscape of intrasexual competition and the emergent structure of animal societies

Coexistence in unisexual-bisexual species complexes of Poeciliopsis (Pisces: Poeciliidae)

All-female forms of Poeciliopsis rely on males of closely related bisexual species for sperm. The natural habitat of Poeciliopsis in Sonora, Mexico, consists of a variety of small ponds connected by intermittent watercourses. Optimal areas, containing mixed female aggregates, are defended by territorial males. Social structure in natural populations very closely resembles that of laboratory experiments, wherein subordinant males show reduced mate discrimination and inseminate unisexuals. An equation relating male density to unisexual inseminations is used in a computer simulation model of a population. A stable equilibrium is inherent in unisexual-bisexual species complexes but the level of equilibrium is affected by the environment. Coexistence does not require niche separation. The simulations predict the percentage of unisexuals pregnant in natural populations and explain their distribution pattern. The strength of the mechanism is demonstrated by a natural population in which the percentage of unisexuals pregnant responded strongly to a modest change in unisexual-bisexual composition