Exploring the role of vision in social foraging: What happens to group size,vigilance, spacing,aggression and habitat use in birds and mammals that forage at night?

I examined the role of vision in social foraging by contrasting group size, vigilance, spacing, aggression and habitat use between day and night in many species of birds and mammals. The literature review revealed that the rate of predation/disturbance was often reduced at night while food was considered more available. Social foraging at night was prevalent in many species suggesting that low light levels at night are not sufficient to prevent the formation and cohesion of animal groups. Group sizes were similar or larger at night than during the day in more than half the bird populations and in the majority of mammal populations. Factors such as calls, feeding noises or smells may contribute to the formation and cohesion of groups at night. Larger numbers of foragers at night may also facilitate the aggregation of more foragers. Vigilance levels were usually lower at night perhaps as a response to the lower predation risk or to the decreased value of scanning for predators that are difficult to locate. Low light levels may also make visual cues that promote aggression less conspicuous, which may be a factor in the lower levels of aggression documented at night. Spacing varied as a function of time of day in response to changes in foraging mode or food availability. Habitats that are avoided during the day were often used at night. Foraging at night presents birds and mammals with a new set of constraints that influence group size, time budgeting and habitat use.     

What determines the growth of individual castes in social trematodes?

Phenotypic diversification among colony members often leads to formation of physical castes which are morphologically specialised for particular tasks within the colony. The relative abundance of these castes and their body sizes represent two key aspects of the demography of a colony that may reflect the colony’s needs and conditions, and ultimately influence its survival and reproductive success. In a recently discovered social trematode, Philophthalmus sp., which exhibits a reproductive division of labour, the role of competition and colony composition in shaping reproductive success and behaviour of colony members has been documented. As body size variation within physical castes often influences colony efficiency, we investigated how the growth of reproductive and non-reproductive morphs of Philophthalmus sp. responds to competitive pressure, and to other attributes of colony demography such as colony size and composition. Our survey of a natural population and in vitro experiments demonstrate that the growth of reproductive colony members reflects the interaction between colony composition and the presence of a competitor, while the non-reproductive members simply grow larger in the presence of the intra-host competitor, Maritrema novaezealandensis. Furthermore, the close association between the volume and reproductive capacity of the reproductive members corroborates an adaptive value of colony member size in determining the fitness of the trematode colony as a whole. The present study is the first to demonstrate a fitness consequence, and identify the determinants, of the growth of colony members in social trematodes.     

Does serotonin influence aggression? comparing regional activity before and during social interaction

Serotonin is widely believed to exert inhibitory control over aggressive behavior and intent. In addition, a number of studies of fish, reptiles, and mammals, including the lizard Anolis carolinensis, have demonstrated that serotonergic activity is stimulated by aggressive social interaction in both dominant and subordinate males. As serotonergic activity does not appear to inhibit agonistic behavior during combative social interaction, we investigated the possibility that the negative correlation between serotonergic activity and aggression exists before aggressive behavior begins. To do this, putatively dominant and more aggressive males were determined by their speed overcoming stress (latency to feeding after capture) and their celerity to court females. Serotonergic activities before aggression are differentiated by social rank in a region-specific manner. Among aggressive males baseline serotonergic activity is lower in the septum, nucleus accumbens, striatum, medial amygdala, anterior hypothalamus, raphe, and locus ceruleus but not in the hippocampus, lateral amygdala, preoptic area, substantia nigra, or ventral tegmental area. However, in regions such as the nucleus accumbens, where low serotonergic activity may help promote aggression, agonistic behavior also stimulates the greatest rise in serotonergic activity among the most aggressive males, most likely as a result of the stress associated with social interaction.     

What affects mRNA levels in leaves of field-grown aspen? A study of developmental and environmental influences

We have analyzed the abundance of mRNAs expressed from 11 nuclear genes in leaves of a free-growing aspen (Populus tremula) tree throughout the growing season. We used multivariate statistics to determine the influence of environmental factors (i.e. the weather before sampling) and developmental responses to seasonal changes at the mRNA level for each of these genes. The gene encoding a germin-like protein was only expressed early in the season, whereas the other tested genes were expressed throughout the season and showed mRNA variations on a day-to-day basis. For six of the genes, reliable models were found that described the mRNA level as a function of weather, but the leaf age was also important for all genes except one encoding an early light-inducible protein (which appeared to be regulated purely by environmental factors under these conditions). The results confirmed the importance of several environmental factors previously shown to regulate the genes, but we also detected a number of less obvious factors (such as the variation in weather parameters and the weather of the previous day) that correlated with the mRNA levels of individual genes. The study shows the power of multivariate statistical methods in analyzing gene regulation under field conditions.     

Innovative foraging behaviour in birds: what characterizes an innovator?

Innovative foraging behaviour has been observed in many species, but little is known about how novel behaviour emerges or why individuals differ in their propensity to innovate. Here, we investigate these questions by presenting 36 wild-caught adult male Carib grackles (Quiscalus lugubris) with a novel problem-solving task. Twenty birds solved the task (“innovators”) while 16 did not (“non-innovators”). We compared innovators to non-innovators and explored variation in latency to innovate to determine the characteristics of an innovative bird. Innovativeness was not predicted by any morphological trait, but innovators had higher exploration scores and lower object neophobia scores than non-innovators. Within the innovators, latency to innovate was positively correlated with learning speed. Video analysis also revealed a marked difference in the way individuals interacted with the novel apparatus: when innovators contacted the correct part of the apparatus, they continued to do so until they solved the problem. Non-innovators often contacted the correct part of the apparatus, but did not persist in doing so. The importance of obstacle movement cues was confirmed by an experiment where they were manipulated.     

Does the match between individual and group behavior matter in shoaling sticklebacks?

In animals living in groups, the social environment is fundamental to shaping the behaviors and life histories of an individual. A mismatch between individual and group behavior patterns may have disadvantages if the individual is incapable of flexibly changing its state in response to the social environment that influences its energy gain and expenditure. We used different social groups of juvenile three‐spined sticklebacks (Gasterosteus aculeatus) with experimentally manipulated compositions of individual sociability to study the feedback between individual and group behaviors and to test how the social environment shapes behavior, metabolic rate, and growth. Experimentally created unsociable groups, containing a high proportion of less sociable fish, showed bolder collective behaviors during feeding than did corresponding sociable groups. Fish within groups where the majority of members had a level of sociability similar to their own gained more mass than did those within mismatched groups. Less sociable individuals within sociable groups tended to have a relatively low mass but a high standard metabolic rate. A mismatch between the sociability of an individual and that of the majority of the group in which it is living confers a growth disadvantage probably due to the expression of nonadaptive behaviors that increase energetic costs.     

What determines the impact of alien birds and mammals in Europe?

An often-cited reason for studying the process of invasion by alien species is that the understanding sought can be used to mitigate the impacts of the invaders. Here, we present an analysis of the correlates of local impacts of established alien bird and mammal species in Europe, using a recently described metric to quantify impact. Large-bodied, habitat generalist bird and mammal species that are widespread in their native range, have the greatest impacts in their alien European ranges, supporting our hypothesis that surrogates for the breadth and the amount of resources a species uses are good indicators of its impact. However, not all surrogates are equally suitable. Impacts are generally greater for mammal species giving birth to larger litters, but in contrast are greater for bird species laying smaller clutches. There is no effect of diet breadth on impacts in birds or mammals. On average, mammals have higher impacts than birds. However, the relationships between impact and several traits show common slopes for birds and mammals, and relationships between impact and body mass and latitude do not differ between birds and mammals. These results may help to anticipate which species would have large impacts if introduced, and so direct efforts to prevent such introductions.     

Natal philopatry in passerine birds: genetic or ecological influences?

The degree of natal philopatry (the likelihood that individualsbreed at or near their place of origin) can influence the extentof inbreeding in animal populations. Passerine birds have beencited as typically showing high natal philopatry, and natalphilopatry has been proposed as an adaptation to promote optimalinbreeding. A review of published and unpublished studies ofpasserines showed that natal philopatry was typically low, somaintaining a high level of inbreeding appears relatively unimportantfor such birds. Rather, natal philopatry appeared to be morestrongly influenced by ecological factors. Migratory passerineexhibited low natal philopatry compared to resident passerines,as predicted if dispersal costs for young birds are an importantdeterminant of natal philopatry. The erroneous view that natalphilopatry for passerines is generally high has resulted froma reporting bias toward resident species that have sufficientnatal philopatry to study. Natal philopatry was found to beevolutionarily labile; populations of the same species and pairsof closely related species that differed in their degree ofisolation differed considerably in their degree of philopatry.Future studies of natal philopatry should consider both theecological factors that could affect dispersal costs and thereporting biases that influence which data on philopatry tendto be reported.     

Is individual consistency in body mass and reproductive decisions linked to individual specialization in foraging behavior in a long‐lived seabird?

Individual specialization in diet or foraging behavior within apparently generalist populations has been described for many species, especially in polar and temperate marine environments, where resource distribution is relatively predictable. It is unclear, however, whether and how increased environmental variability – and thus reduced predictability of resources – due to global climate change will affect individual specialization. We determined the within‐ and among‐individual components of the trophic niche and the within‐individual repeatability of δ¹³C and δ¹⁵N in feathers and red blood cells of individual female southern rockhopper penguins (Eudyptes chrysocome) across 7 years. We also investigated the effect of environmental variables (Southern Annular Mode, Southern Oscillation Index, and local sea surface temperature anomaly) on the isotopic values, as well as the link between stable isotopes and female body mass, clutch initiation dates, and total clutch mass. We observed consistent red blood cell δ¹³C and δ¹⁵N values within individuals among years, suggesting a moderate degree of within‐individual specialization in C and N during the prebreeding period. However, the total niche width was reduced and individual specialization not present during the premolt period. Despite significant interannual differences in isotope values of C and N and environmental conditions, none of the environmental variables were linked to stable isotope values and thus able to explain phenotypic plasticity. Furthermore, neither the within‐individual nor among‐individual effects of stable isotopes were found to be related to female body mass, clutch initiation date, or total clutch mass. In conclusion, our results emphasize that the degree of specialization within generalist populations can vary over the course of 1 year, even when being consistent within the same season across years. We were unable to confirm that environmental variability counteracts individual specialization in foraging behavior, as phenotypic plasticity in δ¹³C and δ¹⁵N was not linked to any of the environmental variables studied.     

Genetic and environmental influences on body fat distribution, fasting insulin levels and CVD: are the influences shared?

Central body fat distribution has been shown to be related to hyperinsulinemia, insulin resistance, hypertriglyceridemia, and atherosclerosis to a greater degree than general obesity. There are known to be both genetic and environmental effects on all components of this clustering. Whether these genetic effects are due to one set of genes in common to the components or whether genetic influences on insulin resistance and/or general/abdominal fatness 'turn on' other genes that affect other components of the syndrome is not clear. We analyzed data from the Swedish Adoption/Twin Study of Aging (60% female; monozygotic = 116, dizygotic = 202; average age 65 years) to determine whether there were genetic and/or environmental factors shared among general body fat distribution, abdominal body fat distribution, fasting insulin levels and cardiovascular disease. We found additive genetic effects in males to be significantly different from those in females with genetic effects accounting for variance in waist-hip ratio (males = 28%; females = 49%), body mass index (males = 58%; females = 73%), fasting insulin levels (FI) (males = 27%; females = 49%), and cardiovascular disease (CVD) (males = 18%; females = 37%). There were also shared genetic and environmental effects among all the variables except CVD, but a majority of the genetic variance for these measures was trait specific.     

Does social status within a dominance hierarchy mediate individual growth,residency and relocation?

The availability of food, and hence energy, is known to influence the abundance, habitat choice and growth of individuals. In contrast, there is a paucity of knowledge on how the interaction of energy supply and social status determines patterns of residency and movement. This study tests whether the presence of conspecifics and an individual’s social status in relation to food supply influence the fitness and movement of a drift-feeding fish (Galaxias fasciatus). Using an information-theoretic approach (AIC), our analysis indicated that the most parsimonious model of fish movement among pools was one that included food supply, social rank and fish relative growth rate. Our results indicated that subordinate fish relocated more frequently compared to dominant fish, most likely as a consequence of intra-specific competition that limited the access of these smaller fish to resources and constrained their growth. Our results suggest that energy constraints may force individuals to explore new habitats in an effort to find more energetically profitable patches. We conclude that intra-specific competition mediated through the social hierarchy amongst closely interacting individuals plays a key role in determining individual growth, residency and relocation.     

Is social coordination during escape flights a general phenomenon in birds?

Escape from predatory attack as a socially coordinated group is observed in many social animals, including birds, especially those in more open habitats where the group itself may be the only source of protection from an attacking predator. For many social birds, however, woody vegetative cover is the main refuge from attack, but such birds might nevertheless benefit from social coordination during escape flights to cover. Such benefits could reflect the confusion effect, selfish herd effect, or the simple dilution of risk. We examined this possibility of coordinated escape in mixed flocks of wintering passerellid sparrows (Passerellidae). These free-living birds fed in a patch of food flanked on opposite sides by two refuges composed of woody cover. Under such conditions, coordination in escape behavior should be expressed as a tendency to escape together as a group to the same cover location. Such behavior, however, was not the rule. During spontaneous flushes to cover, a group of escaping birds stayed together only when one cover location was clearly closer than the other. With cover equidistant from the food patch, escaping flocks tended to split about evenly between cover locations. Birds in close proximity prior to an escape flight did not show enhanced escape coordination, nor did those feeding at significant distances from protective cover. Evidence of escape coordination was observed in small groups (two–four birds), but even in such groups, flock splitting during escape was generally the rule. Flock splitting during attacks might reflect some sort of strategic decision-making process that lessens the risk of capture, but the most parsimonious explanation is that (all else equal) birds head for the nearest refuge, largely irrespective of the behavior of their flockmates. Our results thus provide little evidence of flock-wide social coordination during escape flights in cover-dependent birds.     

What defines successful integration into a social group for hand-reared chimpanzee infants?

Hand-rearing of captive great ape infants is sometimes necessary but can have negative behavioral consequences. Modern hand-rearing protocols, including early integration into a diverse group of conspecifics, appear to reduce the negative consequences of hand-rearing, but the process of integration is not well studied. We investigated six potential metrics of success during the introduction of two hand-reared chimpanzee infants into a troop of nine other chimpanzees at the Maryland Zoo in Baltimore. Little aggression was observed and the infants continue to be maintained in the troop at publication. As we predicted, during the introduction the hand-reared infants showed consistent levels of stress-related behaviors, participated in affiliative interactions with all available partners, and acted, received, and mutually engaged in these interactions. Solitary behaviors by these infants were similar to a mother-reared infant in the same group. Each infant also formed a relationship with a specific female that involved nest-sharing, carrying, retrieval, and intervening to reduce risk to the infant; these relationships could be classified as allomothering because they involved maternal behavior but occupied significantly less of the infants’ time than a maternal relationship. Contrary to our prediction, the hand-reared infants therefore spent significantly less time in social behavior than a mother-reared infant of the same age. In addition, the hand-reared infants continued to show strong social preferences for each other as introductions progressed and to direct a low but consistent number of nonfeeding social behaviors to humans. The successful introduction of hand-reared infants appeared to involve adding conspecific social relationships to the infants’ social repertoire, but not eliminating social interactions directed at humans.     

Schooling,dusk flight and dance: social organisations as amplifiers of individual quality?

One striking aspect of certain types of animal assemblages, for example fish schools or bird flocks, is the level of synchrony and spatial regularity that group members achieve. Although the evolutionary mechanisms leading to the formation of animal aggregations appear to be understood reasonably well, the evolution of spatial regularity and the high levels of synchrony that typify the groups in which certain animals move are less clear. Traditional explanations have generally focused on benefits gained during interspecific interactions, particularly the improvement of antipredator responses, or have suggested aero- or hydrodynamic advantages during locomotion. However, since the latter benefits of structural regularity may be largely rejected on theoretical grounds, and because many examples of spatially regular, synchronous groupings – such as dusk-flying flocks of some birds – may occur in the absence of predators, we suggest that these behaviours may not be explained solely in terms of locomotory efficiency or performance in predator-prey interactions. Instead, we suggest that the maintenance of regular spatial positions and the level of synchrony achieved within certain social groups may reveal honest information about an individual's neurosensory or locomotory performance, and that these behaviours may have evolved as amplifiers of individual quality. The evolution of such behaviour therefore need not have occurred as a result of interspecific interactions, but could have happened in the arena of conspecific evaluation.     

Do heterospecific size and demeanour influence visitation behaviour of birds at urban foraging patches?

We compared the feeding behaviour of garden birds in the presence of four heterospecific decoy species at suburban feeding stations to assess the relative importance of body size (large vs. small) and demeanour (high vs. low potential for inter-specific aggression) as cues for threat recognition. We conducted separate trials with live, caged Australian magpie, Cracticus tibicen, and common myna, Acridotheres tristis, large and small species known to chase and harass heterospecifics, and comparably sized species not known for inter-species aggression (i.e. rock dove, Columba livia, and ringneck dove, Streptopelia risoria). Birds of all species arrived at feeding stations sooner and displayed higher-risk activities in the presence of small decoys. The two most common species that visited the feeding stations, silvereye, Zosterops lateralis, and house sparrow, Passer domesticus, were most likely to perform high-risk behaviours (i.e. landing on the stimulus cage and feeding from the station) in the presence of common mynas. The activities were performed least frequently in the presence of Australian magpies. As garden birds likely had the most experience interacting with common mynas, the results suggest that a two-step decision rule, with size and familiarity as important cues, may be used to recognize potential threats.     

What is cooperative breeding in mammals and birds? Removing definitional barriers for comparative research

Cooperative breeding (i.e. when alloparents care for the offspring of other group members) has been studied for nearly a century. Yet, inconsistent definitions of this breeding system still hamper comparative research. Here, we identify two major inconsistencies, discuss their consequences and propose a way forward. First, some researchers restrict the term ‘cooperative breeding’ to species with non-breeding alloparents. We show that such restrictive definitions lack distinct quantitative criteria to define non-breeding alloparents. This ambiguity, we argue, reflects the reproductive-sharing continuum among cooperatively breeding species. We therefore suggest that cooperative breeding should not be restricted to the few species with extreme reproductive skew and should be defined independent of the reproductive status of alloparents. Second, definitions rarely specify the type, extent and prevalence of alloparental care required to classify species as cooperative breeders. We thus analysed published data to propose qualitative and quantitative criteria for alloparental care. We conclude by proposing the following operational definition: cooperative breeding is a reproductive system where >5% of broods/litters in at least one population receive species-typical parental care and conspecifics provide proactive alloparental care that fulfils >5% of at least one type of the offspring's needs. This operational definition is designed to increase comparability across species and disciplines while allowing to study the intriguing phenomenon of cooperative breeding as a behaviour with multiple dimensions.     

Group self-determination,individual rights,or social inclusion? Competing frames for ethnic counting in Hungary

Abstract

Despite increasing demand from policymakers and academics alike, effective policies on ethnic data collection for social inclusion purposes are still absent in most of Europe. This paper proposes to explain the failure to produce these policies by the coexistence of and tensions among contradictory frames on ethnic counting. An in-depth analysis of Hungarian policies reveals that three mutually inconsistent policy frames connect ethnic counting to ethnic diversity in many different ways. These frames are group self-determination, individual rights, and social inclusion. This paper illustrates the tensions among the three through a discussion of two core but divisive aspects of collecting ethnic statistics: defining ethnic classifications for counting and defining membership in ethnic groups for policy purposes. Tensions among the three result in inconsistent and inefficient policies of ethnic counting.