CiteULike: adriandefroment's library [1027 articles]

Information gathering and decision making about resource value in animal contests

Gareth Arnott — 2008-07-01T22:11:50-00:00

Animal Behaviour, Vol. In Press, Corrected Proof

Contestants are predicted to adjust the cost of a fight in line with the perceived value of the resource and this provides a way of determining whether the resource has been assessed. An assessment of resource value is predicted to alter an animal's motivational state and we note different methods of measuring that state. We provide a categorical framework in which the degree of resource assessment may be evaluated and also note limitations of various approaches. We place studies in six categories: (1) cases of no assessment, (2) cases of internal state such as hunger influencing apparent value, (3) cases of the contestants differing in assessment ability, (4) cases of mutual and equal assessment of value, (5) cases where opponents differ in resource value and (6) cases of particularly complex assessment abilities that involve a comparison of the value of two resources. We examine the extent to which these studies support game theory predictions and suggest future areas of research.

Inaugural Article: Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli

Zachary Blount — 2008-06-05T14:39:36-00:00

Proceedings of the National Academy of Sciences (4 June 2008), 0803151105.

The role of historical contingency in evolution has been much debated, but rarely tested. Twelve initially identical populations of Escherichia coli were founded in 1988 to investigate this issue. They have since evolved in a glucose-limited medium that also contains citrate, which E. coli cannot use as a carbon source under oxic conditions. No population evolved the capacity to exploit citrate for >30,000 generations, although each population tested billions of mutations. A citrate-using (Cit+) variant finally evolved in one population by 31,500 generations, causing an increase in population size and diversity. The long-delayed and unique evolution of this function might indicate the involvement of some extremely rare mutation. Alternately, it may involve an ordinary mutation, but one whose physical occurrence or phenotypic expression is contingent on prior mutations in that population. We tested these hypotheses in experiments that "replayed" evolution from different points in that population's history. We observed no Cit+ mutants among 8.4 x 1012 ancestral cells, nor among 9 x 1012 cells from 60 clones sampled in the first 15,000 generations. However, we observed a significantly greater tendency for later clones to evolve Cit+, indicating that some potentiating mutation arose by 20,000 generations. This potentiating change increased the mutation rate to Cit+ but did not cause generalized hypermutability. Thus, the evolution of this phenotype was contingent on the particular history of that population. More generally, we suggest that historical contingency is especially important when it facilitates the evolution of key innovations that are not easily evolved by gradual, cumulative selection. 10.1073/pnas.0803151105

Genes and causation.

Denis Noble — 2008-06-19T15:26:18-00:00

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences (17 June 2008)

Relating genotypes to phenotypes is problematic not only owing to the extreme complexity of the interactions between genes, proteins and high-level physiological functions but also because the paradigms for genetic causality in biological systems are seriously confused. This paper examines some of the misconceptions, starting with the changing definitions of a gene, from the cause of phenotype characters to the stretches of DNA. I then assess whether the 'digital' nature of DNA sequences guarantees primacy in causation compared to non-DNA inheritance, whether it is meaningful or useful to refer to genetic programs, and the role of high-level (downward) causation. The metaphors that served us well during the molecular biological phase of recent decades have limited or even misleading impacts in the multilevel world of systems biology. New paradigms are needed if we are to succeed in unravelling multifactorial genetic causation at higher levels of physiological function and so to explain the phenomena that genetics was originally about. Because it can solve the 'genetic differential effect problem', modelling of biological function has an essential role to play in unravelling genetic causation.

Policies Designed for Self-Interested Citizens May Undermine "The Moral Sentiments": Evidence from Economic Experiments

Samuel Bowles — 2008-06-20T08:07:59-00:00

Science, Vol. 320, No. 5883. (20 June 2008), pp. 1605-1609.

High-performance organizations and economies work on the basis not only of material interests but also of Adam Smith's "moral sentiments." Well-designed laws and public policies can harness self-interest for the common good. However, incentives that appeal to self-interest may fail when they undermine the moral values that lead people to act altruistically or in other public-spirited ways. Behavioral experiments reviewed here suggest that economic incentives may be counterproductive when they signal that selfishness is an appropriate response; constitute a learning environment through which over time people come to adopt more self-interested motivations; compromise the individual's sense of self-determination and thereby degrade intrinsic motivations; or convey a message of distrust, disrespect, and unfair intent. Many of these unintended effects of incentives occur because people act not only to acquire economic goods and services but also to constitute themselves as dignified, autonomous, and moral individuals. Good organizational and institutional design can channel the material interests for the achievement of social goals while also enhancing the contribution of the moral sentiments to the same ends. 10.1126/science.1152110

Assessment during aggressive contests between male jumping spiders

Damian Elias — 2008-07-01T21:35:22-00:00

Animal Behaviour, Vol. In Press, Corrected Proof

Assessment strategies are an important component in game theoretical models of contests. Strategies can be either based on one's own abilities (self-assessment) or on the relative abilities of two opponents (mutual assessment). Using statistical methodology that allows discrimination between assessment types, we examined contests in the jumping spider Phidippus clarus. In this species, aggressive interactions can be divided into [`]precontact' and [`]contact' phases. Precontact phases consist of bouts of visual and vibratory signalling. Contact phases follow where males physically contact each other (leg fencing). Both weight and vibratory signalling differences predicted winners, with heavier and more actively signalling males winning more contests. Vibratory behaviour predicted precontact phase duration, with higher signalling rates and larger differences between contestants leading to longer precontact interaction times. Contact phase duration was predicted most strongly by the weight of losing males relative to that of winning males, suggesting that P. clarus males use self-assessment in determining contest duration. While a self-assessment strategy was supported, our results suggest a secondary role for mutual assessment ([`]partial mutual assessment'). After initial contest bouts, male competitors changed their behaviour. Precontact and contact phase durations were reduced while vibratory signalling behaviour in winners was unchanged. In addition, only vibratory signalling differences predicted winners in subsequent bouts, suggesting a role of experience in determining contest outcomes. We suggest that the rules and assessment strategies that males use can change depending on experience and that assessment strategies are probably a continuum between self-assessment and mutual assessment.

Repeated measures of shoaling tendency in zebrafish (Danio rerio) and other small teleost fishes

Dominic Wright — 2008-06-22T17:31:26-00:00

Nat. Protocols, Vol. 1, No. 4. (November 2006), pp. 1828-1831.

Why social dominance theory has been falsified

JC Turner — 2008-04-15T20:53:27-00:00

British Journal of Social Psychology (June 2003), pp. 199-206.

Schmitt, Branscombe and Kappen (2003) and Wilson and Lui (2003) present a persuasive series of studies which raise major problems for the conceptualization of social dominance orientation in social dominance theory. Building on these and other data in the literature, this commentary summarizes six fundamental criticisms which can be made of the theory. We conclude that social dominance theory is flawed by conceptual inconsistencies and has been disconfirmed empirically in relation to its key hypothesis of behavioural asymmetry. The reaction of subordinate groups to the social hierarchy is better explained by social identity theory.

Social defeat as a stressor in humans

Kaj Björkqvist — 2008-05-14T13:33:08-00:00

Physiology & Behavior, Vol. 73, No. 3. (June 2001), pp. 435-442.

Studies on social defeat in humans, and their similarities with studies on social defeat in animals are reviewed. Studies on social defeat in humans typically are conducted as a branch of social psychology, most often focusing on bullying in schools and in workplaces. Victims of bullying are known to suffer from depression, anxiety, sociophobia, loss of self-esteem, psychosomatic diseases, and other behavioral symptoms. On the other hand, animal studies on social defeat, usually based on the rodent resident-intruder paradigm, present findings related to physiological rather than to behavioral consequences of defeat. The two branches use different terminology, e.g., "dominant" and "subordinate" (animal studies) and "bully" and "victim" (human studies). It is suggested that the two fields could benefit from a mutual exchange in theory and methodology.

Expectations, Legitimation, and Dominance Behavior in Task Groups

Cecilia Ridgeway — 2008-05-14T13:32:04-00:00

Determinants of Dominance in Male Sticklebacks (Gasterosteus Aculeatus L.)

Th Bakker — 2008-05-14T13:29:48-00:00

Behaviour (1983), pp. 55-71.

When two males of the three-spined stickleback (Gasterosteus aculeatus L.) in reproductive condition are placed in a tank of small size, one becomes dominant over the other in a very short time. In this way a group of isolated reproductive males were tested pairwise on their capacity to become dominant. It appeared that the males could be arranged in a linear order of dominance. Their rank was to some extent correlated with their territorial aggressiveness as assessed in other tests. Their experience in previous dominance tests played a more important role. The brightness of their colouration, however, was probably the most consistent and decisive determinant of dominance. The interaction of colour and experience could be traced in the outcome of the dominance tests. The occurrence of roundabout fighting is discussed.

Social Status and Mating Activity in Elephant Seals.

Burney J Le Boeuf — 2008-05-14T13:27:35-00:00

Science (New York, N.Y.), Vol. 163, No. 3862. (3 January 1969), pp. 91-93.

Individually marked male elephant seals, Mirounga angustirostris, observed on an island off central California participate in a social hierarchy resembling the peck order of domestic chickens. Individuals achieve status by fighting and maintain it by stereotyped threat displays. The higher the status of a male, the more readily he approaches and copulates with females. Four percent of the males inseminated 85 percent of the females.

Social Dominance and Energy Reserves in Flocks of Willow Tits

Simon — 2008-05-14T13:22:40-00:00

Environmental and Social Determinants of Winter Fat Storage in the Great Tit Parus major

Andrew Gosler — 2008-05-14T13:21:17-00:00

It Is Expensive to Be Dominant

Olav Hogstad — 2008-05-14T13:19:52-00:00

The Cost of Dominance and Advantage of Subordination in a Badge Signaling System

Sievert — 2008-05-14T13:18:30-00:00

Effects of Dispersal Date on Winter Flock Establishment and Social Dominance in Marsh Tits Parus palustris

Jan-Ake — 2008-05-14T13:17:23-00:00

Phenotypic Correlates and Ecological Consequences of Dominance in Song Sparrows

P Arcese — 2008-05-14T13:16:37-00:00

Age-Related Effects of Testosterone, Plumage, and Experience on Aggression and Social Dominance in Juvenile Male Satin Bowerbirds (Ptilonorhynchus violaceus)

Ken Collis — 2008-05-14T13:13:16-00:00

Status Signaling in Harris Sparrows: Some Experiments in Deception

Sievert Rohwer — 2008-05-14T13:12:33-00:00

Behaviour (1977), pp. 107-129.

(1) Harris Sparrows signal their social dominance status by variations in the amount of black feathering on their crowns and throat. The potential ability of individuals to cheat on such a status signaling system was experimentally investigated by dyeing and bleaching some free-ranging individuals in a flock attracted to a bait station. As discussed in detail, cheating is a theoretically important problem because survival studies have shown subordinates to be much less likely to survive over winter than dominants. If true, this should result in strong directional selection toward the dominant plumage type. (2) Subordinates dyed to mimic the highest ranking birds of the winter hierarchy were, with but one exception, persecuted by the legitimate studlies. The single exception was apparently a bird which had underestimated his status during the fall molt when the appropriate plumage signal is produced. (3) Bleached birds were forced to fight much more for their status, as dramati. cally shown by what was likely the first encounter between a bleached bird and a normal individual of just slightly lower rank. Eventually the bleached birds behaved as though all others around them were perceived as disrespectful, and despotically attacked birds at an abnormally high rate. (4) While these data strongly suggest that cheating is socially controlled, such a social organization raises some complex evolutionary issues. An alternative explanation of the apparent social control of cheating is that the unusual behavior observed in response to my manipulations merely represented normal defense of winter resources. This explanation requires that the rate of winter dominance inter-actions be controlled by (1) the risk of attack, and (2) the importance of resource defense. If this is true, the dyed birds may have appeared sick since no hormonal manipulation accompanied their dyeing; thus they may have been attacked more because perceived risk was down and potential gain high (beat the toughy while he is down). Likewise, the bleached birds may have become unusually aggressive because the closer approach of low ranked birds suggested to them that a much more active defense of resources was required. Experiments distinguishing these hypothesis have not yet been performed.

Social rank in winter flocks of Willow Tits Parus montanus

OLAV Hogstad — 2008-05-14T13:10:14-00:00

Ibis, Vol. 129, No. 1. (1987), pp. 1-9.

The social hierarchies in winter of ten flocks of Willow Tits Parus montanus were studied when the birds were foraging naturally and when visiting feeders. All the flocks consisted of one adult mated pair together with two juvenile males and two juvenile females (probably pairs). All flocks studied had a stable composition and the hierarchies remained constant throughout the study period. The hierarchies were linear and unilateral. The adults of each sex dominated the respective juveniles and within each age group the male dominated the female. The dominance relationships between the age and sex groups were not consistent. Although the males dominated all the females in six flocks, in one flock the adult female dominated both the juvenile males, but only one of them in three other flocks. The degree of aggression between flock-members was 0.8 encounters per hour, and males initiated 94% of all attacks. Body-weight explained 77% of the variation in dominance rank. It is suggested that the dominance rank of a male is also a function of his seniority, while the rank of a juvenile female is correlated with the rank of her mate.

The interaction of dominance status and supplemental tryptophan on aggression in Gallus domesticus males

Margaret Shea — 2008-05-14T13:08:28-00:00

Pharmacology Biochemistry and Behavior, Vol. 38, No. 3. (March 1991), pp. 587-591.

In previous studies, we have found that supplemental dietary tryptophan (TRP) decreases aggression in feed-restricted male chickens (Gallus domesticus). The objective of this study was to determine if social status influences the effect which TRP has on aggression. In both experiments, Gallus males were placed on a commercial feed restriction program in which measured amounts of feed are delivered on alternate days beginning at 4 weeks of age. In the first study, birds were fed either 0.19 (control), 0.75 and 1.5% dietary TRP. In the second study, birds were fed either 0.19, 0.38, 0.75 or 1.5% dietary TRP. Dominance hierarchies were linear (p < 0.05) in all treatment groups as indicated by Landau's indices, which ranged from 0.87 to 0.98. A significant interaction was found between dominance status and supplemental TRP for aggression, with TRP decreasing pecking more in dominant than subordinate birds. In Experiment 1, there were positive correlations (p < 0.05) between body weight and dominance status in both the control and 0.75% TRP group (p < 0.05) and no correlation in the 1.5% TRP group. The decrease in aggression by dominant males may have allowed subordinate birds to gain greater access to the feed. Our results indicate that dominant and subordinate males show a differential sensitivity to the effects of dietary TRP, with TRP decreasing pecking more in dominant birds.

Behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl.

JA Mench — 2008-05-14T13:08:08-00:00

Hormones and behavior, Vol. 25, No. 1. (March 1991), pp. 112-122.

An experiment was conducted to determine the behavioral and hormonal correlates of social dominance in stable and disrupted groups of male domestic fowl (Gallus domesticus). In addition, the relative importance of visual and auditory cues in the maintenance of dominance status in this species was assessed. Alpha roosters were removed from their six-bird home pens for 1 week, and placed in either (1) and adjacent pen in visual contact with penmates, (2) and adjacent pen where visual, but not auditory, contact was prevented, or (3) a different building where they were in visual and auditory isolation. Dominance rank, aggressive activity, and crowing frequency were intercorrelated during the premove period. There was a significant increase in both aggression and crowing among the males remaining in the home pen following removal of the alpha male, except in the treatment in which males were still in visual contact with the removed alpha, in which only aggression increased. Increases in crowing frequency were also noted in alpha males. High levels of aggression occurred when alpha males were returned except in those pens in which visual contact had been maintained. Visual cues thus appear to be more important than auditory cues alone with respect to the maintenance of dominant social status in roosters. There were no clear correlations between behavioral variables and plasma androgen or corticosterone levels in either the stable or disrupted flocks, and no consistent changes in the levels of these hormones as a result of experimental manipulation; several possible explanations for this finding are discussed.

Social rank in house mice: differentiation revealed by ultraviolet visualization of urinary marking patterns.

C Desjardins — 2008-05-14T13:06:46-00:00

Science (New York, N.Y.), Vol. 182, No. 115. (20 November 1973), pp. 939-941.

Ultraviolet light has been used to examine urine marks deposited by adult male house mice on filter paper on the floors of their cages during overnight tests. Both the urination frequency and the pattern in which urine was deposited on the filter paper depended upon social rank. Dominant males vigorously marked their entire cage floor, whereas subordinate males typically voided urine in only two to four pools in the corners of their cages.

Behavioural, physiological and immunological consequences of social status and aggression in chronically coexisting resident-intruder dyads of male rats

A Raab — 2008-05-14T13:06:11-00:00

Physiology & Behavior, Vol. 36, No. 2. (1986), pp. 223-228.

The behavioural and physiological consequences of social status and reciprocal fighting in resident-intruder dyads of Long Evans male rats were evaluated. Before a chronic cohabitation of 10 days, residents and intruders were individually housed for one month to increase their aggressiveness. Control animals included isolates, i.e., animals kept individually housed throughout the experiment and pair-housed rats, i.e., pairs of rats housed together from their rats in the laboratory. In 19 out of 20 dyads, a clear dominance relationship developed with an advantage to the resident in 68% of the cases. Dominants showed more exploratory activity than subordinates in an open-field test at the end of the cohabitation period; subordinates groomed longer than animals from other experimental groups. Dominants had lower pain thresholds than individually and pair-housed animals. Both dominants and subordinates had higher tyrosine hydroxylase enzymatic activities in the left adrenal than isolated and pair-housed rats. Subordinates lost body weight and had higher plasma corticosteroid concentrations than animals from the other experimental groups. In addition, they had smaller thymus glands and reduced spleen lymphocyte responses to mitogenic stimulation in vitro, in comparison to dominant animals. These results show that subordination in the dyadic resident-intruder paradigm leads to a complex syndrome of behavioural and physiological changes, some of which may be modulated by the intensity of aggressive interactions.

Interindividual Variability in Swiss Male Mice: Relationship between Social Factors, Aggression, and Anxiety

PF Ferrari — 2008-05-14T13:03:31-00:00

Physiology & Behavior, Vol. 63, No. 5. (March 1998), pp. 821-827.

In the present study we carried out a series of experiments in Swiss albino male mice to investigate a) the effects of previous social experience on the levels of anxiety in the elevated plus-maze (EPM) and b) whether the response of males in the EPM differs in relation to the different social status. In Experiment 1 we tested in the EPM male mice that received different social experience. Results showed that individually housing generally increased measures of anxiety in the EPM compared with the group-housing condition. Moreover, aggressive males, screened during dyadic encounters in a neutral cage, displayed the highest levels of anxiety relative to the other experimental conditions. In Experiment 2 male mice remained group-housed and were observed to record their social status. Results showed that those animals rated as socially dominant displayed a higher level of EPM anxiety relative to subordinates. From an ethological perspective our findings may be interpreted in terms of coping strategies, with aggressive/dominant animals typified by higher levels of risk assessment and open-arm avoidance than defensive/subordinate animals.

Chemistry of male dominance in the house mouse,Mus domesticus

M Novotny — 2008-05-14T13:02:39-00:00

Cellular and Molecular Life Sciences (CMLS), Vol. 46, No. 1. (1 January 1990), pp. 109-113.

Summary Two terpenic constituents, E,E,-α-farnesene and E-β-farnesene, were found to be elevated in dominant male urine when compared to subordinate or control males. These two urinary compounds were absent in the bladder urine of males; however, they were the most prominent constituents of the preputial gland's aliquots. The results of a two-choice preference test, conducted on ICR/Alb subordinate males, gave a strong indication that these two terpenic constituents introduced into the previously attractive stimulus significantly discouraged prolonged investigations by male mice. The compounds, whether present in the urine matrix or water, rendered the stimulus with a quality behaviorally similar to the urine of dominant males. It appears that they may be synonymous with the previously described aversion signal produced by dominant males. We suggest that these compounds may play a wide-ranging role in the territorial marking behavior of male mice.

Social stress in mice: Gender differences and effects of estrous cycle and social dominance

Paola Palanza — 2008-05-14T13:01:45-00:00

Physiology & Behavior, Vol. 73, No. 3. (June 2001), pp. 411-420.

A large discrepancy in the possibility of inducing social stress in the two genders exists. Since generalizations of findings from one sex to the other appear not to be valid, reliable models of social stress in females are needed. We examined the effects of social context in the housing environment, as a possible source of stress, on exploration and anxiety in male and female mice, taking into account the estrous phase for females and the social status for males as additional variables. Mice housed individually or with siblings were tested in a free-exploratory paradigm of anxiety (where test animals have a choice to stay in their home cage or to explore an open field, OF). Individually housed females did not leave their home cage for long periods, explored less the unfamiliar area and displayed higher risk assessment, a behavioral profile suggestive of lower propensity for exploration and higher level of anxiety compared with group-housed females. Individually housed males tended to show an opposite profile. Proestrus mice were less sensitive to the decrease of exploratory propensity induced by individually housing compared to estrus and diestrus mice. Social dominants and social subordinates in sibling groups did not differ in their exploratory responses to the OF. Different housing procedures, as means to provide different social environment, may differentially induce mild social stress in male and female mice.

Effects of environmental enrichment on aggressive behavior, dominance hierarchies, and endocrine states in male DBA/2J mice

Andreas Haemisch — 2008-05-14T13:00:26-00:00

Physiology & Behavior, Vol. 56, No. 5. (November 1994), pp. 1041-1048.

Adult male mice (DBA/2J) siblings were housed three per cage for 6 wk, either in standard cages (SC) or in enriched cages (EC). Both attacks among group members and attacks against strange intruders were monitored once a week within each of 22 experimental groups. According to its attacking behavior, each mouse was categorized into one of three dominance categories: dominant, subdominant active, subdominant passive. Aggressive behavior and social organization were compared between the two types of housing conditions, and the effects of housing condition and dominance category on endocrinological and some organometrical parameters were analysed. The main findings were: (a) Mice in EC attacked intruders significantly more frequently compared to mice in SC; (b) In EC groups the position of the dominant male was less stable than in SC groups; (c) Plasma corticosterone titers (PCT) were significantly elevated in EC. Activities of tyrosinehydroxylase (TH) and phenylethanolamine-N-methyltranferase (PNMT) did not differ significantly between the housing conditions; (d) TH and PNMT activity were significantly enhanced in the dominant males of SC groups compared to subdominant passive males. Intermediate activities for both enzymes were determined for subdominant active males; and (e) PCT were significantly elevated in dominant males of the EC groups compared to subdominant active and subdominant passive males and also compared to the dominant males in the SC groups. Findings suggest that keeping adult male mice in structured cages can result in increased aggression towards intruders, a change in the social organization, and altered endocrine states, depending on the individual dominance position.

Can laboratory studies on dominance predict fitness of young brown trout in the wild?

Johan Höjesjö — 2008-05-14T12:59:20-00:00

Behavioral Ecology and Sociobiology, Vol. 52, No. 2. (1 July 2002), pp. 102-108.

Laboratory studies suggest that dominance and aggression increase fitness, but this hypothesis has rarely been tested under natural conditions. We therefore designed a combined laboratory-field experiment to detect how social status and aggression relate to growth rate, movement and habitat choice in a natural stream. In 1998 and 1999, juvenile brown trout were caught in the wild and paired in staged dyadic contests in the laboratory where relative dominance rank was determined. Three categories of fish could be distinguished: dominants, subordinates and non-aggressive individuals of indeterminate status. All tested fish were released back into the stream and recaptured after 3 and 8 weeks. Dominant fish grew faster than subordinates, but non-aggressive fish grew as fast as dominants. Social status had no significant effect on recapture rates. Movement was not significantly related to status, but smaller individuals were more mobile and preferred faster-flowing habitats closer to the shore than larger fish. The utilisation of pool and riffle habitats varied among status categories, but this relationship was not consistent between years. These results support the hypothesis that dominance increases fitness in the wild. However, our findings also indicate that less aggressive individuals can be successful in heterogeneous natural habitats. Thus, studies performed under laboratory conditions may overestimate the fitness advantage of aggressive behaviour.

Intraspecific variation in competitive ability and food intake in salmonids: consequences for energy budgets and growth rates

NB Metcalfe — 2008-05-14T12:57:42-00:00

Journal of Fish Biology, Vol. 28, No. 5. (1986), pp. 525-531.

The interactions between dominance status, feeding rate and growth in rainbow trout, Salmo gairdneri Richardson, were analyzed using published data on experimental populations. There was a positive correlation between metabolic expenditure and food intake in both dominant and subordinate fish, but dominants obtained a greater intake for a given expenditure than did subordinates. Subordinates that adopted a high-return/high-cost foraging strategy actually expended more energy than they acquired, whereas those that minimized energy expenditure obtained a net energy gain. This led to the surprising finding that the growth rate of subordinates was negatively correlated with food intake.

Relationships between social status, otolith size at first feeding and subsequent growth in Atlantic Salmon (Salmo salar)

Neil Metcalfe — 2008-05-14T12:55:04-00:00

Early social status and the development of life-history strategies in Atlantic salmon.

NB Metcalfe — 2008-05-14T12:52:22-00:00

Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain), Vol. 236, No. 1282. (22 February 1989), pp. 7-19.

Atlantic salmon have a variable life cycle. In good growing conditions, underyearling fish may metamorphose into the migratory smolt phase during their second spring, or delay at least a further year. The strategy adopted by particular fish appears to become fixed during their first summer. This paper examines whether either feeding efficiency or dominance in mid-summer correlates with the life-history strategy adopted. Eighty fish were individually marked and their feeding efficiency (= mean handling time for food items) and dominance rank measured under laboratory conditions in mid-July. Growth rates of the fish were then monitored over the next three months, until developmental strategies became apparent. Discriminant and logistic regression analyses revealed that both dominance rank and size attained by July were independent, significant predictors of future developmental pattern (the age at metamorphosis being correctly predicted on the basis of rank and size in 84% of cases) whereas feeding efficiency had no effect. Thus fish that were dominant or larger two months after first feeding or both had a greater probability of migrating after only one year in freshwater than those more subordinate or smaller or both.

Foraging under the risk of predation in juvenile Atlantic salmon (Salmo salar L.) : effects of social status and hunger

Vytenis Gotceitas — 2008-05-14T12:51:26-00:00

Behavioral Ecology and Sociobiology, Vol. 29, No. 4. (1 November 1991), pp. 255-261.

Following exposure to a predator, socially dominant individuals may reduce their risk of predation by waiting until subordinates have resumed foraging before doing so themselves. Although such status-related ordering in the resumption of foraging activity has been observed in several bird species, the underlying mechanism(s) facilitating such a delay remains unknown. Social status per se and status-related foraging benefits prior to a threat of predation (i.e., individual hunger level) have both been suggested as possible mechanisms. We tested between these two alternative suggestions using pairs of stream-dwelling juvenile Atlantic salmon, for which the dominant-subordinate relationship was known. Fish were tested at equal and unequal hunger levels. Fish were presented with drifting prey, followed by a predation threat in the form of an aerial predator model. Which fish (i.e., dominant or subordinate) initially resumed foraging activity after exposure to the predator model was recorded. When both fish were at an equal hunger level, the dominant fish was more likely to resume foraging first. When the dominant and subordinate fish differed in their hunger level, the hungrier fish was the first to resume foraging regardless of social status. These results support the conclusion that hunger level, rather than social status per se, determines the order in which juvenile Atlantic salmon resume foraging after exposure to a predator.

Effect of Dominance Status on Sex Hormone Levels in Laboratory and Wild-Spawning Male Trout

James Cardwell — 2008-05-14T12:50:42-00:00

General and Comparative Endocrinology, Vol. 101, No. 3. (March 1996), pp. 333-341.

We investigated the relationship between male social status and hormone levels in salmonids spawning under laboratory and field conditions. In small groups of rainbow trout (Onchorhynchus mykiss) spawning in the laboratory, dominant males had higher plasma levels of testosterone (T) and 17[alpha],20[beta]-dihydroxy-4-pregnen-3-one (17,20[beta]-P) compared with subordinates. Steroid levels increased in subordinate males that became dominant after dominant males were experimentally removed; higher steroid levels in dominant males appears to be a result rather than a cause of their social status. In free-ranging brown trout (Salmo trutta) sampled in the field, we found higher levels of 11-ketotestosterone (11KT) but not T in dominant males. No significant differences in levels of either androgen were found between dominant and subordinate male brook trout (Salvelinus fontinalis) sampled at the same field location. Furthermore, in marked contrast with the laboratory fish, there were no significant differences in plasma 17,20[beta]-P between dominant and subordinate males in either species of fish in the wild. The different findings in the laboratory and field may indicate species differences in behavioral endocrinology among brook, brown, and rainbow trout. Alternatively, the greater differential in hormonal profile of dominant and subordinate males in the laboratory may reflect the relative uniformity of the laboratory environment; this simple environment may allow competitively superior males to more completely dominate less competitive tank-mates and to exclude them from female sexual cues. In any case, these results suggest that the relationship between steroid hormones and spawning behavior in male salmonids is likely more complex than suggested by experiments conducted solely on laboratory-held rainbow trout.

Early predictors of life-history events: the link between first feeding date, dominance and seaward migration in Atlantic salmon, Salmo salar L.

NB Metcalfe — 2008-05-14T12:49:51-00:00

Journal of Fish Biology, Vol. 41, No. sb. (1992), pp. 93-99.

Previous studies have suggested that the earliest fry to emerge from a salmonid redd may have an advantage in the subsequent competition for feeding sites, partly through a 'prior residence' effect. Here we examined whether there was any relationship between the relative date of first feeding and subsequent dominance status and growth in a sibling group of Atlantic salmon, Salmo salar L., fry. Earlier-feeding fry were dominant over their later-feeding siblings (controlling for prior residence), despite not being any larger. However, these early fish soon established and then maintained a size advantage. This led to an increased probability of early-feeding fish migrating to sea at age 1 year (rather than 2 or more). Thus a difference of less than 1 week in the relative timing of first feeding can translate into a year's difference in the timing of migration.

INDIVIDUAL AND STATUS RECOGNITION IN THE CRAYFISH, ORCONECTES RUSTICUS: THE EFFECTS OF URINE RELEASE ON FIGHT DYNAMICS

Rebecca Schneider — 2008-05-14T12:49:23-00:00

Behaviour (2001), pp. 137-153.

This study examined individual and status recognition in dyadic interactions between crayfish and determines how blocking the release of urine, a known source of chemical cues, may influence recognition. Behavioral characteristics of agonistic interactions were compared between crayfish pairs that fought each other previously (familiar) and pairs derived from individuals with past status history but no previous experience with one another (unfamiliar). To address the role of urine born chemical cues in recognition, fight dynamics were examined in urine blocked and non-blocked familiar and unfamiliar pairs. Our results indicate the existence of status recognition in crayfish as first fights were longer than second fights and the statistical interaction between fight number and familiar/unfamiliar treatment was similar. Urine cues play a role in social recognition in that fights are longer and more intense when urine cues are absent than when urine cues are present. Communication of behavioral state through urine appears to play an important role in the agonistic interactions of crayfish.

Physiological effects of dominance hierarchies: laboratory artefacts or natural phenomena?

KA Sloman — 2008-05-14T12:47:40-00:00

Journal of Fish Biology, Vol. 61, No. 1. (2002), pp. 1-23.

Studies of fish behaviour have demonstrated the existence of social interactions that result in dominance hierarchies. In environments in which resources, such as food, shelter and mates, are limited, social competition results in some fish becoming dominant and occupying the most profitable positions. This behaviour has been observed in natural environments and also in many laboratory-based experiments. When two fish have been confined in a small tank, one of them usually has exhibited behaviour that suggests it is dominant over the other submissive animal. Physiological consequences of social interaction can be seen in both dominants and subordinates but are more extreme in the subordinate. However, this scenario is without doubt an artificial situation. Fewer experiments have been conducted using laboratory experiments that are more socially and physically complex than those experienced by dyads in tanks. In simple fluvial tanks, through which water is recirculated, the physiological responses of fish to social competition have generally been qualitatively similar to those recorded among dyads. However, when environmental disturbances, complex resource distributions, increase in water flushing, presence of predators and competing species of fish have been included in experimen-tal designs, there have been fewer, diminished or no physiological dierences between dominant and subordinate fish. There have been very few studies of physiology in relation to dominance in natural habitats, and those that have been conducted suggest that under some circumstances hierarchies may cause less intense physiological responses than have been suggested based on results of laboratory studies in simple environments. Possible reasons for these variations are discussed. The need is identified for a well structured experimental approach to the investi-gation of the causes and consequences of hierarchies if the ecology of wild fish is to be modelled eectively based on physiological processes. It is also suggested that the further development and application of techniques for monitoring physiologies of fish in the wild is important.

The Effect of Social Experience on Serotonergic Modulation of the Escape Circuit of Crayfish

Shih-Rung Yeh — 2008-05-14T12:36:29-00:00

Science, Vol. 271, No. 5247. (19 January 1996), pp. 366-369.

10.1126/science.271.5247.366

The effects of cage cleaning on aggression within groups of male laboratory mice

Samantha Gray — 2008-05-14T12:35:14-00:00

Animal Behaviour, Vol. 49, No. 3. (March 1995), pp. 821-826.

Cage cleaning is an unavoidable but frequent source of disturbance for mice maintained in the laboratory. A series of tests was conducted to assess how physical disturbance, the removal of odour cues and exposure to the odours of strangers experienced during cage cleaning affects aggression within established groups of male CFLP mice, Mus musculus. Handling mice decreased the latency to attack and increased the frequency and duration of aggression within groups. Transferring mice into completely clean cages reduced aggression compared to those replaced in home cages that had not been cleaned. Exposure to the odours of strangers while males were held temporarily in a handling bin had no significant effect on aggression when the males were transferred to clean cages or returned to their home cages. Aggression was greatest when mice were replaced in home cages that had not been cleaned but that had a clean sawdust substrate, and decreased with increasing removal of home cage odours on the cage base and grill. Common cage-cleaning practices in which only the substrate and parts of the cage are cleaned, and other procedures that involve daytime handling and replacing mice in their home cage may thus promote aggression within male groups. Transferring mice into completely clean cages is recommended when aggression within caged groups of males is a concern.

The response of subordinate male mice to scent marks varies in relation to their own competitive ability

Morris Gosling — 2008-05-14T12:34:58-00:00

Animal Behaviour, Vol. 52, No. 6. (December 1996), pp. 1185-1191.

Previous work has shown that dominant male mice,Mus musculus, are usually attracted to scent-marked areas while subordinates avoid them. In this study, the responses of subordinates were highly variable, and the idea that the probability of intruding onto a scent-marked substrate depends on their competitive ability was tested. Subjects were kept in dominant/subordinate pairs of males and tested with scent marks of an unfamiliar male. Subordinates who were large in relation to their dominant partners were more likely to choose a scent-marked substrate in a Y-maze choice against a blank substrate; relatively small subordinates were more likely to avoid scent marks. Males that chose scent marks also tended (P=0.08) to be more often involved in escalated contests with their dominant partners. Body size is known to affect the outcome of fights between strangers and these results could be explained if relatively large subordinates are (1) more likely to be able to defeat the resident of a scent-marked area (and thus benefit from its resources) and (2) if large subordinates pose a greater threat of a dominance reversal to their dominant partners than would a relatively small subordinate.

Badge, Body and Testes Size in House Sparrows Passer domesticus

Møller — 2008-05-14T12:33:06-00:00

Social rank and antipredator behaviour of Willow Tits Parus montanus in winter flocks

OLAV Hogstad — 2008-05-14T12:32:30-00:00

Ibis, Vol. 130, No. 1. (1988), pp. 45-56.

Field experiments on three free-ranging Willow Tit winter flocks, each consisting of one adult pair and two male and two female juveniles (first-year birds), were performed to examine whether preferences for feeding site and antipredator behaviour are related to social rank. The dominance structure was the same in all flocks; adult male > juvenile male 1 > juvenile male 2 > adult female > juvenile female 1 > juvenile female 2. The proportion of time spent scanning for predators was positively correlated with distance from cover, and adults scanned relatively more than juveniles at the same controlled distance from cover, especially in the afternoon. Given a choice between feeders placed 1 m, 3 m, 5 m, 10 m and 20 m from the forest edge, the tits preferred feeders close to cover. Low-ranking individuals used feeders farther from cover indicating that higher ranked tits prevented them from using the feeders close to cover by means of social dominance. When only the 10m and 20 m feeders were baited, only low-ranked juveniles visited the feeders, subordinate females slightly more than males. The subordinate juveniles increased their use of exposed feeders at low ambient temperature, suggesting that they are prepared to take greater risks during cold periods. The sequence of return to a feeder, after a life-like stuffed predator model mounted 1 m from a feeder opening was removed, was positively correlated with dominance status, revealing that subordinates take the greatest predation risks.

Badge size in the house sparrow Passer domesticus

Anders M//oller — 2008-05-14T12:30:29-00:00

Behavioral Ecology and Sociobiology, Vol. 22, No. 5. (1 May 1988), pp. 373-378.

I studied female mate choice in house sparrows Passer domesticus in relation to the size of the black throat patch of males (badge size), which is a signal of dominance status, and to territory quality. Males with large badges obtained a mate earlier in spring than males with small badges. Males which remained unmated during the entire breeding season had smaller badges than mated males, even when controlling for the effect of other morphological traits and age. Largebadged males had territories with more breeding sites than small-badged males. Territories defended by males with large badges primarily had hole nest sites, which were safe from predators, and nestlings rarely fell from hole nests. Females were implanted with estradiol to induce copulation solicitation displays. Females responded more strongly to a male taxidermic mount and song than to song alone, and they responded more strongly and frequently to male mounts with large badges. Female house sparrows chose mates on the basis of male badges and perhaps on the basis of the quality of the nesting territories offered.

Early Social Status and the Development of Life-History Strategies in Atlantic Salmon

Metcalfe — 2008-05-14T12:28:09-00:00

Metabolic rate, social status and life-history strategies in Atlantic salmon

Neil Metcalfe — 2008-05-14T12:25:18-00:00

Animal Behaviour, Vol. 49, No. 2. (February 1995), pp. 431-436.

An animal's relative social status has major short- and long-term consequences, yet its determinants are rarely known. Here a strong relationship between status and standard metabolic rate (SMR) in juvenile Atlantic salmon,Salmo salar, is demonstrated; the higher the SMR, the more dominant the fish. After controlling for SMR, the relative size, weight or date of first feeding of two opponents had no effect on the outcome of encounters. Moreover, these differences in SMR are not a consequence of experience in encounters, since it has previously been shown that the onset of aggressive behaviour occurs later. Since relative social status has a significant influence on subsequent developmental pathways in this species, these results indicate an indirect link between intraspecific variation in metabolic rates and life-history strategies.

Trade-off between growth rate and aggression in juvenile coho salmon, Oncorhynchus kisutch

Leif Vøllestad — 2008-05-14T03:26:32-00:00

Animal Behaviour, Vol. 66, No. 3. (September 2003), pp. 561-568.

In juvenile salmon and trout, there seems to be a positive phenotypic correlation between individual aggression level and growth rate. Aggressive fish are dominant, and they obtain and defend territories, giving them access to good feeding sites. Being aggressive may increase predation risk, and may also carry costs such as increased metabolic demand, with effects on growth. To test the hypothesis that there is a trade-off between individual growth rate and aggression, we mated 12 female coho salmon with two unique males each, creating 24 full-sibling families. Growth of individually marked fish from each family was estimated in a situation where food could not be monopolized. Thereafter, individual fish were tested for mirror-elicited agonistic behaviour. We found significant variation between families in early growth rate, with a high heritability (1.04). There was also significant between-family variation in agonistic behaviour, but activity was generally low and heritability was low (0.25) and not significant. Growth rate and agonistic behaviour were negatively correlated. These results imply that aggressive behaviour has an energetic cost. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.

Social Status and Susceptibility to Respiratory Infections

Sheldon Cohen — 2008-05-14T03:17:38-00:00

Annals of the New York Academy of Sciences, Vol. 896, No. 1. (1999), pp. 246-253.

Abstract: Adults and children of lower socioeconomic status (SES) are at higher risk for a wide range of communicable infectious diseases, especially respiratory infections. Greater risk for infectious illness among people with lower SES is thought to be attributable to increased exposure to infectious agents and decreased host resistance to infection. We summarize three studies that examine the prospective association of several markers of social status (unemployment, perceived and observed social status) with host resistance to upper respiratory infections. Unemployment was associated with increased susceptibility to infection in adult humans. Lower social status in male monkeys was also associated with increased susceptibility, as was lower perceived social status in humans. The association of social status and susceptibility was accounted for primarily by increased risk in the lowest social status groups. However, further increases in social status were associated with further decreases in susceptibility in both monkeys and humans.

Chronic social stress, social status, and susceptibility to upper respiratory infections in nonhuman primates

S Cohen — 2008-05-14T03:16:59-00:00

Psychosom Med, Vol. 59, No. 3. (1 May 1997), pp. 213-221.

Does dominance status correlate with growth in wild stream-dwelling Atlantic salmon (Salmo salar)?

Andrew Harwood — 2008-05-14T03:14:41-00:00

Behav. Ecol., Vol. 14, No. 6. (1 November 2003), pp. 902-908.

Social hierarchies result in the unequal distribution of resources, with dominant individuals able to monopolize access to food, shelter, and reproductive opportunities. However, the short-term benefits of priority access to resources have not always translated into long-term benefits in terms of growth and survival. In the present study, we test whether dominant Atlantic salmon (Salmo salar) that were able to monopolize a food source in laboratory conditions had a growth advantage over subordinates in their natural stream. There was no relationship between initial size and rank, and high-ranking individuals showed no growth advantage over subordinates over a 2-month period when returned to the wild. A fish's growth rate in the wild was also unrelated to its sex or initial size, or the density of other salmon of the same age class within each experimental site. There was, however, spatial variability in growth, with salmon in one site gaining twice as much weight as did fish from the other sites. This suggests that at most of the sites, resources were limited in availability and that the absence of a relationship between growth and dominance rank was not owing simply to an excess of food being available. The lack of a positive correlation between social status and growth in the wild may be explained by several mechanisms, including the spatio-temporal variability in resources, interspecific interactions, fluctuations in habitat, or the presence of predators. 10.1093/beheco/arg080

The influence of social status on the rate of growth, eye color pattern and Insulin-like Growth Factor-I gene expression in Nile tilapia, Oreochromis niloticus

Vera — 2008-05-14T03:13:07-00:00

Hormones and Behavior, Vol. 51, No. 5. (May 2007), pp. 611-619.

Many aspects of teleost physiology are subject to regulation by social interactions. To evaluate the relationship of social status with growth, eye color pattern and hepatic Insulin-like Growth Factor-I (IGF-I) mRNA expression, 30 Oreochromis niloticus were isolated for 10 days and were used in a social pair study. Results revealed that growth of both dominant (except 1 day after social interaction) and subordinate individuals was suppressed, but growth suppression was greater in the subordinates. The dominant fish completely inhibited the feeding of the subordinate individuals during and 1 day after they were introduced into the aquaria together. After that, a pattern of highly aggressive attacks by dominant fish only partially inhibited feeding by the subordinates. Differential alterations in growth rate between dominants and subordinates were attributed more to behavioral changes (i.e., feeding) as transduced by physiological regulators (i.e., IGF-I level and possibly serotonin and/or neuropeptide Y) but may also be due to changes in metabolism. The fish's relative position in the social hierarchy consistently influenced the levels of IGF-I mRNA in the liver and the eye color pattern. Lower social status depressed hepatic IGF-I levels while dominant status stimulated hepatic IGF-I production, possibly in response to inhibition of somatostatin release in the hypothalamus, leading to greater secretion of pituitary growth hormone (GH). A significant positive association was detected between the IGF-I mRNA expression of the dominant fish and the level of aggression (number of attacks) during the encounter. Social status also influenced the eye color pattern of the fish. During aggressive interactions, most of the fish (22 out of 24) displayed decreased eye darkening. At the later part of the encounter, all subsequent subordinates displayed eye-darkening patterns which acted as a social signal announcing social submission. After the encounter dominant fish had paler eye color pattern than subordinates.