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PubMed2006

Modulation of aggressive behaviour by fighting experience: mechanisms and contest outcomes.

Experience in aggressive contests often affects behaviour during, and the outcome of, later contests. This review discusses evidence for, variations in, and consequences of such effects. Generally, prior winning experiences increase, and prior losing experiences decrease, the probability of winning in later contests, reflecting modifications of expected fighting ability. We examine differences in the methodologies used to study experience effects, and the relative importance and persistence of winning and losing experiences within and across taxa. We review the voluminous, but somewhat disconnected, literature on the neuroendocrine mechanisms that mediate experience effects. Most studies focus on only one of a number of possible mechanisms without providing a comprehensive view of how these mechanisms are integrated into overt behaviour. More carefully controlled work on the mechanisms underlying experience effects is needed before firm conclusions can be drawn. Behavioural changes during contests that relate to prior experience fall into two general categories. Losing experiences decrease willingness to engage in a contest while winning experiences increase willingness to escalate a contest. As expected from the sequential assessment model of contest behaviour, experiences become less important to outcomes of contests that escalate to physical fighting.A limited number of studies indicate that integration of multiple experiences can influence current contest behaviour. Details of multiple experience integration for any species are virtually unknown. We propose a simple additive model for this integration of multiple experiences into an individual's expected fighting ability. The model accounts for different magnitudes of experience effects and the possible decline in experience effects over time. Predicting contest outcomes based on prior experiences requires an algorithm that translates experience differences into contest outcomes. We propose two general types of model, one based solely on individual differences in integrated multiple experiences and the other based on the probability contests reach the escalated phase. The difference models include four algorithms reflecting possible decision rules that convert the perceived fighting abilities of two rivals into their probabilities of winning. The second type of algorithm focuses on how experience influences the probability that a subsequent contest will escalate and the fact that escalated contests may not be influenced by prior experience. Neither type of algorithm has been systematically investigated.Finally, we review models for the formation of dominance hierarchies that assume that prior experience influences contest outcome. Numerous models have reached varied conclusions depending on which factors examined in this review are included. We know relatively little about the importance of and variation in experience effects in nature and how they influence the dynamics of aggressive interactions in social groups and random assemblages of individuals. Researchers should be very active in this area in the next decade. The role of experience must be integrated with other influences on contest outcome, such as prior residency, to arrive at a more complete picture of variations in contest outcomes. We expect that this integrated view will be important in understanding other types of interactions between individuals, such as mating and predator-prey interactions, that also are affected significantly by prior experiences.

Aggression↗
PubMed2002

Sex differences in play fighting revisited: traditional and nontraditional mechanisms of sexual differentiation in rats.

In the traditional model for sexual differentiation in mammals, the female phenotype is the default condition. That is, the female-typical pattern will persist unless acted upon by hormones early in development. The frequency of play fighting in rats, as in most other mammals, is sexually differentiated, and conforms to the traditional model. Males engage in more play fighting than females, and this can be reduced to female-typical levels by neonatal castration. Furthermore, females can be induced to play fight at male-typical levels if treated with testosterone neonatally. Fractionation of play fighting into its constituent components, attack and defense, reveals that it is the frequency of attack that is sexually differentiated, not the likelihood of defense. However, in males, defensive behavior changes at puberty so that the play becomes "rougher." For males to switch to this rougher form of play fighting, they have to be androgenized perinatally. Hence, for males, this second aspect of play fighting that is sexually differentiated also follows the traditional model. In marked contrast, development of the female-typical pattern does not. Neonatal treatment of females with testosterone has no effect; at puberty, they still show the female-typical pattern. On the the other hand, ovariectomy, either at birth or at weaning, leads to females exhibiting the male-typical transition to rougher play fighting at puberty. That is, ovarian hormones appear to actively inhibit the expression of a male-typical trait in females. Play fighting, then, is a mixture of traits, with some features conforming to the traditional model and some not. For some phenotypic features, ovarian hormones appear to exert an active role in their development.

Animals↗
PubMed2005

A century of getting to know the chimpanzee.

A century of research on chimpanzees, both in their natural habitat and in captivity, has brought these apes socially, emotionally and mentally much closer to us. Parallels and homologues between chimpanzee and human behaviour range from tool-technology and cultural learning to power politics and intercommunity warfare. Few behavioural domains have remained untouched by this increased knowledge, which has dramatically challenged the way we view ourselves. The sequencing of the chimpanzee genome will no doubt bring more surprises and insights. Humans do occupy a special place among the primates, but this place increasingly has to be defined against a backdrop of substantial similarity.

Aggression↗
PubMed1982

Type A behavior and self reports of cardiovascular arousal in adolescents.

The association of adolescent Type A behavior with reports of cardiovascular arousal and sleep disturbances was examined. Previous research on the Framingham cohort indicates a cross-sectional relationship between symptoms of arousal and Type A behavior in both sexes, and a prospective relationship between arousal and coronary heart disease incidence in women. Certain sleep patterns have been related to behavior pattern status in a college-aged population. In the current study, Type A behavior was assessed by the Adolescent Structured Interview (ASI), which yields three factor scores: interview behaviors, impatience, and harddriving. Endorsement of symptoms of cardiovascular arousal and sleep disturbances was compared for subjects above and below the median on each of the factor scores. The results showed that the impatience score is strongly related to reports of cardiovascular arousal, the harddriving factor yields a weaker relationship, and the interview behaviors factor was unrelated to reports of arousal. No relationship of Type A behavior and sleep disturbances was found. These data support the usefulness of the component scoring of the ASI, and are encouraging of future research on the cardiovascular processes of the young.

Adolescent↗
PubMed2006

The prerequisites for and likelihood of generalist-specialist coexistence.

Mathematical models of three-consumer-two-resource systems are used to explore the possibility of coexistence when one consumer is a generalist utilizing both resources, and the other two are specialists utilizing only one. Such coexistence requires strongly saturating functional or numerical responses in at least one consumer and the presence of sustained asynchronous variation in resource abundances. Given these conditions, the effects of three dichotomous factors on the range of parameters allowing coexistence are examined: flexible versus inflexible resource choice by the generalist, endogenous or exogenous cause of resource cycles, and location of the two resources in a single habitat versus two habitats. Coexistence of all three species is found to be possible for all combinations of these factors except for inflexible choice in a two-habitat environment. Generalists experience frequency-dependent fitness because, when they are abundant, they synchronize resource cycles and/or reduce their amplitude. When the generalist can adaptively adjust its relative foraging on the two resources, coexistence conditions are broadened considerably, and coexistence commonly occurs readily with exogenous variation in resource growth and with resources located in distinct habitats. Adaptive behavior increases the generalist's ability to both synchronize and dampen resource cycles.

Animals↗
PubMed2006

Infanticide by subordinates influences reproductive sharing in cooperatively breeding meerkats.

In cooperative animal societies, dominant females typically show higher breeding success than subordinates, and are commonly believed to control the extent of reproductive sharing. However, studies of social insect societies reveal that subordinates too can interfere with the breeding attempts of others, with important implications for the distribution of fitness within colonies. Here, we show that subordinate females in a high-skew vertebrate (the meerkat, Suricata suricatta), also exert a substantial influence over the reproductive attempts of others. In meerkat societies, pregnant dominants are known to kill subordinate litters, but we show that pregnant subordinates also kill pups; not only those of other subordinates but the dominant's as well. Litters born to females of any rank were half as likely to survive their first 4 days if a subordinate was pregnant. However, dominant females were more likely than subordinates to give birth when no other females were pregnant, and so lost fewer litters to infanticide than subordinates. This is probably due in part to dominants employing counter-tactics to reduce the incidence of subordinate pregnancy. We discuss the broad implications of subordinates having a degree of control over reproductive sharing for future attempts to understand the distribution of reproduction in animal societies.

Aggression↗
PubMed2006

Testing game theory models: fighting ability and decision rules in chameleon contests.

Game theory models of animal contests make many non-mutually exclusive predictions, complicating empirical tests. These predictions regard the relationship between contest parameters and fighting ability, for which body size is usually used as a proxy. However, in many systems, body size may be a limited proxy since multiple traits and contextual factors such as experience influence fighting ability. Using contests between male Cape dwarf chameleons, Bradypodion pumilum, I test alternative game theory models of extended contests. I show how the most likely candidate model can be identified through a process of elimination, based on tests of key predictions. In addition, I present a measure of fighting ability based on multiple traits that allows ability to change as experience changes. In dwarf chameleons, persistence is based on loser thresholds rather than assessment of relative ability, ruling out the sequential assessment model. Winners and losers do not match behaviours in early parts of the contest, arguing against all types of war of attrition models. Although the cumulative assessment model remained as the most likely candidate model, not all specific predictions of this model were upheld.

Aggression↗
PubMed2006

Volatile emission by contest losers revealed by real-time chemical analysis.

Animal interactions often involve chemical exchange but simultaneous evaluation of chemistry and behaviour has been problematical. Here we report findings from a novel method, atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) coupled with manipulation of molecular-mass achieved by rearing organisms on deuterium-enhanced nutrients. This allows real-time monitoring of the occurrence and quantity of volatile chemicals released by each of two interacting individuals, in tandem with behavioural observations. We apply these methods to female-female contests in the parasitoid wasp Goniozus legneri. We show that this species emits the spiroacetal 2-methyl-1,7-dioxaspiro[5.5]undecane. Chemical release is most common in more behaviourally aggressive contests, which occur when prior resource owners successfully resist take-over by similar-sized intruder females. Volatiles released during contests are always emitted by the loser. Aggression in contests is reduced after spiroacetal release. We suggest that the spiroacetal functions as a weapon of rearguard action. We anticipate that APCI-MS, which is rapid, non-intrusive and relatively inexpensive to operate, will be widely applied in studies linking chemistry and behaviour.

Aggression↗
PubMed1977

The organization of agonistic relations within two captive groups of Java-monkeys (Macaca fascicularis).

The paper offers a detailed quantitative descripition of the distribution of agonistic activities over the members of two groups of Java-monkeys (Macaca fascicularis). These groups lived in captivity and were well-established: i.e. they had an extensive network of genealogical relationships. The study pays special attention to agonistic interactions with three or more participants. Its main purpose is an analysis of the way dyadic agonistic relations (e.g. dominance relations) are affected by third group members and the relations among these. The paper presents data on the ontogeny of 'dependent dominance', the 'control role' of the alpha-male, and the functions of different types of alliances.

Age Factors↗