Attack Latency Research Articles

How Do Predators Learn to Recognize a Mimetic Complex: Experiments with Naive Great Tits and Aposematic Heteroptera

AbstractWe tested the importance of innate wariness, avoidance learning, memory and generalization for the formation of predatory behaviour in naive great tits (Parus major) towards mimetic complex of four aposematic species of true bugs (Insecta: Hemiptera: Heteroptera): Lygaeus equestris, Spilostethus saxatilis, Pyrrhocoris apterus and Graphosoma lineatum. The birds showed almost no innate wariness against the aposematically coloured bugs, although a hidden wariness elicited by defensive chemicals of some of the bug species is not excluded. Naive birds learned to avoid different species at different rates, which resulted in different prey mortalities. The avoidance learning was faster when the defensive chemicals produced an immediate irritating effect (particularly when squirted into distance – G. lineatum) than when they caused sickness several minutes after the consumption (P. apterus). The experience of birds from learning to avoid a particular species of bug affected their subsequent behaviour to other species – experience with better‐defended species resulted in longer attack latencies, more cautious attacks, broader generalization and lower prey mortality. The least defended species, P. apterus, benefited from the experience of birds with better‐defended species, whereas the birds' experience with P. apterus did not reduce mortality risk of the other species comparably. Judging from the inexperienced young birds, the mimetic relationships are likely to be quasi‐Batesian. However, as wild‐caught great tits avoid all the four species to the same extent, the relationships may become more mutualistic (quasi‐Müllerian) in later phases of learning under natural conditions. The relationships among species in the mimetic complex thus seem to depend on the amount of experience of the bird predators.

Age over experience: Consistency of aggression and mounting behaviour in male and female pigs

Excessive aggression between pigs at mixing is a welfare and production issue resulting in stress, injuries and economic losses. If it can be demonstrated that aggression is a consistent behaviour trait, it might provide a means to reduce these losses. To test for consistency of aggressiveness, 163 male and female damline pigs, mixed at weaning (mean±SD day=33.7±3.4), were given resident-intruder tests (RITs) on successive days (test pairs a and b) on up to three occasions: day 60 (test 1); day 95 (test 2); and day 130 (test 3). Pigs tested at all three time points (T123 n=90) showed consistency in occurrence of attacking within (a vs. b) and between tests (1 vs. 2, 2 vs. 3 and 1 vs. 3), suggesting that aggressiveness is a moderately stable temperament trait. Compared to previous studies of this kind there were clear differences between male and female pigs, with a higher than expected rate of mounting in male pigs. Mounting also appeared to be a consistent trait, beginning from a surprisingly early age (day 60). Latency to attack decreased in the female pigs (n=53) after test 1a, but did not change after this, although a further unexpected finding, was an effect of boar line on the occurrence of attacking in female pigs. In the male pigs (n=37) aggression reduced over time, which we propose was primarily as a result of increased mounting. Sex differences in aggression and mounting were also seen when the behaviour of pigs naive to the RIT were first tested (test 1, treatments T123, n=90 and T13, n=22; test 2 T23, n=24; test 3, T3, n=27), suggesting they result from age rather than experience. The effect of prior RIT experience on aggression in the final test (test 3) was examined in terms of: (1) the amount of experience, by comparing pigs with no (T3), one (T23 and T13) or two (T123) previous experiences of the RIT; and (2) the age at first experience, by comparing pigs first tested in test 1 (T13) or test 2 (T23). Prior RIT experience made little difference to the level of aggression (attack latency), although more experienced pigs were more likely to attack than to mount. In conclusion, pigs showed stable individual differences in both aggression and mounting, which were affected more by sex and age than by prior test experience.

The ability of North Island Robins to discriminate between humans is related to their behavioural type.

Animals are able to learn to identify persistent threats to themselves and their offspring. For example, birds are able to quickly learn to discriminate between humans that have previously threatened their nests from humans with whom they have had no prior experience. However, no study has yet examined whether a bird's ability to discriminate between humans is related to the bird's underlying behavioural type. In this study, we examined whether there were differences among North Island (NI) robins (Petroica longipes), based on their underlying behavioural type, in their abilities to discriminate between familiar and novel human observers. Using a simple feeding experiment, we timed how long it took birds to attack a food item placed next to an observer on each of 7 days. On the eighth day, a different observer timed the birds. We found that birds could be split into two behaviour types based on their attack behaviour: fast attackers (latencies <20 sec) and slow attackers (latencies >20 secs). Interestingly, the fast birds did not increase their attack latency in response to the novel observer whereas the slow attackers did. This result, for the first time, demonstrates that a bird's ability to discriminate between humans can vary among birds based on their behavioural type.

Fertility control of Rattus nitidus using quinestrol: effects on reproductive organs and social behavior

Fertility control has been identified by studies in the laboratory and the field as a more appropriate and long-term control strategy for rodent pests than lethal control. In this study, we investigated the effects of quinestrol on mass of reproductive organs and on social behaviors in female and male Indochinese forest rat (Rattus andamanensis (Blyth, 1860)] using approach of morphometrics and genetics). [corrected]. A total of 16 adult females and 16 adult males were randomly assigned to 4 groups. One male and one female group were fed rice with 0.005% quinestrol by weight for 7 days, and another 2 groups were fed rice only. After 7 days, rats were assigned to 10 min dyadic encounters between groups, and investigation, aggression, defense and attack latency were quantified. All animals were killed on day 10, and reproductive organs were dissected and weighed. Dyadic encounter data showed that there were obvious changes in social behaviors of quinestrol-treated rats. Quinestrol significantly inhibited the investigative behavior of quinestrol-treated males toward control females in Rattus nitidus, but seldom affected investigation between control males and quinestrol-treated females. Aggression of control females toward quinestrol-treated males was higher than that of quinestrol-treated females, and defense of quinestrol-treated males toward control females was more remarkable than that of control males. Quinestrol remarkably decreased wet masses of epididymis and spermotophore in males and ovaries in females, but had no effect on wet masses of testes and uteri after quinestrol treatment. These results indicate that the anti-fertility effects of quinestrol on R. nitidus are attributed to not only suppressing reproductive organs but also impacting social behaviors associated with territory defense and mate choice.

Low‐level copper exposures increase visibility and vulnerability of juvenile coho salmon to cutthroat trout predators

Copper contamination in surface waters is common in watersheds with mining activities or agricultural, industrial, commercial, and residential human land uses. This widespread pollutant is neurotoxic to the chemosensory systems of fish and other aquatic species. Among Pacific salmonids (Oncorhynchus spp.), copper-induced olfactory impairment has previously been shown to disrupt behaviors reliant on a functioning sense of smell. For juvenile coho salmon (O. kisutch), this includes predator avoidance behaviors triggered by a chemical alarm cue (conspecific skin extract). However, the survival consequences of this sublethal neurobehavioral toxicity have not been explored. In the present study juvenile coho were exposed to low levels of dissolved copper (5-20 microg/L for 3 h) and then presented with cues signaling the proximity of a predator. Unexposed coho showed a sharp reduction in swimming activity in response to both conspecific skin extract and the upstream presence of a cutthroat trout predator (O. clarki clarki) previously fed juvenile coho. This alarm response was absent in prey fish that were exposed to copper. Moreover, cutthroat trout were more effective predators on copper-exposed coho during predation trials, as measured by attack latency, survival time, and capture success rate. The shift in predator-prey dynamics was similar when predators and prey were co-exposed to copper. Overall, we show that copper-exposed coho are unresponsive to their chemosensory environment, unprepared to evade nearby predators, and significantly less likely to survive an attack sequence. Our findings contribute to a growing understanding of how common environmental contaminants alter the chemical ecology of aquatic communities.

A pharmacological evidence of positive association between mouse intermale aggression and brain serotonin metabolism

The neurotransmitter serotonin (5-HT) is involved in the regulation of mouse intermale aggression. Previously, it was shown that intensity of mouse intermale aggression was positively associated with activity of the key enzyme of 5-HT synthesis – tryptophan hydroxylase 2 (TPH2) in mouse brain. The aim of the present study was to investigate the effect of pharmacological activation or inhibition of 5-HT synthesis in the brain on intermale aggression in two mouse strains differing in the TPH2 activity: C57BL/6J (B6, high TPH2 activity, high aggressiveness) and CC57BR/Mv (BR, low TPH2 activity, low aggressiveness). Administration of 5-HT precursor l-tryptophan (300mg/kg, i.p.) to BR mice significantly increased the 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels in the midbrain as well as the number of attacks and their duration in the resident-intruder test. And vice versa, administration of TPH2 inhibitor p-chlorophenylalanine (pCPA) (300mg/kg, i.p., for 3 consecutive days) to B6 mice dramatically reduced the 5-HT and 5-HIAA contents in brain structures and attenuated the frequency and the duration of aggressive attacks. At the same time, l-tryptophan or pCPA did not influence the percentage of aggressive mice and the attack latency reflecting the threshold of aggressive reaction. This result indicated that the intensity of intermale aggression, but not the threshold of aggressive reaction is positively dependent on 5-HT metabolism in mouse brain.

Context-dependent responses to novelty in Rainbow trout (Oncorhynchus mykiss), selected for high and low post-stress cortisol responsiveness

Previous studies in a rainbow trout model, selectively bred for high (HR) and low (LR) post stress plasma cortisol levels, have yielded data that are indicative of contrasting stress coping styles. Fish from the HR line have been suggested to display a more diverse behavioral repertoire in challenging situations than the LR counterpart. The present study addressed whether such variation in behavioral flexibility traits was evident in different experimental settings using these selection lines. The fish were subjected to three sets of challenges (novel object test, resident–intruder test and confinement stressor test), all which were repeated a week later. Introducing a novel object evoked a divergent behavioral response in association with feeding: fish from the LR line displayed consistently suppressed feed intake while the HR fish remained unaffected. This observation was found to be repeatable along with attack latency and movement activity from the resident–intruder and confinement stressor tests. These results indicate that the behavioral responses in this animal model are context-dependent and shed new light on the expression of behavioral flexibility.

Impulsivity and aggressive behavior in Roman high and low avoidance rats: Baseline differences and adolescent social stress induced changes

Adverse and stressful experiences during adolescence are often of a social nature. The social defeat model in rats is used as an animal model for bullying in humans. Usually large individual differences in response to social defeat are found. The personality type that is mostly affected and the underlying mechanisms are unknown. We used male rats of the Roman selection lines to test whether social defeat (between postnatal days 45 and 57) followed by social isolation has a different impact in animals with divergent levels of emotional reactivity and coping style. The level of offensive aggression, impulsivity and performance during frustrating non-reward (extinction) were used as measures for the adult coping style of animals. Impulsivity was measured by performance on an unpredictable operant conditioning schedule (variable interval-15, VI-15) for food reinforcement.This study demonstrates that the adult, baseline level of impulsivity is higher in Roman high avoidance (RHA) rats. RHA rats showed a higher number of lever presses compared to Roman low avoidance (RLA) rats on a VI-15 schedule. The level of offensive aggression did not differ between the two lines. Surprisingly, a tendency towards more offensive aggression in RLA rats was found.Social stress during adolescence disturbed the normal development of adult personality, mostly in RHA rats. RHA rats that were defeated during adolescence reduced the number of lever presses on the VI-15 schedule of reinforcement and were more persistent during a session of frustrating non-reward. However, we did not find an effect of social defeat on performance during extinction. A tendency towards increased attack latencies after social defeat in adolescence was found. The time spent on offensive aggression was unaffected by social defeat.

Number of eyespots and their intimidating effect on naïve predators in the peacock butterfly

Predation experiments have shown that the large eyespots (concentric rings of contrasting colors) found on the wings of several lepidopteran species intimidate passerine predators. According to the eye mimicry hypotheses, the intimidation is caused by predators associating the eyespots with the presence (of the eyes) of their own enemy. The conspicuousness hypothesis suggests, instead, that it is simply the conspicuousness of eyespot patterns that is intimidating, possibly due to a sensory bias. We studied how the number of eyespots, 2 or 4, influences intimidation. We predicted that if eye mimicry is important, the maximum response would be reached with a pair of eyespots. On the other hand, if conspicuousness is important, then more than 2 eyespots should result in an even stronger response. The peacock butterfly, Inachis io, has 4 large eyespots on its wings. We presented naïve insectivorous birds (pied flycatcher, Ficedula hypoleuca) 2 different prey items made from wings of dead peacock butterflies and a mealworm between the wings. One group of birds received prey that had no or only 2 eyespots visible and the other group received prey that had no or all 4 eyespots visible. Eyespots clearly increased hesitation before attacks. Because the birds were naïve, this difference in response to the eyespots was innate. Importantly, there was no difference in attack latency between 2 and 4 eyespots. We conclude that it is unlikely that conspicuousness as such has selected for eyespots in the peacock butterfly.

Diet-dependent intraguild predation between the predatory mites Neoseiulus californicus and Neoseiulus cucumeris

Based on the hypothesis that matching diets of intraguild (IG) predator and prey indicate strong food competition and thus intensify intraguild predation (IGP) as compared to non-matching diets, we scrutinized diet-dependent mutual IGP between the predatory mites Neoseiulus cucumeris and N. californicus. Both are natural enemies of herbivorous mites and insects and used in biological control of spider mites and thrips in various agricultural crops. Both are generalist predators that may also feed on plant-derived substances such as pollen. Irrespective of diet (pollen or spider mites), N. cucumeris females had higher predation and oviposition rates and shorter attack latencies on IG prey than N. californicus. Predation rates on larvae were unaffected by diet but larvae from pollen-fed mothers were a more profitable prey than those from spider-mite fed mothers resulting in higher oviposition rates of IG predator females. Pollen-fed protonymphs were earlier attacked by IG predator females than spider-mite fed protonymphs. Spider mite-fed N. californicus females attacked protonymphs earlier than did pollen-fed N. californicus females. Overall, our study suggests that predator and prey diet may exert subtle influences on mutual IGP between bio-control agents. Matching diets did not intensify IGP between N. californicus and N. cucumeris but predator and prey diets proximately influenced IGP through changes in behaviour and/or stoichiometry.

LISISAP

For any communication (wired or wireless) such as control and data, the identity of source and destination is revealed in the header portion of the packet. Adversaries obtain sensitive in-formation such as the identity, location of a critical node, route, data, etc., during communication by using traffic analysis at-tacks, viz., similarity attack, data integrity attack, packet count-ing attack, latency attack, and clogging attack. Anonymous communication prevents adversaries from doing traffic analysis against the routing information embedded in the routing mes-sages and data packets. In order to thwart such traffic analysis, anonymous communication protocols were developed. In this paper, the existing anonymous communication protocols were analyzed in terms of techniques used, challenges, and applications. Anonymous Routing protocol with Multiple Routes (ARMR) is one of the existing protocols that achieves better route anonymity using fake routes and multiple paths. However, in ARMR, adversaries can modify the data with genuine user pseudonyms and send the modified data to the destination. In order to prevent data modification by adversary at link level, in this paper a Link level SIgnature based Secure Anonymous Protocol (LISISAP) protocol is proposed. In LISISAP, source node generates a signature for the data and sends the signature along with the encrypted data to the next node. Further, the next node verifies the signature. If signature matches, it generates its own signature and sends the encrypted data to its next node. Otherwise, it discards the packet. Verified data and signature are sent by each intermediate node until it reaches the destina-tion. In LISISAP, even if adversaries modify the data, every node in the route including the destination node verifies the data and discards the data if there is no match in the signature. Similarity attacks can be prevented by making the data look different on each hop which could be achieved by encrypting the data with link key. Proposed protocol, LISISAP is imple-mented and tested in Smart and Secure Network. From the ex-perimental results, it is evident that the data generated by source node is sent anonymously to the destination. Thus, in LISISAP protocol, communication is secure between nodes without revealing the node identities. Anonymous properties such as identity privacy, location privacy, route anonymity, and robustness against several attacks were achieved.

Temperature Mediates Shifts in Individual Aggressiveness, Activity Level, and Social Behavior in a Spider

Although in recent years behavioral syndromes have received a wealth of attention, how traits within syndromes respond to changing environments is not well resolved. Here, we test the effects of temperature on a suite of behavioral traits in the spider Anelosimus studiosus to determine (1) whether there are shifts in individuals’ social tendency, activity level, and foraging behavior in response to temperature, (2) if these traits shift are in the direction predicted by within-population axes of trait covariance, and (3) whether the effects of temperature differ among individuals. In previous work, we documented a behavioral syndrome in A. studiosus where increased tolerance of conspecifics is correlated with decreased activity level and aggressiveness toward prey. Furthermore, there are distinct among-population differences in behavior, where individuals from warm sites tend to be more aggressive and active than individuals from cold sites. Our data here reveal that at warmer temperatures A. studiosus exhibit diminished tolerance of conspecifics, increased activity levels, shorter latencies of attack, and increased tendencies to attack multiple prey items. Furthermore, we found that individual differences in behavior were consistent across temperature regimes for the majority of behavioral traits considered here: social tendency, activity level, and latency of attack. These findings are consistent with the hypothesis that these behaviors are linked together by shared genetic underpinnings (e.g., metabolic differences) and shift non-independently in response to contemporary abiotic environment (i.e., temperature). Furthermore, our data suggest that temperature itself could be responsible for the among-population variation in social structure in A. studiosus.

The aggressive behavior of Nile tilapia introduced into novel environments with variation in enrichment

Many studies show environmental enrichment is correlated with benefits to captive animals; however, one should not always assume this positive relationship given that enrichment increases the amount of resources that a territorial animal must defend and possibly affects its aggressive dynamics. In this study, we tested if environmental enrichment affects aggressive interactions in the aggressive fish Nile tilapia ( Oreochromis niloticus). We compared fights staged between pairs of male tilapia of similar size (= matched in resource holding potential) in a novel arena that was either barren or enriched, to examine whether enrichment enhances territory value in line with theoretical predictions, with the potential for compromised welfare. We evaluated time elapsed until the first attack (latency), frequency of aggressive interactions and fight duration. We detected fight dynamic differences at the pair level. Higher resource value generated increased aggression but had no effect on fight duration or latency. This conclusion is in line with game theory predictions concerning resource value and contradicts the theory that enrichment of the environment will serve welfare purposes.

Effect of Domestication on Aggression in Gray Norway Rats

A comparative analysis of intermale aggression in the resident-intruder test was conducted with gray rats from a wild unselected population bred at the laboratory for three generations and gray rats selected for elimination (tame) and enhancement (aggressive) of aggressiveness towards human for 71-72 generations. Males from the laboratory line Wistar were used as neutral opponents. Rats from the tame line were characterized by reduced aggression manifest as longer attack latency, decreased number of attacks, upright postures, chases, kicks, and shorter total time of aggressive behavior compared to unselected males. There was no significant difference in the attack latency and the total time of aggression between rats of the aggressive line and unselected rats. A trend to decrease in the number of attacks, chases and upright postures and to increase in contribution of lateral threat postures to the total time of aggression was observed for males of the aggressive line. Plasma corticosterone in unselected males not presented with intruders and after their presentation was higher than in males of both selected lines. Comparative behavioral analysis of agonistic behaviors in rats from the aggressive and tame lines to opponents of different lines (Wistar, tame, aggressive) showed that the presence of an intruder from the aggressive line can enhance aggressive responses in residents from the tame line. Thus, selection for domestication of gray rats caused a significant attenuation of aggressive behavior without affecting the basic agonistic repertoire.

Observaciones sobre algunos aspectos del comportamiento depredador en condiciones naturales y en cautividad de la serpiente diurna mastigodryas pleei (dumeril, bibron y dumeril 1854)

Se evaluaron algunos aspectos del comportamiento depredador de la serpiente diurna Mastigodryas pleei frente a dos tipo de presa: mamíferos (ratón de laboratorio) y lagartos (Cnemidophorus lemniscatus), cuantificando la duración de cada paso en la secuencia de depredación y midiendo variables como el número de movimientos de la lengua (tongue flicks), latencia de ataque, distancia de ataque y posición de la mordida sobre el cuerpo de la presa. Se encontró que la máxima distancia de ataque para este colúbrido diurno varia dependiendo de la naturaleza de la presa. La máxima distancia de ataque registrada (12 cm) desplegada durante el ataque a un lagarto y la minima (3 cm) desplegada a un ratón. La distancia de ataque puede estar relacionada con el reconocimiento de un peligro potencial atribuido a las características de una presa, exhibiendo tácticas diferenciales de aproximación y captura para atacar presas inofensivas o presas potencialmente peligrosas. Este hecho se evidencia durante la secuencia de depredación en el lugar específico en donde se propicia la mordida y la distancia relativa del ataque. Los tiempos de cada paso en la secuencia y el número de movimientos de lengua no mostraron diferencias significativas entre tratamientos.

Selection against aggressiveness in pigs at re-grouping: practical application and implications for long-term behavioural patterns

AbstractThe routine mixing of pigs causes aggression that cannot be greatly reduced by low-cost environmental changes. The variability and heritability of aggressiveness are discussed and both appear adequate to make selection against aggressiveness worthwhile in grower-stage pigs. Selection would require rapid phenotyping of many animals for which a validated indicator genetically correlated to aggressive behaviour is required. Three potential indicators are discussed (attack latency, number of skin lesions and relationship to non-social behavioural traits). Attack latency correlates with post-mixing aggressiveness under research conditions but attacks are delayed under commercial conditions reducing the practicability of the trait for selection. Correlations between aggressiveness and responses to non-social challenges, such as the back-test, are not always consistent. Lastly, the counting of skin lesions is rapid, and the number of lesions has a moderate heritability and is genetically correlated with involvement in aggressive behaviour. The wider effects of selection against post-mixing aggressiveness are discussed. Examining the behavioural strategies of unaggressive pigs, especially their response to defeat, would reveal how selection may alter aggressive tactics. Selection against lesions from mixing is also expected to reduce their number in more stable social conditions, but the implications for aggression between sows and that of sows towards their piglets and humans needs to be investigated. Aggressiveness is genetically correlated with response to handling involving components of social isolation, human presence and novelty. Identifying how unaggressive pigs respond to other challenging situations differing in these components may be worthwhile. Selection against aggression using skin lesions appears to be achievable although the full value of this would benefit from estimations of the genetic correlations with the traits outlined above.

Subclinical effects of saxitoxin and domoic acid on aggressive behaviour and monoaminergic turnover in rainbow trout ( Oncorhynchus mykiss)

The algal produced neurotoxins saxitoxin and domoic acid may have serious effects on marine life and can be responsible for the intoxication of for instance sea mammals, sea birds and fish. Given that farmed fish cannot escape algal blooms, they may be more susceptible to intoxication than wild stocks. In the present study, subclinical effects of saxitoxin and domoic on aggressive behaviour and monoaminergic systems in the brain of the rainbow trout ( Oncorhynchus mykiss) were investigated. The resident-intruder test was used to measure aggression where only the resident fish were subjected to the toxins and analysed for monoamines and their metabolites. The resident-intruder test was carried out on two consecutive days. On day one basal aggression was measured in the four groups. On day two three of the groups were injected with subclinical doses of one of the following: saxitoxin (1.752 μg/kg bw), domoic (0.75 mg/kg bw) or 0.9% saline solution. This was performed 30 min prior to the aggression test. Handling stress and injection affected aggressive behaviour, cortisol and the serotonergic system in telencephalic brain regions. Cortisol levels were elevated in all of the injected groups when compared to the control group. An increase in serotonergic turnover was evident when all injected groups were pooled and compared to the control group. All together this suggests that the handling stress in connection with the injection was similar in all of the three injected groups. In contrast to both the undisturbed control group and the toxin-injected groups, the saline-injected group displayed a reduction in aggressive behaviour which was evident in increased attack latency. Furthermore the domoic injected group displayed more aggressive attacks towards their conspecifics than the saline-injected group. Consequently the two toxins appear to mask the stress induced alteration in aggressive behaviour. Monoamine levels and monoaminergic turnover could not be demonstrated to be directly affected by the two toxins at the given doses in the investigated brain regions (dorsal and ventral parts of telencephalon, optic tectum, locus coeruleus, raphe nucleus, molecular and granular layer of cerebellum). This could indicate that the toxins mediate aggressive behaviour either through other systems than the monoaminergic systems, such as neuroactive amino acids, or that the mediation occurs in other brain regions.

Effects of photoperiod and experience on aggressive behavior in female California mice

Aggressive behavior among females is observed in many species, but the mechanisms of this behavior have historically been understudied. In many species of rodents, winter-like short day photoperiods induce increased aggression levels compared to summer-like long day photoperiods. Recent reports in hamsters show that short days also increase aggression in females. We examined the effects of photoperiod on aggression in female California mice, and for the first time compare brain activity of aggression-tested female rodents under different photoperiods. We observed that female California mice were more aggressive when housed in short days versus long days. Intriguingly, we also observed that under long days female attack latency decreases with repeated testing in resident–intruder tests. These data suggest that winner effects that have been described in males may also occur in females. We also used the expression of phosphorylated extracellular signal-regulated kinases (pERK) in the brain to estimate brain activity during aggression tests. pERK can alter neuronal activity in the short term and in the long term can act as a transcription factor. Using immunoblot analyses we observed that aggression-induced pERK expression in the female bed nucleus of the stria terminalis and medial amygdala occurs under both long and short days. Thus, the mechanisms controlling increased aggression under short days are still unclear and additional study is needed.

Animal violence demystified.

Violence has been observed in humans and animals alike, indicating its evolutionary/biological significance. However, violence in animals has often been confounded with functional forms of aggressive behavior. Currently, violence in animals is identified primarily as either a quantitative behavior (an escalated, pathological and abnormal form of aggression characterized primarily by short attack latencies, and prolonged and frequent harm-oriented conflict behaviors) or a qualitative one (characterized by attack bites aimed at vulnerable parts of the opponent's body and context independent attacks regardless of the environment or the sex and type of the opponent). Identification of an operational definition for violence thus not only helps in understanding its potential differences from adaptive forms of aggression but also in the selection of appropriate animal models for both. We address this issue theoretically by drawing parallels from research on aggression and appeasement in humans and other animals. We also provide empirical evidences for violence in mice selected for high aggression by comparing our findings with other currently available potentially violent rodent models. The following violence-specific features namely (1) Display of low levels of pre-escalatory/ritualistic behaviors. (2) Immediate and escalated offense durations with low withdrawal rates despite the opponent's submissive supine and crouching/defeat postures. (3) Context independent indiscriminate attacks aimed at familiar/unfamiliar females, anaesthetized males and opponents and in neutral environments. (4) Orientation of attack-bites toward vulnerable body parts of the opponent resulting in severe wounding. (5) Low prefrontal serotonin (5-HT) levels upon repeated aggression. (6) Low basal heart rates and hyporesponsive hypothalamus–pituitary–adrenocortical (HPA) axis were identified uniquely in the short attack latency (SAL) mice suggesting a qualitative difference between violence and adaptive aggression in animals.

Food imprinting revisited: early learning in foraging predatory mites

Learning is a ubiquitous phenomenon in foraging animals, allowing behavioural optimisation in variable environments. Food imprinting is a specific form of learning restricted to the early stages of life and with long lasting consequences. However, since coining of the term four decades ago, the uniqueness of food imprinting has been largely questioned due to a putative mechanistic similarity with associative learning. Here, we demonstrate food imprinting in the predatory mite Neoseiulus californicus , which primarily feeds on spider mites but may use thrips as alternative prey. Brief (24 h) exposure to thrips (contact without feeding) early in life resulted in shorter attack latencies and consistently higher predation rates on thrips during adulthood. Predation and oviposition rates were positively correlated but oviposition did not differ between naive and experienced females. Our results suggest that food imprinting is indeed special because, unlike associative learning, it occurred without reinforcement, was restricted to a sensitive phase and persisted into adulthood. Food imprinting seems particularly advantageous when prey species availability varies little within generations and a given prey is difficult to ingest for young small but not older larger life stages. Food imprintability could be used to improve the efficacy of biocontrol agents such as N. californicus .