Tactical deception to hide sexual behaviour: macaques use distance, not visibility.

Although tactical deception (TD) may be employed to hide sexual behaviour, there is as yet no firm evidence for it. Hiding may be guided by cognitive mechanisms consistent with either no, low or high level TD, such as exploiting male peripheral positions (no TD), creating distance (TD level 1) or hiding behind screens (TD level 1.5 which involves visual perspective taking (VPT)). Macaques are capable of VPT in a food context, suggesting that they may employ TD level 1.5. We investigated, in an observational study with temporarily provided hiding screens, which strategy was used to hide sexual behaviour in captive groups of two macaque species (Macaca mulatta and Macaca fascicularis). Sexual behaviour only sporadically took place near screens, and the few copulations near screens were not systematically hidden from the alpha male, precluding TD level 1.5. Instead, both females and non-alpha males were at a larger distance from the alpha male during sexual interactions than otherwise, consistent with TD level 1. Creating peripheral locations (TD level 1) may be effective in improving sexual opportunities in many species.

Long-tailed macaques (Macaca fascicularis) understand what conspecifics can see in a competitive situation.

Visual perspective taking (VPT), an understanding of what others can see, is a prerequisite for theory of mind (ToM). While VPT in apes is proven, its presence in monkeys is much-debated. Several different paradigms have been developed to test its existence, but all face interpretational problems since results can be explained by simpler cognitive mechanisms than VPT. Therefore, we adjusted one method where two individuals compete for access to food, visible or invisible for the dominant competitor, to preclude cognitively simpler mechanisms. The subordinate long-tailed macaques tested, selected significantly more often the food item invisible than the item visible to the dominant. In most trials, subjects retrieved only one food item and preferred the invisible food item. Surprisingly, they occasionally adopted an alternative strategy to obtain both food items, by first choosing the visible, most at risk food item. Faster animals adopted this strategy proportionally more often than slower ones. Contrary to previous research, our results cannot be explained by simpler cognitive mechanisms, since behavioural reading was prevented by a one-way mirror between the competitor and the food, and accessibility was equal to both food items. This is the first unequivocal evidence of VPT in a monkey species, suggesting that this precursor to ToM is an evolutionarily conserved capacity present in monkeys, apes and humans.

High-throughput phenotyping of avoidance learning in mice discriminates different genotypes and identifies a novel gene.

Recognizing and avoiding aversive situations are central aspects of mammalian cognition. These abilities are essential for health and survival and are expected to have a prominent genetic basis. We modeled these abilities in eight common mouse inbred strains covering ∼75% of the species' natural variation and in gene-trap mice (>2000 mice), using an unsupervised, automated assay with an instrumented home cage (PhenoTyper) containing a shelter with two entrances. Mice visited this shelter for 20-1200 times/24 h and 71% of all mice developed a significant and often strong preference for one entrance. Subsequently, a mild aversive stimulus (shelter illumination) was automatically delivered when mice used their preferred entrance. Different genotypes developed different coping strategies. Firstly, the number of entries via the preferred entrance decreased in DBA/2J, C57BL/6J and 129S1/SvImJ, indicating that these genotypes associated one specific entrance with the aversive stimulus. Secondly, mice started sleeping outside (C57BL/6J, DBA/2J), indicating they associated the shelter, in general, with the aversive stimulus. Some mice showed no evidence for an association between the entrance and the aversive light, but did show markedly shorter shelter residence times in response to illumination, indicating they did perceive illumination as aversive. Finally, using this assay, we screened 43 different mutants, which yielded a novel gene, specc1/cytospinB. This mutant showed profound and specific delay in avoidance learning. Together, these data suggest that different genotypes express distinct learning and/or memory of associations between shelter entrance and aversive stimuli, and that specc1/cytospinB is involved in this aspect of cognition.

Sneaky monkeys: an audience effect of male rhesus macaques (Macaca mulatta) on sexual behavior.

Males and females have different sexual interests and subsequently may show conflicting sexual strategies. While dominant males try to monopolize females, promiscuity benefits females and subordinate males. One way to escape monopolization by dominant males is to copulate in their absence. We tested this inhibitory effect of males on the sexual behavior of their group members in captive group-living Rhesus macaques. Copulations between females and nonalpha males almost exclusively took place when the alpha male was out of sight. Furthermore, the inhibiting effect was not unique for the alpha male. An upcoming nonalpha male also inhibited copulations of its group members, and three other nonalpha males inhibited female copulation solicitations. Females adjusted their behavior to the presence of bystander males, as they initiated and accepted initiations more often in absence than in presence of bystander males. Although not significant, in males, a similar pattern was found. The observed reduction in mating behavior in presence of bystander males is in accordance with an "audience effect," in which the behavior is modulated in relation to the presence or absence of third parties. This audience effect may serve as an important mechanism to reduce (aggressive) interruptions of subordinate male copulations.

Quantified tracking and monitoring of diazepam treated socially housed cynomolgus monkeys.

Quantitative assessment of behavioural patterns is frequently used in rodent toxicity studies, however only limited approaches are available for monkeys. Often qualitative behavioural scoring using functional observation batteries (FOBs) is performed, with difficulties like poor reproducibility or lack of sensitivity. In this study, we investigated whether quantitative behavioural monitoring can be applied to group-housed cynomolgus monkeys. Video-tracking EthoVision® XT system and special analysis software were used to evaluate diazepam (i.v. 1mg/kg) related behavioural changes in group-housed animals. Recordings were made predose and at the anticipated time of maximum drug exposure (T(max)). General parameters such as distance travelled and velocity did not reveal the known sedative effects of diazepam. However, inspection of the automatically generated track images indicated that diazepam-treated animals had more a meandering movement pattern suggesting that diazepam induced a loss of balance which was regained by corrective movements. Therefore, parameters revealing specific aspects of the meandering movement pattern such as velocity profiles and turn angles have been analyzed and revealed an increase in the curvature and in the number of directional changes of the movement path.

Characterization of febrile seizures and febrile seizure susceptibility in mouse inbred strains.

Febrile seizures (FS) are the most prevalent seizures in children. Although FS are largely benign, complex FS increase the risk to develop temporal lobe epilepsy (TLE). Studies in rat models for FS have provided information about functional changes in the hippocampus after complex FS. However, our knowledge about the genes and pathways involved in the causes and consequences of FS is still limited. To enable molecular, genetic and knockout studies, we developed and characterized an FS model in mice and used it as a phenotypic screen to analyze FS susceptibility. Hyperthermia was induced by warm air in 10- to 14-day-old mice and induced FS in all animals. Under the conditions used, seizure-induced behavior in mice and rats was similar. In adulthood, treated mice showed increased hippocampal Ih current and seizure susceptibility, characteristics also seen after FS in rats. Of the seven genetically diverse mouse strains screened for FS susceptibility, C57BL/6J mice were among the most susceptible, whereas A/J mice were among the most resistant. Strains genetically similar to C57BL/6J also showed a susceptible phenotype. Our phenotypic data suggest that complex genetics underlie FS susceptibility and show that the C57BL/6J strain is highly susceptible to FS. As this strain has been described as resistant to convulsants, our data indicate that susceptibility genes for FS and convulsants are distinct. Insight into the mechanisms underlying seizure susceptibility and FS may help to identify markers for the early diagnosis of children at risk for complex FS and TLE and may provide new leads for treatment.

Influence of environmental enrichment and handling on the acute stress response in individually housed mice.

In this study we investigated the effect of environmental enrichment and handling on the acute physiological stress response caused by short periods of restraint in individually housed female mice. Heart rate (HR) and body temperature (BT) were measured by radiotelemetry and compared with plasma corticosterone (pCORT) levels. Also, postmortem thymus weight and tyrosine hydroxylase (TH) activity were assessed. The acute stress response was seen in both HR and BT. Enrichment and handling were found to increase rather than decrease this stress response, but pCORT values, measured 90 min after restraint, suggested a lower stress response in the enriched groups. No effect was found with thymus weight or TH as parameters.

Reduced 5-HT1A- and GABAB receptor function in dorsal raphé neurons upon chronic fluoxetine treatment of socially stressed rats.

Autoinhibitory serotonin 1A receptors (5-HT(1A)) in dorsal raphé nucleus (DRN) have been implicated in chronic depression and in actions of selective serotonin reuptake inhibitors (SSRI). Due to experimental limitations, it was never studied at single-cell level whether changes in 5-HT(1A) receptor functionality occur in depression and during SSRI treatment. Here we address this question in a social stress paradigm in rats that mimics anhedonia, a core symptom of depression. We used whole cell patch-clamp recordings of 5-HT- and baclophen-induced G-protein-coupled inwardly rectifying potassium (GIRK) currents as a measure of 5-HT(1A)- and GABA(B) receptor functionality. 5-HT(1A)- and GABA(B) receptor-mediated GIRK-currents were not affected in socially stressed rats, suggesting that there was no abnormal (auto)inhibition in the DRN on social stress. However, chronic fluoxetine treatment of socially stressed rats restored anticipatory behavior and reduced the responsiveness of 5-HT(1A) receptor-mediated GIRK currents. Because GABA(B) receptor-induced GIRK responses were also suppressed, fluoxetine does not appear to desensitize 5-HT(1A) receptors but rather one of the downstream components shared with GABA(B) receptors. This fluoxetine effect on GIRK currents was also present in healthy animals and was independent of the animal's "depressed" state. Thus our data show that symptoms of depression after social stress are not paralleled by changes in 5-HT(1A) receptor signaling in DRN neurons, but SSRI treatment can alleviate these behavioral symptoms while acting strongly on the 5-HT(1A) receptor signaling pathway.

Effect of restraint and injection methods on heart rate and body temperature in mice.

Routine procedures in the laboratory, inducing acute stress, will have an impact on the animals and might thereby influence scientific results. In an attempt to gain more insight into quantifying this acute stress by means of the parameters heart rate (HR) and body temperature (BT), we subjected mice to different restraint and injection methods. We first compared the treatment response of HR and BT, measured by means of radiotelemetry, with the treatment response of plasma corticosterone (pCORT), a common and well-validated parameter for measuring acute stress responses. It was found that HR, and to a lesser extent also BT, parallels pCORT values after subjecting the animals to different methods of restraint. Secondly, the acute stress response caused by different injection methods was evaluated. Again, HR was found to be a more sensitive parameter than BT. We found that, in case of sham injections, the acute stress response after an intraperitoneal (i.p.) injection was more pronounced than after intramuscular (i.m.) or subcutaneous (s.c.) injections, but this difference was found to be inconsistent when saline was used as injection fluid. In a third experiment we investigated if the level of experience of the animal technician influenced the stress response after s.c. injections, but no differences were found. Overall, the results have indicated that HR might be considered as a useful parameter for measuring acute stress responses to routine procedures, but the value of BT seems to be of limited value in this respect.

Novel approach to the behavioural characterization of inbred mice: automated home cage observations.

Here we present a newly developed tool for continuous recordings and analysis of novelty-induced and baseline behaviour of mice in a home cage-like environment. Aim of this study was to demonstrate the strength of this method by characterizing four inbred strains of mice, C57BL/6, DBA/2, C3H and 129S2/Sv, on locomotor activity. Strains differed in circadian rhythmicity, novelty-induced activity and the time-course of specific behavioural elements. For instance, C57BL/6 and DBA/2 mice showed a much faster decrease in activity over time than C3H and 129S2/Sv mice. Principal component analysis revealed two major factors within locomotor activity, which were defined as 'level of activity' and 'velocity/stops'. These factors were able to distinguish strains. Interestingly, mice that displayed high levels of activity in the initial phase of the home cage test were also highly active during an open-field test. Velocity and the number of stops during movement correlated positively with anxiety-related behaviour in the elevated plus maze. The use of an automated home cage observation system yields temporal changes in elements of locomotor activity with an advanced level of spatial resolution. Moreover, it avoids the confounding influence of human intervention and saves time-consuming human observations.

Slaughter of poultry during the epidemic of avian influenza in the Netherlands in 2003.

During an outbreak of avian influenza in the Netherlands in spring 2003, the disease was controlled by destroying all the poultry on the infected farms and on all the farms within a radius of 3 km. In total, 30 million birds were killed on 1242 farms and in more than 8000 hobby flocks, by using mobile containers filled with carbon dioxide, mobile electrocution lines and by gassing whole poultry houses with carbon monoxide or carbon dioxide. Observations of these methods were used to compare their effectiveness and capacity, and their effects on the welfare of the birds. Gassing whole poultry houses had a much greater capacity than mobile equipment, and catching live birds to bring them to a mobile killing device caused extra stress and could cause pain due to injuries inflicted when catching and handling them. Gassing whole poultry houses with carbon monoxide requires strict safety regulations and, therefore, gassing with carbon dioxide was considered preferable. However, this method is not suited to all types of housing, and in these circumstances mobile killing devices were a useful alternative.

Susceptibility of duck and turkey to severe hypercapnic hypoxia.

Large groups of poultry, including ducks and turkeys, are killed for disease control purposes with CO2. In this study, we examined the physiological reaction of White Pekin ducks and turkeys to increasing CO2 concentrations. Additionally, we examined the suitability of killing both species with increasing CO2 concentrations. Blood gas values showed similar reaction patterns for both species: a strong increase in pCO2 from approximately 40 to 200 mmHg, decreasing pO2 and O2 saturation, a decrease in pH from 7.4 to 6.7, and a strong shift in acid-base equilibrium (averaging 0 to -23). On the electroencephalogram, theta and sigma waves occurred at 21 to 23% CO2, and suppression to a near isoelectric electroencephalogram occurred between 41.8 and 43.4% CO2 in inhaled air. Heartbeat declined from approximately 300 beats per min (bpm) at the start to 225 bpm at loss of posture to 150 bpm at 1 min before the heartbeat ceased. During the last phase of heart activity, an irregular rhythm and fibrillation were observed in addition to a decline in bpm. Blood gas values and electrophysiological data confirmed that ducks and turkeys lose consciousness before a level of 25% CO2 in inhaled air is reached and that both ducks and turkeys die within 13 min in an environment of 45% CO2 in inhaled air.

Increased gabaergic input to ventral tegmental area dopaminergic neurons associated with decreased cocaine reinforcement in mu-opioid receptor knockout mice.

There is general agreement that dopaminergic neurons projecting from the ventral tegmental area (VTA) to the nucleus accumbens and prefrontal cortex play a key role in drug reinforcement. The activity of these neurons is strongly modulated by the inhibitory and excitatory input they receive. Activation of mu-opioid receptors, located on GABAergic neurons in the VTA, causes hyperpolarization of these GABAergic neurons, thereby causing a disinhibition of VTA dopaminergic neurons. This effect of mu-opioid receptors upon GABA neurotransmission is a likely mechanism for mu-opioid receptor modulation of drug reinforcement. We studied mu-opioid receptor signaling in relation to cocaine reinforcement in wild-type and mu-opioid receptor knockout mice using a cocaine self-administration paradigm and in vitro electrophysiology. Cocaine self-administration was reduced in mu-opioid receptor knockout mice, suggesting a critical role of mu-opioid receptors in cocaine reinforcement. The frequency of spontaneous inhibitory post-synaptic currents onto dopaminergic neurons in the ventral tegmental area was increased in mu-opioid receptor knockout mice compared with wild-type controls, while the frequency of spontaneous excitatory post-synaptic currents was unaltered. The reduced cocaine self-administration and increased GABAergic input to VTA dopaminergic neurons in mu-opioid receptor knockout mice supports the notion that suppression of GABAergic input onto dopaminergic neurons in the VTA contributes to mu-opioid receptor modulation of cocaine reinforcement.

Reaction to frustration in high and low feather pecking lines of laying hens from commercial or semi-natural rearing conditions.

The effect of rearing conditions on feather pecking and reaction to frustration was studied in two lines of laying hens. From commercial rearing conditions (large group, no mother hen), seven birds from a high feather pecking line (HC birds) and eight birds from a low feather pecking line (LC birds) were used. From semi-natural rearing conditions (small group, mother hen present) seven birds from the high feather pecking line (HN birds) were used. Feather pecking behaviour of HC, LC, and HN groups was recorded for 30 min. After that, each bird was food deprived and trained to peck a key for a food reward in a Skinnerbox. After training, each bird was subjected to a frustration session in a Skinnerbox, where the feeder was covered with Perspex. Three HC birds showed severe feather pecking, compared with one HN bird and zero LC birds. Differences in reaction to frustration were found between birds from different lines, but not in birds from different rearing conditions. LC birds tended to put their head in the feeder more frequently than HC birds over all sessions. Although limited, this study indicates that rearing conditions influence feather pecking, but not reaction to frustration.

Spatial, contextual and working memory are not affected by the absence of mossy fiber long-term potentiation and depression.

The mossy fibers of the hippocampus display NMDA-receptor independent long-term plasticity. A number of studies addressed the role of mossy fiber long-term plasticity in memory, but have provided contrasting results. Here, we have exploited a genetic model, the rab3A null-mutant, which is characterized by the absence of both mossy fiber long-term potentiation and long-term depression. This mutant was backcrossed to 129S3/SvImJ and C57Bl/6J to obtain standardized genetic backgrounds. Spatial working memory, assessed in the eight-arm radial maze, was unchanged in rab3A null-mutants. Moreover, one-trial cued and contextual fear conditioning was normal. Long-term spatial memory was tested in the Morris water maze. Two different versions of this task were used, an 'easy' version and a 'difficult' one. On both versions, no differences in search time and quadrant preferences were observed. Thus, despite the elimination of mossy fiber long-term plasticity, these tests revealed no impairments in mnemonic capabilities. We conclude that spatial, contextual and working memory do not depend on mossy fiber plasticity.

Decision support system for overall welfare assessment in pregnant sows A: model structure and weighting procedure.

The problem of how to objectively assess the overall welfare status of animals under farming conditions has contributed to an ongoing debate that has hampered actual decision making on animal welfare. For this reason we constructed a model based on the assumed hierarchical organization of the animals' needs for overall welfare assessment in the case of pregnant sows. This model is implemented in a computer-based decision support system that takes a description of a housing and management system as input and produces a welfare score as output. A formalized procedure was used to construct the model for welfare assessment in pregnant sows on the basis of available scientific knowledge. This SOWEL (from SOw WELfare) model contains 37 attributes that describe the welfare-relevant properties of housing and management systems. In the decision support system these attributes are linked to scientific statements and a list of needs to provide a scientific basis for welfare assessment. Weighting factors that represent the relative importance of the attributes are derived from the scientific statements about the various welfare performance criteria that have been measured by scientists. The welfare score is calculated as the weighted average score. All information in the decision support system is stored in tables in a relational database such that newly available knowledge and insights can be incorporated to refine the model. The model has been developed in line with several existing models but it differs from these models in that it is the first to provide a formalized procedure to explicate the reasoning steps involved in welfare assessment based on available scientific knowledge.

Decision support system for overall welfare assessment in pregnant sows B: validation by expert opinion.

This paper examines the validity of a model that is embedded in a computer-based decision support system to assess the welfare status of pregnant sows in housing and management systems. The so-called SOWEL (SOw WELfare) model was constructed using a formalized procedure to identify and weight welfare-relevant attributes of housing systems in relation to the animal's needs, and evidenced by scientific statements collected in a database. The model's predictions about welfare scores for 15 different housing systems and weighting factors for 20 attributes were compared with expert opinion, which was solicited using a written questionnaire for pig-welfare scientists. The experts identified tethering and individual housing in stalls as low welfare systems. The group of midwelfare systems contained indoor group-housing systems and an individual-housing system with additional space and substrate. The five best systems were all systems with outdoor access and the provision of some kind of substrate such as straw. The highest weighting factors were given for the attributes "social contact," "health and hygiene status," "water availability," "space per pen," "foraging and bulk," "food agonism," "rooting substrate," "social stability," and "movement comfort." The degree of concordance among the experts was reasonable for welfare scores of housing systems, but low for weighting factors of attributes. Both for welfare scores and weighting factors the model correlated significantly with expert opinion (Spearman's Rho: 0.92, P < 0.001, and 0.72, P < 0.01, respectively). The results support the validity of the model and its underlying procedure to assess farm-animal welfare in an explicit and systematic way based on available scientific knowledge.

Individual housing during the play period results in changed responses to and consequences of a psychosocial stress situation in rats.

In the present study, the consequences of individual rearing during the play period on adult responses to aggression were investigated in a complex social setting. In a group of either socially or individually reared rats, an aggressor was repeatedly introduced. Separate control groups of individually and socially reared rats were not exposed to an aggressor. To allow an interpretation of the altered reactivity to aggression in terms of (in)efficient or (in)adequate behavior, not only the responses in the presence of the aggressor but also the consequences of the altered reactivity on subsequent behavior in the absence of the aggressor were observed. We demonstrated that a higher number of injuries, more agitation of the aggressor, and more ultrasonic distress vocalizations accompanied the altered responses of individually reared rats in the presence of the aggressor. In the absence of the aggressor, individually reared rats displayed less social stress-reducing behaviors (play and social grooming) than socially reared rats. It was concluded that individually reared rats display a less adequate response to aggression in this social context.

Imipramine restores the long-term impairment of appetitive behavior in socially stressed rats.

RATIONALE: Previous observations revealed that defeated and subsequently individually housed rats do not display behavioral anticipatory responses to the conditioned presentation of a bell/light stimulus associated with free access to a 5% sucrose solution reward. The absence of the appetitive responses suggests a decreased sensitivity to reward. This might be homologous to anhedonia, a symptom of human depression. OBJECTIVES: To further validate the inability to anticipate as indicative for a depressionlike state we investigated whether antidepressant treatment restores the impaired anticipatory responses in defeated and subsequently individually housed animals. METHODS: Male rats were defeated and subsequently individually housed or subjected to a control treatment. In the 19-20th weeks after the exposure to defeat rats were either injected daily with imipramine (20 mg/kg per os, dissolved in water) or water. Anticipatory behavior was measured both before and after 3-5 weeks of chronic treatment with imipramine. RESULTS: The long-term impairment of anticipatory behavior in defeated and subsequently individually housed rats was restored by chronic imipramine treatment. Impaired appetitive behavior in socially stressed rats was not accompanied by a decreased consumption of the 5% sucrose solution in the anticipatory tests. The recovery of the appetitive responses was independent of open field activity, body weight, and 5% sucrose preference in the home cage. CONCLUSIONS: Chronic imipramine administration restores the anhedonialike absence of anticipatory behavior in socially stressed rats. Predictive validity of the social stress model of human depression is suggested by the similar action of imipramine on the modeled behavior and on the anhedonia symptoms in depressive human patients.

Chronic imipramine treatment partially reverses the long-term changes of hippocampal synaptic plasticity in socially stressed rats.

In the present study, we investigated whether synaptic plasticity changes in the hippocampus of depressive-like socially stressed rats could be reversed by chronic antidepressant treatment. To that end, rats were either defeated and subsequently individually housed or subjected to control treatment followed by social housing. After a period of at least 3 months, rats were either treated chronically with imipramine (20 mg/kg per day, per os for at least 3 months) or the solvent solution (i.e. water). Then, long-term potentiation and depression were measured in the CA1 region of the hippocampus in vitro. Chronic imipramine treatment partially restored the attenuated induction of long-term potentiation and suppressed the facilitation of long-term depression-induction in socially stressed rats. The altered synaptic plasticity after social stress is discussed in relation to cognitive deficits and hippocampal changes that are observed in depressive patients.