Investigation Of Behavior Research Articles

Eliciting a predatory response in the eastern corn snake (Pantherophis guttatus) using live and inanimate sensory stimuli: implications for managing invasive populations

North America's eastern corn snake (Pantherophis guttatus) has been introduced to several islands throughout the Caribbean and Australasia where it poses a significant threat to native wildlife. Invasive snake control programmes often involve trapping with live bait, a practice that, as well as being costly and labour intensive, raises welfare and ethical concerns. This study assessed corn snake response to live and inanimate sensory stimuli in an attempt to inform possible future trapping of the species and the development of alternative trap lures. We exposed nine individuals to sensory cues in the form of odour, visual, vibration and combined stimuli and measured the response as rate of tongue-flick (RTF). The RTF was significantly higher in odour and combined cues treatments, and there was no significant difference in RTF between live and inanimate cues during odour treatments. Our findings suggest chemical cues are of primary importance in initiating investigatory behaviours and that an inanimate odour stimulus, absent of simultaneous visual and vibratory cues, is potentially a low-cost alternative trap lure for the control of invasive corn snake populations.

Pharmacological profiling of Argemone mexicana for its aphrodisiac potentials in male Wistar rats

Abstract Objective To study the aphrodisiac potentials of ethanol extract of Argemone mexicana L. ( A. mexicana ) of Papaveraceae family in sexually sluggish male Wistar rats. Methods The sexually inactive male rats were divided into two groups of 8 rats each. The test group animals were treated with ethanol extract of A. mexicana (EEAM) at 1 g/kg daily oral dose for 28 days. Other group animals were treated with sildenafil citrate at an oral dose of 5 mg/kg. The latencies of mount, intromission, ejaculation; post ejaculatory pause and frequencies of mount, intromission, and ejaculation were measured on 0, 7th, 14th, 21st and 28th days. Serum testosterone levels were estimated using ELISA. Results The EEAM was nonlethal even at dose of 4.0 g/kg. The oral dosing of EEAM has significantly enhanced the orientation of males towards female by increase in ano-genital investigatory behavior, frequencies of mount, intromission, and ejaculation ( P P P Conclusion The EEAM has elevated sexual dysfunctions in male rats. These potentials may be related to protopine alkaloids and flavanols by means of physiological stimulus for penile vasculature. Thus, results support the use of EEAM in enhancing sexual behavior in sluggish male rats.

Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system1,2

Free-access stalls allow sows to choose the protection of a stall or use of a shared group space. This study investigated the effect of group space width, 0.91 (SS), 2.13 (IS), and 3.05 (LS) m, on the health, production, behavior, and welfare of gestating sows. Nine replications of 21 (N = 189) gestating sows were used. At gestational d 35.4 ± 2.3, the pregnant sows were distributed into 3 pens of 7 sows, where they remained until 104.6 ± 3.5 d. Each treatment pen had 7 free-access stalls and a group space that together provided 1.93 (SS), 2.68 (IS), or 3.24 (LS) m(2)/sow. Baseline measurements were obtained before mixing. Back fat depth, BW, BCS, and lameness were measured monthly, and skin lesions were scored weekly. Blood was collected monthly for hematological, immunological, and cortisol analyses. Sow behavior was video recorded continuously during the initial 4 d of treatment and 24 h every other week thereafter. Behavior was analyzed for location, posture, pen investigation, social contact, and aggression. Skin response to the mitogen concanavalin A (Con A) was tested at mean gestational d 106. Litter characteristics including size and weight were collected at birth and weaning. The data were analyzed using a mixed model. Multiple comparisons were adjusted with the Tukey-Kramer and Bejamini-Hochberg methods. Group space allowance had no effect on any measure of sow health, physiology, or production (P ≥ 0.10). Sows in the SS, IS, and LS pens spent 77.88% ± 3.88%, 66.02% ± 3.87%, and 63.64% ± 3.91%, respectively, of their time in the free-access stalls (P = 0.12). However, SS sows used the group space less than IS and LS sows (P = 0.01). Overall, pen investigatory behavior was not affected by group space allowance (P = 0.91). Sows in the LS pens spent more time in a social group than SS sows (P = 0.02), whereas sows in IS pens were intermediate to, but not different from, the other treatments (P ≥ 0.10). The size of the social groups was also affected by the group space allowance (P = 0.03), with SS sows forming smaller groups than LS sows; again, IS sows were intermediate to, but not different from, the other treatments. Although the group space allowance had no measurable impact on the health, physiology, or productivity of the sows, the lower group space use and social contact of the SS sows reduced the behavioral diversity benefits of group housing and may indicate an avoidance of social stressors or a lack of physical comfort in the smallest pens.

Possible scavenging behavior in Ornate Hawk-Eagle (Spizaetus ornatus) in Amazonas, Brazil

We provide documentation of the first observations of interactions with carrion in the Ornate Hawk-Eagle (Spizaetus ornatus), a species formerly assumed only to prey on live food items. During fieldwork in RESEX Medio-Jurua reserve, in Amazonas, Brazil, in June–August 2009, images were captured by remote camera traps of an Ornate Hawk-Eagle interacting with a cattle femur, indicating possible scavenging behavior. Additionally, apparent investigatory behavior was also recorded in Slate-colored Hawk (Buteogallus schistaceus), a previously unrecorded behavior for the species. We suggest that additional work with camera traps monitoring carrion may reveal opportunistic scavenging to be more widespread in tropical forest raptors than has generally been assumed.

Effect of Aqueous Extract of <i>Phoenix dactylifera</i> Pollen on Dopamine System of Nucleus Accumbens in Male Rats

Background: Dopamine has been known to facilitate male sexual function. Methods: The effect of aqueous extract (140 mg/kg) of Phoenix dactylifera date palm pollen on sexual behavior and determining of dopamine transmission in the nucleus accumbens was studied in male rats using in vivo microdialysis. Results: Releasing of dopamine increased significantly in the nucleus accumbens when a receptive female was introduced behind a screen (p 0.001). During copulation, dopamine increased markedly in control and treated rats. Phoenix dactylifera Date Palm Pollen enhanced the orientation of males towards females by increasing mounting and ano-genital investigatory behavior. Improving of sexual behavior and dopamine release was higher in treated rats in comparison with control (p 0.001). Conclusion: These results indicate a neurochemical basis for interaction between dopaminergic agents and male sexual behavior. Therefore, Phoenix dactylifera Date Palm Pollen seems to act as a dopamine agonist and to cure male infertility. It can be used as an aphrodisiac that leads to further increases in dopamine release.

The effects of mild maternal undernutrition on the post-weaning behaviour of rabbits

The objective of the present experiment was to investigate the implications of mild maternal undernutrition on the post-weaning behaviour of rabbits. Twenty-six dams were randomly assigned to two groups: the control group (C) that was fed ad libitum throughout pregnancy and the undernourished group (U) that was fed 75% of the recommended maintenance requirements between the 6th and 26th day of pregnancy. At the age of 50 and 65 days old, behaviour of rabbits in cages was recorded and rabbits were further subjected to an open-field test; a paradigm used as an indicator of fear and emotional distress.There were only limited differences between the examined groups in the exhibition of behaviour in the cages; values for frequencies of eating and drinking were higher in the controls compared to the prenatally undernourished rabbits (P<0.05). Duration of drinking appeared to be higher in the group of rabbits born from undernourished does at the age of 50 days compared to the other groups (P<0.05). Duration of resting and comfort behaviours was significantly increased at the age of 65 days in both groups (P<0.05 and P<0.01, respectively). In both groups, a decreased activity of rabbits during the light period was observed (as expected), whereas a reduction in frequencies of eating and drinking, and duration of locomotory and investigatory behaviours was observed at the age of 65 days (P<0.05).Rabbits born to undernourished does displayed reduced rates of the sitting still and standing stretched behaviours compared to the controls during the implementation of the open-field test (P<0.05). No other significant differences in the exhibition of the examined behaviours were found between the treatment groups.Although some differences were found in specific behavioural patterns, it is concluded that mild maternal undernutrition (75% of ad libitum intake) during pregnancy has generally only little effect on rabbits’ post-weaning behaviour.

Alterations in the endocannabinoid system in the rat valproic acid model of autism

The endocannabinoid system plays a crucial role in regulating emotionality and social behaviour, however it is unknown whether this system plays a role in symptoms associated with autism spectrum disorders. The current study evaluated if alterations in the endocannabinoid system accompany behavioural changes in the valproic acid (VPA) rat model of autism. Adolescent rats prenatally exposed to VPA exhibited impaired social investigatory behaviour, hypoalgesia and reduced lococmotor activity on exposure to a novel aversive arena. Levels of the endocananbinoids, anandamide (AEA) and 2-arachidonylglycerol (2-AG) in the hippocampus, frontal cortex or cerebellum were not altered in VPA- versus saline-exposed animals. However, the expression of mRNA for diacylglycerol lipase α, the enzyme primarily responsible for the synthesis of 2-AG, was reduced in the cerebellum of VPA-exposed rats. Furthermore, while the expression of mRNA for the 2-AG-catabolising enzyme monoacylglycerol lipase was reduced, the activity of this enzyme was increased, in the hippocampus of VPA-exposed animals. CB1 or CB2 receptor expression was not altered in any of the regions examined, however VPA-exposed rats exhibited reduced PPARα and GPR55 expression in the frontal cortex and PPARγ and GPR55 expression in the hippocampus, additional receptor targets of the endocannabinoids. Furthermore, tissue levels of the fatty acid amide hydrolase substrates, AEA, oleoylethanolamide and palmitoylethanolamide, were higher in the hippocampus of VPA-exposed rats immediately following social exposure. These data indicate that prenatal VPA exposure is associated with alterations in the brain's endocannabinoid system and support the hypothesis that endocannabinoid dysfunction may underlie behavioural abnormalities observed in autism spectrum disorders.

Aphrodisiac Activity of Aqueous Extract of &amp;lt;i&amp;gt;Phoenix dactylifera&amp;lt;/i&amp;gt; Pollen in Male Rats

Aim of study: Ancient literature alluded to the use of a number of plants/preparations as sex enhancer. One of such botanicals is Phoenix dactylifera in which the pollen grain has been acclaimed to be used as an aphrodisiac. However, the validity has not been scientifically tested. Dopamine is known to facilitate male sexual function. Therefore, the present study was undertaken to evaluate the effect of aqueous extract of Phoenix dactylifera pollen on the sexual behavior of male rats and to measure of serum Estradiol and Testostrone. Also, dopamine transmission in the nucleus accumbence (NAc) was studied in male rats using in vivo microdialysis. Methods and Materials: sixty male rats were randomized into 6 groups (A-F). Group A received 0.2 ml of Normal Saline mixed with Dimethyl Sulphate (DMSO), while groups B-F were injected same volume containing 35 mg/kg, 70 mg/kg, 105 mg/kg, 140 mg/kg and 350 mg/kg of DPP extract, respectively. Sexual behavioral parameters including mounting, intromission and ejaculation frequencies and latencies were recorded in male rats one hour after injection of extract by mating with a receptive female (1:1). The male serum testosterone and estradiol concentrations were also determined. Results: All doses stimulated male sexual behavior. Extract significantly increased mount, ejaculation, intromission frequencies and ejaculation latency in comparison to controlled ones (p 0.001). Mount and intromission latencies significantly reduced (p 0.001). Maximum effect was observed in dose 140 mg/kg. This extract was found to enhance Testestrone, Estradiol and the orientation of males toward female ones by increasing mounting and ano-genital investigatory behavior. Conclusions: Data from this study identified that the aqueous extract of Phoenix dactylifera pollen grain enhanced sexual behaviour in male rats. The improved sexual appetitive behaviour in male rats may be attributed, to the alkaloids, saponins, and or flavonoids since these phytochemicals has engorgement, androgen enhancing. Also, our findings support the traditional use of this plant as acclaimed aphrodisiac and for the treatment of pre-ejaculation and impotency.

Seasonal and Diurnal Variations in African Elephant (Loxodonta africana) and Black Rhinoceros (Diceros bicornis) Behavior in a Northern Climate Zoo

African elephants (Loxodonta africana) and black rhinoceroses (Diceros bicornis) are charismatic mammals that help draw visitors into zoological institutions. Because they evolved in the same habitat utilizing similar food resources, the two species have many physiological similarities yet behaviorally remain very different. Limitations of the zoo environment, such as constraints on exhibit size, social complexity, and behavior, may be associated with health and behavioral problems seen in both species and thought to be exacerbated in northern, temperate climates. The purpose of this study was to determine how the behavioral patterns of two large-bodied African ungulate species were affected by seasonal changes in a northern climate zoo. The behavior of three African elephants and three black rhinoceroses was observed for one year at Cleveland Metroparks Zoo. We found average resting levels of African elephants and black rhinos were similar to expected values based on data from wild and captive studies. Both species adapted their behavior to cope with high temperatures and increased sun exposure. Increased time spent inside during winter months was associated with decreased investigatory behaviors in elephants and decreased locomotion in rhinos. To increase species-typical behaviors, exhibits should include substrates for dusting, mud wallows, shade structures, and resting sites for all individuals. Time spent feeding may be increased through natural food items such as browse. Indoor exhibits should include environmental variation, enrichment, and adequate space so as to encourage these behaviors. Physiological and health measurements might be measured to determine sufficient levels of exercise for zoo-housed elephants and rhinos.// //

Mating-relevant olfactory stimuli activate the rat brain in an age-dependent manner

Chemosensory stimulation is vital for the expression of rodent sexual behavior. As sexual activity decreases with aging, this study investigated whether aging also impacts the integration of sex-relevant chemosensory cues. To this end, several measures were obtained from adult (10-12 months) and aged (30-36 months) male rats after exposure to a conspecific estrous female. These included rates of investigatory behaviors, levels of stimulus-induced Fos immunoreactivity, activation of gonadotropin-releasing hormone-containing cells, and levels of circulating testosterone and corticosterone. The results indicated no significant differences in investigatory behaviors, levels of corticosterone, or activation of gonadotropin-releasing hormone-containing cells between the two groups. As has been reported previously, the levels of testosterone were lower in the aged rats. However, stimulus-induced neural activity was higher in the bed nucleus of the stria terminalis and the medial preoptic area of aged rats, whereas no differences were found in the main olfactory bulb, accessory olfactory bulb, medial amygdala, ventral tegmental area, or nucleus accumbens. These findings suggest the presence of a compensatory mechanism in the hypothalamus of aged animals versus adults, whereby more cells are recruited to elicit a sexual response in the presence of a sexually exciting stimulus.

Acute illness-induced behavioral alterations are similar to those observed during withdrawal from acute alcohol exposure

Exposure to an immunogen results in a constellation of behavioral changes collectively referred to as “sickness behaviors,” with alterations in cytokine expression previously shown to contribute to this sickness response. Since behaviors observed during ethanol withdrawal are strikingly similar to sickness behaviors, we hypothesized that behavioral manifestations of ethanol withdrawal might be an expression of sickness behaviors induced by ethanol-related changes in peripheral and/or central cytokine expression. Accordingly, behaviors exhibited during a modified social investigation test were first characterized in male rats following an acute injection of lipopolysaccharide (LPS; 100μg/kg). Subsequently, behavioral changes after either a high (4-g/kg; Experiment 2) or low dose (0.5g/kg; Experiment 3) of ethanol were also examined in the same social investigation test, as well as in the forced-swim test (FST; Experiment 4). Results from these experiments demonstrated similar reductions in both exploration and social investigatory behavior during acute illness and ethanol withdrawal, while a seemingly paradoxical decrease in immobility was observed in the FST during acute ethanol withdrawal. In follow-up studies, neither indomethacin (Experiment 5) nor interleukin-1 receptor antagonist (Experiment 6) pre-exposure reversed the ethanol withdrawal-induced behavioral changes observed in this social investigation test. Taken together, these studies demonstrate that the behavioral sequelae of acute illness and ethanol withdrawal are similar in nature, while antagonist studies suggest that these behavioral alterations are not reversed by blockade of IL-1 receptors or inhibition of prostaglandin synthesis. Though a direct mechanistic link between cytokines and the expression of acute ethanol withdrawal-related behaviors has yet to be found, future studies examining the involvement of brain cytokines as potential mediators of ethanol effects are greatly needed.

Sex Differences in Social Investigation: Effects of Androgen Receptors, Hormones and Test Partner

We examined the role of the androgen receptor (AR) in the investigatory behaviour of conspecifics using mice carrying the testicular feminisation mutation (X(Tfm) Y). Responses to members of the same and opposite sex were evaluated in a habituation/dishabituation task. Adult mice were gonadectomised and treated with oestradiol (E(2) ) or testosterone. After E(2) treatment, regardless of the sex of the stimulus mouse, wild-type (WT) males engaged in significantly more investigation than WT females. X(Tfm) Y males treated with E(2) showed 'male-like' behaviour in response to a male but behaved 'female-like' when the stimulus was a female. Because WT and X(Tfm) Y males behaved the same in response to another male, we used two additional mouse models to ask whether sex chromosomes were responsible for this phenomenon. Regardless of sex chromosome complement, gonadal males displayed high levels of investigation. When mice were treated with testosterone, investigation by WT females was enhanced, which eliminated the sex differences. Most strikingly, X(Tfm) Y males receiving testosterone-treatment increased the investigation of females to levels equal to those shown by WT mice. Given that testosterone, but not its metabolite E(2) , caused X(Tfm) Y males to investigate female conspecifics at high levels, it is plausible that nonclassical actions of AR, and/or activation of a novel AR, may be involved in this behaviour. Taken together, our data show that AR activation during adulthood is not required for males to investigate mice of either sex. However, 'male-like' levels of investigation of a female stimulus may depend on neonatal activation of the classic nuclear AR.

A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore.

The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear ‘marking trees’ to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively ‘safe’ time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears.

Circuit Specific Functions of Cannabinoid CB1 Receptor in the Balance of Investigatory Drive and Exploration

Well balanced novelty seeking and exploration are fundamental behaviours for survival and are found to be dysfunctional in several psychiatric disorders. Recent studies suggest that the endocannabinoid (eCB) system is an important control system for investigatory drive. Pharmacological treatment of rodents with cannabinergic drugs results in altered social and object investigation. Interestingly, contradictory results have been obtained, depending on the treatment, drug concentration and experimental conditions. The cannabinoid type 1 (CB1) receptor, a central component of the eCB system, is predominantly found at the synapses of two opposing neuronal populations, i.e. on inhibitory GABAergic and excitatory glutamatergic neurons. In the present study, using different transgenic mouse lines, we aimed at investigating the impact of CB1 receptor inactivation in glutamatergic or GABAergic neurons on investigatory behaviour. We evaluated animate (interaction partner) and inanimate (object) exploratory behaviour in three different paradigms. We show that exploration was increased when CB1 receptor was deleted from cortical and striatal GABAergic neurons. No effect was observed when CB1 receptor was deleted specifically from dopamine receptor D1-expressing striatal GABAergic medium spiny neurons. In contrast, deletion of CB1 receptor from cortical glutamatergic neurons resulted in a decreased exploration. Thus, our results indicate that exploratory behaviour is accurately balanced in both, the social and non-social context, by the eCB system via CB1 receptor activation on cortical glutamatergic and GABAergic neurons. In addition, the results could explain the contradictory findings of previous pharmacological studies and could further suggest a possibility to readjust an imbalance in exploratory behaviour observed in psychiatric disorders.

Synergistic interaction between baclofen administration into the median raphe nucleus and inconsequential visual stimuli on investigatory behavior of rats.

Noncontingent administration of amphetamine into the ventral striatum or systemic nicotine increases responses rewarded by inconsequential visual stimuli. When these drugs are contingently administered, rats learn to self-administer them. We recently found that rats self-administer the GABA(B) receptor agonist baclofen into the median (MR) or dorsal (DR) raphe nuclei. We examined whether noncontingent administration of baclofen into the MR or DR increases rats' investigatory behavior rewarded by a flash of light. Contingent presentations of a flash of light slightly increased lever presses. Whereas noncontingent administration of baclofen into the MR or DR did not reliably increase lever presses in the absence of visual stimulus reward, the same manipulation markedly increased lever presses rewarded by the visual stimulus. Heightened locomotor activity induced by intraperitoneal injections of amphetamine (3 mg/kg) failed to concur with increased lever pressing for the visual stimulus. These results indicate that the observed enhancement of visual stimulus seeking is distinct from an enhancement of general locomotor activity. Visual stimulus seeking decreased when baclofen was co-administered with the GABA(B) receptor antagonist, SCH 50911, confirming the involvement of local GABA(B) receptors. Seeking for visual stimulus also abated when baclofen administration was preceded by intraperitoneal injections of the dopamine antagonist, SCH 23390 (0.025 mg/kg), suggesting enhanced visual stimulus seeking depends on intact dopamine signals. Baclofen administration into the MR or DR increased investigatory behavior induced by visual stimuli. Stimulation of GABA(B) receptors in the MR and DR appears to disinhibit the motivational process involving stimulus-approach responses.

Testing declarative memory in laboratory rats and mice using the nonconditioned social discrimination procedure

Testing declarative memory in laboratory rodents can provide insights into the fundamental mechanisms underlying this type of learning and memory processing, and these insights are likely to be applicable to humans. Here we provide a detailed description of the social discrimination procedure used to investigate recognition memory in rats and mice, as established during the last 20 years in our laboratory. The test is based on the use of olfactory signals for social communication in rodents; this involves a direct encounter between conspecifics, during which the investigatory behavior of the experimental subject serves as an index for learning and memory performance. The procedure is inexpensive, fast and very reliable, but it requires well-trained human observers. We include recent modifications to the procedure that allow memory extinction to be investigated by retroactive and proactive interference, and that enable the dissociated analysis of the central nervous processing of the volatile fraction of an individual's olfactory signature. Depending on the memory retention interval under study (short-term memory, intermediate-term memory, long-term memory or long-lasting memory), the protocol takes ~10 min or up to several days to complete.

The effect of mirrors on the behaviour of singly housed male and female laboratory rabbits

AbstractIt is widely recognised that single housing is detrimental to the welfare of social species. However, some experimental procedures dictate that laboratory animals are housed individually. There is evidence to suggest that, by mimicking social contact, mirrors are beneficial to the welfare of singly housed horses and heifers. However, experiments with singly caged laboratory mice have found mirrors to be mildly aversive. The present study investigated the behavioural response of singly housed male and female rabbits to a mirror in their cage. After a period of pre-trial behavioural observations, rabbits were provided with an acrylic mirror, either at the front or the back of their cage, for a period of seven days. This was followed by a post-trial period, at the beginning of which all mirrors were removed. Both sexes showed some changes in behaviour and in the use of space within the cage. The addition of a mirror significantly reduced grooming in females, which was previously considered to be at high levels. Both males and females showed an increase in investigatory behaviour, although the patterns of change differed between the sexes. Differences between males and females are attributed to differences in socio-sexual strategies between the sexes. It is concluded that, when single housing is unavoidable, mirrors might be appropriate to partially compensate for social contact in female laboratory rabbits. Further research using a wide range of welfare indicators is needed to establish whether the provision of a mirror could be used as a successful method of improving laboratory rabbit welfare.

Syrian hamster males below an age threshold do not elicit aggression from unfamiliar adult males

In many species, young males are the dispersers, leaving their natal area after weaning to establish a breeding area of their own. As young males disperse, however, they are bound to encounter unfamiliar adult males with established territories. Such interactions between an adult male and a young male may always be agonistic. Alternatively, there may be an age threshold below which aggression is not elicited and above which the adult male is aggressive toward the juvenile male. To test these two alternative hypotheses, we paired 47 young Syrian hamster (Mesocricetus auratus) males ranging from 24 to 65 days of age with 47 adult male hamsters and measured aggressive and investigatory behavior for 5 min. We observed no aggression by the adult toward young males between 24 and 47 days of age or toward the single male that was 49 days of age. Young males that were 50 days of age or older, however, elicited significant levels of aggression from the adults. These results indicate that in Syrian hamsters, young males are less vulnerable to adult aggression up to an age threshold and are more vulnerable to adult aggression beyond that threshold. This pattern may facilitate the establishment of territories by dispersing young males below that age threshold.

The effects of pramipexole on prepulse inhibition and locomotor activity in C57BL/6J mice

Pramipexole (PRA) is a preferential D3R agonist that, in rats and humans, modifies prepulse inhibition (PPI) of the acoustic startle reflex, an operational measure of sensorimotor gating. The ability to use similar PPI measures across species, and the relative ease of genetic manipulations in mice, suggests that molecular studies of the D3R regulation of sensorimotor gating might be best pursued in mice. Here, we evaluate the effects of PRA on PPI and locomotion in C57BL/6J mice, the background strain for many gene knockout mouse models. Male C57BL/6J mice were tested for PPI and locomotor activity after injection of PRA. No significant effects of PRA on PPI were observed at any dose (0.1-10.0 mg/kg), but a significant reduction in startle magnitude was observed after 10 mg/kg PRA. In contrast, the D1/2 agonist, apomorphine (5 mg/kg) significantly reduced PPI in these mice. At doses of PRA that did not alter startle magnitude (0.3, 1, 3 mg/kg), significant decreases in the amount of locomotor and investigatory behavior were observed. Distinct from findings in rats and humans, it seems that either: (i) PRA does not activate D3Rs in C57BL/6J mice, or (ii) D3R agonists are not sufficient to alter PPI in this mouse strain.

Effect of Individual, Group or ESF Housing in Pregnancy and Individual or Group Housing in Lactation on Sow Behavior

To evaluate the effect of different housing systems on sow behavior, 80 gilts were randomly allocated at puberty to four treatments: i) sow stall in gestation followed by farrowing crate (SC), ii) group housing with individual feeding in gestation followed by farrowing crate (GC), iii) ESF (Electronic Sow Feeding) system in gestation followed by farrowing crate (EC), and iv) ESF system followed by group farrowing pen (EG). Behavioral observations were carried out on a total of 16 animals per treatment at the following stages: first day of allocation to housing treatment, day of service, 80 days after service, 109 days after service on entry to farrowing accommodation, 24 h before farrowing, day of farrowing, 14, 27 and 28 days after farrowing, at weaning. On each occasion, individual animals were observed for a 24 period with one minute time sampling. There were significant differences (p<0.001) between stages of the reproductive cycle for all the behavior patterns in all treatments. On the first day in experimental housing treatments, sows spent more time rooting and dog-sitting. Activity and investigatory behavior decreased as pregnancy progressed. An activity peak was apparent just before farrowing, followed by a high level of inactivity on the day of farrowing. Time spent active, eating and drinking increased as lactation progressed, and greatest activity and locomotion was seen immediately following weaning. There were significant differences between housing treatments (p<0.01 ) for standing, moving, eating, drinking, dog-sitting and lying. During pregnancy SC sows spent more time standing, rooting, drinking and dog sitting, while EC sows spent less time rooting and drinking and more time lying. During lactation, GC sows spent more time standing, moving and eating, less time dog sitting and lateral lying. Nursing frequency was reduced in GC sows (p<0.001). The maternal and piglet behaviors were influenced strongly by environment during lactation. However, it was also shown that previous housing history can influence the maternal behavior in the pre-farrowing stage and during early lactation.