Form Of Environmental Enrichment Research Articles

Dehydrated and live black soldier fly larvae as environmental enrichment in indigenous slow-growing chickens: performance, gut health, and chitinolytic enzyme activity

The demand for sustainable and ethically farmed animal products is on the rise as consumers become more environmentally and animal welfare conscious. The need to diminish the consumption of soybean meal is urgent, and companies are looking for ways to respond to this necessity by looking for alternatives to soybean meal. This study assessed the impact of introducing whole dehydrated and live black soldier fly larvae (BSFL) into the diet of an indigenous chicken breed as environmental enrichment. A total of 144 39-day-old male Bianca di Saluzzo chickens were distributed among 18 pens and assigned to three different experimental groups. The control group received a diet where soybean meal was entirely replaced by alternative ingredients. The two experimental groups were given the same diet supplemented with 5% of the expected daily feed intake of whole dehydrated BSFL or whole live BSFL. Throughout the trial period (from the bird age of 39–174 days of age), live weight was recorded every 21 days, and the average daily gain, daily feed intake, and feed conversion ratio were calculated. The time required for the birds to consume the larvae was recorded three times a week. At age 147 and 174 days, 12 birds per treatment were selected based on mean live weight and slaughtered. Measurements included hot and chilled carcass weights, organ weights (spleen, liver, heart, stomach), breast and thigh muscle weights, and the corresponding yields were calculated. Acid protease activity was measured in proventriculus extract, and chitinase and chitosanase activity was calculated based on the release of reducing sugars from chitin or chitosan. The results showed little improvement in final live weights and daily feed intakes of the animals fed the insect larvae compared with control birds. Larva supplementation had no negative impact on the overall well-being of the animals assessed by blood analysis and histopathological assessment of the intestinal tract, spleen, and liver. No differences were found between the dehydrated vs live insect larvae consumption times, with all larvae being eaten up very rapidly (<3 min). The birds fed BSFL showed an increase in chitinase activity. These findings support the potential use of whole BSFL as a form of environmental enrichment, particularly in their dehydrated form, being more convenient to use and store, which would also encourage the uptake of this practice by farmers.

Preening cups in duck housing are associated with an increase in central dopamine activity that suggests a negative affective state

Preening cups are a form of environmental enrichment that provides Pekin ducks a semi-open water source to express their natural behaviors. We recently observed that preening cups may increase feather pecking behaviors in ducks. Thus, we set out to determine if this form of enrichment can impact the affective state of Pekin ducks. To accomplish this goal, we evaluated the effect of preening cups on serotonin (5-HT) and dopamine (DA) turnover via mass spectrometry and their respective synthetic enzyme gene expression via qRT-PCR. Our study investigated the link between aggressive pecking with levels and activity of brain 5-HT and DA. Brain 5-HT and DA levels and activity have been established for decades to be associated with affective states. Grow-out Pekin ducks (n = 260) were housed at Purdue and raised per industry standards. On day 18, brains were collected from ducks in pens before preening cups were placed (PRE, n = 6) and, again on day 43, in pens with (PC, n = 6) and without (CON, n = 6) preening cups. Brains were dissected into right and left halves, then further microdissected into 4 brain areas: caudal mesencephalon (CM), rostral mesencephalon (RM), diencephalon (DI), and forebrain (FB). The right hemisphere was used for mass spectrometry to determine the neurotransmitter concentration (ng/mg of tissue) and those concentrations were applied to neurotransmitter turnover equations. There were no differences across treatments for 5-HT turnover in any brain area. There were differences in DA turnover across age (P = 0.0067) in the CM and across treatments (P = 0.003) in the RM. The left hemisphere of the brain was used to perform qRT-PCR on the genes of 5-HT and DA production enzymes. Within the CM, day 43 duck brains had increased (P = 0.022) tryptophan hydroxylase and tyrosine hydroxylase relative mRNA levels. All other brain areas showed no differences. Our data suggest that ducks housed with preening cups and that showed increased feather pecking are associated with increased brain DA activity. The increased DA in the brain may lead to a predisposition for increased aggression in the form of feather pecking.

Variable ambient temperature promotes song learning and production in zebra finches.

Current climate change is leading to increasingly unpredictable environmental conditions and is imposing new challenges to wildlife. For example, ambient conditions fluctuating during critical developmental periods could potentially impair the development of cognitive systems and may therefore have a long-term influence on an individual's life. We studied the impact of temperature variability on zebra finch cognition, focusing on song learning and song quality (N = 76 males). We used a 2 × 2 factorial experiment with two temperature conditions (stable and variable). Half of the juveniles were cross-fostered at hatching to create a mismatch between pre- and posthatching conditions, the latter matching this species' critical period for song learning. We found that temperature variability did not affect repertoire size, syllable consistency, or the proportion of syllables copied from a tutor. However, birds that experienced variable temperatures in their posthatching environment were more likely to sing during recordings. In addition, birds that experienced variable prenatal conditions had higher learning accuracy than birds in stable prenatal environments. These findings are the first documented evidence that variable ambient temperatures can influence song learning in zebra finches. Moreover, they indicate that temperature variability can act as a form of environmental enrichment with net positive effects on cognition.

Assessment of animal management and habitat characteristics associated with social behavior in bottlenose dolphins across zoological facilities.

Bottlenose dolphins are a behaviorally complex, social species that display a variety of social behaviors. Because of this, it is important for zoological facilities to strive to ensure animals display species-appropriate levels of social behavior. The current study is part of the multi-institutional study entitled “Towards understanding the welfare of cetaceans in zoos and aquariums” commonly referred to as the Cetacean Welfare Study. All participating facilities were accredited by the Alliance of Marine Mammal Parks and Aquariums and/or the Association of Zoos and Aquariums. Behavioral data were collected on 47 bottlenose dolphins representing two subspecies, Tursiops truncatus and Tursiops aduncus, at 25 facilities. The social behaviors of group related activity (group active) as well as interacting with conspecifics (interact with conspecific) were examined for their relationships to both animal management factors and habitat characteristics. The behavioral state of group active and the rate of interact with conspecific were both positively related to the frequency of receiving new forms of environmental enrichment. Both were inversely related to the random scheduling of environmental enrichment. Additional results suggested interact with conspecific was inversely related with daytime spatial experience and that males displayed group active more than females. Overall, the results suggested that animal management techniques such as the type and timing of enrichment may be more important to enhance social behavior than habitat characteristics or the size of the habitat. Information gained from this study can help facilities with bottlenose dolphins manage their enrichment programs in relation to social behaviors.

A Good Life for Laboratory Rodents?

Most would agree that animals in research should be spared "unnecessary" harm, pain, or distress, and there is also growing interest in providing animals with some form of environmental enrichment. But is this the standard of care that we should aspire to? We argue that we need to work towards a higher standard-specifically, that providing research animals with a "good life" should be a prerequisite for their use. The aims of this paper are to illustrate our vision of a "good life" for laboratory rats and mice and to provide a roadmap for achieving this vision. We recognize that several research procedures are clearly incompatible with a good life but describe here what we consider to be the minimum day-to-day living conditions to be met when using rodents in research. A good life requires that animals can express a rich behavioral repertoire, use their abilities, and fulfill their potential through active engagement with their environment. In the first section, we describe how animals could be housed for these requirements to be fulfilled, from simple modifications to standard housing through to better cage designs and free-ranging options. In the second section, we review the types of interactions with laboratory rodents that are compatible with a good life. In the third section, we address the potential for the animals to have a life outside of research, including the use of pets in clinical trials (the animal-as-patient model) and the adoption of research animals to new homes when they are no longer needed in research. We conclude with a few suggestions for achieving our vision.

Music exposure attenuates anxiety- and depression-like behaviors and increases hippocampal spine density in male rats

Epidemiological and clinical studies suggest that early-life stress (ELS) may lead to the development of mental disorders in adulthood. Maternal separation (MS) is a valid animal model of ELS that produces detrimental effects on brain and behavior of experimental animals. Positive environmental stimuli have been shown to counteract the behavioral deficits of ELS and enhance neuroplasticity. Recent data indicate that music may serve as a form of environmental enrichment in experimental animals. However, the underlying mechanisms through which musical enrichment exerts its effects are poorly understood. Male Sprague–Dawley rats were submitted to a 3 h MS protocol during postnatal days (PND) 2–14, while another group was left undisturbed. Half of the animals within each group were exposed from PND 21 to PND 76 for 12 h/day to Mozart K. 448. At approximately three months of age, elevated plus maze procedure, forced swim test and social approach task were applied to test whether music exposure can mitigate the effects of MS stress on animal emotional behaviors. Moreover, we investigated the effects of these treatments on dendritic spine density in the CA1 region of hippocampus. As expected, MS rats showed decreased sociability, increased anxiety- and depressive-like behaviors, and decreased mature dendritic spines in the CA1 region of hippocampus in adulthood. Musical enrichment reversed these effects. Our results suggest that musical enrichment can reverse the negative effects of MS on anxiety, depression, and sociability in adult rats and modulate neuronal plasticity and provide additional data for a new therapeutic intervention to rescue emotional symptoms.

Impairments in reversal learning following short access to cocaine self-administration

BackgroundCocaine use disorder is characterized by compulsive drug-seeking that persists long into abstinence. Work using rodent models of cocaine addiction has found evidence for reversal learning deficits 21 days after non-contingent cocaine administration and 60 days after self-administration. Here we sought to determine if a deficit in reversal learning is present 3–4 weeks after cessation of cocaine self-administration, when relapse to cocaine-seeking is robust. Conversely, we hypothesized that reversal learning training would protect against relapse, similar to other forms of environmental enrichment. MethodsMale rats underwent short access (ShA, 2 h/10d) or long access (LgA, 1 h/7d then 6 h/10d) cocaine self-administration, followed by 21–29 days of abstinence. During abstinence, a subset of rats underwent training in a plus-maze that required an egocentric strategy to earn a sucrose reward. Following response acquisition and retention, the ability to reverse the spatial navigation strategy was tested. ResultsTotal trials to criteria and total errors made did not differ between the groups during response acquisition, retention, or reversal. On the first reversal test, ShA rats performed better than LgA and control rats. ShA rats’ performance worsened over time. There were no effects of cognitive training or length of cocaine access on context-primed relapse of cocaine-seeking. ConclusionsThe present data indicate that perhaps LgA cocaine self-administration does not produce adaptations to regions mediating context-primed relapse as it does for cocaine and cocaine-associated cue-induced reinstatement of drug-seeking. A time-dependent deficit in reversal learning was found only in ShA rats. Reversal learning training did not protect against cocaine relapse.

Nature and nurture: environmental influences on a genetic rat model of depression.

In this study, we sought to learn whether adverse events such as chronic restraint stress (CRS), or ‘nurture' in the form of environmental enrichment (EE), could modify depression-like behavior and blood biomarker transcript levels in a genetic rat model of depression. The Wistar Kyoto More Immobile (WMI) is a genetic model of depression that aided in the identification of blood transcriptomic markers, which successfully distinguished adolescent and adult subjects with major depressive disorders from their matched no-disorder controls. Here, we followed the effects of CRS and EE in adult male WMIs and their genetically similar control strain, the Wistar Kyoto Less Immobile (WLI), that does not show depression-like behavior, by measuring the levels of these transcripts in the blood and hippocampus. In WLIs, increased depression-like behavior and transcriptomic changes were present in response to CRS, but in WMIs no behavioral or additive transcriptomic changes occurred. Environmental enrichment decreased both the inherent depression-like behavior in the WMIs and the behavioral difference between WMIs and WLIs, but did not reverse basal transcript level differences between the strains. The inverse behavioral change induced by CRS and EE in the WLIs did not result in parallel inverse expression changes of the transcriptomic markers, suggesting that these behavioral responses to the environment work via separate molecular pathways. In contrast, ‘trait' transcriptomic markers with expression differences inherent and unchanging between the strains regardless of the environment suggest that in our model, environmental and genetic etiologies of depression work through independent molecular mechanisms.

Effects of 2 forms of environmental enrichment on a group of captive blackbucks (Antilope cervicapra): A pilot study

Abstract The aim of this preliminary study was to assess the effects of 2 forms of environmental enrichment (i.e., branched tree trunk and brushes) on the behavior of a group of 8 captive blackbucks. Animals were directly observed for 4 hours a day (09:30-11:30 and 12:30-14:30), on days 1, 3, 6 (pre-enrichment phase, before the new individual was born), 8, 10, 15, 17 (pre-enrichment phase, after the birth of the new individual), 22, 24, 29, 31, 43, 64 (enrichment phase), using instantaneous scan sampling every minute. Video recordings were also performed in days 24, 43, 64, from 09:30 to 11:00 and from 12:30 to 14:00 and analyzed using a continuous behavioral sampling method, for activities directed to the tree trunk. Friedman and Wilcoxon tests were performed both on the total number of scans and on the percentage of scans in which the animals were not out-of-sight. The blackbucks interacted significantly more with the tree trunk than with the brushes ( P = 0.012). The duration of the interactions with the tree trunk declined over time ( P

Effect of two forms of environmental enrichment on small felids in captivity

s / Journal of Veterinary Behavior 9 (2014) e1ee19 e7 features that fulfil dog needs (e.g., off-leash exercise) that also encourage human social interactionmay be incentivising. The effects of policy and cultural practices relating to dog ownership and walking should be investigated. Future studies must use higher quality methodological designs, including accounting for the effects of confounding between variables, and testing of interventions in a controlled design in order to infer causality.

Cellular and molecular mechanisms of immunomodulation in the brain through environmental enrichment.

Recent studies on environmental enrichment (EE) have shown cytokines, cellular immune components [e.g., T lymphocytes, natural killer (NK) cells], and glial cells in causal relationship to EE in bringing out changes to neurobiology and behavior. The purpose of this review is to evaluate these neuroimmune mechanisms associated with neurobiological and behavioral changes in response to different EE methods. We systematically reviewed common research databases. After applying all inclusion and exclusion criteria, 328 articles remained for this review. Physical exercise (PE), a form of EE, elicits anti-inflammatory and neuromodulatory effects through interaction with several immune pathways including interleukin (IL)-6 secretion from muscle fibers, reduced expression of Toll-like receptors on monocytes and macrophages, reduced secretion of adipokines, modulation of hippocampal T cells, priming of microglia, and upregulation of mitogen-activated protein kinase phosphatase-1 in central nervous system. In contrast, immunomodulatory roles of other enrichment methods are not studied extensively. Nonetheless, studies showing reduction in the expression of IL-1β and tumor necrosis factor-α in response to enrichment with novel objects and accessories suggest anti-inflammatory effects of novel environment. Likewise, social enrichment, though considered a necessity for healthy behavior, results in immunosuppression in socially defeated animals. This has been attributed to reduction in T lymphocytes, NK cells and IL-10 in subordinate animals. EE through sensory stimuli has been investigated to a lesser extent and the effect on immune factors has not been evaluated yet. Discovery of this multidimensional relationship between immune system, brain functioning, and EE has paved a way toward formulating environ-immuno therapies for treating psychiatric illnesses with minimal use of pharmacotherapy. While the immunomodulatory role of PE has been evaluated extensively, more research is required to investigate neuroimmune changes associated with other enrichment methods.

Mental health of dogs formerly used as ‘breeding stock’ in commercial breeding establishments

Canine commercial breeding establishments (CBEs) are kennel facilities where puppies are produced in large numbers for commercial sale. In the popular media, CBEs are commonly referred to as “puppy mills” or “puppy farms.” Conditions in CBEs vary widely in quality. Dogs in these facilities are routinely housed for their entire reproductive lives in cages or runs, and provided with minimal to no positive human interaction or other forms of environmental enrichment. Numerous anecdotal reports have suggested that after removal from CBEs many of the former breeding dogs display persistent behavioural and psychological abnormalities when compared with the general pet dog population. The purpose of this study was to determine if this anecdotal evidence could be confirmed empirically. Behavioural evaluations of the dogs were obtained from current owners/fosterers using the Canine Behavioural Assessment and Research Questionnaire (C-BARQ), which utilizes ordinal scales to rate either the intensity or frequency of the dog's behaviours. A total of 1169 former CBE dogs were included in the study. Among the CBE ex-breeding dogs, 76 different breeds were represented. With the exception of the Bichon Frise (31.5%), all other breeds comprised <5% of the dogs. The sex ratio was 70.3% females and 29.7% males. The dogs had been living in their adoptive homes for an average of 2 years when the C-BARQ was completed. When compared with a convenience sample of pet dogs matched for breed, sex, age and neuter status, former CBE breeding dogs were reported as showing significantly higher rates of health problems (23.5% versus 16.6%, P = 0.026). With respect to behaviour, CBE dogs displayed significantly higher rates of fear (both social and nonsocial; ordinal GLM models, P < 0.001), house-soiling ( P < 0.001), and compulsive staring ( P < 0.005); and significantly lower rates of aggression (toward strangers and other dogs; P < 0.0001), trainability ( P < 0.0001), chasing small animals ( P < 0.0001), excitability ( P < 0.0001), and energy ( P < 0.0001). By demonstrating that dogs maintained in these environments develop extreme and persistent fears and phobias, possible learning deficits as evidenced by lower trainability, and often show difficulty in coping successfully with normal existence, this study provides the first quantitative evidence that the conditions prevailing in CBEs are injurious to the mental health and welfare of dogs.

The effect of environmental enrichment on the behavior of captive tufted capuchin monkeys (Cebus apella)

The authors provided different forms of environmental enrichment to six old laboratory male tufted capuchin monkeys (Cebus apella) and studied the behavior of the monkeys during a baseline period and during three enrichment periods. Each observation period lasted 5 d, with an interval of 6 d between periods. During the first enrichment period, the authors provided Buster cubes and wood cylinders with drilled holes filled with gum arabic. During the second enrichment period, monkeys were provided with a deep litter of bark shavings, and during the third enrichment period, they were given Buster cubes, wood cylinders and bark shavings. When provided with enrichment, the monkeys engaged in natural, species-specific activities and began to exhibit behavioral profiles that more closely resembled those of their natural counterparts. This suggests that their psychological well-being had improved and that group housing combined with environmental enrichment can improve the welfare of old laboratory tufted capuchin monkeys that were previously housed individually.

Enriquecimento ambiental para leitões na fase de creche advindos de desmame aos 21 e 28 dias

The work aims at promoting the environmental enrichment of piglets during nursery coming from weaning at 21 and 28 days, through the placement of toys within the bays. A behavior study of these animals and an assessment of the health challenge was made and the performance from January to June 2009 was accompanied. Two nursery rooms, side by side, were used, one with piglets weaned at 21 days and the other at 28 days. The animals used were hybrids of the Penarlan breed. Two treatments were studied within each room, with and without environmental enrichment. The environmental&nbsp; enrichment was made with the animals weaned at 28 days, as required by the law for animal welfare, and they showed a higher incidence of stress behavior at the nursery and worsening of the piglets performance; the placement of toys within the bay as a form of environmental enrichment was very attractive to the animals at the nursery, but once they got used to the toys, playing with other swine became more interesting for the animals.

The Effect of Feeding Enrichment on the Moloch Gibbon (Hylobates Moloch)

This study explored the effect of 3 feeding devices (food-filled baskets, polyvinyl chloride tubes, frozen ice pops) on the behavior of 4 zoo-housed moloch gibbons. The project studied the gibbons for 5 days during a control condition (no feeding enrichment) and 5 days per condition of feeding enrichment, when 3 of the same type of feeding device were suspended within the animals' exhibit. The gibbons interacted with the feeders an average of 172.25 times. The animals showed no significant difference in the total number of times that they interacted with the 3 different feeding devices but were slower to approach the food-filled tubes than the baskets or ice pops. There was no sign of habituation to any of the feeding devices over their 5 days of presentation. Feeding enrichment significantly influenced certain components of the gibbons' behavior. The animals spent more of the observation time outside and showed more instances of foraging and fewer occurrences of moving during the enrichment conditions than the control. The study concluded that feeding devices may offer a viable form of environmental enrichment for captive moloch gibbons.

Reduction of Amyloid Angiopathy and Aβ Plaque Burden after Enriched Housing in TgCRND8 Mice: Involvement of Multiple Pathways

Reduction of Amyloid Angiopathy and Aβ Plaque Burden after Enriched Housing in TgCRND8 Mice: Involvement of Multiple Pathways

The influence of toys on the behaviour and welfare of kennelled dogs

AbstractThis study explored the influence of five toys (squeaky ball, non-squeaky ball, Nylabone chew, tug rope and Boomer ball) on the behaviour of 32 adult dogs housed in a rescue shelter. The dogs were exposed to each toy separately for six days, with an intervening period of one day between toys. The dogs' location in their kennels (front or back), activity (moving, standing, sitting or resting) and vocalisation (barking, quiet or other) were recorded over 4 h at 10 min intervals on Days 1, 3 and 5 during a control condition (no toy present) and during five experimental (toy) conditions. Whether or not the dogs were observed playing with the toys during the experimental conditions was also recorded. The dogs spent relatively little (&lt;8%) of the overall observation time playing with the toys. The toys elicited varying degrees of interest, with dogs showing a preference for the Nylabone chew over the other toys. The dogs' interest in the toys waned over time, but the speed of habituation to the Nylabone chew was slower than to any of the other toys. The dogs' activity was significantly related to toy condition: dogs spent more time moving and less time standing during the Nylabone chew, squeaky ball and non-squeaky ball conditions than during any of the other conditions. It is suggested that the welfare of kennelled dogs may be slightly enhanced by the addition of suitable toys to their kennels. It is advised, however, that toys are rotated to encourage exploration and reduce habituation. The provision of other forms of environmental enrichment is also recommended.

Foraging in captive hamadryas baboons: implications for enrichment

Many animals will work for food even if food is freely available or the animal is satiated, suggesting that foraging behaviour is inherently rewarding and that there is a behavioural need to forage. We investigated whether members of a hamadryas baboon ( Papio hamadryas hamadryas) troop at the Johannesburg Zoo, South Africa would forage in non-provisioned areas of their enclosure when excluded from a high quality, clumped, monopolisable food source by another member of the troop. We studied foraging behaviour during two baseline treatments when enclosures were not altered, and during four experimental treatments in which we introduced either an empty small box (SBE), a small box containing food (SBF), an empty big box (BBE), or a big box containing food (BBF). We also recorded aggressive interactions during all treatments. During the SBF treatment, individuals excluded from the device by the dominant male increased foraging elsewhere, without any concomitant increase in aggressive behaviour compared with baseline values. In contrast, foraging rates at the device increased during the BBF treatment, as did incidences of aggression. We suggest that the redirected foraging behaviour provided by the SBF treatment could be exploited as a form of environmental enrichment.

Gorilla behavior in response to systematic alternation between zoo enclosures

To determine the effects of relative novelty on captive gorilla behavior, the regular alternation of two groups between complex naturalistic enclosures was studied at Zoo Atlanta. A continuous behavioral change sampling method was used to obtain information on behavior, and instantaneous scans at 10-min intervals provided information on the location of all gorillas in the focal group. An analysis of 226 h of behavioral data and 1386 map location scans showed enclosure rotation was associated with increased enclosure use and feeding and a decrease in self-directed behavior. Gorillas were more likely to increase exhibit use and visibility to zoo visitors during a 4-day novel phase compared to subsequent days in the exhibit. Because of constraints in exhibit design, however, increased use of exhibit did not always result in greater visibility of gorillas to zoo visitors. Gorillas increased locomotion, social distance, use of grass areas, and visibility to the public in their “Away” exhibit compared to their “Home” exhibit. Regularly alternating gorillas between zoo exhibits is a form of environmental enrichment that can increase gorillas’ use of exhibit space and increase activity level.

Effects of different forms of environmental enrichment on behavioral, endocrinological, and immunological parameters in male mice

This study investigated effects of different forms of environmental enrichment on behavioral, endocrinological, and immunological parameters in male mice. For this purpose, animals of the inbred strain CS were kept in groups of four males under three different housing conditions: (A) nonstructured Makrolon type III laboratory cages (“standard-housing” = S); (B) equivalent laboratory cages that were enriched with a box and a scaffolding (“enriched-housing” = E); and (C) spacious terraria that were structured richly (“super-enriched-housing” = SE). Both forms of enrichment caused a sharp rise in aggressive behavior, though play behavior was increased in E and SE mice, too. Levels of sociopositive behaviors in S and SE mice were higher than those in E mice. Plasma corticosterone concentrations and adrenal tyrosine hydroxylase activities were significantly increased in male mice kept in both forms of enriched cages, indicating an activation of the pituitary–adrenocortical and the adrenomedullary systems. The behavioral and endocrinological differences were partly reflected by immunological parameters: SE mice had levels of IgG1 and ratios of IFN-γ/IL-10 and IL-2/IL-10 significantly lower than those of S mice. Ratios of IgG2a/IgG1 were significantly higher in SE mice. The absolute percentages of CD8 cells in E-mice were significantly lower than those in S mice. Despite the elevated levels of stress hormones under both forms of enriched housing, the behavioral parameters also indicate positive effects of the enrichment, especially on SE animals. Obviously, an environmental enrichment is beneficial for male mice as long as the spatial conditions are generous enough to allow coping with the increased aggression brought about by the enrichment.