Physical Environmental Effects on Infant Care and Development in Captive Callithrix jacchus

Environmental enrichment may affect infant care and development in captive primates. We investigated the effects of this factor in laboratory common marmosets (Callithrix jacchus). An enriched physical environment enhanced the social activities of the marmosets and elicited a greater repertoire of behaviors, without negatively affecting the provision of infant care. In addition, infants in enriched cages displayed certain behaviors sooner than infants in non-enriched cages did, which suggests an increased developmental rate. Infants in enriched cages also ate more solid food and engaged in solitary play and exploration more than ones in non-enriched cages did. Play and exploration probably improve spatial cognition and motor skills, which, together with a higher degree of independence, may allow infants to cope better with laboratory routines and general social interactions later in life than their counterparts reared in less complex enclosures. We conclude that laboratories can significantly increase the welfare of marmosets by providing a more complex physical environment.     

Environmental enrichment promotes neural plasticity and cognitive ability in fish

Different kinds of experience during early life can play a significant role in the development of an animal''s behavioural phenotype. In natural contexts, this influences behaviours from anti-predator responses to navigation abilities. By contrast, for animals reared in captive environments, the homogeneous nature of their experience tends to reduce behavioural flexibility. Studies with cage-reared rodents indicate that captivity often compromises neural development and neural plasticity. Such neural and behavioural deficits can be problematic if captive-bred animals are being reared with the intention of releasing them as part of a conservation strategy. Over the last decade, there has been growing interest in the use of environmental enrichment to promote behavioural flexibility in animals that are bred for release. Here, we describe the positive effects of environmental enrichment on neural plasticity and cognition in juvenile Atlantic salmon (Salmo salar). Exposing fish to enriched conditions upregulated the forebrain expression of NeuroD1 mRNA and improved learning ability assessed in a spatial task. The addition of enrichment to the captive environment thus promotes neural and behavioural changes that are likely to promote behavioural flexibility and improve post-release survival.     

Environmental enrichment and prior experience of live prey improve foraging behaviour in hatchery‐reared Atlantic salmon

Atlantic salmon salmo salar L. parr were reared for 3 months under standard hatchery conditions or in a structurally enriched tank (containing plants, rocks and novel objects). Half of each of these fish had prior exposure to live prey in the form of live bloodworm while the other half were fed hatchery‐pellets. After 12 days all fish were tested on a novel live prey item (brine shrimp). A significant interaction between the two factors (prior exposure to live prey and rearing condition) revealed that foraging performance was only enhanced in fish that had been reared in a complex environment and exposed to live prey. It appears that the ability to generalize from one live prey type to another is only enhanced in fish that had been reared in an enriched environment. The findings support the assertion that the provision of enriched environments in combination with exposure to live prey prior to release may significantly improve the post‐release survival rates of hatchery‐reared fishes. As both the environmental enrichment and the prior foraging experience procedures were comparatively simple, the provision of such pre‐release experiences are likely to prove cost effective to hatcheries.     

Environmental enrichment induces intergenerational behavioural and epigenetic effects on fish

Parental effects influence offspring phenotypes through pre‐ and post‐natal routes but little is known about their molecular basis, and therefore their adaptive significance. Epigenetic modifications, which control gene expression without changes in the DNA sequence and are influenced by the environment, may contribute to parental effects. We investigated the effects of environmental enrichment on the behaviour, metabolic rate and brain DNA methylation patterns of parents and offspring of the highly inbreed mangrove killifish (Kryptolebias marmoratus). Parental fish reared in enriched environments had lower cortisol levels, lower metabolic rates and were more active and neophobic than those reared in barren environments. They also differed in 1,854 methylated cytosines (DMCs). Offspring activity and neophobia were determined by the parental environment. Among the DMCs of the parents, 98 followed the same methylation patterns in the offspring, three of which were significantly influenced by parental environments irrespective of their own rearing environment. Our results suggest that parental environment influences the behaviour and, to some extent, the brain DNA methylation patterns of the offspring.     

Effects of habitat enrichment and food availability on the foraging behaviour of juvenile Atlantic Cod (<Emphasis Type="Italic">Gadus morhua L</Emphasis>)

The environment can play an important role in shaping how an animal behaves, and how well the animal performs in a particular environment can be influenced by early experiences. The tradition of releasing captive-reared juveniles into the wild in an effort to strengthen wild fish populations has often had little success owing to high post-release mortality. Fish reared under standard hatchery conditions are provided with fewer stimuli and they receive excess quantities of pellet food that are easy to handle and consume. Captive reared fish therefore appear to be under-stimulated and overfed. Several studies have demonstrated that simple structural enrichment in the rearing facilities promotes flexible behaviour compared to fish reared in plain, standard hatchery tanks. Less attention has been given to the effects of the diet. Here we use a cross-factored design to test the relative role of food ration and spatial enrichment on foraging behaviour. Our results show that fish from enriched environments, regardless of previous food-ration size, were more reluctant to start feeding on the first day in a novel arena. On day two and three, however, fish with prior experience of a low food ration showed greater foraging activity and efficiency than fish fed on full rations. On the second and third day, prior experience with enrichment was less important. We discuss how early feeding experience in combination with structural enrichment may contribute in producing fish that are better suited for release into the wild.     

Effects of environmental enrichment on survivorship,growth, sex ratio and behaviour in laboratory maintained zebrafish Danio rerio

Environmental enrichment involves increasing the complexity of a fish's environment in order to improve welfare. Researchers are legally obliged to consider the welfare of laboratory animals and poor welfare may result in less robust data in experimental science. Laboratory zebrafish Danio rerio are usually kept in bare aquaria for ease of husbandry and, despite being a well-studied species, little is known about how laboratory housing affects their welfare. This study shows that environmental enrichment, in the form of the addition of gravel substratum and plants into the tank, affects survivorship, growth and behaviour in laboratory-maintained D. rerio. Larvae reared in enriched tanks had significantly higher survivorship compared with larvae reared in bare tanks. Effects of the tank conditions on growth were more variable. Females from enriched tanks had a higher body condition than females maintained in bare tanks, but intriguingly this was not the case for males, where the only difference was a more variable body condition in males maintained in bare tanks. Sex ratio in the rearing tanks did not differ between treatments. Resource monopolisation was higher for fish in enriched tanks than for those in bare tanks. Fish from enriched tanks displayed lower levels of behaviours associated with anxiety compared with fish from bare tanks when placed into a novel environment. Thus, this study demonstrates differences in welfare for D. rerio maintained under different environmental conditions with enhancements in welfare more commonly associated with tank enrichment.     

Enrichment from Birth Accelerates the Functional and Cellular Development of a Motor Control Area in the Mouse

Background

There is strong evidence that sensory experience in early life has a profound influence on the development of sensory circuits. Very little is known, however, about the role of experience in the early development of striatal networks which regulate both motor and cognitive function. To address this, we have investigated the influence of early environmental enrichment on motor development.

Methodology/Principal Findings

Mice were raised in standard or enriched housing from birth. For animals assessed as adults, half of the mice had their rearing condition reversed at weaning to enable the examination of the effects of pre- versus post-weaning enrichment. We found that exclusively pre-weaning enrichment significantly improved performance on the Morris water maze compared to non-enriched mice. The effects of early enrichment on the emergence of motor programs were assessed by performing behavioural tests at postnatal day 10. Enriched mice traversed a significantly larger region of the test arena in an open-field test and had improved swimming ability compared to non-enriched cohorts. A potential cellular correlate of these changes was investigated using Wisteria-floribunda agglutinin (WFA) staining to mark chondroitin-sulfate proteoglycans (CSPGs). We found that the previously reported transition of CSPG staining from striosome-associated clouds to matrix-associated perineuronal nets (PNNs) is accelerated in enriched mice.

Conclusions/Significance

This is the first demonstration that the early emergence of exploratory as well as coordinated movement is sensitive to experience. These behavioural changes are correlated with an acceleration of the emergence of striatal PNNs suggesting that they may consolidate the neural circuits underlying these behaviours. Finally, we confirm that pre-weaning experience can lead to life long changes in the learning ability of mice.     

Environmental enrichment alters the behavioral profile of ratsnakes (Elaphe)

This study investigated the effects of environmentally enriched and standard laboratory housing conditions on behavioral performance in 16 subadult ratsnakes (Elaphe obsoleta) using a split-clutch design. In a problem-solving task, snakes housed in enriched environments (EC) exhibited shorter latencies to the goal hole as compared to snakes housed in standard conditions (SC). In an open field task, EC snakes tended to habituate more quickly than SC snakes with repeated testing. A feeding task did not reveal any significant differences between EC and SC snakes. A discriminant function analysis correctly assigned all snakes to their appropriate housing treatment groups, based on the responses in each of the behavioral tasks. This suggests that each group had a distinct behavioral profile; that is, EC snakes were more behaviorally adaptive than SC snakes. This study demonstrated that housing conditions can affect the behavior of captive snakes and produce improvements in behavior similar to those seen in mammalian enrichment studies.     

Effects of Enriched Physical and Social Environments on Motor Performance,Associative Learning,and Hippocampal Neurogenesis in Mice

We have studied the motor abilities and associative learning capabilities of adult mice placed in different enriched environments. Three-month-old animals were maintained for a month alone (AL), alone in a physically enriched environment (PHY), and, finally, in groups in the absence (SO) or presence (SOPHY) of an enriched environment. The animals'' capabilities were subsequently checked in the rotarod test, and for classical and instrumental learning. The PHY and SOPHY groups presented better performances in the rotarod test and in the acquisition of the instrumental learning task. In contrast, no significant differences between groups were observed for classical eyeblink conditioning. The four groups presented similar increases in the strength of field EPSPs (fEPSPs) evoked at the hippocampal CA3-CA1 synapse across classical conditioning sessions, with no significant differences between groups. These trained animals were pulse-injected with bromodeoxyuridine (BrdU) to determine hippocampal neurogenesis. No significant differences were found in the number of NeuN/BrdU double-labeled neurons. We repeated the same BrdU study in one-month-old mice raised for an additional month in the above-mentioned four different environments. These animals were not submitted to rotarod or conditioned tests. Non-trained PHY and SOPHY groups presented more neurogenesis than the other two groups. Thus, neurogenesis seems to be related to physical enrichment at early ages, but not to learning acquisition in adult mice.     

The roles of motor activity and environmental enrichment in intellectual disability

In people with intellectual disabilities, an enriched environment can stimulate the acquisition of motor skills and could partially repair neuronal impairment thanks to exploration and motor activity. A deficit in environmental and motor stimulation leads to low scores in intelligence tests and can cause serious motor skill problems. Although studies in humans do not give much evidence for explaining basic mechanisms of intellectual disability and for highlighting improvements due to enriched environmental stimulation, animal models have been valuable in the investigation of these conditions. Here, we discuss the role of environmental enrichment in four intellectual disabilities: Foetal Alcohol Spectrum Disorder (FASD), Down, Rett, and Fragile X syndromes.     

Experimental Tests for Heritable Morphological Color Plasticity in Non-Native Brown Trout (Salmo trutta) Populations

The success of invasive species is frequently attributed to phenotypic plasticity, which facilitates persistence in novel environments. Here we report on experimental tests to determine whether the intensity of cryptic coloration patterns in a global invader (brown trout, Salmo trutta) was primarily the result of plasticity or heritable variation. Juvenile F₁ offspring were created through experimental crosses of wild-caught parents and reared for 30 days in the laboratory in a split-brood design on either light or dark-colored gravel substrate. Skin and fin coloration quantified with digital photography and image analysis indicated strong plastic effects in response to substrate color; individuals reared on dark substrate had both darker melanin-based skin color and carotenoid-based fin colors than other members of their population reared on light substrate. Slopes of skin and fin color reaction norms were parallel between environments, which is not consistent with heritable population-level plasticity to substrate color. Similarly, we observed weak differences in population-level color within an environment, again suggesting little genetic control on the intensity of skin and fin colors. Taken as whole, our results are consistent with the hypothesis that phenotypic plasticity may have facilitated the success of brown trout invasions and suggests that plasticity is the most likely explanation for the variation in color intensity observed among these populations in nature.     

Increasing activity in captive orangutans: Provision of manipulable and edible materials

The purpose of this research was to explore the impact of the provision of manipulable and edible materials on the activity level of captive orangutans. The effects of three environmental conditions—bare exhibit, manipulables present, and manipulables plus edibles present—on the gross motor activity of four captive orangutans were compared using a multielement design. Results indicated that activity increased under the enriched conditions with increases in activity type specific to the environmental change. In addition, zoo visitors rated the exhibit more favorably on days the enriched conditions were in effect than on bare exhibit days.     

大鼠成年前异常生活环境对其成年后恐惧记忆的影响

为了探讨早期饲养环境对成年后大鼠条件化恐惧的影响,实验采用巴氏恐惧条件化的方法对不同饲养环境下的大鼠进行了行为检测.具体操作为:把断奶后的大鼠饲养在3个不同的人工控制的环境中(丰富环境、社群环境和贫瘠环境);8周后进行恐惧条件化训练和测试(指标为僵直百分比),以及检测不同饲养环境下的大鼠的体重、自发活动和足部电击敏感性.结果显示:与社群组相比,丰富组的大鼠条件化僵直水平明显增加,而贫瘠组的明显减少;丰富和贫瘠环境明显的影响了大鼠的体重;不同环境对自发活动和足部电击敏感性没有影响.这些结果说明幼年期的丰富环境能提高成年后大鼠的由声音诱发的条件化恐惧反应,而贫瘠环境则削弱了这种反应.     

Early behavioral development and temperamental traits in mother- vs peer-reared rhesus monkeys

Behavioral characteristics (“traits”) of 24 mother-reared and 24 nursery/peer-reared rhesus monkey infants were assessed via rating scales from the third through the seventh month of life while housed with their rearing partners, and from months 8–10 after all animals had been placed in novel peer groups. The animals were also tested at 8 months of age on the Bayley Scales of Infant Development adapted for nonhuman primates. During the early period effects noted were primarily developmental. Peer-reared animals were rated as increasingly less cautious and more attentive to the outside environment over time, while mother-reared infants declined in ratings of dependence on their mothers. All animals were rated as increasingly active and excitable, and less fearful, over time. For the period of months 8–10, peer-reared animals showed higher confidence ratings in month 10, and all animals showed a decline in attachment to cagemates. Mother-reared animals showed more hostility to the examiner during Bayley testing, whereas peer-reared animals showed more fear. Sex effects included greater ratings for independence from mothers, greater activity over both the early and later periods, greater excitability, greater attentiveness to the extra-cage environment, less cautiousness, and better performance on one Bayley problem for females.     

Environmental enrichment improves mating success in fruit flies

Environmental enrichment, defined as housing conditions that include a combination of complex inanimate and social stimulation, has strong positive effects on brain and behaviour in various species. We extended previous studies to evaluate how enrichment affects mating success. In a series of experiments, we found that male fruit flies, Drosophila melanogaster, reared in an enriched environment were twice as successful in acquiring mates as were males from standard rearing conditions. The dominant factor increasing mating success was the larger space available per fly. Flies from enriched and standard environments showed no significant behavioural differences, leading us to suggest that different social environments at high and low per capita spaces are associated, on average, with either subtle behavioural differences or distinct pheromonal profiles to which females are sensitive while choosing mates.     

Effects of environmental conditions in the period of early ontogenesis on the formation of defensive behavior in juvenile roach Rutilus rutilus (Cyprinidae)

The feeding and defensive behavior of juvenile roach Rutilus rutilus (offspring of one pair of spawners) that were held at early stages of ontogenesis under conditions of differently enriched environments was studied. After the beginning of active swimming (the 12th day upon hatching), roach were reared for 95 days under different environmental conditions (feeding on active or immobilized organisms, the presence or absence of constant water flow, and the presence or absence of a predator), after which comparison of the efficiency of feeding behavior in the presence of a predator in juveniles of different groups was performed. It was established that the degree of environmental richness at early stages of ontogenesis exerts a determining effect on the formation of habits of defensive and feeding behavior. The most efficient behavior was observed in individuals that were held together with the predator during rearing.     

Rearing in Seawater Mesocosms Improves the Spawning Performance of Growth Hormone Transgenic and Wild-Type Coho Salmon

Growth hormone (GH) transgenes can significantly accelerate growth rates in fish and cause associated alterations to their physiology and behaviour. Concern exists regarding potential environmental risks of GH transgenic fish, should they enter natural ecosystems. In particular, whether they can reproduce and generate viable offspring under natural conditions is poorly understood. In previous studies, GH transgenic salmon grown under contained culture conditions had lower spawning behaviour and reproductive success relative to wild-type fish reared in nature. However, wild-type salmon cultured in equal conditions also had limited reproductive success. As such, whether decreased reproductive success of GH transgenic salmon is due to the action of the transgene or to secondary effects of culture (or a combination) has not been fully ascertained. Hence, salmon were reared in large (350,000 L), semi-natural, seawater tanks (termed mesocosms) designed to minimize effects of standard laboratory culture conditions, and the reproductive success of wild-type and GH transgenic coho salmon from mesocosms were compared with that of wild-type fish from nature. Mesocosm rearing partially restored spawning behaviour and success of wild-type fish relative to culture rearing, but remained lower overall than those reared in nature. GH transgenic salmon reared in the mesocosm had similar spawning behaviour and success as wild-type fish reared in the mesocosm when in full competition and without competition, but had lower success in male-only competition experiments. There was evidence of genotype×environmental interactions on spawning success, so that spawning success of transgenic fish, should they escape to natural systems in early life, cannot be predicted with low uncertainty. Under the present conditions, we found no evidence to support enhanced mating capabilities of GH transgenic coho salmon compared to wild-type salmon. However, it is clear that GH transgenic salmon are capable of successful spawning, and can reproduce with wild-type fish from natural systems.     

Are the effects of different enrichment designs on the physiology and behaviour of DBA/2 mice consistent?

Environmental enrichment is intended to improve the well-being of laboratory animals. Although many researchers have indicated that environmental enrichment may enhance animal well-being, there is some evidence that enrichment differs in its effects on physiology and behaviour between species and strains. The present study focuses on the effects of different enrichment designs on the physiology and behaviour of male and female DBA/2 mice. A total of 48 DBA/2J mice, 24 males and 24 females were used for this experiment. Upon arrival at about 3 weeks of age, the animals were randomly allotted to three experimental groups: NE, non-enrichment; E1, enriched with nest box, wooden climbing bar and nest material according to Scharmann (1993); E2, enriched with horizontal and vertical dividers, modified from Haemisch and G?rtner (1994). Same-sex groups of four mice were housed for 12 weeks in type III Makrolon cages with (E1 or E2) or without (NE) enrichment objects. Behavioural performance (Open Field, Food Drive and Elevated Plus Maze tests) and physiological traits (haematological variables, body weight and organ weights, corticosterone and thyroxine levels) were measured. This study observed that enrichment had significant effects on the mean values of body weight (females), Open Field and Food Drive tests. The most significant housing differences were found between the E2 and NE/E1 groups. Furthermore, sex differences in the NE, E1 and E2 groups were not consistent for several variables (growth rate, relative weights of spleen, kidney and heart, Food Drive and Elevated Plus Maze behavioural performance). There was often a higher coefficient of variation (CV) in the E1 and E2 groups as compared to the NE group, chiefly in physiological traits and in the Open Field and Food Drive tests. The results of this study indicate, that the effects of enrichment designs used in the present study are not consistent, but vary according to sex and the variable studied.     

Effects of shelter type,early environmental enrichment and weather conditions on free-range behaviour of slow-growing broiler chickens

Free-range use by broiler chickens is often limited, whereas better use of the free-range area could benefit animal welfare. Use of free-range areas could be stimulated by more appropriate shelter or environmental enrichment (by decreasing birds’ fearfulness). This study aimed to assess the effects of shelter type, early environmental enrichment and weather conditions on free-range use. Three production rounds with 440 slow-growing broiler chickens (Sasso T451) were carried out. Birds were housed indoors in four groups (two with males, two with females) from days 0 to 25, during which two of the groups received environmental enrichment. At day 23 birds’ fearfulness was assessed with a tonic immobility (TI) test (n=100). At day 25 all birds were moved (in mixed-sex groups) to mobile houses, and provided with free-range access from day 28 onwards. Each group could access a range consisting for 50% of grassland with 21 artificial shelters (ASs, wooden A-frames) and for 50% of short rotation coppice (SRC) with willow (dense vegetation). Free-range use was recorded by live observations at 0900, 1300 and 1700 h for 15 to 21 days between days 28 and 63. For each bird observed outside the shelter type (AS or SRC), distance from the house (0 to 2, 2 to 5, >5 m) and its behaviour (only rounds 2 and 3) were recorded. Weather conditions were recorded by four weather stations. On average, 27.1% of the birds were observed outside at any given moment of observation. Early environmental enrichment did not decrease fearfulness as measured by the TI test. It only had a minor effect on the percentage of birds outside (0.4% more birds outside). At all distances from the house, SRC was preferred over AS. In AS, areas closer to the house were preferred over farther ones, in SRC this was less pronounced. Free-range use increased with age and temperature and decreased with wind speed. In AS, rainfall and decreasing solar radiation were related to finding more birds outside, whereas the opposite was true in SRC. Behaviour of the birds depended on shelter type, distance from the house, early environmental enrichment, time of day and age. Chickens ranged more and farther in SRC, possibly because this provided a greater sense of safety because of the amount of cover and/or better protection against adverse weather conditions. These results indicate that SRC with willow is a more appropriate shelter for slow-growing broiler chickens than A-frames.