Form Of Environmental Enrichment Research Articles

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.

Rats Demand Social Contact

AbstractThere is some evidence that rats benefit from social housing and from some forms of environmental enrichment, such as platforms and shelters. It is less clear whether they benefit from more spacious cages. There is a lack of information about the relative benefits of social contact, enrichment and increased space, because existing studies tend to concentrate on only one of these variables at a time. The current experiment used economic demand procedures as a method to compare, on a single scale, qualitatively different environments with a standard home cage. The data indicate that rats show a high demand for social contact, and a low demand for a larger cage or one containing pillars or novel objects. This finding suggests that social housing of laboratory rats should be strongly advocated.

Pecking at other birds and at string enrichment devices by adult laying hens

1. Bunches of white string (polypropylene twine) are particularly attractive pecking stimuli for both chicks and adult laying hens. Furthermore, these devices can retain the birds' interest over lengthy periods. It has also been demonstrated that birds with trimmed feathers elicit feather pecking. The present study was designed to determine whether string devices would retain their attractiveness in the presence of a competing stimulus: a trimmed hen. 2. Lohmann Brown hens were reared in 20 groups of 5 in floor pens with perches from 17 weeks of age. They were exposed to one of two treatments when they were 23 weeks old. One hen was removed from every pen and the feathers on her rump were trimmed. Immediately before her return two string devices were suspended from a perch in treatment 1 whereas no devices were included in treatment 2. Pecking behaviours were immediately observed for 30 min; this procedure was repeated later that day. The devices remained in the pens used in treatment 1 and these birds were observed again for 15 min after 14 d. 3. The string devices were pecked earlier and more than either the trimmed or untrimmed hens. Furthermore, the devices were still being pecked 2 weeks after their introduction. 4. The virtual absence of severe feather pecking and of aggressive head pecks precluded test of our hypothesis that the devices would divert potentially injurious pecking away from other birds. However, the fact that the birds showed sustained interest in the devices, even in the presence of a competing stimulus, supports our proposal that string may represent a practicable and effective form of environmental enrichment.

Assessment of cage use by laboratory-bred common marmosets (Callithrix jacchus).

The way in which breeding families of laboratory-born marmosets used the space provided by their cages, and a small protruding 'veranda', was assessed in order to determine the popularity of the veranda as a form of environmental enrichment, and the extent to which the marmosets confined themselves to only part of the cage. The veranda was found to be of enduring interest to the marmosets whose occupancy of this space was an order of magnitude greater than the rest of the cage. The upper part of the cage was preferred to the bottom half. This preference was greater in larger cages and decreased when larger cages were temporarily reduced in size. It is unlikely, however, that the distribution of the occupancy of different parts of the cage resulted primarily from a fear of people in the holding room. The veranda, which was the most preferred place in the cage, was the nearest part of the cage to people in the room. Occupancy of the lower part of the cage increased when human observers sat on the floor, suggesting that some of the marmosets' behaviour comprised approaching, rather than avoiding, the observers, possibly for reasons of curiosity and social interaction.

The use and perceived importance of three resources which provide caged laboratory mice the opportunity for extended locomotion

Several species of animal are routinely housed in small, barren cages with little opportunity for extended or complex locomotion. Various resources could be provided to overcome this limitation, however, these differ in their practicality, cost and presumably in their suitability as perceived by the animal. This study examined the activity of 5 laboratory mice within three resources which provided the opportunity for extended or complex locomotion, namely, a ‘locomotion-loop’ (a 40 cm torus of plastic tunnel), a complex tunnel environment and a running-wheel. In addition, the perceived importance of these resources was determined by measuring the persistence of their use when the operant cost (switch pressing) of gaining access was increased. When the lowest cost of 1 press/visit was imposed, the mice used the three resources to different extents: the running-wheel was used for the greatest proportion of each 24 h (9.1%), the tunnel system was used for an intermediate amount of time (8.1%) and the loop was used the least (0.3%) (all differences were significant). At the lowest cost the running-wheel was visited 13.7 times each 24 h, the tunnels 14.6 times and the loop only 4.7 times. Over the 15-day duration of the study, the mice reduced the frequency of visits and activity in the loop and tunnel system, but not the running-wheel, i.e. the mice habituated to the loop and tunnels, but not the running-wheel. When the cost of access was increased, the frequency of visits decreased for all three resources. However, activity within visits increased and the duration of visits remained constant for the running-wheel, whereas both decreased for the loop or remained constant for the tunnel system. Therefore, as the costs increased within the range studied here, the mice defended the proportion of 24 h in the running-wheel to a greater extent than time in the tunnel system or the loop. Of the 3 resources, use of the running-wheel was least affected by increasing the cost of access, indicating this resource was perceived as the most important. These results in combination with previous investigations indicate that wheel-running is a higly motivated behaviour. The present results show that caged laboratory mice perceived running-wheels to be an important resource and as such, indicate these might be an appropriate form of environmental enrichment.

Effects of environmental conditions on the psychological well- being of primates: A review of the literature

Amendments made to the Animal Welfare Act in 1985 require primate researchers to provide “a physical environment adequate to promote the psychological well-being of primates”. Regulations have not yet been promulgated, in part because “the psychological well-being” of primates is extremely difficult to define. Ideally, those regulations would be based upon observable changes in behavior rather than assumed psychological changes. Regardless, new primate care regulations pertaining to social environment, cage size, exercise and other forms of environmental enrichment are anticipated. A review of the literature suggests that there is little scientific data to support changing existing regulations. For instance, although it is clear that total social isolation in very young primates can be behaviorally devastating in terms of normal social behaviors, there are few, if any, demonstrable adverse effects of individual housing in adult primates. On the other hand, group housing, particularly with groups changing frequently in composition, increases aggression, trauma and disease transmission. In addition, existing research suggests there are important species differences in terms of social preferences. It is impossible to justify an increase in cage size based upon the available literature. An additional practical consideration is that any change in cage size requirements will necessitate replacement of current primate housing on a national level, an enormously expensive proposition. Regarding environmental enrichment, research suggests that providing a naturalistic environment is not as critical as arranging dynamic events that are contingent upon behavior. However, new research is necessary to specify the types of environmental enrichment that are valuable and appropriate before useless, even damaging, and expensive changes are mandated.