Response,use and habituation to a mouse house in C57BL/6J and BALB/c mice

Animal welfare depends on the possibility to express species-specific behaviours and can be strongly compromised in socially and environmentally deprived conditions. Nesting materials and refuges are very important resources to express these behaviours and should be considered as housing supplementation items. We evaluated the effects of one item of housing supplementation in standard settings in laboratory mice. C57BL/6JOlaHsd (B6) and BALB/cOlaHsd (BALB) young male and female mice, upon arrival, were housed in groups of four in standard laboratory cages and after 10 days of acclimatization, a red transparent plastic triangular-shaped Mouse House™ was introduced into half of the home cages. Animals with or without a mouse house were observed in various contexts for more than one month. Body weight gain and food intake, home cage behaviours, emotionality and response to standard cage changing procedures were evaluated. The presence of a mouse house in the home cage did not interfere with main developmental and behavioural parameters or emotionality of BALB and B6 male and female mice compared with controls. Both strains habituated to the mouse house in about a week, but made use of it differently, with BALB mice using the house more than the B6 strain. Our results suggest that mice habituated to the mouse house rather quickly without disrupting their home cage activities. Scientists can thus be encouraged to use mouse houses, also in view of the implementation of the EU Directive (2010/63/EU).     

Testing resource value in group-housed animals: an investigation of cage height preference in laying hens

To avoid unpredictable social effects, animals' behavioural priorities are almost always tested using individuals housed singly, yet many species kept commercially are social animals housed in groups. Our aim was to develop a method of investigating environmental preference in group-housed laying hens, Gallus gallus domesticus, that maximised the external validity of our findings. In a simple test of preference, eight groups of ten hens were given free choice between furnished cages with minimum heights of 38 cm (low) and 45 cm (high). A preference for one cage height over the other would be evident as a shift from a binomial distribution of flock sizes in the two cages. No height preference was found as hens distributed evenly between the two cages more frequently than was expected. This suggests at high stocking densities maximising average inter-individual distance could be a priority over increased cage height. In a second experiment, to investigate the value that hens placed on a change in cage height; a 'cost' in the form of a narrow gap was imposed on movement from a low or high start cage to a high or low target cage, respectively. Cage height did not influence the latency of the first three hens to enter the target cage. However, latencies for subsequent hens were shorter and more hens worked to access a high target cage than a low target cage. We suggest that titrating animals' willingness to tolerate higher stocking densities against access to a resource could be an effective way to compare responses of group-housed animals to resources that are expected to satisfy the same motivational state.     

Cage-change interval preference in mice

Before animal research facilities began using individually ventilated cage (IVC) systems for mice, cages were often changed one or more times per week. When using IVC systems, however, it is standard practice to change cages only once every 2-3 weeks. When deciding how often to change cages, personnel may consider the cost of labor needed to change the cage, as well as the cage type and bedding type, rather than animal preference or concern for animal well-being. The authors carried out a simple preference test in groups of mice. Mice were allowed to choose between an unsoiled cage and cages that had not been changed for 1 d, 7 d or 14 d. When evaluating where mice positioned their nests and the amount of time mice spent in the various cages, the authors found that the mice preferred the unsoiled cage. Younger mice (<150 d old) showed a stronger preference for the unsoiled cage than did older mice (>150 d old). Further studies are warranted to evaluate mice's preferences for cages changed at different intervals and to determine whether prolonging the interval between cage changes has any negative effects on mice.     

Perception or preference? Mediation of gene effects in the colour choices of naive quail chicks (C. coturnix japonica)

The purpose of this study was to examine gene effects in the peripheral and central neural mediation of colour preferences in artificially selected Japanese quail chicks (Coturnix coturnix japonica). Behavioural data indicated preferences of blue over red and red over blue in the respectively selected genetic lines, and general preferences for white in both lines. Preferences were influenced by luminance variations of testing stimuli. Choices between segmented stimuli that combined blue, red, and white, in various patterns of systematically varied hues and luminances, indicated perceptual discrimination of colours in each line. Preference values combined within stimuli summated additively in choice responses, suggesting no genetic association between colour preference and colour perception. Electrophysiological data indicated systematic differences between waveshapes of averaged evoked potentials according to hues of eliciting stimuli. These data also counterindicated the involvement of colour perception in the genetic variations of colour preference. However, no significant differences between waveshapes were found in relation to genetic variations in preferences.     

Preferences of cedar waxwings in the laboratory for fruit species,colour and size: A comparison with field observations

Fruit preferences of cedar waxwings, Bombycilla cedrorum, in the laboratory were compared with preferences in the field to identify fruit characteristics that influence choice by avian dispersers. Waxwings ate 12 of 13 species of fruits offered individually in laboratory tests, but in the field ate only eight of the same 13 species. When given a choice of 10 fruit species offered simultaneously, waxwings showed a strong preference for fruits that were small or red. Preferences for fruit species in the laboratory were not correlated with morphological or nutritional characteristics of the fruits. When offered food that differed only in colour, waxwings initially preferred red over blue, yellow and green. In later tests, preference for red fruit was less marked. In tests for size preference, waxwings preferred small pieces of fruit (6 mm) over medium pieces (9 mm), and medium pieces over those that were large (12 mm). Sizes of fruits preferred in the field and in the laboratory tests were approximately 6·0–7·5 mm. Thus, waxwings can discern differences in food items and they have definite preferences. The lack of complete agreement between preferences for fruits in the field and in the laboratory suggests that factors important in the field but controlled in the laboratory (e.g. abundance, location) override preferences for certain fruits. However, some fruit characteristics, particularly size, were consistently influential in the laboratory and in the field.     

Common variations in the pretest environment influence genotypic comparisons in models of anxiety

The behavioral characterization of rodent strains in different studies and laboratories can provide unreplicable results even when genotypes are kept constant and environmental control is maximized. In the present study, the influence of common laboratory environmental variables and their interaction with genotype on the results of behavioral tests of anxiety/emotionality were investigated. To this end, the inbred rat strains Lewis (LEW) and spontaneously hypertensive rats (SHR), which are known to differ for numerous emotionality-related behaviors, were tested in the open field (OF), elevated plus maze (EPM) and black/white box (BWB), while three environmental factors were systematically controlled and analyzed: (1) the experimenter handling the animal (familiar or unfamiliar); (2) the position of the home cage (top or bottom shelf of the rack) and (3) the behavioral state of the animal immediately before the test (arousal or rest). Experimenter familiarity did not alter the behavior of rats in the OF. Cage position, on the other hand, influenced the behavior in the OF and BWB, with rats housed in top cages appearing less anxious than those housed in the bottom. In the BWB (but not in the OF), these effects were genotype dependent. Finally, the behavioral state of the animals prior to testing altered the results of the EPM in a strain-dependent manner, with some anxiety-related genotypic differences being found only among rats that were aroused in their home cages. This study showed that common variations in the laboratory environment interact with genotype in behavioral tests of anxiety/emotionality. Recognizing and understanding such variations can help in the design of more effective experiments.     

Colour learning in two behavioural contexts: how much can a butterfly keep in mind?

Here we examine the ability of butterflies to learn colour cues in two different behavioural contexts, nectar foraging and oviposition, more or less simultaneously. We first trained female Battus philenor (Papilionidae) butterflies to associate a given colour with the presence of host plant leaf extract and assayed their colour preference; we then trained a subset of these butterflies to associate a second colour with the presence of sucrose solution and assayed colour preference once more. When offered an array of four unscented and unrewarding coloured models, ‘single-trained’ butterflies consistently alighted most frequently on their oviposition training colour. Green-trained butterflies landed on nontrained colours only about 4% of the time, while butterflies trained to red, yellow or blue made about 23% of their landings on nontrained colours; of those nontrained landings, most were on green. The majority of ‘dual-trained’ butterflies made the greatest number of visits to both training colours in the appropriate behavioural context; that is, they probed the models of their sucrose-associated colour and alighted on the models of their oviposition-associated colour. Landings or probes on nontrained colours in one context were consistently biased towards what was learned in the alternative context, suggesting an information-processing constraint in the butterflies. This paper provides a clear demonstration that butterflies can learn in two behavioural contexts within a short span of time. A capacity for such dual conditioning presumably permits female butterflies to forage effectively for egg-laying sites and nectar resources even when those activities are intermingled in time. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.       

Behaviour and pleiotropy: Generalization of gene effects in the colour preferences of Japanese quail chicks (C. coturnix japonica)

Two lines of Japanese quail (Coturnix coturnix japonica) were artificially selected for colour preferences in 16 generations; one line for preference of blue over red, another for preference of red over blue. A genetic control line was maintained without selection, in parallel generations. Subjects of the blue-selected line exhibited general preferences for the shorter over the longer wavelengths, when tested with stimulus pairs of large hue differences. In similar situations red-line subjects preferred the shorter wavelength, within pairs above 542 nm. The relative strength of colour preferences in the three lines remained significantly different under conditions of both large and small hue differences. Genetic influences in preferences and preference, generalizations were detectable equally well with stimuli administered through wide-band gelatin filters and stimuli administered through narrow-band interference filters. In addition to demonstrating behavioural pleiotropy, the data counterindicated genetic variation in colour vision as a factor in the mediation of gene effects in the quail's colour preferences.     

Effects of ambient colour on colour preference and growth of juvenile rainbow trout Oncorhynchus mykiss (Walbaum)

Colour preference of individual juvenile rainbow trout Oncorhynchus mykiss was tested at 1 and 12° C, and also at 12° C after a 42 day growth experiment under white, blue, green, yellow or red ambient colour. All experiments were carried out under controlled laboratory conditions and the preference was assessed by the location of the fish in a preference tank with four chambers. Rainbow trout showed a preference for blue and green at 1° C and for green at 12° C. After the growth experiment the fish reared in blue tanks preferred blue and green but green was the most preferred colour for the fish reared in green, yellow and red tanks. Yellow and especially red chambers were avoided, irrespective of the ambient colour during the growth trial. The final mass of fish reared in the red aquaria was significantly smaller than that of the fish in green tanks. In addition, when the data of the preference tests were correlated with the data of the growth experiment using mean values of the four tested colours, a very good linear relationship was observed between the preference ( i.e. visit frequency in coloured compartments) and growth rate as well as food intake. When considering the results both from the preference and growth trials it is suggested that green is the best environmental colour for rearing juvenile rainbow trout while rearing in a red environment cannot be recommended.     

Validation of an automatic system (DoubleCage) for detecting the location of animals during preference tests

Preference tests have often been performed for collecting information about animals' acceptance of environmental refinement objects. In numerous published studies animals were individually tested during preference experiments, as it is difficult to observe group-housed animals with an automatic system. Thus, videotaping is still the most favoured method for observing preferences of socially-housed animals. To reduce the observation workload and to be able to carry out preference testing of socially-housed animals, an automatic recording system (DoubleCage) was developed for determining the location of group-housed animals in a preference test set-up. This system is able to distinguish the transition of individual animals between two cages and to record up to 16 animals at the same time (four animals per cage). The present study evaluated the reliability of the DoubleCage system. The data recorded by the DoubleCage program and the data obtained by human observation were compared. The measurements of the DoubleCage system and manual observation of the videotapes are comparable and significantly correlated (P < 0.0001) with good agreement. Using the DoubleCage system enables precise and reliable recording of the preferences of group-housed animals and a considerable reduction of animal observation time.     

Plant scents modify innate colour preference in foraging swallowtail butterflies

Flower-visiting insects exhibit innate preferences for particular colours. A previous study demonstrated that naive Papilio xuthus females prefer yellow and red, whereas males are more attracted to blue. Here, we demonstrate that the innate colour preference can be modified by olfactory stimuli in a sexually dimorphic manner. Naive P. xuthus were presented with four coloured discs: blue, green, yellow and red. The innate colour preference (i.e. the colour first landed on) of the majority of individuals was blue. When scent from essential oils of either orange flower or lily was introduced to the room, females’ tendency to select the red disc increased. Scents of lavender and flowering potted Hibiscus rosa-sinensis, however, were less effective. Interestingly, the odour of the non-flowering larval host plant, Citrus unshiu, shifted the preference to green in females. In males, however, all plant scents were less effective than in females, such that blue was always the most favoured colour. These observations indicate that interactions between visual and olfactory cues play a more prominent role in females.     

Improving housing conditions for laboratory mice: a review of "environmental enrichment"

Laboratory animal facilities have been designed to provide a standard environment where animals can be kept in good physical health at the same time as economic and ergonomic considerations are met. Recognizing the potential welfare problem associated with behavioural restriction in such housing systems, a number of attempts have been made to improve this environment, generally described under the term "environmental enrichment". Modifications of cages for mice usually consist of providing material for nest building and structures which can serve as hiding places and/or for climbing. We have reviewed 40 studies carried out between 1987 and 2000, in which preferences as well as the effect of housing modifications have been studied. Mice will work for access to nesting material and make use of this material to make nests in which they rest. They prefer a more complex cage to the standard cage and will also work for access to cages with shelter and raised platforms. On the basis of present knowledge, it is recommended that mice should have access to nesting material. Strategies for future research are outlined in the article.     

Fruit Colour Preferences of Redwings (Turdus iliacus): Experiments with Hand-Raised Juveniles and Wild-Caught Adults

Certain fruit colours and their contrast with the background coloration are suggested to attract frugivorous birds. To test the attractiveness of different colours, we performed three experiments in laboratory with controlled light conditions. In the first two experiments, we studied the fruit colour preferences of naive juvenile redwings. In the third experiment, we continued to investigate whether the contrast of the fruit colour with the background coloration affects the preference of both naive juveniles and experienced adult redwings. In the first experiment, juvenile birds preferred black, UV‐blue and red berries, to white ones. In pairwise trials, a new set of juveniles still preferred red berries to white ones. When testing the effect of contrasts on their choice, juveniles preferred UV‐blue berries to red ones on a UV‐blue background. However, no preference was found, when the background was either red or green. Adult redwings preferred UV‐blue berries to red ones on all backgrounds. According to these results, juveniles seem to have an innate avoidance of white berries. Furthermore, the foraging decisions of fruit‐eating birds are affected more by fruit colour than its contrast with background coloration, at least when contrasting displays are encountered from relatively short distances. Differences in preferences of adult and juvenile birds also indicate that learning seems to play a role in fruit choices.     

The influence of the location of a nest box in an individually ventilated cage on the preference of mice to use it

The improvement of housing conditions for mice by using environmental enrichment materials is of high concern for the scientific community. Plastic, autoclavable nest boxes are commercially available and ready to use for specific cases such as in individually ventilated cages, metabolic cages, or during toxicological studies. The aim of this study was to see if the location of the nest box within the cage could influence the mice to prefer and use it. Located on the cage floor or hung from the cage lid, a nest box (MPLEX, Otto Environmental, Milwaukee, Wisconsin), enriched the cages. The study concluded that the location of the nest boxes in the individually ventilated cage plays a significant role in the mice preferring to use it or to avoid it. It is also important to use environmental enrichment items that provide animals with the possibility of expressing their preferences and manipulating them in a way to cope better with their environmental conditions.     

The Influence of the Location of a Nest Box in an Individually Ventilated Cage on the Preference of Mice to Use It

The improvement of housing conditions for mice by using environmental enrichment materials is of high concern for the scientific community. Plastic, autoclavable nest boxes are commercially available and ready to use for specific cases such as in individually ventilated cages, metabolic cages, or during toxicological studies. The aim of this study was to see if the location of the nest box within the cage could influence the mice to prefer and use it. Located on the cage floor or hung from the cage lid, a nest box (MPLEX, Otto Environmental, Milwaukee, Wisconsin), enriched the cages. The study concluded that the location of the nest boxes in the individually ventilated cage plays a significant role in the mice preferring to use it or to avoid it. It is also important to use environmental enrichment items that provide animals with the possibility of expressing their preferences and manipulating them in a way to cope better with their environmental conditions.     

What weta want: colour preferences of a frugivorous insect

Plants use colours as signals to attract mutualists and repel antagonists. Fleshy-fruits are often conspicuously coloured to signal different types of information including fruit maturity and spatial location. Previous work on fruit colour selection focus on large diurnal vertebrates, yet fruit colours are perceived differently by frugivores with different types of visual systems. Here, we tested whether a nocturnal, frugivorous, seed-dispersing insect selects fruits based on their pigmentation and whether different lighting conditions affect fruit colour selection. We captured 20 Wellington tree weta (Hemideina crassidens) from a forest reserve on the North Island of New Zealand and brought them into laboratory conditions to test their fruit colour preferences. The fruits of Coprosma acerosa, a native shrub species that naturally produces translucent, blue-streaked fruits, were dyed either red or blue. Fruits were then offered to weta in a binary (y-maze) choice test in two light conditions, either at night during a full moon or under artificial light conditions in the lab. Weta preferred unmanipulated, naturally blue-streaked fruits and artificially-blue coloured fruits over those dyed red. Furthermore, their colour preferences were unaffected by light environment. Our results therefore suggest that weta can discriminate between colours (using colour vision) in both light and dark light environments. Their consistent preferences for colours other than red indicate that weta might be responsible for the unusual colours of fleshy-fruits in New Zealand.     

Signals of profitability? Food colour preferences in migrating juvenile blackcaps differ for fruits and insects

Red is a common colour signal in both aposematic warning displays, and in fruit displays. One common feature is that red is conspicuous against the natural background of the prey and fruits. However, there is a potential conflict between fruits and aposematic prey in how a bird predator should react to red colours, where fruits aim to attract birds and aposematic insects aim to ward off, often the same bird individuals. Here we investigate possible differences in red/green colour preferences of frugivorous, wild-caught, young blackcaps (Sylvia atricapilla), when food is either a fruit or an insect. Birds in two groups were presented with a series of pairs of food items that had been artificially painted red and green, in the order of (I) fruits, crickets and maggots, or (II) crickets, fruits, and maggots. Birds first presented with crickets or fruits differed in first attacks directed at the two colours: They showed no colour preference between fruits, but showed a clear preference for green over red crickets. Also, birds in both experimental groups clearly preferred green to red maggots. These results provide evidence that wild, frugivorous birds are able to differentiate between prey types, and show different colour preferences depending on whether food is insect or fruit. We conclude that blackcaps show an attack bias against red insects, and that one important function of the signal in insects, is to inhibit attack after discovery. However, the lack of preference for red fruits suggests other functions to red fruit displays, such as facilitating discovery per se, rather than directly stimulating attack after discovery.     

Juvenile colour polymorphism in the red rock crab,Cancer productus: patterns,causes, and possible adaptive significance

Juveniles of the common red rock crab of the Northeastern Pacific, Cancer productus, display a stunning diversity of colours and patterns, while adults all have the same drab colouration. Although this is widely known, key questions remain: (1) Does the frequency of different juvenile colours or patterns vary among collection sites or seasonally? (2) Does juvenile colour polymorphism reflect genetic heterogeneity or phenotypic plasticity in response to variable environmental conditions? (3) Do juveniles of different colours or patterns prefer substrata of different heterogeneity or brightness? We therefore: (i) described the variation in colour and pattern of juvenile C. productus; (ii) tested for associations between colour/pattern morphs and crab size, collection site, and season, in the field; (iii) conducted preliminary tests for habitat preferences (background colour, substratum type, light level) of different colour/pattern morphs in laboratory experiments, and (iv) tested the effect of diet (mussels versus shrimp) and feeding rate (high versus low) on juvenile colour/pattern. We describe 30 phenotypes that embrace a wide range of colour and pattern variants. The proportions of these phenotypes did not vary significantly among four collection sites, but they did vary significantly with season: over the summer and fall, juvenile colour and pattern variation was gradually replaced by the uniform adult colouration. The number of crabs displaying adult colouration also increased with crab size. Laboratory experiments suggest no significant preferences of different juvenile morphs for different backgrounds, substrata, or light levels. Diet (mussels versus shrimp) and feeding frequency had no effect on colour/pattern. Collectively, these results, although limited in scope, are not consistent with two likely hypotheses that could explain the extensive colour and pattern variation in juvenile C. productus: (i) selection for background matching by different cryptic forms and (ii) direct effects of diet or feeding rate on colour or pattern. Most probably, the large variety of different juvenile morphs is a result of frequency-dependent selection in which abundant variants are attacked disproportionately often and rarer forms are favoured. Juvenile colour polymorphism in C. productus may reduce the vulnerability to visual predators, impede the formation of a search image, and consequently decrease the risk of predation during the juvenile stages.     

The effects of the visual environment on responses to colour by domestic chicks

It is well known that development of vision is affected by experience, but there are few studies of environmental effects on colour vision. Natural scenes contain predominantly a restricted range of reflectance spectra, so such effects might be important, perhaps biasing visual mechanisms towards common colours. We investigated how the visual environment affects colour preferences of domestic chicks ( Gallus gallus), by training week-old birds to select small food containers distinguished from an achromatic alternative either by an orange or by a greenish-blue colour. Chicks that had been raised in control conditions, with long-wavelength-dominated reflectance spectra, responded more readily to orange than to blue. This was not due to avoidance of blue, as increasing saturation enhanced the chicks' preference for the same hue. The advantage of orange was, however, reduced or abolished for chicks raised in an environment dominated by blue objects. This indicates that responses to coloured food are affected by experience of non-food objects. If colours of ordinary objects in the environment do influence responses to specialised visual signals this might help explain why biological signals directed at birds are often coloured yellow, orange or red; long-wavelength-dominated spectra being more prevalent than short-wavelength-dominated spectra.     

Artificial selection for food colour preferences

Colour is an important factor in food detection and acquisition by animals using visually based foraging. Colour can be used to identify the suitability of a food source or improve the efficiency of food detection, and can even be linked to mate choice. Food colour preferences are known to exist, but whether these preferences are heritable and how these preferences evolve is unknown. Using the freshwater fish Poecilia reticulata, we artificially selected for chase behaviour towards two different-coloured moving stimuli: red and blue spots. A response to selection was only seen for chase behaviours towards the red, with realized heritabilities ranging from 0.25 to 0.30. Despite intense selection, no significant chase response was recorded for the blue-selected lines. This lack of response may be due to the motion-detection mechanism in the guppy visual system and may have novel implications for the evolvability of responses to colour-related signals. The behavioural response to several colours after five generations of selection suggests that the colour opponency system of the fish may regulate the response to selection.