Rafał Stryjek

How domestication modulates play behavior: A comparative analysis between wild rats and a laboratory strain of Rattus norvegicus.

Laboratory rats have been widely used to study the development and neural underpinnings of play behavior. However, it is not known whether domestic rats play in the same way and at the same frequency as their wild counterparts. In this study, the play of juvenile rats from a colony of wild rats maintained in captivity was compared to that of a strain of domesticated rats (e.g., Long Evans hooded). Three predictions were tested. First, it was predicted that wild rats would incorporate more agonistic behavior in their play. This was not found, as in all cases, both the wild and the laboratory rats attacked and defended the nape during play, a nonagonistic body target. Second, because play is typically more frequent in domesticated animals than their wild progenitors, it was predicted that the wild rats should play less than the laboratory rats. This was found to be the case. Third, because wild animals tend to be less tolerant of proximity by conspecifics and tend to be more agile in their movements, it was predicted that there would be less contact between wild pair mates. This was found to be the case; data show that the play of laboratory rats involves the same target (i.e., the nape of the neck) and tactics of defense as those used by wild rats. However, the laboratory rats initiated playful attacks more frequently, and were more likely to use tactics that promoted bodily contact. These similarities and differences need to be considered when using laboratory animals as models for play in general.

Species Specific Behavioural Patterns (Digging and Swimming) and Reaction to Novel Objects in Wild Type, Wistar, Sprague-Dawley and Brown Norway Rats

Background The purpose of the present study was to analyse species-specific forms of behaviour (digging and swimming) and response to novelty in laboratory rats and their wild type counterparts at a very early stage of laboratorization. Three behavioural phenomena were taken into account: burrowing, spontaneous swimming, and neophobic behaviour. Principal Findings Wild-type rats and three strains of laboratory rats were involved in experiments: Warsaw-Wild-Captive-Pisula-Stryjek (WWCPS), Wistar, Sprague-Dawley, and Brown Norway rats were compared in spontaneous swimming test, while WWCPS and Wistar rats were studied in burrowing and neophobia experiments. Wild rats were found to be faster at building tunnels than Wistar rats and at constructing more complex burrow systems. The experiment on neophobia showed that Wistar rats exhibited less neophobic responses and were more often trapped. WWCPS rats showed highly neophobic behaviour and were rarely trapped in this experiment. The experiment on swimming showed that WWCPS rats showed more complex water tank related activity than their laboratory counterparts. They swam and explored under surface environment. Conclusions The three experiments showed profound behavioural differences in quasi-natural forms of behaviour between wild type rats (WWCPS) and three laboratory strains frequently used in behavioural studies.

Circadian Rhythm of Outside-Nest Activity in Wild (WWCPS), Albino and Pigmented Laboratory Rats

The domestication process of the laboratory rat has been going on for several hundred generations in stable environmental conditions, which may have affected their physiological and behavioural functions, including their circadian system. Rats tested in our ethological experiments were laboratory-bred wild Norway rats (WWCPS), two strains of pigmented laboratory rats (Brown Norway and Long Evans), and two strains of albino rats (Sprague-Dawley and Wistar). Rats were placed in purpose-built enclosures and their cycle of activity (time spent actively outside the nest) has been studied for one week in standard light conditions and for the next one in round-the-clock darkness. The analysis of circadian pattern of outside-nest activity revealed differences between wild, pigmented laboratory, and albino laboratory strains. During daytime, albino rats showed lower activity than pigmented rats, greater decrease in activity when the light was turned on and greater increase in activity when the light was switched off, than pigmented rats. Moreover albino rats presented higher activity during the night than wild rats. The magnitude of the change in activity between daytime and nighttime was also more pronounced in albino rats. Additionaly, they slept outside the nest more often during the night than during the day. These results can be interpreted in accordance with the proposition that intense light is an aversive stimulus for albino rats, due to lack of pigment in their iris and choroid, which reduces their ability to adapt to light. Pigmented laboratory rats were more active during lights on, not only in comparison to the albino, but also to the wild rats. Since the difference seems to be independent of light intensity, it is likely to be a result of the domestication process. Cosinor analysis revealed a high rhythmicity of circadian cycles in all groups.

Domestication and Diversification: A Comparative Analysis of the Play Fighting of the Brown Norway, Sprague-Dawley, and Wistar Laboratory Strains of (Rattus norvegicus)

Laboratory strains of rats are a commonly used subject to study play behavior. Recent research has shown that play in one laboratory strain of rat (e.g., Long-Evans hooded) differs in a number of ways from its wild counterparts. These findings suggest that domestication affects some aspects of play behavior. However, there are multiple strains of laboratory rats, which have been domesticated through different lineages all derived from wild rats and it cannot be assumed that all domestic strains are identical in their play. Therefore, the aim of this study was to compare the play behavior of three other strains of laboratory rats (e.g., Wistar, Sprague-Dawley, and Brown Norway). All strains were similar to each other as they all engaged in high frequencies of play, tolerated similar interanimal distances before initiating playful defense and displayed similar acrobatic capacities, suggesting domestication produces some common changes in play and other factors that influence play. However, strains differed significantly from one another in the use of tactics that promote bodily contact during play. Indeed, in this regard, some strains were more similar to wild rats than others, suggesting that some domestication-induced changes are either unique or more prominent in some laboratory strains than others. Such a mosaic pattern of transformation not only offers the possibility of using strain differences to characterize the genetic factors contributing to different facets of play, but also cautions researchers from making rat-general conclusions from studies on any one strain.

Food neophobia in wild and laboratory rats (multi-strain comparison).

Although empirical studies comparing neophobia in wild and laboratory rats have been conducted in the past, a few decades have passed since most of them were completed. This is a substantial period of time in the case of fast-breeding animals such as rats. Equally important are the inconsistencies in research findings with respect to comparisons between wild and laboratory rats, and within domesticated strains. As well as having the aim of updating knowledge of neophobia among different types of rats, the present experiment was also an attempt to isolate a specific fear of a new food from a general fear of a novel object. The procedure was that rats accustomed to one type of food served in a specific location and in a familiar container were given a different type of food. Test trials were preceded by food deprivation. The following variables were measured: feeding latency, the pace of eating, the number of approaches to the container, and the number of times food was sampled in each trial. The amount of food consumed in each trial was weighed and also taken into account. Grooming time served as the measure of stress among the rats in the experiment. The results of the experiment did not confirm the assertion of some authors that wild rats avoid eating unfamiliar foods. All groups demonstrated only a temporary decrease in the amount of food consumed, the magnitude of which was similar in all strains. No evidence of particularly low neophobia in albino rats was found. However, the behavioral symptoms indicated higher levels of stress in wild rats compared to the other groups.

Response to novelty in the laboratory Wistar rat, wild-captive WWCPS rat, and the gray short-tailed opossum (Monodelphis domestica).

Behavior of the laboratory gray short-tailed opossums (Monodelphis domestica), Warsaw Wild Captive Pisula Stryjek rats (WWCPS) and laboratory rats (Wistar) has been registered in the period of familiarization with a new environment and consecutive confrontation with a novel, innocuous object placed in that familiarized environment. In the new environment the sequence of anxiety, investigation, and habituation was shortest in the opossum, longer in the laboratory rat and longest in the WWCPS rat. When placed in it, gray short-tailed opossums investigated the new environment with the shortest delay and most intensity. In reaction to novel objects, opossums and laboratory rats prolonged the time spent in the proximity of the new object, while the WWCPS rat did not show that reaction. Both opossums and laboratory rats increased the number of contacts with the new object, whereas WWCPS rats reduced those contacts. Behavior of all three species and lines grouped in different clusters. Some other quantitative and qualitative differences in behavior of the investigated animals are also described, showing a higher level of anxiety in both lines of rats than in the opossum. Behavioral differences between species and lines of animals used in this study may be attributed to different ecological adaptations of rats and opossums and to the effect of domestication in the laboratory rats. These behavioral differences make comparisons of opossums vs rat, and wild rat vs laboratory rat interesting models for studying the brain mechanisms of anxiety and neotic motivations.

A transportation device for rats.

Subjecting laboratory animals to handling-induced stress can lead to variable experimental errors. Additionally, handling wild species may endanger laboratory staff and the animals themselves. To protect both laboratory staff and laboratory animals, the author created a useful device for transporting wild rats (Rattus norvegicus). Though the author designed this device for moving wild rats, he suggests that it could be used with all mammals of comparable size. Here, the author describes this device, which he has found to be particularly helpful when physical contact between animals and humans is a problem.

Food Neophobia in Wild Rats (Rattus norvegicus) Inhabiting a Changeable Environment-A Field Study.

Food neophobia is a reaction to novel food observed in many animal species, particularly omnivores, including Rattus norvegicus. A neophobic reaction is typically characterised by avoidance of novel food and the necessity to assess both its potential value and toxicity by the animal. It has been hypothesised that this reaction is not observed in rats inhabiting a changeable environment with a high level of variability with regard to food and food sources. This study was conducted in such changeable conditions and it aims to demonstrate the behaviour of wild rats R. norvegicus in their natural habitat. The rats were studied in a farm setting, and the experimental arena was demarcated by a specially constructed pen which was freely accessible to the rats. At regular intervals, the rats were given new flavour- and smell-altered foods, while their behaviour was video-recorded. The results obtained in the study seem to confirm the hypothesis that rats inhabiting a highly changeable environment do not exhibit food neophobia. The observed reaction to novel food may be connected with a reaction to a novel object to a larger extent than to food neophobia. The value of the results obtained lies primarily in the fact that the study was conducted in the animals’ natural habitat, and that it investigated their spontaneous behaviours.

Neophobia in wild rats is elicited by using bait stations but not bait trays

ABSTRACT Brown rats (Rattus norvegicus) are among the most common vertebrates often becoming a major pest in urban environments. Managing rat populations is difficult, given the complex behaviours these murids can display. To help improve local control, we studied the response of wild rats to bait stations comparing baits placed on three different kinds of surfaces (on the ground, on trays and in bait stations) near burrows. We show that rats neither avoided nor preferred any tray type in particular – the latency to pick up the food pellet from the ground did not differ from the latency to pick it up from trays. However, the latency to pick the food pellet was significantly higher when food was placed in bait stations. We conclude that for effective administration of toxic baits, common bait stations are not the most effective method and should be used only in cases when placing baits directly on the ground or on a tray poses a threat to other animals and humans.

Predator odor induced defensive behavior in wild and laboratory rats: A comparative study

Laboratory rats are frequently used as animal models in research. Since the 1920s rats are bred and reared in laboratories which affects anatomy, physiology, and behavior responses. In the present study we exposed laboratory and wild rats to predator odor and comparatively analyzed their behavioral and physiological responses. In detail, Warsaw Wild Captive Pisula Stryjek (WWCPS) rats and Lister Hooded (LH) rats were exposed to the predator odor 2,3,5-trimethyl-3-thiazoline (TMT), their behavior was videotaped and blood samples were collected for subsequent serum corticosterone analysis. In both rat stocks, exposure to TMT induced avoidance behavior and increased freezing behavior. Notably, the increase in freezing was based on an increase number of freezing events in LH rats whereas WWCPS rats prolonged the mean duration of the single freezing events. Interestingly, TMT exposure lead to a serum corticosterone increase in WWCPS rats but not in LH rats. Furthermore, WWCPS rats generally expressed decreased but faster locomotor activity, as well as more grooming behavior than LH rats. Taken together, these data indicate differences in behavioral and physiological defensive responses to predator odors in the two rat stocks.