Domestic Norway Rats Research Articles

Bacteria Isolated from Conspecific Bite Wounds in Norway and Black Rats: Implications for Rat Bite–Associated Infections In People

Bites associated with wild and domestic Norway and black rats (Rattus norvegicus and Rattus rattus) may have a variety of health consequences in people. Bite-related infections are among the most significant of these consequences; however, there is little data on the infectious agents that can be transmitted from rats to people through biting. This is problematic because without an accurate understanding of bite-related infection risks, it is difficult for health professionals to evaluate the adequacy of existing guidelines for empirical therapy. The objectives of this study were to increase our knowledge of the bacterial species associated with rat bites by studying bite wounds that wild rats inflict upon one another and to review the literature regarding rat bites and bite wound management. Wild Norway and black rats (n=725) were trapped in Vancouver, Canada, and examined for bite wounds in the skin. All apparently infected wounds underwent aerobic and anaerobic culture, and isolated bacteria were identified. Thirty-six rats had bite wound-related infections, and approximately 22 different species of bacteria belonging to 18 genera were identified. Staphylococcus aureus was the most common isolate; however, the majority of infections (72.5%) were polymicrobial. Rat bites can result in infection with a number of aerobic and anaerobic Gram-positive and Gram-negative bacteria. In humans, these wounds are best managed through early recognition and cleansing. The benefit of prophylactic antimicrobial treatment is debatable, but given the deep puncturing nature of rodent bites, we suggest that they should be considered a high risk for infection. Antibiotics selected should include coverage for a broad range of bacterial species.

New insights into the karyotypic evolution in muroid rodents revealed by multicolor banding applying murine probes

Muroid rodents are composed of a wide range of species characterized by extensive karyotypic evolution. Even if this group includes such important laboratory animal models as domestic mouse (Mus musculus), Norway rat (Rattus norvegicus), Chinese hamster (Cricetulus griseus), and golden hamster (Mesocricetus auratus), comparative cytogenetic studies between rodents are difficult due to the characteristic rapid karyotypic evolution. Molecular cytogenetic methods can help resolve problems of comparing muroid chromosomes. Here, we used cross-species comparative multicolour banding with probes obtained from mouse chromosomes 3, 6, 18, and 19 to study the karyotypes of nine muroid species from the three subfamilies Murinae, Cricetinae, and Arvicolinae. Results from multicolour banding with these murine probes (mcb) allowed us to improve the comparative homology maps between these species and to obtain new insights into their karyotypic evolution. We identified evolutionary conserved chromosomal breakpoints and revealed four previously unrecognized homologous segments, four inversions, and 14 evolutionary new centromeres in the nine muroid species studied. We found Mus apomorphic rearrangements, not seen in other muroids, and defined several subfamily specific chromosome breaks, characteristic for Arvicolinae and Cricetinae. We show that mcb libraries are an effective tool both for the cytogenetic characterisation of important laboratory models such as the rat and hamster as well as elucidating the complex phylogenomics relationships of muroids.

How does the ecological foraging behavior of desert kangaroo rats (Dipodomys deserti) relate to their behavior on radial mazes?

Experiment 1 showed that laboratory-reared desert kangaroo rats, like domestic Norway rats, efficiently search for food on a radial arm maze (RAM) by avoiding revisiting arms within a trial. By placing an RAM on the floor so the animals could approach food from any direction, Experiment 2 tested whether efficient search by kangaroo rats was based on tactics of distance minimizing, central-place foraging, trail following, or meandering. In contrast to the dominant trail-following tactic of domestic Norway rats (Hoffman, Timberlake, Leffel, & Gont, 1999), kangaroo rats tended to distance minimize, whether maze arms were present or not. Experiment 3 indicated that kangaroo rats treated a floor configuration of eight food cups as two patches of four, based on beeline travel between patches and meandering within them. We conclude that similar performance in an elevated RAM by different species can be based on different tactics, and we suggest that a laboratory apparatus can be used to cast light on niche-related mechanisms.

Gnawing and retrieval of inedible objects by Norway rats: Motivational interactions and habituatory effects

The relation between gnawing and retrieval of inedible, partible objects (wooden blocks) by domestic Norway rats ( Rattus norvegicus Berkenhout) was examined by manipulating the tendency to gnaw and testing subsequent retrieval. Experiments 1 and 2 established that rats gnaw wooden blocks but do not ingest them even during food deprivation, and that gnawing declines (habituates) over days for most rats. In Experiment 3, food deprivation produced a decrease in retrieval of blocks that was reversed under subsequent ad lib conditions. This result was confirmed in Experiment 4, which also demonstrated concommitant changes in gnawing and object retrieval as well as effects on component responses of the retrieval sequence. In Experiment 5, continuous exposure to blocks sufficient to reduce gnawing to a low level led to a decline in retrieval of these objects that was not reversed by discontinuing exposure. These results are consistent with the incentive-motivational account of retrieval preferences developed in earlier work, and some inferences are made about the kinds of processes that could mediate the effects of deprivation and habituation.

Cross-species fostering affects meat preferences of wild house mice.

Wild-strain male house mice were fostered at birth onto conspecifics, deer mice, or domestic Norway rats. In adulthood, their flesh-eating preferences were tested by allowing them to feed from freshly asphyxiated conspecifics and either deer mice or rats. The mice ate significantly more conspecific flesh than contraspecific flesh, except when the flesh offered was that of the contraspecies upon which the mouse had been fostered at birth. The failure of cross-species-fostered mice to discriminate between their own species and their foster species in flesh-preference tests is attributed to their having learned early in life to respond to the foster species in the same way they normally respond to conspecifics, that is, by approaching them, investigating them, and, when finding them dead, feeding upon them.

Passing as an Indicator of Social Dominance Among Female Wild and Domestic Norway Rats

AbstractThe most frequent form of social interaction between pairs of wild or domestic rats (Rattus norvegicus) was passing behaviour in the narrow burrows and open field of seminatural environments. This behaviour occurs when a moving rat approaches another, either head-to-head or head-to-tail; the passed animal freezes while the passing rat continues, side touching side. The social dominance manifest by this behaviour correlated significantly with fighting dominance, particularly among female wild and domestic rats. In addition, dominance during displacements for access to food and water correlated with the dominance relationship in passing within pairs of domestic female rats. Although both passing and general activity had the same crepuscular daily rhythm, passing dominance did not correlate with individual differences in general activity level. Thus passing indicates social order and is not simply a by-product of general activity. Because passing occurs ten times more frequently than fights, in future studies it may be a more powerful indicator of female dominance and social order.

Effects of the nonagouti pelage-color allele on the behavior of captive wild Norway rats (Rattus norvegicus).

The objective of the present study was to determine the extent to which the nonagouti pelage-color allele influences selected behaviors (including docility) of the wild Norway rat. Agouti and nonagouti (black) littermates were compared in tests for handling, open-field behavior, platform jumping, and response to a novel food item, all of which clearly differentiate wild and domestic rats. Nonagouti rats were significantly easier to approach, capture, and handle than their agouti sibs. However, differences between agouti and nonagouti rats for the other variables studied were not significant. Although the presence of the nonagouti allele cannot fully account for the behavioral differences between wild and domestic Norway rats, it may have facilitated the domestication of this species by improving ease of handling.

Establishment of dominance in domestic Norway rats: Effects of the degree of captivity and social experience

The effect of the level of captivity and prior social experience on the establishment of dominance was examined in 16 colonies of albino rats. Males were assigned to one of four treatment groups: aggressive experience, defeat experience, exposure to electric shock, and controls. Following treatment, colonies of four males were established for 12 days in one of three different captive setings: a large outdoor pen, an indoor pen, or laboratory group cages. Effects of treatment were minimal; however, the degree of captivity significantly affected the display of aggression and the establishment of dominance relationships. In the two pen settings, attacks were more frequent and dominance relationships were established in six of eight colonies. Attacks in the laboratory cages occurred almost exclusively during the first 2 days, and no dominance relationships were established in any of eight laboratory cage colonies.

Sensory control of suckling-associated behaviours in the domestic Norway rat, Rattus norvegicus

Our research presents a detailed parametric study of suckling under different stimulus conditions in rat pups of different ages. In it we examined the effects of deprivation, nipple odours, and background female (dam versus virgin) odours on suckling-associated behaviours in 7, 13, and 18-day-old domestic, albino Norway rats ( Rattus norvegicus) by placing pups individually on the ventrum of anaesthetized adult female rats and videotaping the behaviour of the pups for 5 min. Suckling deprivation (deprivation time increased with each progressive age-group) markedly increased most active behaviours and reduced resting. Deprivation also sensitized pups to the olfactory configuration formed by the combination of nipple odours and background female odours. The presence of configurations discrepant from that of the normal dam greatly augmented both searching in Day 7 pups and licking in Day 18 pups. Lastly, it was clear that nipple odours exerted direct control over probing.

Degrees of captivity and aggressive behavior in domestic Norway rats

Six categories of aggressive behaviors were studied in groups of domestic rats observed for 3 months and in three settings of varying degrees of captivity. In the least captive situation, a large outdoor pen, aggression frequently took a wild-type form (aggressive side postures, biting attacks) and infrequently took a “playful” form (pins, aggressive grooms) relative to aggression shown by rats in the most captive situation, laboratory cages. Rats housed in an intermediate degree of captivity showed intermediate levels of both serious and playful types of aggression. Male and female intruders were attacked by residents of all three settings, most seriously in the outdoor pen. These results indicate that captivity may have a powerful effect on the form of aggression shown by domestic rats.

Behavioral comparability of wild and domesticated rats

The oft-repeated concern for the lack of behavioral comparability of domestic rats with wild forms of Rattus norvegicus is unfounded. Laboratory rats appear to show the potential for all wild-type behaviors, including the most dramatic social postures. Moreover, domestics are capable of assuming a feral existence without difficulty, one where they readily behave in a fashion indistinguishable from wild rats. The one behavioral difference that is clearly established concerns performance in laboratory learning paradigms. The superiority of domestics in these laboratory tasks speaks more to quieting the concerns of degeneracy theorists than to problems of using domestic Norway rats as subjects representative of their species.

Schedule-induced polydipsia in F1 hybrid rats of wild-caught and domestic Norway rats

Five F1 hybrid rats of a wild-caught Norway male rat and a domestic, albino Norway female rat and five domestic, albino Norways rats were tested on fixed-time 1-min food schedules for the development of schedule-induced polydipsia. All five F1 hybrid rats and three domestic rats developed polydipsia. These data generalized schedule-induced polydipsia to the F1 hybrid generation of wild-caught and domestic rats. The implications of these results for Symons and Sprott's [12] suggestion of a genetic component for schedule-induced polydipsia are discussed.

Sexual behaviour and reproductive competition in male wild and domestic Norway rats

The copulatory behaviour of male wild Norway rats ( Rattus norvegicus) exposed individually to females in hormone-induced oestrus is characterized by fewer mounts and intromissions per ejaculatory series, shorter ejaculation latencies, and longer ejaculatory clasps than the copulatory behaviour of domestic males. Competition between wild and domestic males tested simultaneously in pairs produced only minor changes in copulatory behaviour. The reproductive success of wild and domestic male pairs simultaneously exposed to naturally cycling females was nearly equal in both the laboratory and an outdoor enclosure. Genotype of the female had little effect on male copulatory behaviour. The copulatory behaviour of sexually naive and experienced domestic rats did not differ. However, most sexually naive wild males failed to exhibit copulatory behaviour under the test conditions employed.

A parametric investigation into the generality of schedule-induced polydipsia to wild-caught Norway and wild-caught cotton rats

In Experiment 1, wild-caught Norway rats failed to develop schedule-induced polydipsia at 80% free-feeding weight when placed on several fixed-time schedules. During Experiment 2 all of the wild-caught rats became polydipsic when body weight was reduced to 70% of free-feeding weight. Domestic Norway rats developed polydipsia at 80% free-feeding weight and remained polydipsic during body weight and fixed-time manipulations. Experiment 3 tested the generality of schedule-induced polydipsia to wild-caught and domestic cotton rats under several fixed-time schedules, body weight levels, and during a normal and reverse light/dark cycle. None of the domestic rats, and only one wild-caught rat, developed polydipsia. The findings extend schedule-induced polydipsia to wild-caught Norway rats but not to domestic or wild-caught cotton rats.

A test of the generality of schedule-induced polydipsia to wild-caught Norway rats

Four of 5 food-deprived wild-caught Norway rats failed to develop schedule-induced polydipsia when placed on a fixed-time 1-min food schedule of 45 mg pellets for 30 1-hr sessions. The one wild-caught rat that displayed schedule-induced polydipsia was retarded in the development and only reached session intake level approximately one half that of a control group of domestic laboratory-reared Norway rats. All 5 domestic rats readily acquired schedule-induced polydipsia. The wild-caught and domestic Norway rats differed in their probability of initiating a bout of drinking but not in their lick pattern, bout size or lick efficiency. These data appear to challenge the generality of schedule-induced polydipsia.

Genotype versus experience effects on aggression in wild and domestic Norway rats.

AbstractThe agonistic behavior of field-trapped and first-generation laboratory-reared wild male Norway rats was compared in a resident-intruder context in order to examine the hypothesis that aggressive behavior is significantly reduced by laboratory rearing. In addition isolate and group-reared wild and domestic rats were compared in order to determine the effect of early social deprivation on levels of aggression. Experimental subjects were housed in test chambers for at least one month prior to their exposure to anosmic hybrid (wild X domestic) intruders. Agonistic behaviors of both residents and intruders were recorded in two 30-minute trials. Field-trapped males were significantly more aggressive than any of the laboratory-reared groups. The behavior of isolate-reared subjects of both stocks did not differ significantly from their group-reared counterparts. Three hypotheses were advanced to account for the greater aggressiveness of the wild-caught rats. The evidence favors an interpretation based on the greater opportunity for social conditioning in the field environment and the blocking of habitual behavior patterns (i.e. escape) in captivity.

The Role of the Female During Copulation in Wild and Domestic Norway Rats (Rattus Norvegicus)

AbstractThe copulatory behavior of both wild and domestic strains of Rattus norvegicus was observed via continuous video monitoring as it spontaneously occurred in the large seminatural environment and under standard laboratory conditions. A factorial design demonstrated that the female Norway rat has the major role determining the amount and timing of copulation once mating begins. Copulation between wild pairs was characterized by fewer ejaculatory series than domestic pairs. The first ejaculatory series of wild pairs contained more intromissions at longer intervals. Domestic pairs had the same total number of intromissions in a copulatory session, but spread over multiple ejaculatory series with few intromissions at short intervals in the first series. The characteristic differences between the copulatory patterns of wild and domestic pairs was determined by the female's strain condition and was either statistically independent or opposite to the male's strain condition. Specifically, the population pattern of a wild female was characterized by fewer ejaculatory series and more intromissions at longer intervals before the first ejaculation than the pattern of a domestic female. These differences between wild and domestic populations were produced by differences in the rate of active solicitations for an intromission by individual females : the solicitation occurred virtually in a one-to-one correspondence with an intromission. There were no gross anatomical differences between the vaginal size and placement of the two strains. The female solicitation is a distinct and quantifiable behavior not found in the standard testing cage: its occurrence depends on a larger and more complex environment. In addition, copulation in the larger seminatural environment is characterized by fewer intromissions in each ejaculatory series of a session at longer copulatory intervals. The role of the female is discussed both in terms of the individual interactions which underlie it and in terms of its physiological functions for successful reproduction in the rat. Copulation with a wild male is characterized by longer intervals between the intromissions of the first ejaculatory series than with a domestic male. The wild condition of both the pair and the female showed the opposite effect. This difference is evaluated in terms of the different mating strategies for the two sexes on a population level and in terms of the individual interactions that allow a compromise for successful reproduction of the pair.

Burrowing in Wild and Domestic Norway Rats

Burrowing in Wild and Domestic Norway Rats

Maternal behavior of wild and domestic stocks of Norway rats

The maternal behaviors (nursing, pup-retrieval, and nest-building) of lactating female wild and domestic Norway rats were compared on Days 1, 5, 9, and 13 following parturition. In addition, postpartum aggression was investigated by exposing mothers to strange female intruders on Days 6, 7, and 8. The maternal behaviors of wild and domestic mothers were very similar. However, wild mothers tended to be more efficient in pup-retrieval, whereas domestic females showed shorter latencies for nest construction. Both domestic and field-trapped wild mothers displayed relatively high levels of aggression toward intruders. These results support the hypothesis that domestication has had relatively little impact on maternal behaviors in this species.

Glucose preferences in wild and domestic guinea pigs

Male wild (Cavia aperea) and domestic (C. porcellus) guinea pigs were tested in two-bottle choice tests for preferences between glucose solutions of different concentrations and de-ionized water. Wild males showed significant preferences for concentrations between 0.025 and 0.4 M glucose while domestic males preferred only the 0.2 M glucose solution to de-ionized water. C. aperea males also consumed significantly greater volumes of liquid per kg body wt. 3 4 during the glucose tests than did the C. porcellus males. These comparative results contrast sharply with those obtained by other authors with wild and domestic Norway rats.