How golden hamsters (Mesocricetus auratus) discriminate top from bottom flank scents in over-marks.

Using a habituation-discrimination paradigm, the authors investigated what cues male golden hamsters (Mesocricetus auratus) use to determine the top and bottom positions in flank gland over-marks. A difference in the ages of 2 hamsters' marks did not, by itself, produce differential memory or evaluation of the 2 scents. A spatial configuration of marks suggestive of an overlap was sufficient for the apparently overlapping scent to be remembered or valued more than the apparently underlying scent. Cues from the overlap of 2 hamsters' marks were also sufficient. These results, consistent with those previously found for responses to hamster vaginal scent over-marks, suggest that hamsters use similar cues to analyze scent over-marks that are different in chemical composition and in social functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scent counter-marks: Specialized mechanisms of perception and response to individual odors in golden hamsters (Mesocricetus auaratus).

Scent counter-marking is a widespread phenomenon among mammals that is not well understood. Using a habituation paradigm, it was found that male golden hamsters (Mesocricetus auratus) exposed to partially overlapping scents of 2 females behaved on test trials as if they remembered the top scent but not the bottom scent. If the 2 females' scents did not overlap during exposure trials, males remembered both of them. Thus, if 2 individual scents partially overlap, hamsters (1) perceive which of the 2 scents was deposited most recently and (2) either remember the top scent and forget the bottom scent or attach greater significance to the top scent. These results indicate the existence of specialized perceptual and cognitive or motivational mechanisms that are used for interpretation and response to complex arrays of social odors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What kind of information do meadow voles (Microtus pennsylvanicus) use to distinguish between the top and bottom scent of an over-mark?

This study investigated how voles (Microtus pennsylvanicus) determine which scent is the top scent of an over-mark and how this information influences memory for the top scent. This series of experiments shows that a region of overlap is necessary for both a preference and a differential memory for 1 of the 2 scents, and a difference in the area covered by one of the two overlapping scents is not sufficient by itself to cause these effects. These results suggest that voles have specialized perceptual and evaluative mechanisms for the analysis of scent over-marks. Thus, voles may attach a greater importance to the odor of the top-scent donor than that of the bottom-scent donor of an over-mark. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female voles discriminate males' over-marks and prefer top-scent males

Scent over-marking is a common form of competitive advertisement among many species of mammals. Recent observations in golden hamsters, Mesocricetus auratushave suggested that individuals have specialized mechanisms for interpretation of and response to such over-marks. In this study, we examined whether meadow voles, Microtus pennsylvanicushave similar abilities. Female voles were first exposed to anogenital scent marks of two males and were then tested in a Y-maze for their preferences for whole-body odours of these two males. Experiments were run using a variety of configurations of scent marks during the exposure phase, but all experiments yielded consistent results. If the scent marks of the two males overlapped, females later preferred the whole-body odours of the male whose scent was on top; if the two scent marks did not overlap, females showed no preference. Females also preferred odours of familiar males over novel males, and preferred both top-scent and bottom-scent males over novel males. The results suggest that female voles can tell which individual's scent is on top in an over-mark and that they prefer this top-scent male, even though they know that both males' scents were present during the exposure phase. We suggest that these odour preferences reflect mate preferences and discuss possible reasons why females might prefer top-scent males.1997The Association for the Study of Animal Behaviour     

Memory for individual scent in hamsters (Mesocricetus auratus) as assessed by habituation methods.

The memory of hamsters (Mesocricetus auratus) for the flank scent of older male hamsters was investigated in a series of habituation experiments. In 2 types of habituation tasks (Exps 1 and 2), male hamsters habituated to the flank scent of 1 male and then increased their level of investigation to that of a novel male; similar results were obtained when the intervals between trials ranged from 1 sec to 2 days. When the test trial was 10 or 21 days after habituation (Exp 3), males discriminated between familiar and novel flank scents at 10 days but not at 21 days. The results demonstrate recognition of familiar and unfamiliar individual odors and excellent memory for these differences. Habituation techniques yield extremely robust results and may be useful for investigations of other aspects of individual signatures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the hippocampal system in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Female golden hamsters (Mesocricetus auratus) received aspiration lesions of the parahippocampal region (PARA) or electrolytic lesions of the fimbria-fornix (FNX) and were tested for their (a) discrimination between odors of individual males in a habituation-discrimination task, (b) preference for male over female odors, and (c) scent-marking in response to conspecific odors. Both lesion groups habituated to repeated presentations of a male's odor. However, only FNX females discriminated between scents of individual males, whereas PARA females did not. Neither lesion eliminated female preferences for male odors. Females with FNX lesions showed decreased levels of scent marking, but those with PARA lesions had more subtle deficits. Thus, the PARA, but not the subcortical connections of the hippocampus, is critical for discrimination of the odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of frontal cortex in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Orbital/agranular insular (ORB/AI) cortex has been implicated in traditional olfactory learning tasks and social behavior but its precise role in discriminating-learning social odors is not known. Female golden hamsters received aspiration lesions of ORB/AI or dorsomedial (DM) frontal cortex and were tested for their ability to (a) discriminate between odors of individual males in a habituation-discrimination task, (b) show preferences for male over female odors, and (c) scent-mark in response to male odors. Lesioned females readily discriminated between scents of individual males. Neither lesion altered female preferences for male odors. Females with DM lesions showed increased levels of scent marking to male odors, but those with ORB/AI cortex lesions did not differ from controls. Thus, ORB/AI cortex does not appear to be critical for discrimination of odors of individuals or sex or for scent-marking responses based on these discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunogold localisation of the intermediate chain within the protein complex of cytoplasmic dynein

Seasonal differences exist in the attractiveness of scents in meadow voles, Microtus pennsylvanicus. To determine whether photoperiodically induced changes in the attractiveness of a sex-specific scent is governed by melatonin, we implanted long-photoperiod male and female scent donors with a Silastic implant containing a 10-mm active length of melatonin, a 20-mm active length of melatonin, or no melatonin. The first experiment shows that 8 weeks of melatonin treatment is sufficient to induce long-photoperiod voles to produce scents that are no longer attractive to the opposite sex. The second experiment shows that a similar time course of melatonin treatment was sufficient to induce long-photoperiod females treated with melatonin to produce scents that are attractive to short-photoperiod females. Melatonin implants lowered the gonadal hormone titers and reduced the weight of the gonads of treated long-photoperiod voles to titers and weights that are characteristic of short-photoperiod voles. In both experiments, the behavioral and physiological effects were independent of whether scent donors received 10- or 20-mm implants of melatonin. Together, the results of the two experiments reveal that melatonin mediates the photoperiodically induced changes in gonadal hormone titers that control the seasonal differences in the sexual attractiveness of the anogenital area scent produced by meadow voles.     

Causes of scent marking in female golden hamsters (Mesocricetus auratus): Specific signals or classes of information?

Odor-elicited scent marking is common among mammals, but the proximate causes of marking are not well understood. Scent marking by female hamsters in response to 8 different male odors was investigated. Two odors (flank, mouth) increased flank marking and 2 (flank, rump) increased vaginal marking; in the latter case the effects of flank and rump odors were additive. Two odors (feces, urine) decreased flank marking but did not affect vaginal marking; other odors (foot, ear, ano-genital) had no influence on either scent-marking behavior. Results show that scent marking by females is influenced by a limited number of male odors, suggesting specific effects of particular odors. Classes of information (such as sexual identity) were not relevant causes of scent marking, as some odors containing such information were effective but others were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral discrimination between circumgenital odor from peri-ovulatory dominant and anovulatory female common marmosets (Callithrix jacchus)

Social peer groups of callitrichid monkeys [marmosets and tamarins] exhibit intrasexual dominance hierarchies in captivity. This laboratory study employed two-choice behavioral discrimination bioassys to test the hypothesis that scent from female common marmosets contains chemical cues that permit discrimination between dominant females in the periovulatory versus luteal phase of the ovarian cycle and females holding dominant versus subordinate status. When scent from only dominant females was presented, marmosets directed significantly greater amounts of investigatory behavior toward peri-ovulatory scent versus scent collected during the luteal phase of the ovarian cycle. Animals of both sexes demonstrated significant discriminatory behavior between scent deposited by dominant versus subordinate females, but only when the dominant female was in the peri-ovulatory phase of the ovarian cycle. Test animals directed equal amounts of investigative behavior toward scent from luteal-phase dominant females and subordinate females. Female test subjects deposited significantly more scent marks over presented scents than did male subjects, particularly when the scent had been donated by a peri-ovulatory female. Chemical odors specific to the periovulatory and luteal phases of the ovarian cycle may play a role in mediating behavioral interactions among marmosets.     

The role of scent marks in female choice of territories and refuges in a lizard (Podarcis hispanica).

Female mate choice based on male phenotypic traits is controversial in lizards, particularly in territorial species. In this study, we examine female choice of male scent marks in a territorial lacertid lizard (Podarcis hispanica) in which scent marks have been shown to signal male size (i.e., an important determinant of competitive ability in this species). Females were simultaneously exposed to three naturalized 4 m2 choice areas bearing: (1) no scent marks (i.e., control), (2) scent marks of large males, and (3) scent marks of small males. Although female lizards preferentially associated with scent marked choice areas, we found no evidence that females chose territories marked by large males. Furthermore, in response to experimentally induced dusk at the end of choice trials, females preferentially took shelter in refuges scent marked by small males. Our results suggest that, like males in this species, females are able to use male scent marks to assess the body size of resident territorial males, but do not show a preference for territories occupied by large males. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Responses to olfactory stimuli in spotted hyenas (Crocuta crocuts): II. Discrimination of conspecific scent.

Scent marking in spotted hyenas (Crocuta crocuta) includes the deposition of anal sac secretions, or "paste," and presumably advertises territorial ownership. To test whether captive hyenas classify and discriminate individuals using odor cues in paste, the authors conducted behavioral discrimination bioassays and recorded hyena investigation of paste extracted from various conspecific donors. In Experiment 1, subjects directed most investigative behavior toward scents from unfamiliar hyenas and members of the opposite sex. In Experiment 2, male hyenas discriminated between concurrent presentations of paste from various unfamiliar females in similar reproductive states. Thus, pasted scent marks convey information about the sex, familiarity, and even identity of conspecifics. Aside from territory maintenance, scent marking may also communicate information about individual sexual status. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Panoramic Search: The Interaction of Memory and Vision in Search Through a Familiar Scene.

How do observers search through familiar scenes? A novel panoramic search method is used to study the interaction of memory and vision in natural search behavior. In panoramic search, observers see part of an unchanging scene larger than their current field of view. A target object can be visible, present in the display but hidden from view, or absent. Visual search efficiency does not change after hundreds of trials through an unchanging scene (Experiment 1). Memory search, in contrast, begins inefficiently but becomes efficient with practice. Given a choice between vision and memory, observers choose vision (Experiments 2 and 3). However, if forced to use their memory on some trials, they learn to use memory on all trials, even when reliable visual information remains available (Experiment 4). The results suggest that observers make a pragmatic choice between vision and memory, with a strong bias toward visual search even for memorized stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions centered on the medial amygdala impair scent-marking and sex-odor recognition but spare discrimination of individual odors in female golden hamsters.

The medial amygdala (Me) has been implicated in various social behaviors that depend on chemosensory cues, but its precise role in discriminating and learning social odors is not known. Female golden hamsters (Mesocricetus auratus) received electrolytic lesions of the Me or sham surgery and were tested for their ability to (a) discriminate between odors of individual males in a habituation–discrimination task, (b) show preferences for male over female odors in a Y maze, and (c) scent-mark in response to male and female odors. All females discriminated between scents of individual males. In contrast, Me lesions eliminated female preferences for male odors in a Y maze. Females with Me lesions also showed a substantial reduction in vaginal marking and virtually no flank marking in response to odors. Thus, the Me in female hamsters is critical for differential investigation of opposite-sex odors and for scent-marking behavior but is not involved in discrimination between odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences Between Golden Hamsters (Mesocricetus auratus) and Norway Rats (Rattus norvegicus) in Preference for the Sole Diet That They Are Eating.

D. DiBattista (2002) reported that hamsters but not rats showed reduced preferences for the sole diet they had eaten for 10 days. In the current study, the authors fed Norway rats (Rattus norvegicus) a nutritious diet for either 3 or 10 days, then tested them either immediately or 1 or 3 days later. The authors found that like golden hamsters (Mesocricetus auratus), rats exhibited reduced preferences for a prefed diet but only if tested either immediately or 1 day after prefeeding, not if tested 3 days later (when D. DiBattista tested his hamsters). Rats and hamsters differed in the longevity, not the development, of reduced preferences for a palatable food eaten for several consecutive days. Such a response might aid dietary generalists in constructing balanced diets when no single available food is nutritionally adequate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dietary self-selection of golden hamsters in response to acute food deprivation and chronic food restriction.

Adult male golden hamsters were maintained on either Purina Rat Chow (Chow diet) or a self-selection diet consisting of high-protein chow, pure fat, and pure carbohydrate (Choice diet). In Experiment 1, animals were deprived of food for single periods of up to 48 hr. Animals on the Chow diet did not increase intake at any time after deprivation; animals on the Choice diet selectively increased their consumption of fat-derived calories and increased their total caloric intake during the first 6 hr of refeeding, but not thereafter. The nature of the diet did not influence the rate at which animals regained weight following deprivation. In Experiment 2, hamsters were placed on food-restriction schedules (access to food either for 1 hr/day only or on alternate days only) until they lost 20% of starting body weight. Chow-fed animals demonstrated little or no change in food intake either during or after food restriction. Hamsters on the Choice diet consumed more calories and lost weight more slowly than did chow-fed animals during 1-hr/day feeding; intake of fat-derived calories was elevated during restriction. Choice hamsters increased total caloric intake only towards the end of the alternate-days restriction schedule. Choice hamsters were hyperphagic following both types of food-restriction schedules, but no increased preference for fat-derived calories was observed. Factors influencing food consumption of hamsters in response to deprivation and restriction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory stimulation induces filial preferences for huddling in rat pups.

Rat pups of all ages huddle with conspecifics, but the sensory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present 2 experiments with 150 Sprague-Dawley rat pups indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in Ss from both scented and nonscented litters. Ss from scented nests preferred to huddle with a scented stimulus rat, whereas control Ss preferred a nonadulterated rat stimulus. Additional testing indicated that the affirmative preferences were specific to rearing odor and were not based on decreased aversion to test scents or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social Transmission of Flavor Preferences in Two Species of Hamsters (Mesocricetus auratus and Phodopus campbelli).

Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Angiotensin II receptor blockade in Syrian hamster (T0-2) cardiomyopathy does not affect microscopic cardiac material properties: implications for mechanisms of tissue remodeling

This study delineates the role of angiotensin II type I (AT1) receptor in the remodeling of Syrian cardiomyopathic hamsters. Twelve cardiomyopathic (T0-2) hamsters received L-158,809 treatment and libitum in their drinking water (27 micrograms/ml) and 9 cardiomyopathic and 9 normal FL-B hamsters received tap water from 1 to 4 months of age. Although pharmacologically effective with regard to complete suppression of the blood pressure response to angiotensin II infusion, L-158,809 did not diminish the progression or severity of cardiomyopathy. Heart weight/100 g body weight and left ventricular wall thickness adjusted for body weight of both L-158,809 and cardiomyopathic control hamsters did not differ and exceeded those of F1-B controls (p < 0.05). Myocardial material properties (e.g., stiffness and density) of cardiomyopathic hamsters treated with L-158,809 were not affected. Thus, the progression of fibrosis, calcification, and necrosis in T0-2 cardiomyopathic hamsters was not sensitive to AT1 receptor blockade.     

A comparison of liver protein changes in mice and hamsters treated with the peroxisome proliferator Wy-14,643

Interspecies differences in the liver response to Wy-14,643, a potent peroxisome proliferator in rats and mice, have been demonstrated. While both rats and mice show dramatic increases in the number of peroxisomes, the activity of peroxisomal enzymes involved in the beta-oxidation of fatty acids, and heptocyte replication, Syrian hamsters have a more moderate peroxisome proliferation response and no sustained increase in cell replication. Rats and mice, but not hamsters, develop hepatocellular carcinoma after prolonged exposure to Wy-14,643. To further characterize this species difference, two-dimensional gel electrophoresis (2-DE) has been used to compare the effect of 14-day exposure to various dietary concentrations of Wy-14,643 on liver protein expression in male mice and hamsters. Digitized images of the 2-DE protein maps were searched for significant changes. The peroxisome bifunctional enzyme (PBE) enoyl CoA hydratase/3-hydroxyacyl dehydrogenase, which migrates to the same position in mouse and hamster liver protein 2-DE patterns, increased in abundance by more than three times the control level in both mice and hamsters. In addition to the quantitative change in PBE, significant quantitative changes (P < 0.001) were found in 49 mouse liver proteins (47 decreasing and 2 increasing) and in 35 hamster liver proteins (27 decreasing and 8 increasing). There was little overlap in the mouse and hamster proteins showing quantitative changes in response to Wy-14,643, with the exception of PBE and one unidentified liver protein with an approximate molecular weight of 50,000. These results show that although peroxisome proliferation occurs in the livers of both mice and hamsters exposed to Wy-14,643, other species-specific changes in proteins occur that are independent of the peroxisome proliferation response and that could be related to species-specific susceptibility or resistance to liver tumor induction.