Joanna Kapusta

Prenatal stress modifies behavior in offspring of bank voles (Clethrionomys glareolus)

The aim of the present study was to investigate the effect of prenatal stress on behavior of adult bank vole males and females. Pregnant females were submitted to stress by short encounters of two females at the same stage of pregnancy, to crowded condition by transfer to a cage with four to five nonpregnant females, or stressed by immobilization. The stressors were applied on Days 13, 14, and 15 of pregnancy. The results indicate that prenatal stress influenced adult offspring behavior tested in the presence of the same sex, as compared to controls. Females and males differ in their reactions to stress. Prenatal stress decreased the nonaggressive behavior of females but males did not change their amicable approaches toward males. In bank vole males, prenatal social or immobilization stress increased aggression, but females made more attacks only after prenatal stressing by immobilization. This indicates that in bank vole females classical stressor involved different mediators from those associated with prenatal social stresses. Our results indicate that prenatal stress in bank voles decreases the social activity of female offspring and increases aggression in male offspring. Social stress applied to females in late pregnancy may increase the number of aggressive males in a population.

Gonadal hormones and intrasexual aggressive behavior in female bank voles (Clethrionomys glareolus)

The effects of gonadal hormones on aggressive behavior in the female bank vole was investigated in 10 min home cage tests. Ovariectomized (ovx) or intact females injected with oil, with progesterone (P), with a mixture of progesterone and estrogen (P+E), or with testosterone (T) alone were confronted in a resident-intruder test with unfamiliar, nonoperated females as intruders. Intact females showed aggressive behavior more frequently than ovx females. Ovx females injected with P, with P+E, or with T made significantly more attacks, and these attacks lasted longer than those observed for oil-treated voles. The results indicate that P, the typical female hormone, is responsible for aggressive behavior in female bank voles; however, only T increased the duration of interfemale aggression. Aggr. Behav. 24:63–70, 1998.

Ultrasonic calls of bank vole pups isolated and exposed to cold or to nest odor.

Bank vole pups produce ultrasounds when isolated from the nest, as other rodents do. The present study was intended to elucidate the possible interaction between the social stress of isolation from the mother and the physical stress of low ambient temperature during the nesting period. Although bank vole pups removed from nests and monitored at nest temperature vocalized at high frequency, the number and duration of signals increased at lower ambient temperature. In the tested voles it appears that exposure to cold was the most important stimulus of vocalization during the preweaning period. This effect can be enhanced by prolonged isolation from the mother, manifested as longer duration of calls. Moreover, vocalization was reduced not only by the odor from the home nest, but also by exposure to bedding of an alien lactating bank vole or even a lactating mouse fed the same diet. This suggests that the olfactory signals affecting the ultrasonic vocalization of bank vole pups probably are a mixture of volatile metabolites related to the physiological status and diet of rodent females. The reported experiments provide convincing evidence that the vocalization of bank vole pups is affected by isolation from the mother, by ambient temperature, and by olfactory signals released by lactating rodent females.

Interfemale aggression in adult bank voles (Clethrionomys glareolus)

Agonistic interaction may play a large role in shaping the social structure and spatial distribution of rodents such as Clethrionomys glareolus. Aggressive and non-aggressive behaviors of adult bank vole females were investigated with a home cage test during 10 min sessions. The number of attacks was significantly higher in virgin females kept with intact adult males than in singly reared females or those exposed to male urine. Bulbectomy of the tested females completely inhibited the male stimulating effect. This indicates that males influence the behavior of females by activating their olfactory systems. Aggressive behavior in pregnant or lactating females, which is linked to maternal behavior, was also tested. Female bank voles between 11 and 17 days of pregnancy or lactating at 3–4 days or 9–10 days attacked their partners significantly more frequently than virgins did. Females that had direct contact with males, even if they were not fertilized, appeared to be more successful in same-sex competition. Aggr. Behav. 24:53–61, 1998.

Aggression and vocalization behaviour of three sympatric vole species during conspecific and heterospecific same-sex encounters

The purpose of the present study was to compare the behaviour with vocalization of three sympatric species of voles during encounters within a species and during interactions between particular pairs of species. Bank voles, common voles and field voles were trapped in southeastern Poland and their behaviour and vocalization investigated using 10-min open field tests. Results showed clear differences in behaviour and vocalization between the species of voles. Bank vole interactions were more agonistic than those of common voles and of field voles as seen in the number of attacks, latency to the first attack and duration of attack. Females of the latter two species emitted significantly more ultrasounds than female bank voles. During male encounters common voles produced the highest numbers of ultrasounds. The ultrasonic calls emitted by female and male field voles occurred at a higher frequency (kHz) than those of both bank voles and common voles. The duration of these sounds was similar for all three species of voles. Voles in heterospecific encounters emitted very few ultrasounds. Our results have shown that ultrasounds are a part of bank vole, common vole and field vole behaviour and could play a significant role in vole communication.

ULTRASONIC RESPONSE OF CBA NEWBORN MICE TO BEDDING ODOUR

A drop in ambient temperature which increases thermogenesis is the fundamental factor stimulating ultrasonic vocalization in newborn rodents. Neonatal mice modify ultrasonic calling in response to olfactory cues. When removed from the nest and cooled, CBA-strain mouse pups produced ultrasonic calls on the 3rd, 5th and 7th days of life. The presence of conspecific bedding affected their ultrasonic vocalization. The number and duration of calls were higher in 3-day-old CBA pups exposed to bedding of C57BL lactating females than in newborns tested in the presence of bedding from CBA lactating females. This indicates that CBA pups discriminate between the odours of the two genotypes. The influence of postnatal experiences on the ability to differentiate odours was investigated. Three-day-old CBA mice nursed by their own mothers vocalized at higher frequencies than did newborns fostered by C57BL lactating females. It is suggested that ultrasonic vocalization in CBA pups is affected by genetic factors and postnatal environmental conditions.

Home bedding modifies ultrasonic vocalization of infant bank voles.

Bank vole,Clethrionomys glareolus, pups, similar to many other infant rodents, emit ultrasonic vocalizations when they are removed from the nest and cooled. Infants exposed to bedding from their home cage produced fewer and shorter calls than infants tested without bedding. Sound frequencies were significantly higher in infants exposed to home bedding than in other experimental groups. These results provide evidence that infant bank voles are able to identify the presence of home bedding, probably on the basis of odor. This appears to be the first report of shifts in frequency of pup ultrasonic calls in response to olfactory cues.

Male–female interactions and ultrasonic vocalization in three sympatric species of voles during conspecific and heterospecific encounters

Using ultrasonic vocalization, the present study examined the behaviour of three sympatrically living species of voles: common voles, field voles and bank voles during heterosexual encounters both within and between species. Voles were trapped in south-eastern Poland and their behaviour and vocalization investigated using 10-min open field tests. Conspecific heterosexual pairs of all three species of voles presented high social activity but the kind of behaviour was different. Bank vole male–female interactions were more agonistic than those of common voles and of field voles as seen in the number of aggressive approaches and latency to the first attack. Common voles and field voles emitted significantly more ultrasounds and spent longer time on the production of ultrasonic calls than bank voles. The duration of sounds was similar but the frequency of calls emitted by field voles was higher than those of common voles and bank voles. Voles in heterospecific encounters of male with female showed shorter duration of sniffing and emitted very few ultrasounds. The current work has shown that ultrasounds are part of male–female behaviour in common voles, field voles and bank voles and could play a significant role in vole communication.

Removal of the olfactory system modifies male bank vole behaviour in the presence of females

The role of the olfactory and vomeronasal systems of male bank voles in behavioural interaction with females was investigated. Bulbectomy (OBX), but not vomeronasalectomy (VNX), resulted in a decrease of female-stimulated ultrasonic calling by males, manifested as longer latency to the first call and fewer calls by OBX males in comparison to VNX or sham-operated (SHAM) animals. OBX males showed significantly fewer non-aggressive approaches but more attacks toward females. Females were less aggressive toward OBX males than toward VNX or SHAM animals, manifested as longer latency to the first attack and fewer attacks toward OBX males during 10 min encounters. The report may be regarded as the first evidence that bulbectomy of the male can evoke a behavioural reaction which in turn alters the activity of a female partner.

VOCALIZATION OF TWO PALAEARCTIC SPECIES OF HAMSTER: EVERSMANN HAMSTER ALLOCRICETULUS EVERSMANNI AND GREY HAMSTER CRICETULUS MIGRATORIOS

ABSTRACT This study compared the vocalization of two sympatrically occurring species of hamster: the Eversmann hamster Allocricetulus eversmann and the Grey hamster Cricetulus migratorius. The animals were tested in conspecific pairs for 5 min. Because of the high level of aggressiveness of both species, the hamsters were separated by a mesh partition, but they had olfactory, visual and acoustic contact. Female and male Eversmann hamsters vocalized more than those of Grey hamsters. This was expressed by emission of low-frequency calls as well as by ultrasounds. The difference in vocalization between the two species was also reflected in the basic structure of ultrasonic vocalizations. Grey hamster high-frequency (ultrasonic) pulses were longer and had larger bandwidths and lower minimum frequencies than Eversmann hamster calls. Within-species comparison of vocalization indicated that males of both species emitted fewer ultrasounds than females did. These differences could have an important role in communication within and between species living in the same area and preferring the same habitats.