Małgorzata Kruczek

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.

CONTEST WINNING AND METABOLIC COMPETENCE IN MALE BANK VOLES CLETHRIONOMYS GLAREOLUS

Famale bank voles prefer dominant males as mates, and it has been suggested that this preference may benefit females genetically, via increased fitness of their progeny. This requires that male ability to win intrasexual contests is associated with their genetic quality. An important aspect of individual quality is metabolic competence. Here, we investigated whether male ability to win contests is correlated with aerobic capacity (the maximum rate of oxygen consumption) or factorial aerobic scope (the ratio of aerobic capacity to basal metabolic rate [BMR]). The ability to win was assessed as proportion of dominant behaviours in staged contests with five other males, and aerobic capacity was measured both during exercise (swimming) and during cold-exposure trials. Contest winning ability was not correlated with the aerobic capacity (p > 0.6), the factorial metabolic scope (p > 0.25) or BMR (p = 0.24; all the traits were corrected for the effect of body mass). Thus, the results indicate that the trait (male dominance) subject to female preference in the bank vole fails to reveal an important aspect of male quality, i.e. his metabolic competence.

Behavioural development of conspecific odour preferences in bank voles, Clethrionomys glareolus.

Biological odours of conspecifics are known to have strong influences on behavioural interaction in bank voles Clethrionomys glareolus. This experiment tested two hypotheses. (1) Olfactory cues from familiar and unfamiliar mature opposite-sex conspecifics differ in their attractiveness to males and females, and their behavioural reactions change with age. (2) A genetically based mechanism is involved in female recognition of kin.In a two-choice preference test, prepubertal males and females were more attracted to familiar than to unfamiliar odours of opposite-sex conspecifics, as manifested by more time spent sniffing familiar voles. As the young reached sexual maturity they shifted their odour preferences. Mature males and females preferred the novel odour of unrelated opposite-sex conspecifics to that of relatives. The results of experiments testing the second hypothesis indicate that females use a genetically based mechanism to recognise their kin. Young and mature females were able to recognise the odour of their biological but socially unknown fathers, and showed the same pattern of behaviour as females in previous experiments.The possible biological functions of kin recognition in bank voles are discussed.

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.

Seasonal variations in male mice at the time of sexual maturation

The sexual maturation of male mice reared under constant laboratory conditions was studied in animals born in different months of the year. The body weights were significantly affected by the month of birth. Males born in March and May were heavier at 4 and 5 weeks of age than those born in autumn and winter. As indicated by the relative weights of accessory glands, males born in spring matured earlier compared with animals born in other months of the year. Variation in the relative testicular weights during maturation was not influenced by the month of birth. Female mice also showed a significant relationship between the month of birth and sexual maturation. Females born in March reached puberty, as measured by the age of vaginal opening and first oestrus, earlier than those born in other months of the year.

Female bank vole (Clethrionomys glareolus) recognition: preference for the stud male

Pregnant and nursing bank vole (Clethrionomys glareolus) females were investigated for their ability to recognize their mated male on the basis of chemical cues. In a two-choice test pregnant females showed a strong preference, manifested by higher frequency of sniffs and time spent sniffing, to the odour of a stud male over that of unfamiliar male, but only during the days after insemination and around implantation. As gestation proceeds females exhibited no affinity for either of these two kinds of males. Olfactory bulbectomy abolished a pregnant females preference for her stud male. A lactating female chose the odour of her sexual partner untill the time of weaning of her young. Separation of the female from her pups during the early post partum period shortens the time of memory for the scent of the stud male. The results indicate that bank vole females form olfactory memory to the odour of stud males and its duration depends on physiological state of the females.

Mating behaviour of bank voles (Clethrionomys glareolus) modified by hormonal and social factors

Summary The bank vole is a common European rodent. In a natural population the adult females are territorial, and during the breeding season each females home range overlaps with the home range of several males. The aim of the present study was to investigate the influence of sexual experiences of females and males on mating behaviour. The results indicate that the activity of the female was modified by her sexual experience and by the experience of the partner. Females were more active in presence of sexually non-experienced than experienced males. Males also showed higher activity in the presence of virgin than in the presence of experienced females. Females in postpartum estrus were more active than virgins and injection of gonadotropins stimulated virgin females. Males tested with gonadotropin-treated virgin females or postpartum estrous females showed similar sexual activity. Sexual experience increased the activity of males; they approached receptive females frequently and exhibited a higher number of mountings than did non-experienced males. The higher activity of an experienced partner can prevent copulation with another male during the same estrus, so that only one male becomes the father of the offspring. The present results indicate that in sexually experienced males bulbectomy but not vomeronasalectomy decreased the sexual activity and only 2 out of 6 lesioned males copulated with receptive females.

Female-Induced Delay of Puberty in Bank Vole and European Pine Vole Females

In several species of rodents, the rate of sexual maturation and density of natural populations are negatively correlated (Krebs and Myers, 1974). Chemical signals discharged by females could be one of the important factors limiting reproductive activity.

Copper influence on bank vole’s (Myodes glareolus) sexual behavior

The impact of human activity on the environment has led to a steady increase of the amounts of copper in the ecosystems. This element accumulates in plants and water, potentially exposing rodents to its harmful effects. In industrial districts, a decrease in the density of small rodent populations has been observed. This decline may be caused by many factors, including mortality, decreased fertility, or impaired sexual behavior. The decline in the reproductive abilities of small rodents after copper exposure was demonstrated in our previous work (Miska-Schramm A, Kruczek M, Kapusta J, Ecotoxicology 23:1546–1554, 2014). The aim of the presented research was to determine how copper administered at concentrations similar to those recorded in industrial districts (Cu I-150 mg/kg, Cu II-600 mg/kg, C-control) affects the sexual behavior of small rodents. The model species was the bank vole (Myodes glareolus). The behavior and vocalizations of male-female pairs were recorded during open-field tests: ♂C vs. ♀C; ♂Cu I vs. ♀C; ♂Cu II vs. ♀C while in preference tests, female behavior was assessed in the following combinations: ♀C vs. ♂C & ♂Cu I; ♀C vs. ♂C & ♂Cu II. In the presented work, we show that copper decreased the males’ sexual attractiveness. Females showed suppressed preference towards males treated with 600 mg/kg copper. The number of sniffs and a number of approaches towards Cu II males was significantly lower than towards control individuals. Also, in preference test with 150 mg/kg treated animals, total activity was lower towards copper treated animals. At the same time, copper did not influence intra-sexual interactions.