Differences in affiliative behavior, pair bonding, and vaginal cytology in two species of vole (Microtus ochrogaster and M. montanus).

Prairie voles (Microtus ochrogaster) and montane voles (M. montanus) display marked differences in social organization in the field. Trios of 1 male and 2 females were studied in a large enclosure for a 10-day period. Prairie voles spent 59% of the observation time in side-by-side contact, whereas montane voles spent only 7% of the time in contact. Vaginal smears indicated female–female suppression of estrus in prairie voles; female montane voles appeared to cycle in the presence of males. Male prairie voles preferentially paired and nested with 1 of the females, and vaginal estrus generally followed pair formation by 2 days. Male montane voles did not spend time preferentially with either female, even after mating. These results suggest that the contrasting mating systems of these species result from differences in the propensity for affiliative behavior and social bonding rather than from mate availability or female receptivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Male preferences for unmated versus mated females in two species of voles (Micotus ochrogaster and M. montanus).

Examined male preference for unmated vs mated females in 2 species of voles, using 73 prairie voles and 78 montane voles in 2 testing situations each. In Exp I, conducted in a tether test situation, prairie voles spent significantly more time and copulated more with unmated than with mated females. In Exp II, male prairie voles spent significantly more time visiting and investigating anesthetized unmated females than anesthetized mated females. In Exp III, male montane voles showed no significant visitation or copulatory preference for unmated vs mated females in the tether situation. In Exp IV, male montane voles spent more time with unmated, anesthetized females than mated females but displayed no other significant differences. In general, male prairie voles appeared more discriminating in their mate choice than male montane voles. These differences are consistent with differences in male parental effort in the field. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female regulation and choice in the copulatory behavior of montane voles (Microtus montanus).

To study female choice of mating partners in montane voles, a male was tethered at each end of an elongate chamber, and an estrous female was allowed to move betweeen the 2 males and a neutral area. In Exp I, using 16 females and 32 males, females with a choice of 2 gonadally intact males copulated preferentially with 1 of them. Preferred males were more effective than nonpreferred males at gaining intromission and had more thrusts per intromission. In Exp II, with 10 females, 10 castrated males, and 10 sham-operated males, females spent more time with and mated preferentially with intact rather than castrated males. It is therefore suggested that the opportunity to copulate is reinforcing for female voles and that they display distinct preferences, correlated with copulatory stimulation, for some partners. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of the social environment on parental behavior and pup development of meadow voles (Microtus pennsylvanicus) and prairie voles (M. Ochrogaster).

Parental behavior and pup development in meadow and prairie voles were examined. Social units were manipulated for the presence of fathers and of juveniles. Meadow vole mothers alone with pups showed less maternal care and spent more time resting than did mothers with juveniles or with fathers and juveniles. Pups reared only with mothers developed faster than did pups under other conditions. Number of animals in the social unit was negatively correlated with the rate of pup development. Meadow vole fathers and juveniles showed no parental care. In contrast, prairie vole mothers spent less time in the nest when both fathers and juveniles were present. Fathers assisted in rearing pups, and litters developed more rapidly when fathers were present. Juveniles remained in the natal nest and engaged in parentlike behavior. The findings relate to differences in the life history strategy for the 2 vole species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in spatial ability and activity in two vole species (Microtus ochrogaster and M. pennsylvanicus).

The hypothesis that sex differences in maze learning result from sex differences in activity was tested with wild-caught prairie (Microtus ochrogaster) and meadow (M. pennsylvanicus) voles. For 38 voles error production and activity were simultaneously measured in a series of 7 symmetrical mazes. Repeated-measures analyses of variance (ANOVAs) examined species, sex, maze, and interaction effects for 3 dependent variables: errors, activity, and errors/activity. The pattern of significant effects was very different for the errors and activity ANOVAs, which suggests that differential activity cannot explain differential error rates. In contrast, the pattern of effects was very similar for errors and errors/activity ANOVAs, which suggests that controls for activity do not remove differences in error production. These results fail to support the activity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Species differences in the vasopressin-immunoreactive pathways in the bed nucleus of the stria terminalis and medial amygdaloid nucleus in prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus).

Vasopressin-immunoreactive (AVP-ir) cells in the bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MAN) and their AVP-ir projections to the lateral septum were studied in monogamous prairie voles (Microtus ochrogaster) and promiscuous meadow voles (M. pennsylvanicus). A sexually dimorphic AVP-ir pathway was found in both species; males had more AVP-ir cells in the BST and MAN, as well as denser AVP-ir fibers in the lateral septum, than did females. A significant species difference was also found. Overall, meadow voles had more AVP-ir cells in the BST and MAN than did prairie voles. Male prairie voles, however, had a higher density of AVP-ir fibers in the lateral septum than male meadow voles. The species difference in the sexually dimorphic AVP-ir projections in the BST and MAN is implicated in the rodents' different life strategy and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental exposure to oxytocin facilitates partner preferences in male prairie voles (Microtus ochrogaster).

The authors investigated the effects of postnatal manipulations of oxytocin (OT) on the subsequent tendency to form a partner preference in male prairie voles (Microtus ochrogaster). Neonatally, males received either an injection of OT, an oxytocin antagonist (OTA), 0.9% saline vehicle, or handling without injection. As adults, males were tested for partner preference following 1 hr of cohabitation with a nonestrous female. In a 3-hr preference test, males neonatally exposed to exogenous OT exhibited a significant partner preference, not seen in males receiving OTA or saline. Both OT and OTA voles had significantly higher levels of social contact than saline controls. A single neonatal injection of OT increased both total and selective social behaviors in male prairie voles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A possible function of the preference for hind nipples in prairie voles (Microtus ochrogaster).

Prairie vole pups (Microtus ochrogaster) in laboratory cages prefer hind nipples. In this research, the author observed 8 litters of prairie voles in a seminatural environment to confirm the preference for hind nipples and to determine if young on hind nipples were groomed more frequently or dislodged less frequently than were young on other nipples. Prairie vole pups in seminatural environments preferred hind nipples; this preference was illustrated by the progressive use of more anterior nipples only as litter size increased and by the reluctance of pups to voluntarily release their hold on hind nipples. Maternal grooming of young did not vary with suckling location. Prairie vole young on hind nipples, however, were dislodged less frequently than were young on other nipples. Less frequent dislodgment from hind nipples during maternal movements may play a role in the preference for hind nipples in prairie voles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual activity and satiety over an extended observation period in prairie voles (Microtus ochrogaster).

This study was designed to delineate the course of sexual satiation in prairie voles (Microtus ochrogaster). Fourteen male–female pairs were allowed to copulate freely for 24 hr under continuous observation. Copulations occurred predominantly during the first few hours and decreased in frequency thereafter. The mean number of ejaculations per pair was 5.6 (range, 2–9). Two thirds of the ejaculations occurred during the first 3 hr, and over 90% took place within the first 7 hr after the first intromission. No ejaculations were observed during the last 8 hr. These results suggest that male capacity to deliver ejaculations to a female is limited and that direct observations reveal a more limited capacity than observations made with time-lapse videotape. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vasopressin in the lateral septum regulates pair bond formation in male prairie voles (Microtus ochrogaster).

Male prairie voles (Microtus ochrogaster) form a pair bond with a female partner after mating, and this behavior is regulated by the neuropeptide vasopressin (AVP). The authors report that AVP in the lateral septum is important for pair bond formation. Administration of an AVP receptor antagonist in the lateral septum blocked mating-induced pair bonding, whereas administration of AVP induced this behavior in the absence of mating. In addition, administration of an oxytocin (OT) receptor antagonist in the lateral septum also blocked pair bond formation induced by either mating or AVP administration, suggesting that the OT receptor blockade may have interfered with the AVP regulation of behavior. Together, these data provide evidence suggesting that AVP in the lateral septum regulates pair bond formation in male prairie voles and that this process requires access to both AVP and OT receptors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social influences on parental and nonparental responses toward pups in virgin female prairie voles (Microtus ochrogaster).

Pair-bonded prairie votes (Microtus ochrogaster) are biparental after the birth of pups. However, whereas most adult virgin males are parental, most virgin females are not. In 6 experiments, influences on the parental behavior of virgin female prairie votes were examined. It was found that (a) young virgin females were more maternal than older females, (b) the postweaning sex ratio of cage-mates did not affect females' responses to pups, (c) females raised to adulthood with their parents and younger siblings present were highly parental, (d) 48-hr exposure to pups beginning at weaning increased some aspects of later maternal responding, (e) rearing to adulthood with the parents even in the absence of younger siblings also increased females' maternal responding, and (f) the increase was seen only if both parents were present. Continued parental presence promotes alloparental behavior, possibly important if daughters do not disperse from the natal nest. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of oxytocin and vasopressin on partner preferences in male and female prairie voles (Microtus ochrogaster).

This study compared the effects of centrally administered oxytocin (OT) and arginine vasopressin (AVP) on partner preference formation and social contact in male and female prairie voles (Microtus ochrogaster). After 1 hr of cohabitation and pretreatment with either AVP or OT, both males and females exhibited increased social contact and significant preference for the familiar partner. After pretreatment with either an OT receptor antagonist (OTA) or an AVP (V1a) receptor antagonist (AVPA), neither OT nor AVP induced a partner preference. In addition, treatment with OT?+?OTA or AVP?+?AVPA was associated with low levels of social contact in both sexes. Either AVP or OT is sufficient to facilitate social contact if either the OT or AVP receptor is available. However, the formation of partner preferences may require access to both AVP and OT receptors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female meadow voles (Microtus pennsylvanicus) demonstrate same-sex partner preferences.

Female meadow voles (Microtus pennsylvanicus) are territorial during warm months but demonstrate social tolerance under low temperatures. In spring, females nest together and some pairs participate in communal nursing and rearing of young. Because communal nursing involves significant cooperation, selective pair-bonds may develop between 2 nestmates. Using a choice apparatus, the authors determined that (a) captive females demonstrated partner preferences for a nestmate; (b) partner preferences were enduring and persisted after dyadic separation; and (c) following the loss of a nestmate, females did not develop preferences for a new nestmate, even after extended cohabitation. Data support the hypothesis that captive meadow voles develop selective and enduring same-sex social bonds that may, under free-living conditions, facilitate communal nesting and cooperative rearing of young. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine D2 receptors in the nucleus accumbens are important for social attachment in female prairie voles (Microtus ochrogaster).

The prairie vole (Microtus ochrogaster), a monogamous rodent that forms long-lasting pair bonds, has proven useful for the neurobiological study of social attachment. In the laboratory, pair bonds can be assessed by testing for a partner preference, a choice test in which pair-bonded voles regularly prefer their partner to a conspecific stranger. Studies reported here investigate the role of dopamine D2-like receptors (i.e., D2, D3, and D4 receptors) in the nucleus accumbens (NAcc) for the formation of a partner preference in female voles. Mating facilitated partner preference formation and associated with an approximately 50% increase in extracellular dopamine in the NAcc. Microinjection of the D2 antagonist eticlopride into the NAcc (but not the prelimbic cortex) blocked the formation of a partner preference in mating voles, whereas the D2 agonist quinpirole facilitated formation of a partner preference in the absence of mating. Taken together, these results suggest that D2-like receptors in the NAcc are important for the mediation of social attachments in female voles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of experience and motivation on symmetrical-maze performance in the prairie vole (Microtus ochrogaster).

Sex differences in spatial skills are sometimes attributed to sex differences in spatial experience. This hypothesis rests on two assumptions: Spatial experience typically differs with sex, and spatial experience has lasting effects on spatial cognition. We tested the latter assumption in a controlled experiment with wild-caught prairie voles (Microtus ochrogaster) and their spatially deprived, laboratory-reared, first-generation offspring; we found the assumption to be unjustified. Although major differences in spatial experience had no effect on maze performance, relatively small differences in motivation produced a significant difference in error rates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paternal behavior is associated with central neurohormone receptor binding patterns in meadow voles (Microtus pennsylvanicus).

Paternal and nonpaternal voles (microtus) have different arginine-vasopressin (AVP) and oxytocin (OT) receptor patterns in the extended amygdala, a neural pathway associated with parental behavior. Using receptor autoradiography, the authors examined whether AVP and OT receptor patterns were associated with facultative paternal behavior in either sexually and parentally inexperienced or experienced meadow voles (Microtus pennsylvanicus). Experienced, in contrast to inexperienced, males had less AVP binding in the lateral septum (LS), more AVP binding in the anterior olfactory nucleus (AON), and more OT binding in the AON, bed nucleus of the stria terminalis, LS, and lateral amygdala. Thus, specific AVP receptor patterns, which co-occur with paternal care in consistently paternal voles, also may be associated with paternal care (when present) in typically nonpaternal species. This study also demonstrated a possible relationship between OT receptor patterns and paternal state in male mammals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three experiments on mate choice in meadow voles (Microtus pennsylvanicus).

Species differences in selectivity with respect to mate choice have been hypothesized to be related to mating systems. Procedures used in 3 previous experiments on monogamous prairie voles (Microtus ochrogaster) and polygamous montane voles (M. montanus) were used with polygamous meadow voles (M. pennsylvanicus). The expectation was that meadow voles would show few preferences. Female meadow voles preferred mating with familiar versus unfamiliar males but displayed no preference for unmated versus mated males. Male meadow voles displayed no preference for unmated versus mated females. The results are partially consistent with the hypothesis that relates mate choice to social and mating system, as this polygamous species resembles polygamous montane voles species in 2 situations but is similar to monogamous prairie voles in the 3rd. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social transmission and memory of food preferences in pine voles ( Microtus pinetorum ).

The social transmission of food preferences is affected by factors including the length of time preference is maintained. The authors investigated the-social transmission of food preferences in pine voles (Microrus pinelorum) and whether food items had to be present for memory to persist. A demonstrator vole was fed cocoa-flavored food, a nonpreferred food. After interacting with a demonstrator vole, observer voles prefer-red cocoa-flavored food as compared with either naive voles that had not interacted with demonstrators or voles that had been exposed to odors. Observers retained the preference for 72 hr after interacting with an observer whether or not flavored foods were present. The ability to learn which food items are palatable and safe may benefit a generalist herbivore that has face selection to avoid toxic baits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Place learning by three vole species (Microtus ochrogaster, M. montanus, and M. pennsylvanicus) in the Morris swim task.

Place learning was assessed in 3 species of voles (Microtus ochrogaster, M. montanus, and M. pennsylvanicus) with the Morris swim task. The performance of all 3 species and both sexes improved with training on the hidden-platform version of the Morris swim task, which indicates that all groups were able to learn to locate a spatial goal without local cues. Contrary to expectations, no evidence for a sex difference in spatial ability emerged in any of the species. These findings do not provide support for current hypotheses that emphasize a positive correlation between home-range size and laboratory measures of spatial ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive significance of the copulatory behavior pattern of male meadow voles (Microtus pennsylvanicus) in relation to induction of ovulation and implantation in females.

Investigated the adaptive significance of 2 attributes of the male vole copulatory behavior pattern, its elaborateness, and distinct temporal patterning in relation to the induction of ovulation and implantation in females. In Exp I (58 Ss) elaborateness of the male behavior pattern, as evidenced by extensive preejaculatory behavior and multiple ejaculatory series, was necessary for maximal ovulation and implantation in meadow vole females, especially older females. In Exp II, 16 male meadow voles were able to elicit ovulation and luteal activation in 51 females of 2 other Microtus species, even though the temporal patterning of male meadow vole behavior was completely different from the patterning of the females' conspecific males (20 Ss). Implantation did not occur apparently because of incomplete ova development. It is suggested that in Microtus a coadaptation exists between male behavior pattern and female stimulation requirements with respect to amount of stimulation but not to the specific temporal patterning of the stimulation. It is unlikely, therefore, that the different patterns of male copulatory behavior in Microtus would be effective in maintaining reproductive isolation among sympatric species. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)