Agonistic behaviour in males of five species of voles Microtus

Agonistic behaviour of Microtus pennsylvanicus, M. montanus, M. californicus, M. longicaudus, and M. ochrogaster was observed in 160 staged encounters; a natural observation of sympatric species is included. No difference in the character and movements of agonistic behaviour was apparent when arena size was reduced; only a difference in the frequency of postures and movements was observed. In the smaller arena, M. montanus and M. ochrogaster exhibited a significant increase in frequency of agonistic components. The other three species did not show a significant increase. In interspecific pairings, M. montanus won over M. pennsylvanicus, M. californicus and M. longicaudus; M. ochrogaster won over M. montanus and M. pennsylvanicus. Three species used mutual avoidance in maintaining individual distance.     

The effects of mate removal on pregnancy success in prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus).

The effects of removing the stud male have not been controlled in many studies relating pregnancy block to the presence of an unfamiliar male. We examined the effects of removing the male on pregnancy success in prairie voles and meadow voles, two species that differ in degree of paternal investment. Whereas prairie vole males provide extensive care to offspring and accelerate pup development, meadow vole males display little or no care and delay development of pups. We predicted that removal of the stud male would decrease pregnancy success in prairie voles and either have no effect or increase success in meadow voles. In experiment 1, females were in male-induced estrus, and their mates were either left with them or were removed 4 h, 1 day, 2 days, or 8 days after mating. In experiment 2, females were in postpartum estrus, and their mates were either left with them or were removed 1 day, 2 days, or 8 days after birth of their first litter. Removal of the male soon after mating in postpartum estrus decreased pregnancy success in prairie voles and increased success in meadow voles. Thus, although removal of the stud male influenced litter production, the direction of the effect varied with species.     

Sibling recognition in the prairie vole, Microtus ochrogaster

Since mating is seldom observed between sibling prairie voles, Microtus ochrogaster, this, behavioural discrimination was used to investigate sibling recognition in this species. Cross-fostering of 1–3-day-old pups demonstrated that unrelated pups reared together did not breed, whereas siblings reared apart bred readily when paired at weaning. When unrelated voles were paired at 14 days of age, prior to sexual maturity, significantly fewer pairs bred than when strangers were paired at 21 days of age. Separation of 21-day-old siblings for 8 days before pairing overcame incest avoidance; a 15-day separation was required for breeding by siblings that had remained together until they were 50 days old. These results indicate that sibling recognition and, consequently, incest avoidance depend on association prior to weaning.     

Ovulation and implantation in montane voles (Microtus montanus) as a function of varying amounts of copulatory stimulation

Estrous female voles (Microtus montanus) received (a) no copulation, (b) one ejaculatory series, (c) two ejaculatory series, or (d) more than two series. Copulation was shown to be essential for ovulation, and increasing amounts of copulatory stimulation were demonstrated to increase the probability of ovulation. Only 25% of females receiving one ejaculatory series ovulated, whereas 100% of those receiving more than two series ovulated. Thus, multiple ejaculations play an important role in successful reproduction in this species.     

Short-term, postcopulatory changes in receptive and proceptive behavior in the female syrian hamster (Mesocricetus auratus)

The interactions between male and female hamsters were recorded in terms of proximity (approaching, leaving, and following by each member of the pair). The time spent sniffing the partner was also recorded. Mated and unmated females were tested three times on the day of estrus and once on the day following estrus. As expected, receptivity declined rapidly in mated but not unmated females. None of the proximity measures changed during estrus in the unmated females. However, female approaching (Ap% ≈ female approaches as percentage of all approaches) decreased 1–3 hr after mating and was associated with a decline in a number of measures of female proceptive behavior. Female leaving (L% = female leaves as percentage of all leaves) did not change. In unmated females Ap% has decreased and L% has increased by the day after estrus (Day 2 of the estrus cycle). In mated females the decrease in Ap% is accelerated (occurring within the 3 hr after mating) and precedes a change in L% which has occurred by the day after estrus (Day 1 of pregnancy). Thus, mating brings about not only a decrease in receptivity, as has been shown for several species, but also a change in female proceptive behavior and in her stimulus value to the male.     

Mating Behavior of Mahanarva spectabilis (Hemiptera: Cercopidae) Under Laboratory Conditions

The mating behavior of Mahanarva spectabilis (Distant) was studied under laboratory conditions. Virgin adults were individually maintained in transparent cages for observation of the mating sequence. Mating behavior of 23 couples was monitored during the photophase portion of the day. Copulation was observed in 17 of the 23 pairs. The mating sequence includes male approaching the female, mounting of the female, and copulation. Of the 17 mating pairs, 70.6 % mated on the second day after emergence. Most of the copulations began between 8 and 9 h after the onset of photophase. The average duration of copulation was 268?±?24.9 min, and most pairs mated once or twice during their lifetimes. The mating behavior of M. spectabilis is important to understand because it determines the age and ideal time for further behavioral testing, which is essential for determining the cues involved in the communication system of the species.     

Effect of melengestrol acetate (MGA) treatment or temporary kid removal on reproductive efficiency in meat goats

The use of melengestrol acetate (MGA; Summer) or temporary kid removal (4 weeks postpartum; Fall) for inducing/synchronizing estrus was evaluated in goats. In the first trial, 47 does were group-fed a commercial diet to provide 0.25 mg MGA/doe daily (n = 25) or a control diet (n = 22) for a period of 10 days. Twenty-five of the does lambing in the fall from this experiment were used in a second experiment. Beginning on day 28.1 ± 0.8 of lactation, kids from 13 does (kid removal) were removed from their dams for 2 days while kids from the remaining 12 does (control) remained with the dams. Mature bucks wearing marking harnesses were introduced for mating at the end of MGA treatment (Experiment 1) or at the time of kid removal (Experiment 2). Does fed MGA were mated approximately 2.1 days earlier (P < 0.05) than control does. The percentage of does mated (84% versus 100%), pregnancy rate (58% versus 90%), and kidding rate (58% versus 90%) was lower (P < 0.05) for the MGA-treated versus the control does, respectively. In Experiment 2, does with kids removed were mated approximately 1.3 days earlier than the control does, but the mean weaning weight of the kids (11.0 ± 0.4 kg for both treatments) was not influenced by treatment. The mean pregnancy rate, kidding rate, kid birth weight, or kid weaning weight was not influenced by treatment and averaged 73.0 and 79.0%, 3.3 ± 0.2 and 16.8 ± 0.7 kg for both treatments, respectively. Overall, although not necessary for mating, a decreased time to first mating and increased synchrony of estrus followed both MGA treatment or temporary kid removal. This may be implemented if improved estrus synchrony is desired. However, more research is needed to overcome the decreased fertility recorded following MGA use.     

Self-grooming and sibling recognition in meadow voles,Microtus pennsylvanicus,and prairie voles,M. ochrogaster

Self-grooming in response to the odours of an opposite-sex conspecific may reflect sexual motivation on the part of the actor. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, and prairie voles,M. ochrogaster , both self-groom at different rates when exposed to the odours of their siblings as compared to those of nonsiblings. This prediction was studied under the context of social memory for siblings and the effects of isolation on memory for siblings. The hypothesis explains the self-grooming responses of meadow voles isolated from their siblings for 10 days and of prairie voles isolated from their siblings for 20 days. However, 20 days of isolation for male and female meadow voles, and 30 days of isolation for male prairie voles were sufficient to induce these animals to self-groom at a similar rate to both sibling and nonsibling odours, suggesting that after isolation these animals no longer recognized their opposite-sex siblings. Female prairie voles isolated for 30 days self-groomed more in response to the odours of male nonsiblings than to those of male siblings, suggesting that female prairie voles still recognize their male siblings after isolation. This study is the first to provide empirical evidence that, in the context of sibling recognition, self-grooming behaviour is directed at unfamiliar opposite-sex conspecifics, and that the communicative function of self-grooming (sexual motivation) is associated with social memory for siblings. Differences in the self-grooming behaviour of meadow voles and prairie voles may be associated with several aspects of their life history characteristics.     

Postpartum copulatory and maternal behaviour in Norway rats under seminatural conditions

Virgin female rats were mated at a freely cycling oestrus, and then again with the same males at the subsequent postpartum oestrus. Copulatory behaviour at each mating was compared and the temporal patterning of the female's mating and maternal behaviour was analysed. Postpartum females were found to conserve the number of ejaculatory series received, yet the series were shorter, resulting in a shorter time being occupied, by this mating. During mating, females spent little time with their litters, and then mainly in the post-ejaculatory intervals. Ejaculatory series were rarely disrupted by nesting. The postpartum female rat seems to engage in behavioural time-sharing.     

The biosynthesis of the male housefly accessory secretion and its fate in the mated female

Autoradiographic studies of ejaculatory ducts from male houseflies, Musca domestica, previously injected with either tritiated arginine, lysine, or histidine showed that only arginine and lysine were incorporated into the stored accessory secretion. Scintillation spectrophotometry indicated that the amount of [³H] arginine incorporated into the duct correlated with the number of times the male had previously copulated. Cycloheximide and actinomycin D were effective in inhibiting the uptake of [³H] arginine in the ejaculatory ducts of newly emerged males, but only cycloheximide was an effective inhibitor in older males that had mated repeatedly. Autoradiography and electron microscopy showed that during mating the accessory secretion was transferred to the vaginal pouches of the female and that within 10 min after mating began, it was penetrating the intimal lining of the pouches. Cytolysis of many of the cells of these pouches was correlated to the transfer of the secretion during mating. This transfer of the secretion apparently terminated about 40 min after copulation began, although mating usually continued for an additional 10 to 20 min. The amount of ³H-labelled material in the haemolymph of the females increased until the completion of mating and then decreased about 60 per cent after 8 hr.     

Food Deprivation and Restriction During late Gestation Affect the Sexual Behavior of Postpartum Female Meadow Voles,Microtus pennsylvanicus

In many species of small mammals, including meadow voles, Microtus pennsylvanicus, females come into postpartum estrus (PPE) within 12–24 h of giving birth, allowing them to mate and become pregnant while raising the current litter. PPE females show increases in attractivity, proceptivity, and receptivity, the three components of sexual behavior, relative to females not in PPE. Several studies have shown that food deprivation and restriction reduce attractivity, proceptivity, and receptivity of females not in PPE. We tested the hypothesis that food deprivation and restriction during late gestation cause deficits and decrease the attractivity, proceptivity, and receptivity of females when they enter PPE. Our data support the hypothesis. On day 1 of lactation, females that were food deprived and food restricted produced scent marks that were significantly less attractive as those produced by control PPE females. Food deprivation but not food restriction caused females to no longer display significant preferences for the scent marks of males over those of females (proceptivity). Food deprivation and food restriction were sufficient to induce females to become significantly less sexually receptive than control females. Eleven of 12 control PPE females mated, 4 of 12 food‐restricted females mated, and 3 of 12 food‐deprived females mated. Dams facing food deprivation or restriction during late gestation may have to balance the benefits of mating during PPE with the increased costs associated with getting pregnant while they are lactating.     

A comparison of paternal behaviour in the meadow vole Microtus pennsylvanicus,the pine vole M. pinetorum and the prairie vole M. cchrogaster

Paternal care in microtines has been studied infrequently and few studies have compared patterns of direct and indirect paternal investment. The paternal behaviour of three vole species, the meadow vole (Microtus pennsylvanicus), the pine vole (M. pinetorum) and the prairie vole (M. ochrogaster) was examined in a semi-natural setting. Prairie and pine voles were found to exhibit high levels of paternal care. Prairie vole males contributed the most direct care by remaining in the natal nest for long periods of time in contact with the pups. Pine voles contributed less direct care than prairie voles as they spent less time in the natal nest with their offspring. In addition, both prairie and pine vole males were observed to groom their pups and retrieve them back to the nest area. Prairie vole males also engaged in such indirect forms of care as nest construction and maintenance, while pine voles provided indirect care in the form of tunnel construction and food caching. Meadow vole males were the least paternal of the three species and rarely engaged in either direct or indirect care. These findings support predictions that M. pennsylvanicus is promiscuous and that male and female meadow voles occupy separate territories. They are also consistent with studies which indicate that prairie and pine voles are monogamous and have a structured social organization with members interacting closely with one another.     

Geographic differences in the sociability of voles in relation to cyclicity

Bank voles, Clethrionomys glareolus, and field voles, Microtus agrestis, redistribute food hoards and alter the location of their activity upon the introduction of a foreign conspecific in laboratory experiments. This behaviour showed geographic variation in C. glareolus but no clear geographic variation in M. agrestis; north Swedish cyclic C. glareolus were repelled by the new animals while southern non-cyclic C. glareolus were attracted. There were no differences between animals from various population phases at the same locality. The geographic differences were retained in laboratory-born animals kept in an abnormal social environment. Other studies have demonstrated similar differences in M. agrestis. Cyclic voles may be negatively affected by density-related stimuli while non-cyclic ones may instead gather in environments that are fairly safe from predators.     

Sex and the Single Vole: Effects of Social Grouping on Prairie Vole Reproductive Success

Prairie voles (Microtus ochrogaster) have a mating system that is primarily monogamous with paired males and females together defending breeding space against intruders of either sex. Breeding success may be affected when other adults intrude on the territorial space of pairs. We conducted an experiment to determine the impact of additional members of either sex on reproductive success of pairs. In laboratory arenas, we formed pairs (1F:1M) and two kinds of triad (2F:1M, 1F:2M). Females in pairs had the highest conception rates, litter sizes and survival of litters. Females in 1F:2M groups had slightly reduced litter sizes and reduced numbers of weanlings, and some females had litters sired by both males. Females in 2F:1M groups had low conception rates and the smallest litters, and >35% of their litters suffered infanticide; in no case did both females become pregnant. Throughout the trials, individuals of the sex doubly represented in triads were more likely to die than were individuals of the sex singly represented. We conclude that there may be fitness costs associated with the presence of unrelated supernumerary adults during gestation and lactation.     

Effects of a new injectable short-term release deslorelin in foal-heat mares

Mares treated with subcutaneous deslorelin implants on the first postpartum estrus early in the breeding season had significant reductions in the number of large follicles at early pregnancy examinations and delayed return to estrus (in mares that failed to become pregnant); these adverse effects were attributed to a prolonged release of the drug from the implant. In 2003, an injectable short-term release (<24 h) deslorelin product became available. The objective of this study was to determine if this product would hasten ovulation in early foaling first postpartum estrus mares without reducing the number of large follicles at early pregnancy examination (14-15 days postovulation). Beginning 5-6 days postpartum, first postpartum estrus (foal-heat) mares were teased daily and examined thrice weekly (Tuesday, Thursday and Saturday) by transrectal ultrasonography. Mares in estrus with a follicle > or = 34 mm diameter on Tuesdays or Thursdays were alternately assigned to: Treatment 1, n = 17; 1.5 mg injectable short-term release deslorelin, or Treatment 2, n = 16; Control (no treatment). The schedule allowed accurate determination of the number of mares ovulating within 2 days of treatment (i.e., ovulations detected on Thursday or Saturday). Mares were mated on the day of treatment and at 2-day intervals until either ovulation was confirmed or until behavioral estrus ceased. Transrectal ultrasonography was done 14-15 days after ovulation to assess ovarian follicles and pregnancy status. Fewer covers were required and more mares ovulated within 2 days of treatment in deslorelin-treated versus Control mares (P < 0.01). Pregnancy rates were normal (69%) in deslorelin-treated mares. The number of large follicles 14-15 days after ovulation did not differ between deslorelin-treated and Control mares (P > 0.10), suggesting follicular suppression did not occur with this formulation of deslorelin.     

Trichostatin A (TSA) facilitates formation of partner preference in male prairie voles (Microtus ochrogaster)

In the socially monogamous prairie voles (Microtus ochrogaster), the development of a social bonding is indicated by the formation of partner preference, which involves a variety of environmental and neurochemical factors and brain structures. In a most recent study in female prairie voles, we found that treatment with the histone deacetylase inhibitor trichostatin A (TSA) facilitates the formation of partner preference through up-regulation of oxytocin receptor (OTR) and vasopressin V1a receptor (V1aR) genes expression in the nucleus accumbens (NAcc). In the present study, we tested the hypothesis that TSA treatment also facilitates partner preference formation and alters OTR and V1aR genes expression in the NAcc in male prairie voles. We thus observed that central injection of TSA dose-dependently promoted the formation of partner preference in the absence of mating in male prairie voles. Interestingly, TSA treatment up-regulated OTR, but not V1aR, gene expression in the NAcc similarly as they were affected by mating — an essential process for naturally occurring partner preference. These data, together with others, not only indicate the involvement of epigenetic events but also the potential role of NAcc oxytocin in the regulation of partner preference in both male and female prairie voles.     

Reproductive function in beef cows calving in the spring or fall

Plasma progesterone was determined twice weekly for approximately 100 days postpartum in suckled purebred (Hereford) and crossbred (beef x dairy) cows that calved in the spring or late summer/fall season. The progestèrone profiles and occurrence of estrus were used to determine ovulation times and to monitor ovarian function. Postpartum ovulations occurred significantly earlier in crossbred than in purebred cows (38.1 ± 18.5 vs. 58.1 ± 21.8, P<0.01) and in fall compared to spring calving cows (32 ± 13.9 vs. 59.1 ± 20.3, P<0.001). Rations providing either 70 or 100% of requirements for metabolizable energy were fed from 30 days prepartum until the end of the subsequent rebreeding period. Cows receiving the 70% energy ration ovulated slightly earlier but there was no effect of ration on days to pregnancy. The minimal effect of energy ration was not unexpected in this trial since many of the cows were overconditioned during late gestation.The correlation between calendar date of calving and interval to first ovulation was significant for spring (r = ?0.38, P<0.01) but not for fall calving animals. Since cows were confined and received a balanced ration of stored feeds throughout the year, photoperiod and/or temperature rather than nutritional factors would be the probable cause of delayed ovarian activity in spring calvers.Reproductive performance was assessed during the period when samples were collected and the response for purebred (n=105) and crossbreds (n=142), respectively were: ovulated by day 60 postpartum, 57 vs. 87%; mated by day 100 without conception, 17 vs. 26%; ovulated before day 100 without detection and mating, 10 vs. 4%; anovulatory to day 100, 7 vs. 0%; pregnant by day 100, 67 vs. 70%. Similar comparisons for spring (n=133) and summer/fall (n=144) calvers, respectively, were: ovulated by 60 days postpartum, 56 vs. 96%; mated by day 100 without conception, 27 vs. 17%; ovulated by day 100 without detection and mating, 8 vs. 5%; anovulatory to day 100, 5 vs. 0%; pregnant by day 100, 60 vs. 78%. The difference with the greatest practical significance is that a higher proportion of the late summer/fall calving animals were pregnant by day 100 postpartum (P<0.01) which indicates that reproductive performance is superior in fall calving beef cows.     

The influence of mating on autogenous egg development in the mosquito, Aedes taeniorhynchus

In several strains of Aedes taeniorhynchus, the presence of males increased the levels of autogeny. To stimulate autogenous egg production, the males had to mate with the females. Ageing further enhanced the rates of autogeny in mated females but not in virgins. Males did not influence the size of the autogenous egg batch. Even after the sixth day following emergence some females still possessed the capacity to respond to the male stimulus. With regard to ovarian maturation in A. taeniorhynchus, there appeared to be 3 types of females: (1) those that did not require a mating stimulus to be autogenous, (2) those that needed this stimulus and (3) those that remained anautogenous whether mated or not.     

Male Seminal Fluid Substances Affect Sperm Competition Success and Female Reproductive Behavior in a Seed Beetle

Male seminal fluid proteins are known to affect female reproductive behavior and physiology by reducing mating receptivity and by increasing egg production rates. Such substances are also though to increase the competitive fertilization success of males, but the empirical foundation for this tenet is restricted. Here, we examined the effects of injections of size-fractioned protein extracts from male reproductive organs on both male competitive fertilization success (i.e., P2 in double mating experiments) and female reproduction in the seed beetle Callosobruchus maculatus. We found that extracts of male seminal vesicles and ejaculatory ducts increased competitive fertilization success when males mated with females 1 day after the females’ initial mating, while extracts from accessory glands and testes increased competitive fertilization success when males mated with females 2 days after the females’ initial mating. Moreover, different size fractions of seminal fluid proteins had distinct and partly antagonistic effects on male competitive fertilization success. Collectively, our experiments show that several different seminal fluid proteins, deriving from different parts in the male reproductive tract and of different molecular weight, affect male competitive fertilization success in C. maculatus. Our results highlight the diverse effects of seminal fluid proteins and show that the function of such proteins can be contingent upon female mating status. We also document effects of different size fractions on female mating receptivity and egg laying rates, which can serve as a basis for future efforts to identify the molecular identity of seminal fluid proteins and their function in this model species.     

How the FSH/LH ratio and dose numbers in the p-FSH administration treatment regimen, and insemination schedule affect superovulatory response in ewes

We wished to evaluate the effects of FSH/LH ratio and number of doses of p-FSH during a superovulatory treatment on ovulation rate and embryo production (Experiment I). In Experiment II, we studied the efficacy of fertilization after various insemination schedules in superovulated donors. In Experiment I estrus was synchronized in 40 ewes (FGA, for 9 days plus PGF2alpha on Day 7) and the ewes were randomly assigned to four treatment groups as follows (n = 10 ewes each): Group A: four p-FSH doses with the FSH/LH ratio held constant (1.6); Group B: four p-FSH doses with the FSH/LH ratio decreasing (FSH/LH 1.6-1.0-0.6-0.3); Group C: eight p-FSH doses with the FSH/LH ratio held constant (1.6); Group D: eight p-FSH doses and FSH/LH ratio decreasing (1.6-1.6, 1.0-1.0, 0.6-0.6, 0.3-0.3). p-FSH administrations were performed twice daily 12 h apart. The ewes were mated at the onset of estrus and again after 12 and 24 h; then, one ram per four ewes was maintained with the ewes for two additional days. Ovarian response and embryo production were assessed on Day 7 after estrus. Experiment II. Three groups (n = 10 each) of superovulated ewes were inseminated as follows: Group M: mated at onset of estrus; Group AI: artificial insemination 30 h after onset of estrus; M + AI) mating at onset of estrus and intrauterine AI performed 30 h from estrus with fresh semen. Results of Experiment I showed that treatment (D) improved (P < 0.05) ovulatory response in comparison to Groups (C) and (A). The fertilization rate was lower (P < 0.01) in Group D) than Group (A). Also the proportion of transferable embryos was lower in Group (D) in comparison to all the other treatments (P < 0.01). Group A gave the best production of embryos (7.3/ewe; 89.0% transferable). In Experiment II, combined mating plus AI improved fertilization rate (80.3%) compared to both mating (P < 0.01) and AI (P < 0.02) alone.