Abstract Climate warming and human disturbance are known to be key drivers in causing range contraction of many species, but quantitative assessment on their distinctive and interactive effects on local disappearance is still rare. In this study, we examined the association of climate warming and human disturbance stressors with local disappearance probability of Brandt's voles (Lasiopodomys brandtii) in a steppe grassland in northern China. We used logistic generalized additive models to quantify the relationship between local disappearance probability of Brandt's voles and environmental variables. The year following the last observation year was used to estimate the disappearance threshold of Brandt's voles. We projected the distribution change of Brandt's voles under future climate warming scenarios. We found climate warming attributed to local disappearance and range contraction for southern populations of Brandt's voles from 1971 to 2020. Human stressors and high vegetation coverage increased the probability of local disappearance of voles in years of abundant precipitation. The southern boundary retreated northward at a speed of 99.0 km per decade with the temperature rise of 0.36°C. The disappearance threshold of maximum air temperature of Brandt's voles in the warmest month (27.50 ± 1.61°C) was similar to the lower critical temperature of its thermal neutral zone. Our study suggests that the rapid climate change over the past decades contributed to the range contraction of its southern boundary of this keystone species in the steppe grassland of China. It is necessary to take actions to preserve the isolated populations of Brandt's voles from the effects of accelerated climate change and human disturbance.

Background: The colonial habit of Brandt's vole (Lasiopodomys brandtii) differs from that of most other species of the genus Microtus. The demographic history of this species and the patterns shaping its current genetic structure remain unknown. Here, we explored patterns of genetic differentiation and infered the demographic history of Brandt's vole populations through analyses of nuclear microsatellite and D-loop sequences.Results: Phylogenetic analyses divided the sampled populations into three main clusters, which represent the southeastern, northeastern and western parts of the total range in Mongolia and China. Molecular data revealed an ancestral area located in the southeast of the extant range, in the Xilinguole District, Inner Mongolia, China, from where Brandt's vole populations began expanding. A gene flow analysis suggested that the most likely colonization route was from the ancestral area and was followed by subsequent northeastward and westward range expansions. We identified decreases in genetic diversity with increasing distance from the founder population within the newly occupied regions (northeastern and western regions), clinal patterns in the allele frequencies, alleles that were rare in the original area that have become common in the newly occupied regions, and higher genetic differentiation in the expanded range compared with the original one.Conclusion: Our results indicate that L. brandtii most likely originated from the southeastern part of its current geographic range, and subsequently colonized into the northeastern and western parts by expansion. The genetic patterns among the derived populations and with respect to the original population are consistent with that expected under genetic surfing models, which indicated that genetic drift, rather than gene flow, is the predominant factor underlying the genetic structure of expanding Brandt's vole populations.

A) Allele frenquency of each locus for Brandt’s vole populations in southeastern and northeastern distribution; B) Allele frenquency of each locus for Brandt’s vole populations in northeastern and western distribution. (XLSX 62 kb)

Studies have rarely focused on the effect of cabergoline dosage and duration on normal male animal and human. We examined the serum concentrations of four hormones, reproductive organ weight, and sperm quality of adult male lesser rice-field rats (Rattus losea) after cabergoline treatment. Forty male rats were randomly divided into five groups and treated with cabergoline given by gavage daily for 3 d at three doses (0, 50, and 100 mu g/kg). Animals were euthanized at 7 and 24 days after the end of treatment. Results showed that cabergoline did not affect follicle-stimulating hormone levels. Compared with control, testosterone concentrations decreased significantly by 48.6% at 7 d after treatment with 100 mu g/kg cabergoline. Luteinizing hormone concentrations were significantly reduced by cabergoline dosage and time course. Time course affected sperm density and sperm deformity rate. Cabergoline dosage and time course significantly affected male sperm vitality at 50 mu g/kg. Moreover, cabergoline significantly decreased the percentage of 'rapid', 'slow or sluggish' progressive motility sperms, and increased the percentage of "immotility" sperms. The present study suggests that cabergoline may reduce luteinizing hormone level, and impair sperm quality, which hint weakening reproductive effects on male R. losea.

Rodent pests occurred very seriously in agricultural landscapes and villages in China.They happened in almost 31 provinces(municipalities or autonomous regions).Rodents occupy 20-40 million hm2 farmlands annually,typically causing annual losses of 5%-10% harvest.In grasslands,episodic outbreaks of rodents occupy 25to 43 million hectares annually,but heavier losses were caused to 15 to 23 million hectares annually.In recent years,management of rodent pests has made great progress in China,and obtained remarkable achievements.Rodent control activities implemented in farmlands account for 50%-80% of total acreage;as for peasant households,it accounts for more than 80% of the total.The control areas in grasslands cover about a third of the seriously damaged lands.Software and hardware for rodent pest monitoring and early-warning were constructed.Some techniques,such as poison bait station,rodenticide resistance monitoring,were used to optimize the traditional chemical method,and minimize the environmental effects of rodenticides.Some new sustainable pest management techniques such as sterile control,TBS technology and ecologically-based rodent management were experimented,and made rapid progress.National standards,industry standards,and optimized management strategies for rodent pest control were promulgated.Integrating different suitable techniques and methods to control rodents has been developed,and obtained good achievements.

Rodent pest population outbreaks occur frequently in grassland ecosystems in northern China. The Mongolian gerbil (Meriones unguiculatus) is a dominant pest rodent which is distributed across the semi-desert grasslands of Inner Mongolia, China. In 2009, we studied the contraceptive effect of levonorgestrel-quinestrol (EP-1), concentration 50 ppm, on a wild Mongolian gerbil population. The one-off contraceptive treatment was compared with a control group using a semi-monthly live trapping method in the Ordos Semi-desert Grassland Region of Inner Mongolia. The results show that juveniles were not recruited in spring in the treatment group. Ratios of juveniles in the control and treatment groups showed significant semi-monthly differences from spring to summer (one-way ANOVA, F2, 14 = 7.53, P < 0.05). Between both groups, annual fluctuations of juvenile and total population densities were significantly different respectively (F2, 14 = 4.64, P < 0.05; F2, 18 = 7.72, P < 0.05). The contraceptive EP-1 delayed the normal reproductive pattern of Mongolian gerbil populations. This suppressed birth rates of gerbil populations, reduced their densities, and changed their age structures. The period of EP-1 baiting should be extended but it could be an ideal method for controlling Mongolian gerbil populations during each breeding season.

The effects of the two sterilants, quinestrol (QE) and levonorgestrel (LNG) on serum prolactin (PRL) level in lactating Mongolian gerbils and reproductive parameters of their offspring were examined in the study. Both sterilants increased the serum PRL level in lactating gerbils. The body weight as well as weights of the ovary, testis, epididymides, and seminal vesicles were lower, whereas that of the uterus was higher in the pups originating from QE-treated mothers in comparison to controls. Histological ovarian sections of the offspring from QE-treated mothers contained only growing follicles, whereas their uterine sections showed a thinner endometrium, thicker myometrium, and greater epithelial-cell height than in controls. The histometrical testis characteristics as well as sperm concentration and motility of male pups from QE-treated mothers were lower compared to those of the control group. The serum gonadotropin levels of female pups from mothers treated with QE were lower, whereas the serum estradiol (E(2)) and progesterone (P(4)) levels were higher than in control gerbils. In contrast, serum gonadotropin and testosterone (T) levels of male pups from QE-treated mothers were lower compared to controls. LNG did not affect the examined parameters of the offspring. The offspring from QE-treated mothers was infertile, whereas the offspring from LNG-treated mothers was fertile. In summary, QE and LNG have a stimulatory effect on PRL level in lactating gerbils. It also appears that QE administered via milk to mothers affects reproductive processes of their offspring.

From March to October in 2010,we have used EP-1(levonorgestrel-quinestrol),a compound sterility mixture,and poisoned baits(bromadiolone),to conduct contraception and lethal controlling contrast experiments on Mongolian gerbil,Meriones unguiculatus,wild population with one-time enough EP-1 and poison baits in spring in Ordos Desert Grasslands,Inner Mongolia.The experiments were conducted in the following aspects: sterile experimental,lethal experimental and control areas,respectively.The gerbils were captured by trapping monthly.The results showed that not only gerbil population age structures were changed,but also population densities and juvenile recruitments have significantly reduced in the sterile experimental area in which EP-1 was used,and the gerbil adults ratio differences were significant in population compared with lethal area(F2,14=5.89,P<0.05),the juvenile recruitments and population densities were on a declining curve(R32=0.8552,R42=0.5126).The EP-1 results an effective sustained control to gerbil population.However,the lethal controlling effects to gerbil population was continued only for three months,which functioned as a short-term controlling effects.

Fertility control has been identified by studies in the laboratory and the field as a more appropriate and long-term control strategy for rodent pests than lethal control. In this study, we investigated the effects of quinestrol on mass of reproductive organs and on social behaviors in female and male Indochinese forest rat (Rattus andamanensis (Blyth, 1860)] using approach of morphometrics and genetics). [corrected]. A total of 16 adult females and 16 adult males were randomly assigned to 4 groups. One male and one female group were fed rice with 0.005% quinestrol by weight for 7 days, and another 2 groups were fed rice only. After 7 days, rats were assigned to 10 min dyadic encounters between groups, and investigation, aggression, defense and attack latency were quantified. All animals were killed on day 10, and reproductive organs were dissected and weighed. Dyadic encounter data showed that there were obvious changes in social behaviors of quinestrol-treated rats. Quinestrol significantly inhibited the investigative behavior of quinestrol-treated males toward control females in Rattus nitidus, but seldom affected investigation between control males and quinestrol-treated females. Aggression of control females toward quinestrol-treated males was higher than that of quinestrol-treated females, and defense of quinestrol-treated males toward control females was more remarkable than that of control males. Quinestrol remarkably decreased wet masses of epididymis and spermotophore in males and ovaries in females, but had no effect on wet masses of testes and uteri after quinestrol treatment. These results indicate that the anti-fertility effects of quinestrol on R. nitidus are attributed to not only suppressing reproductive organs but also impacting social behaviors associated with territory defense and mate choice.

Brandt's vole(Lasiopodomys brandtii),a small rodent is unique in Mongolian Plateau.The habitat characteristics of Brandt's vole were discussed based on a field survey in both China and Mongolia during 2008-2010.The vole density was recorded from 316 selected sites(1 m×1 m quadrates).Then 5~10 sites were randomly selected and vole densities,vegetation coverage,degradation level,vegetation height,closure index,withered grass coverage,elevation and vegetation types were surveyed.Results of correlation analyses and factor analyses showed that Brandt's vole density had significant correlation with vegetation coverage,withered grass coverage,degradation level and closure index.The quantities of Artemisia frigida,Leymus chinensis and Allium polyrhizum,withered grass coverage,vegetation coverage,degradation level and closure index significantly affected voles to select their habitats.Brandt's voles prefer to locate with Artemisia frigida,Leymus chinensis and Allium polyrhizum,high degradation levels,lower vegetation heights and lower withered grass coverage.

在室内条件下采用食毒法研究了浓度为1/20000的复合不育剂EP-1饵料对雄性长爪沙鼠性激素、生殖器官及繁殖行为的作用.结果显示:给药1周后,血清内促卵泡素(FSH )、促黄体素(LH)和雌二醇(E2)水平与对照组相比差异不显著,但睾酮(T)浓度显著下降;试鼠精囊腺重量显著降低;睾丸和附睾重量虽略有降低,但差异均不显著;给药组精子平均畸形率为(55.0±2.79)%,显著高于对照组的(32.00±2.36)%;给药组睾丸曲精小管平均异常率为(22.99±5.00)%,显著高于对照组的(4.21±1.18)%;试鼠配对后主要表现为相互嗅闻,给药组雄鼠主动嗅闻雌鼠频次显著低于对照组,打斗和攻击频次也降低;实验室条件下,40天内对照组繁殖率为55.6%,而给药组均未繁殖.说明EP-1对雄性长爪沙鼠具有明显的抗生育作用.

In natural conditions, animals have to cope with fluctuations of food resources. Animals having experienced prolonged decrease in feeding opportunities may increase their reproductive success when meeting abundant food. Though food restriction is well known to reduce reproductive success of animals, it is not clear whether re-feeding can restore or even overcompensate the reproductive success. In this study, we investigated the differences in reproductive parameters between food-restricted and refed (FR–RF) group and control group of Brandt's vole (Lasiopodomys brandtii). For 4 weeks, FR–RF voles were provided with 70% of their normal daily food intake and then they were fed ad libitum for the next 4 weeks. Voles of control group were fed ad libitum for 8 weeks. Females (FR–RF or control) were mated to non-littermate males of the same group (FR–RF or control), and we found that the mean litter size and survival rate of F1 pups of FR–RF group were significantly higher than those of control group. We also provided a field example showing that the litter size of Brandt's voles tended to be higher if they experienced two consecutive dry and wet months than that of voles didn't have this experience. Our results suggest that re-feeding may have evoked an overcompensatory mechanism of food-restricted voles in reproductive success. This may be an adaptive strategy for Brandt's voles (with oscillating populations) to cope with the fluctuating food resources in natural conditions by adjusting their reproductive success.

The hypothesis that quinestrol exerts testicular damage via oxidative stress was investigated in male gerbils using a daily oral gavage of 3.5 mg/kg body weight for 2 weeks (the multidose-treated group) or 35 mg/kg body weight (the single-dose-treated group). The testicular histological morphology, antioxidant capacity and malondialdehyde (MDA) concentration in testicular tissue and plasma were assessed at 15, 30, and 60 days following treatment. The results showed that the activity of the antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxide (GSH-Px), and total antioxidant capacity (T-AOC), at 15 days after treatment in testicular tissue decreased, which led to the MDA concentration increasing while at the same time germ cells were rarefied and showed an irregular distribution in seminiferous tubules of quinestrol-treated gerbils. At 30 days, the testicular weight and antioxidant capacity continued to decrease, while the MDA concentration continued to increase, and testicular histopathological changes were more pronounced. Single-dose and multidose drug treatment had a similar effect on the antioxidant enzymes and MDA, but testicular damage was relatively severe at 15 and 30 days after multidose treatment. By 60 days of treatment withdrawal, however, the above parameters recovered to control levels. The results show that quinestrol causes reversible damage to gerbil testes that might be caused by the oxidative stress and that multidose treatment has more effects on testicular damage compared with one-dose treatment.

In this study,Mongolian gerbils were randomly divided into multi-dose treated group(MDT group),one-dose treated group(ODT group) and control group(CK group) to explore effects of quinestrol on reproductive organs and reproduction.The epididymides,seminal vesicles and semen quality,fertility were assessed at 15,30,60 and 90 days after treatment.Histopathological changes of epididymides were observed by H.E stain.Results showed that the coefficient of testes,epididymides,and seminal vesicles were significantly decreased(P0.01) at 15 or 30 days after treatment.The normal function of the sex gland was impaired,which led to significant decrease in the density and amount of live spermatozoa and reproductive rates(P0.01),as well as a significant increase of abnormal spermatozoa(P0.01) in both MDT group and ODT group.Compared with the ODT group,the damage for gerbil reproduction in MDT group was more severely at 15 or 30 days after treatment(P0.01).After 60 days of treatment withdrawal,the sex gland in treated group was normalized except for gerbil epididymides in the MDT group,while semen quality and reproductive rates were still lower than those in the control group(P0.01).The physiological indicators were recovered by 90 days of treatment withdrawal.This indicates that quinestrol shows certain effects on reducing the fertility of male gerbil with a reversible effect after 90 days' treatment and multi-dose treatment has more effects to infertility compared with one-dose treatment.

The effects of levonorgestrel (LNG) on serum levels of reproductive hormones and their receptor mRNA expression in the ovary and uterus of Mongolian gerbils were examined. The results show that serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) increased, whereas serum estradiol (E2) and progesterone (P4) decreased profoundly after LNG treatment. LNG down-regulated the mRNA expression of follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), estrogen receptor (ER) β and progesterone receptor (PR) in the ovary, and ERα and PR in the uterus of Mongolian gerbils. The down-regulated effects were time-dependent and dose-dependent. LNG had no obvious effects on ERα mRNA expression in the ovary. The findings suggest that LNG impairs reproductive hormone receptor expression at the molecular level in Mongolian gerbils. Also, the two ER subtypes may play different roles in the ovary, and ERβ may not be the predominant ER subtype in the uterus of Mongolian gerbils. The ovary and uterus may be the important sites of action of LNG through its direct progesterone-like effects in Mongolian gerbils.

To evaluate the antifertility effects of crude ethanol extracts of Tripterygium hypoglaucum (Levl.) Hutch in Mongolian gerbils. Crude ethanol extracts of T. hypoglaucum root (ETHR) were administrated orally at a dose of 160 mg/kg for 30 days. Sperm density, sperm motility levels and the percentage of misshapen sperm in the cauda epididymides were assessed. The fertility rate of mated female gerbils was calculated. The results indicate that ETHR has effect in Mongolian gerbils. Oral administration of ETHR caused an increase of the percentage of misshapen sperm significantly. Testis and epididymis weights, the sperm density and motility were significantly reduced. Compared to the control group, there was a distinct reduction in the number of litters produced, and the average number of pups per male decreased from 3.4 to 0.87. Reversibility tests showed that testis and epididymis weights, sperm indices and fertility started to gradually recover after 30-days cessation of medication. ETHR brought a significant decrease in birth rate of Mongolian gerbils.

Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) levels were examined during consecutive reproductive states in Mongolian gerbils. The results indicate that FSH, LH, and PRL levels peak at proestrus, estrus, and diestrus, respectively. During early gestation in primiparous gerbils, gonadotropin levels were the lowest on day 6. This was followed by an increase in FSH and LH levels until days 18 and 15, respectively, with levels remaining constant until day 21. However, in multiparous gerbils, gonadotropin levels were the lowest on day 12 of gestation and were relatively stable between days 15 to 21. In both primiparous and multiparous gerbils, gonadotropin levels increased rapidly from day 21 of gestation to day 3 of lactation, and kept stable between 6-24 days of lactation. PRL peaked during early gestation on days 9 and 6 in the primiparous and multiparous gerbils, respectively, followed by a decline. PRL levels subsequently peaked again on day 21 before parturition. During lactation, PRL levels peaked on days 6 and 9 in primiparous and multiparous gerbils, respectively, followed by a decline until lactation ended. These findings suggest that variations in gonadotropin during the estrous cycle, gestation, and lactation in Mongolian gerbils are similar to those observed in rats, whereas prolactin levels differ. Changes in gonadotropin and prolactin levels during different reproductive states were found to be similar in primiparous and multiparous gerbils, and were correlated with the reproductive stages of Mongolian gerbils.

The current study evaluated effects of quinestrol on oxidative stress and abnormal spermatogenesis for male Mongolian gerbils. Gerbils were randomly divided into multi-dose treated, single-dose treated, control groups. At 15 days after treatment antioxidant enzymes (SOD, GSH-Px) activities and T-AOC were decreased whereas the MDA concentration was significantly increased, testicular weight and seminiferous tubular areas decreased, germ cells were rarefied and showed irregular distribution in seminiferous tubules, apoptosis was pronounced among spermatocytes and spermatids, the number of dead and abnormal acrosomes of spermatozoa increased significantly in quinestrol treated groups. At 30 days following treatment the testicular histopathological changes were more severe, sperm quality and antioxidant capacity continued to decline, and multi-dose treatment produced more damage to gerbils testes compared with single-dose treatment. The physiological indicators were recovered by 60 days of treatment withdrawal. The results showed oxidative stress induced by quinestrol in relation to abnormal spermatogenesis.

Mongolian gerbils {Meriones unguiculatus) are widely distributed in Inner Mongolia. This species not only has caused damage to grassland or crop production, but has also been a channel for transmitting human plagues in the abovementioned region. From March to October in 2009, we used a contraceptive compound ( EP-1 ) to test its fertility control effect on a wild population of Mongolian gerbils in the Ordos Desert Grasslands, Inner Mongolia. The results show that the breeding, structures and densities of Mongolian gerbil populations were significantly influenced by EP-1. During the first of the two peak breeding periods for gerbil populations, from May to June, juvenile recruitment significantly declined. The proportions of juveniles and of adults fluctuated significantly in the experiment and check areas (P<0.01). Similar fluctuations were seen in August to October in both areas (P<0.05, P<0.01). In the EP-1 treatment area, juvenile recruit-ment began in June, reached its peak in September, and their population density declined during the population growth period. In the control area, the juvenile recruitment peaked in May, and their population density showed an increase during the breeding period. In summary, reproduction, juvenile recruitment, the proportion of juveniles, and the population densities of Mongolia gerbils were significantly reduced during reproductive periods. These observations suggest that EP-1 is a very effective contraceptive for fertility control of this wild species, and may reduce the risk of damage to grass or crop production as well as the spreading of human plagues.

Objective To determine the anti-fertility effect of curcumol baits on Lasiopodomys brandti. Methods The experimental group was fed with baits of 3 doses, 0.1%, 0.2% and 0.4%, respectively, while the control group received nontoxic blanks. The voles freely consumed the baits for 3 consecutive weeks before gross examination, in which the morphology of genital organs was observed, and the organ coefficient calculated. The sperm quality was measured for male animals. Results Curcumol baits were effective anti-fertility agents against both male and female L. brandti. As for female voles, abnormal ovarian development was observed with impaired follicular maturation in the 0.2% and 0.4% dose groups; increased organ coefficient for the uterus was present in each dose group along with uterine edema, the extent of which was positively correlated with the dose administration. As for male animals, intoxicated individuals had lowered sperm motility, concentration and viability in addition to increased risk of sperm malformation, where the most common abnormality was acrosomal loss; their epididymal organ coefficient also declined to a degree positively correlated with the dose. Curcumol did not affect the individual development of either gender. Conclusion While curcumol baits had anti-fertility effects on L. brandti, the duration and recoverability of drug effect should be further studied.