Large manipulative experiments reveal complex effects of food supplementation on population dynamics of Brandt's voles

Although food supplementation is well known to increase population density,there is still debate on the causative effects of food supplementation on reproduction,survival,and immigration.Large manipulative experiments,which exclude any confounding effects of dispersal and predation,are essential for clarifying the debate.In this study,we investigated the effects of food supplementation on Brandt's vole population dynamics and plant community in eight large enclosures(0.48 ha each) from2010 to 2014.Food supplementation showed significant positive effects on population density due to increases in recruitment;however,it showed a complex effect on survival of voles:positive in non-breeding seasons,but negative in breeding seasons.In addition,food supplementation increased the quality of plants(as reflected by increased crude protein content),but decreased the quantity of less preferred plants in experimental enclosures.Thus,food seems to have direct positive effects on small rodents through improvement of food supply and indirect negative effects through food-induced density-dependent effects,and may have long-term effects on rodents through altering plant community composition and abundance.

Changes of Estrogen in Serum and Estrogen Receptor β in the Relevant Brain Regions Following Mating Behavior of the Male Mandarin Vole Microtus mandarinus

In order to investigate the estrogen and estrogen receptor β changes after mating behavior of male mandarin vole （Microtus mandarinus）, the radioimmunoassay （RIA） and immunohistochemistry methods were used to investigate changes of the serum estrogen （E） concentrations, estrogen immunoreactive neurons （E-IRs） and estrogen receptor β immunoreactive neurons （ERβ-IRs） in the relevant brain regions following mating behavior. Fifteen sexually matured male voles were randomly divided into three groups and treated differently： （1） control group： voles were exposed to clean hard-wood shavings （n=5）, （2） exposure group： voles were exposed to the soiled bedding for more than 24h on which estrous females had been placed （n=5）, and （3） mating group： voles were placed with an estrous female for more than 24h （n=5）. The results showed circulating serum E concentrations were significantly higher in the mating group than in the exposure group and the control group, and there were no significant difference between the exposure group and the control group. E-IRs and ERβ-IRs were detected in the following brain regions related to mating behavior： the arcuate nucleus （ARC）, bed nucleus of the stria terminalis （BST）, lateral septal nucleus （LS）, medial amygdaloid nucleus （ME）, medial preoptic area （MPO） and ventromedial hypothalamic nucleus （VMH）. The results showed that there were significantly more E-IRs in the six brain regions in the mating group than in the control group and the exposure group, and there were no significant difference between the exposure group and the control group except for LS. There was no significant difference in ERβ-IRs in the six brain regions among the three groups, and there were some lighter -stained ERβ-IRs in these brain regions. The results suggested that estrogen affect mating activity of male mandarin voles, but ERβ might not play an important role in mating behavior of male mandarin voles. Instead, it might be through other receptors.

Effects of fitch odor (Mustila eversmanni) on behavior and breeding of root voles (Microtus oeconomus)

From April to December in 1997 at Northwest Plateau Institute of Biology, Chinese Academy of Science, the effect of predation risk on social behavior, feeding, reproduction and sexual hormones of the root voles (Microtus oeconomus) was studied when the root voles (Microtus oeconomus ) were exposed to the odor of fitch (Mustila eversmanni). The results showed that the root voles delayed breeding period and the frequency of the copulation significantly lowered (P【0.01). Comparing with the control group, the accumulated time of amicable behavior in females, and general activity of both sexes increased significantly (P【0.01). The frequencies of general activity (P【0.01), investigating activity (females: P【0.05, males: P【0.01), and self-grooming (P【0.01) of both sexes were less significantly. At the same time, the amount of energy intake (P【0.05) and body weight (P【0.01) of the root voles decreased significantly. The litter weight and ovary index of females decreased (P【0.01). For males the sperm count in epididymides also decreased significantly (P【0.01). The progesterone in the blood serum of root voles females increased significantly under fitch odor (P【0.01).

Effect of temperature on antioxidant defense and innate immunity in Brandt’s voles

Ambient temperature is an importa nt factor in flue ncing many physiological processes, in eluding antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatme nt in Bran dt's voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32℃, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature in creased gross en ergy in take (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxyge n species (ROS) levels, in creased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (TAOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4℃ group in contrast to the 23℃ group, whereas spleen mass and white blood cells were un affected by temperature treatment. The levels of testosterone, but not corticostero ne, were in flue need by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and TAOC activity in any detected tissues. Overall, these results showed that temperature had different in flue nces on oxidative stress, an tioxida nt en zymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of an tioxida nt defe nse might be an importa nt mechanism for voles to survive highly variable environmental temperatures.

Mating behavior induces changes of expression of Fos protein,plasma testosterone and androgen receptors in the accessory olfactory bulb (AOB) of the male mandarin vole Microtus mandarinus

In order to investigate the neuroendocrine mechanism of the mating behavior in the adult male mandarin voles Microtus mandarinus,the radioimmunoassay(RIA)and immunohistochemistry methods were used to investigate the differences in plasma testosterone(T)concentrations and distribution of T immunoreactive neurons(T-IRs),androgen receptor immunoreactive neurons(AR-IRs)and Fos protein immunoreactive neurons(Fos-IRs)in the accessory olfactory bulb(AOB)and the main olfactory bulb(MOB)following exposure to clean hard-wood shavings(control group),soiled bedding(exposure group)or contact with an estrous female(mating group).Results showed that plasma T concentration was significantly higher in the mating group than that in the exposure group,and both the mating group and the exposure group displayed significantly higher plasma T concentration than the control group.T-IRs,AR-IRs and Fos-IRs were investigated with the immunohistochemistry method in granule cell(GC)and mitral cell(MC)of the MOB and the AOB in the three groups.There were significantly more T-IRs,AR-IRs and Fos-IRs in MC and GC of the AOB in the mating group than that in the exposure group or the control group.T-IRs,AR-IRs and Fos-IRs did not show significant differences between the exposure group and the control group.Furthermore,obvious differences in MC and GC of the MOB were not found among the three groups.The results confirm that both changes of T and AR in the AOB might be underlying mating behavior in the adult male mandarin voles.

Spontaneous emergence of overgrown molar teeth in a colony of Prairie voles(Microtus ochrogaster)

Continuously growing incisors are common to all rodents, which include the Microtus genus of voles. However, unlike many rodents, voles also possess continuously growing molars. Here, we report spontaneous molar defects in a population of Prairie voles （Microtus ochrogaster）. We identified bilateral protuberances on the ventral surface of the mandible in several voles in our colony. In some cases, the protuberances broke through the cortical bone. The mandibular molars became exposed and infected, and the maxillary molars entered the cranial vault. Visualisation upon soft tissue removal and microcomputed tomography （microCT） analyses confirmed that the protuberances were caused by the overgrowth of the apical ends of the molar teeth. We speculate that the unrestricted growth of the molars was due to the misregulation of the molar dental stem cell niche. Further study of this molar phenotype may yield additional insight into stem cell regulation and the evolution and development of continuously growing teeth.

Interactions between intruders and residents in the mole vole Ellobius talpinus

We studied the behavioral and endocrine responses of the fossorial s ocial rodent, mole vole Ellobius talpinus Pall., to intrusions of strangers int o burrow systems that were occupied by intact families. Both in reproductive and non-reproductive seasons, all intruders disappeared from the burrow systems of residents within two days of introduction, whereas 4 of 7 individuals introduced into empty burrows remained there at least for two days. Introduction of strang ers led to the concentration of residents at the point of release and to an incr ease of plasma corticosterone in both residents and intruders. During the breedi ng season, introduction of strangers was also accompanied by an increase of plas ma testosterone of residents on the day of introduction. Thus, simulation of int rusion of strangers demonstrated the efficient social fence of resident mole vol es that seems to be an important mechanism of stabilization of size and structur e of mole vole families. Encounters of residents and intruders resulted in activ ation of physiological mechanisms of stress, especially during the breeding seas on .

捕食风险应激对雄性布氏田鼠及子代繁殖性能的影响

本研究旨在探讨雄性布氏田鼠暴露于捕食风险应激对自身及后代繁殖性能的影响,以及这种效应的阶段性。青春期是动物生长发育和对外界环境敏感的重要阶段,推测青春期所经历的捕食风险应激对雄鼠和后代繁殖性能的影响更为显著。实验选取90日龄成年期和28日龄青春期雄性布氏田鼠作为亲代,每天分别暴露于蒸馏水、兔尿和猫尿1 h,连续18 d。随后每组随机选取一半田鼠取样检测性腺器官指数、精子质量和数量等参数,另一半与正常雌鼠交配,待后代成年后检测繁殖性能。结果显示,与对照相比,成年期和青春期暴露于猫气味的雄性布氏田鼠精子正常率显著下降,精子畸形率和死亡率显著升高,而暴露于兔气味的雄鼠仅降低了正常精子比例;成年期雄性田鼠暴露于猫气味没有影响繁殖输出,而青春期暴露的雄鼠的后代在出生时雌性比例显著增加;成年期暴露于猫气味和兔气味都没有影响后代的繁殖性能,青春期暴露于猫气味的雄鼠的后代成年后性腺指数、精子密度和精子正常率降低,精子畸形率和死亡率显著升高,而暴露于兔气味仅降低了雄性后代的精子密度和精子正常率。以上结果验证了本研究假设,即捕食风险应激对布氏田鼠亲代和后代的繁殖性能均有一定的抑制作用,且青春期应激的效应更强更持久,存在明显的效应阶段依赖性。

熟悉性对棕色田鼠和根田鼠择偶行为的影响

以两性配对共居至交配或生仔作不同熟悉处理 ,在Y字型选择箱中分别观察棕色田鼠、根田鼠的择偶行为和配偶识别。结果如下 :(1)棕色田鼠雌雄两性均表现出对熟悉异性或配偶的喜好倾向 ;(2 )在根田鼠中 ,只有雌性表现出对熟悉雄鼠或配偶的选择倾向 ,雄鼠无明确的选择取向 ;(3)每种雌性田鼠对 2种熟悉性不同的同种雄性的嗅舔时间均有显著差异性 ,而每种雄性田鼠对 2种熟悉性不同的同种雌性的嗅舔时间均无显著差异性。这些结果表明 :(1)熟悉性对棕色田鼠择偶行为的影响大于对根田鼠的影响 ;(2 )嗅舔时间差异可反映不同田鼠的配偶识别能力 ,熟悉性对棕色田鼠配偶识别能力的影响大于对根田鼠的影响 ;(3) 2种田鼠配偶识别的性别差异的一致性 ,提示这 2种田鼠的雌性配偶识别能力均强于雄性田鼠 ,而雌鼠的配偶识别能力可能取决于雌鼠受交配或分娩刺激的生理状态 ;(4 )棕色田鼠室内所表现的择偶行为的两性熟悉性特征与其单配制有关 ,根田鼠所表现的择偶行为的雌性熟悉性特征与其一雄多雌制有关。

棕色田鼠与沼泽田鼠犁鼻器和副嗅球的组织结构

用组织学方法研究了棕色田鼠 (Microtusmandarinus)、沼泽田鼠 (M .fostis)副嗅球和犁鼻器的结构及其在两种鼠间的差异 ,以此探讨两种田鼠的进化机制与适应功能。两种田鼠的犁鼻器位于鼻腔前端鼻中隔基部的两侧 ,呈管状结构 ;沿着犁鼻器的长轴犁鼻管呈现不同的形态学特征 ,犁鼻管直接开口于鼻腔 ,从前向后沿着长轴旋转 ,中间管壁 (犁鼻粘膜 )变成底部 ,侧面管壁 (假覆层上皮 )变成犁鼻管顶壁 ,最终犁鼻管变小成为一个腺体的分支 ,不同部位具有不同的组织学特征。通过选取中间相似部位对两种田鼠进行比较研究 ,发现棕色田鼠犁鼻粘膜比沼泽田鼠厚 ,而其长度却短于沼泽田鼠。棕色田鼠副嗅球颗粒细胞带宽和僧帽细胞带宽均大于沼泽田鼠 ,而带长却小于沼泽田鼠。相关分析发现 ,犁鼻器和副嗅球形态有一定的对应关系 ,这可能和两个结构之间存在着神经投射有关。棕色田鼠幼体的犁鼻粘膜、神经细胞核、假覆层上皮。

洞庭湖区东方田鼠繁殖特性研究

１９９２年１月～１９９４年１２月，作者在东洞庭湖区岳阳县麻塘区调查，３年捕获并剖检东方田鼠１３９２只，其中雌鼠５９９只，雌性比♀／（♂＋♀）＝４３．０％。该鼠全年繁殖，盛夏５～７月怀孕率较低，冬季１２～２月怀孕率比同域其它鼠种显著偏高。３年合计总怀孕率为２９．２％．平均胎仔数（ｘ±ＳＥ）为５．１３±０．１２只，平均窝仔数４．６０±０．２７只，雌鼠和雄鼠的繁殖强度随年龄增长而递增。室内饲养的东方田鼠妊娠期约２０天，窝仔数４．３３±０．３３只，雌鼠５０～６０天成熟，雄鼠稍迟。枯水期（１１月～翌年４月）东方田鼠主要栖息于湖洲草地，汛期（５～１０月）主要栖息于过垸内稻田。在不同栖息地其繁殖力差别较大，湖洲的繁殖强度最高，稻田区次之，岗地最低，反映它在各栖息地生态适合度不同。文中还对全国４个亚种的繁殖参数作了比较。

布氏田鼠标志种群的繁殖参数

采用标志重捕和染色观测法跟踪了内蒙古典型草原区布氏田鼠野外种群 ,按绝对时间年龄研究其种群繁殖参数。结果表明 :4～ 5月份出生的雄鼠能在当年达到性成熟 ,性成熟发育历期约为 1 5个月 ,6月后出生的雄鼠当年达不到性成熟。在达到性成熟的当年雄鼠中 ,多数个体再度转入性休止期 ,其平均繁殖结束时间要比越冬雄鼠早 1个月 ,而越冬雄鼠则在整个繁殖期保持性活动状态。雌鼠性成熟发育历期约为 1个月 ,首次产仔时间约为2月龄。雌鼠在一年中的产仔窝数与其年龄有关 :越冬鼠能产 3～ 4窝 ,4月份出生的雌鼠能产 2～ 3窝 ,5月份出生的雌鼠当年能产 1～ 2窝 ,6月份出生的雌鼠能产 0～ 1窝 ,7月份之后出生雌鼠当年不参加繁殖。在自然条件下 ,布氏田鼠一生中最多能产

灭鼠后布氏田鼠种群特征的研究

1987和1988年4—5月,笔者在内蒙古正镶白旗布氏田鼠危害严重的草场上,连续两年用药物灭鼠。调查结果表明,在布氏田鼠种群数量上升或下降的年份,春季灭鼠均能控制当年的鼠害。鼠密度高时,灭鼠后鼠种群年龄结构、性比、怀孕率和睾丸下降率均发生改变。鼠密度低时,灭鼠对种群特征影响不显著。

大绒鼠体温调节和产热特征

大绒鼠为横断山脉地区小型哺乳动物的典型代表 ;其体温仅能在 1 5～ 30℃范围内维持稳定 ;在热中性区内 ,最低静止代谢率为 2 71± 0 1 3mlO2 /g h,为其体重预期值的 2 0 3 2±1 0 1 3 % ;F -值 { (RMR/Me) /(Cm/C’) }为 0 99± 0 0 5 ;在 2 5℃的NSTmax为 5 1 8± 0 1 9mlO2 /g h ;BAT重量为 0 33± 0 0 5g,为体重的 0 84% ,BAT细胞线粒体的产热活性较高 ;肝脏也具有较强的产热活性。大绒鼠的产热特征和体温调节模式很可能反映了横断山地区小型啮齿动物的特征。

洞庭湖区洲滩环境演变对东方田鼠暴发成灾的影响

在分析洞庭湖区东方田鼠暴发成灾乡及灾情的基础上，研究了洞庭湖区洲滩演变对东方田鼠暴发成灾的影响。研究认为，中低位洲滩出露出积不断增大使东方田鼠种群迅速膨胀，高位洲滩出露面积减小造成汛期东方田鼠大量向垸内农田迁移；湖区洲滩冬春季连续出露天数增加延长了东方田鼠的繁殖期；汛期洪峰水位增高、洲滩大面积淹没迫使东方田鼠大量迁向垸内；湖内废弃湖堤为东方田鼠逃避洪水提供了中途休养之地；洲滩地抑制东方田鼠种群膨胀的天敌数量已大大减少。据此，本文指出，三峡工程建成后将对洞庭湖区训滩演变产生重大影响，因而将改变东方田鼠种群生态环境条件，引起种群动态变化，值得注意。

布氏田鼠(Microtus brandti)的食性

通过胃内容物显微组织学分析法,研究了内蒙古克什克腾旗阿其乌拉地区布氏田鼠春季和夏季的自然食性。该鼠于春季和夏季都最嗜食羊草,但食性有明显的季节变化,对食物有强烈的选择性特征,专化现象较为明显。植被的物候变化和植物体的蛋白质含量以及硅等矿质元素的含量是影响布氏田鼠进行选食的主要因素。文中还讨论了布氏田鼠的最优觅食行为。

洞庭湖区夏季温光条件及被迫迁移对东方田鼠繁殖的影响

在野外 ,从先年的秋初至当年春末被迫迁移前 ,东方田鼠在湖滩上能保持较高的繁殖能力 ;在夏季 ,不论栖息在农田还是岗地 ,都是东方田鼠的繁殖低谷。夏季 (6～ 8月 )在实验室自然温光条件下与人工控制较低温度条件下同时进行观察 ,结果表明 ,前种条件下东方田鼠的繁殖能力明显低于人工降低温度缩短光照条件下的繁殖力 ,此变动趋势与野外观察到的繁殖力季节动态一致 ,可以说明夏季温光条件不利于东方田鼠的繁殖。另一方面 ,东方田鼠的繁殖能力最低的 6月并非全年最热的月份 ,这是因为东方田鼠的被动迁移对体力的消耗加剧了夏季温光对繁殖的影响程度。因此 ,认为洪水引起的东方田鼠被迫迁移和夏季的温光条件共同影响了东方田鼠的繁殖。洞庭湖区东方田鼠主要在冬春季繁殖 ,而分布在高纬度地区的田鼠类动物和分布在高纬度地区的东方田鼠在夏季繁殖 ,在月份上虽不同 ,但其繁殖盛期的气温则相近 ,其实是田鼠类动物喜寒惧热特性的反映 ,乃是对当地的生态环境的适应。

典型草原区布氏田鼠的活动节律及其季节变化

采用标志重捕、染色标记和野外观测法研究典型草原区布氏田鼠野外实验种群，采用4种活动模式指数（日活动差异指数θ，昼行性指数λ，峰型指数φ；活动强度指数η）分析田鼠昼夜活动节律及其季节变化。结果表明，布氏田鼠全年12个月的昼行性指数A均高于0．542，为典型的昼行性种类。其活动节律的季节变化主要与环境温度有关：1、2、3、4、11、12月，气温较低，布氏田鼠的活动模式呈典型的单峰型；5、6、7月气温较高，为典型的双峰型；而8、9、10月则属于单双峰过渡类型。田鼠的峰型指数西在冬季最低，夏季最高，与月均气温呈显著的正相关关系（r=0．89，n=12，P〈0．05）。活动强度指数研与气温也存在显著的正相关（r=0．94，n=12，P〈0．05）。5～9月，布氏田鼠的活动强度最高，每日活动时问在6h以上；冬季布氏田鼠的日活动量骤降，很少外出活动，尤其在1～2月，布氏田鼠日均地面活动时间不足1min。另外，室内实验表明，布氏田鼠具有在黑暗环境中活动能力，但在野外条件下，夜间活动极少发生。

根田鼠栖息地选择的影响因素

20 0 2年 7～ 9月在中国科学院海北高寒草甸生态系统定位站地区对根田鼠的栖息地选择进行了研究。对根田鼠栖息地利用强度变量 (一定面积内的跑道长度、跑道分叉数、洞口数 )与 12个栖息地特征变量进行多元线性逐步回归分析表明 :显著影响跑道长度的变量为灌丛高度、竞争性啮齿类、电线杆、早熟禾、围栏、灌丛间距和双子叶植物生物量 ;显著影响跑道分叉数的变量为灌丛高度、竞争性啮齿类、电线杆、早熟禾和围栏 ;显著影响洞口数的变量为灌丛高度、土壤含水率和围栏。对影响利用强度变量的因素进行综合生态学分析表明 ,在小生境尺度上 ,研究期间影响根田鼠栖息地选择的因素主要为捕食风险和种间竞争 。

密度因素在布氏田鼠种群调节中的作用

对布氏田鼠栖息密度不同的种群同时进行取样,研究密度因素对布氏田鼠种群发展的调节作用。结果表明,在高密度区布氏田鼠种群繁殖强度受到抑制,雌鼠怀孕率、雄鼠睾丸下降率、贮精囊肥大率和睾丸长度都小于低密度种群。高密度种群繁殖季节结束时间早于低密度种群,幼鼠肥满度较小,性成熟速度较慢,种群年龄结构中,幼年鼠所占比例小于低密度种群。这些都是导致高密度种群增长速度减慢的因素。