高寒草甸生态系统中高原鼠兔和高原鼢鼠的捕食风险及生存对策

调查青藏高原高寒草甸生态系统中两种主要啮齿动物及其天敌动物的种群密度,分析天敌动物对两种啮齿类的捕食方式、捕食强度,探讨啮齿类动物的捕食风险及生存对策。研究结果表明,高原鼠兔和高原鼢鼠的种群密度分别为4．97只／hm^2和10．6只／hm^2,而它们的主要天敌赤狐、艾虎和香鼬的种群密度分别为0．16只／100hm^2、0．37只／100hm^2、3只／100hm^2。艾虎和香鼬在取食过程中主要搜寻啮齿类的洞道系统,全部食物几乎都来源于洞道系统内;赤狐或取食地面活动的鼠兔,或挖掘洞口待高原鼢鼠封闭洞口时取食猎物。高原鼠兔在赤狐、艾虎和香鼬的食物中所出现的频次分别为100％、96．1％、100％,高原鼢鼠在3种天敌动物的食物中所出现的频次分别为87．5％、73．2％、0％。3种天敌动物对高原鼠兔和高原鼢鼠的捕食强度分别为0．703％和0．038％,高原鼠兔和高原鼢鼠所承受的捕食风险分别为0．780和0．393。高原鼠兔在高的捕食风险下通过行为对策和繁殖对策增加其适合度,而承受捕食风险较小的高原鼢鼠主要通过封闭的洞道系统和高的存活率增加其适合度。     

香鼬的活动节律和巢区

本文采用无线电遥测技术对栖息在自然环境中香鼬（Ｍｕｓｔｅａｌａｌｔａｉｃａ）的活动节律及其巢区进行了较为系统的研究。结果表明,香鼬多营独居生活．除繁殖期外,无论雌雄个体均无长期稳定的巢穴,经常更换活动的位置。香鼬的每日活动主要为玩耍、自身的修饰、光浴、探视和取食,在繁殖期还有育幼及对幼鼬的保护。在不同时期香鼬日活动高峰和巢区大小均有不同。幼鼬出洞活动前,其亲体雌性成鼬活动呈现两个明显的高峰,１１：００～１３：００和１６：００～１７：００,雄性成鼬则只有一个活动高峰在１１：００左右;在这一时期,成体香鼬的地面活动高峰与其食物──高原鼠兔的地面活动高峰不相吻合,雌性成鼬的巢区面积为７．２１ｈａ,雄性成鼬的巢区面积为１１．７ｈａ。幼鼬出洞活动后,雌性成鼬的活动高峰为８：００～９：００和１７：００～１９：００,巢区面积平均为８２．７２ｈａ。幼鼬扩散期间;雌性成鼬的活动高峰期分别为８：００～９：００和１５：００～２０：００。在这两个时期。成体香鼬的地面活动高峰与高原鼠兔的地面活动高峰趋于一致。影响香鼬活动和巢区大小的主要因素是食物的丰富度、猎物的活动性和繁殖行为,同时种群密度也是主要因素之一。     

青海门源地区大鵟和雕鸮的食性比较

1999-2002年的6-8月份,在青海门源地区收集了大鵟和雕鸮的吐弃块(pellets)和残留食物(food remains),带回实验室进行分检鉴定、研究分析。大鵟食物中共有736个猎物,其中高原鼢鼠28只、高原鼠兔139只、甘肃鼠兔142只、田鼠科动物422只、雀形目鸟类4只、香鼬1只;各猎物对大鵟食物的生物量贡献率分别为14．26％、40．79％、17．39％、26．99％、0．22％、0．35％。雕鸮食物中共有330个猎物,其中高原鼢鼠17只、高原鼠兔77只、甘肃鼠兔44只、田鼠科动物183只、雀形目鸟类2只、红脚鹬2只、高原兔5只;各猎物对雕鸮食物的生物量贡献率分别为11．83％、30．87％、7．36％、16．00％、0．15％、0．62％、33．17％。雕鸮的食物生态位宽度与大鵟的食物生态位宽度相近,食物生态位高度重叠,但是它们捕食同种猎物的比例显著不同。     

赤狐气味对高原鼠兔繁殖的影响

在野外条件下,利用赤狐的粪尿气味增加高原鼠兔的捕食风险,研究捕食风险对高原鼠兔繁殖的影响。结果表明,作为衡量高原鼠兔繁殖投入大小的定量指标,成体高原鼠兔的体重变化在捕食风险处理样方与对照样方之间没有明显的不同,随着繁殖期的延长,两样方内雌雄个体的体重均显减少,说明捕食风险对高原鼠兔的繁殖投入无明显影响,因此,捕食风险对幼体的生长、发育也无明显的作用。捕食风险增加后,高原鼠兔平均每个雌性成体拥有的后代数目、性比和居留率与对照样方比较均无明显不同,但是由于扩散等原因使每个雄性成体拥有的后代数、繁殖期结束后幼体的性比有明显的差异。以上结果并未显示出捕食气味作为捕食风险对高原鼠兔的繁殖产生抑制作用,其主要原因是捕食风险的类型不同和研究期间高原鼠兔本身承受的捕食风险较大,高原鼠兔可能通过行为变化调节捕食风险增加对其产生的不利影响。     

光周期—褪黑素信号调控高原鼠兔精原细胞分化和季节性精子发生

高原鼠兔是青藏高原特有的小型哺乳动物,其繁殖活动呈现明显的季节性。成年雄性高原鼠兔在繁殖期睾丸重量显著增加,精子发生正常进行,而在非繁殖期睾丸退化,精子发生阻断在未分化精原细胞阶段。光周期控制实验显示,长光照（16h∶8h）诱导非繁殖期高原鼠兔重新启动精原细胞分化和精子发生;而短光照（8h∶16h）显著抑制繁殖期高原鼠兔精子发生。酶联免疫分析发现,褪黑素分泌水平在长日照条件下降低而在短日照条件下升高。非繁殖期高原鼠兔连续注射褪黑素拮抗剂能诱导生殖细胞发育和精子发生恢复。促性腺激素释放激素(GnRH)与黄体生成素(LH)在繁殖期鼠兔下丘脑垂体显著升高,促卵泡素（FSH）水平无显著差异。注射GnRH可以促进非繁殖期高原鼠兔精原细胞分化和精子发生,而褪黑素注射后抑制GnRH的分泌进而负调控性腺轴。综上,高原鼠兔季节性精子发生受光周期-褪黑素信号控制,后者主要通过控制GnRH、LH水平影响精原细胞分化。本研究对理解季节性动物精子发生的调控机制有重要借鉴意义。     

大鵟夏季的活动及取食节律研究

大（Ｂｕｔｅｏｈｅｍｉｌａｓｉｕｓ）于夏季在栖落，梳羽，取食，扑翼飞行，滑翔和捕食上化费的时间分别占整个活动日（１５ｈ）的８１．０１％，８．８６％，４．３９％，３．０９％，２．２４％和０．４１％；从１３０块食物团的分析表明大的食物主要由高原鼢鼠（Ｍｙｏｓｐａｌａｘｂａｉｌｅｙｉ），根田鼠（ＭｉｃｒａｔｕｓＯｅｃｏｎｏｍｕｓ），高原鼠兔（Ｏｃｈｏｔｏｍａｃｕｒｚｏｎｉａ），雀形目小鸟及昆虫组成。一只大平均１ｄ吐１．５±０．６（ｎ＝７），相当于消耗１．６２只鼠。     

青海门源地区大(狂鸟)和雕鸮的食性比较

1999～2002年的6～8月份,在青海门源地区收集了大(狂鸟)和雕鸮的吐弃块(pellets)和残留食物(food remains),带回实验室进行分检鉴定、研究分析.大(狂鸟)食物中共有736个猎物,其中高原鼢鼠28只、高原鼠兔139只、甘肃鼠兔142只、田鼠科动物422只、雀形目鸟类4只、香鼬1只;各猎物对大(狂鸟)食物的生物量贡献率分别为14.26%、40.79%、17.39%、26.99%、0.22%、0.35%.雕鸮食物中共有330个猎物,其中高原鼢鼠17只、高原鼠兔77只、甘肃鼠兔44只、田鼠科动物183只、雀形目鸟类2只、红脚鹬2只、高原兔5只;各猎物对雕鸮食物的生物量贡献率分别为11.83%、30.87%、7.36%、16.00%、0.15%、0.62%、33.17%.雕鸮的食物生态位宽度与大(狂鸟)的食物生态位宽度相近,食物生态位高度重叠,但是它们捕食同种猎物的比例显著不同.     

高原鼠兔季节性繁殖中的神经内分泌调控Ⅱ．不同光制对生殖恢复期的影响

本项研究将野外捕获的成年雄性高原鼠兔（Ｏｃｈｏｔｏｎａｃｕｒｚｏｎｉａｅ）分３组进行不同光制的饲养,以检验光周期对其神经内分泌─—生殖轴功能的影响：（１）长光照组睾丸及附属性腺的重量和血浆睾酮水平均明显高于自然光组（ｐ＜０．０５）和短光照组（ｐ＜０．０１）。（２）长光照组的松果腺重量（１．５±０．１毫克,ｎ＝１５）和褪黑激素含量（８９．７±５．８微微克／松果腺）,均显著低于其它两组。（３）自然光组和短光照组性腺的显著萌发表明,在高原鼠兔季节性繁殖的年周期中,其神经内分泌─—生殖轴对春分前短光照的抑制作用具有不应期。     

艾美耳球虫对高原鼠兔繁殖的影响

寄生物对宿主繁殖的影响取决于宿主对当前繁殖值和剩余繁殖值的权衡。球虫为微型寄生物,而微型寄生物对宿主当前繁殖值的影响较剩余繁殖值要大。因此,本研究检验了寄生在高原鼠兔肠道内的艾美耳球虫可影响其当前繁殖的假设。在繁殖早、中、晚期,野外共观测高原鼠兔170只。结果表明,不同繁殖期感染率有显著差异。在繁殖中期,未感染雌性的妊娠率显著高于感染雌性。且未妊娠雌性较妊娠雌性有更高的感染强度,但在另外两个繁殖期没有发现此效应。在雄性中,任何繁殖期的感染强度和感染率与睾丸和附睾指数均无显著相关性,且感染和未感染球虫雄性睾丸及附睾指数无显著差异。此外,野外观测实验结果表明,感染雌性的胚胎重较未感染雌性显著降低,与野外感染对胚胎重量影响的实验结果相一致。说明艾美耳球虫感染可影响胚胎的发育。上述结果说明,艾美耳球虫对高原鼠兔繁殖的影响随繁殖期而有不同效应,且存在性别间差异,这种效应可能与不同性别间的繁殖对策有关。     

草兔的年龄鉴定和种群结构分析

根据１９９１年２－１０月猎自晋东南的２１２只和１９９０－１９９２年狩猎季节猎自山西和陕西省各地的１５１０只草兔眼晶体重的分布规律并参照繁殖资料,确定２２５毫克为区别１年以下及其以上个体的临界重量。秋－冬季种群中,当年兔占８６．３（７２．２－９３．５）％;随着繁殖季节的推移,当年兔的比例逐渐增加。在４０１１只标本中,雌性占５２．３％;其中１２２６只幼体和１９５只成体中分别有雌性５２．４％和５４．４％。在２－９月所获的９１只当年兔有雌性５０．５％,而成体中雌性则有５８．２％。     

高寒草甸生态系统中高原鼠兔的繁殖特征

2002年4月至8月,在中国科学院海北高寒草甸生态系统定位站附近,采用标志重捕法对高原鼠免的繁殖特征进行了研究。高原鼠兔的繁殖具有明显的季节性差异,4月下旬和5月为繁殖高峰期,雄性的睾丸重而饱满,雌性的怀孕率最大。雄性成体的体重和睾丸重在繁殖期的不同时段具有显的差异,在4月11日至5月10日、6月11日至7月10日体重和睾丸重之间呈显正相关。雌性怀孕早期胚胎数与临产前胚胎数没有显差异,未发现胚胎吸收现象;同时,胚胎数在繁殖期的不同时段存在显差异。采用种群统计学中同生群的划分方法,将5～8月份出生的幼体依次记为L1、L2、L3、L4。在出生后20天内L1、L2幼体存活率明显高于L3、L4;在从出生50天至80天期间L4的存活率显高于L2。当年出生的雌雄幼体在发育上存在不同步现象,当年出生的雌性幼体性成熟早,有的可以直接参加繁殖,但当年出生的雄性幼体却无此现象。结果表明：在海北地区,经过综合治理后,高原鼠兔的生境发生改变,其繁殖策略也随之发生改变,即,减少每次繁殖活动的投入,增加繁殖次数,延长繁殖时间。     

高原鼠兔繁殖期攻击行为的动态格局

为探讨高原鼠兔繁殖期攻击行为强度的变化、检验进化博弈理论有关预测,本研究于2009 年5 ～8 月采用标志重捕和中立竞技场法测定了高原鼠兔自然种群斗殴及进攻等行为的发生频率及持续时间。结果表明:5 月下旬及6 月上旬高原鼠兔雄性斗殴行为发生频率及持续时间显著高于7 月下旬和8 月中旬;而雌性差异不显著。5月下旬和6 月上旬,高原鼠兔雄性个体间的斗殴行为发生频率及持续时间显著高于雌性,其余时期两性间无显著差异。进攻发起者通常是该次殴斗的获胜者;自繁殖高峰期至末期,种群中雄性高原鼠兔鹰对策者比例逐渐下降,与进化博弈论的预测一致。     

高原鼠兔贮草行为初探

2004年7—10月,在青海省果洛州玛沁县境内的大武镇东南方向25 km处的格多牧委会草场,采用 样带法和样方法对高原鼠兔(Ochotona curzoniae)贮草行为过程中刈割植物的种类和放置方式进行初步研究。 结果表明:高原鼠兔在植物的生长旺盛期具有为冬季贮藏干草堆的行为,贮草行为始于7月,结束于10月初。 高原鼠兔对所刈割植物种类的选择,在一定程度上受栖息地植被物种丰富度的影响,并且将刈割植物放置于具 有宽大叶片的植物上,以防止干草的腐烂。挖洞结果显示,高原鼠兔具有洞内贮藏食物的习性。     

高原鼠兔对垂穗披碱草及豆科植物生长特性的影响

高原鼠兔通过取食对高寒草甸产生广泛的影响,从而影响高寒草甸植物的个体生长特征。2012年在青海省果洛州矮嵩草草甸,以高原鼠兔喜食植物(豆科和垂穗披碱草)为研究对象,通过小区控制研究高原鼠兔取食（对照组、低密度处理组、中密度处理组、高密度处理组）对植物个体生长特征的影响。研究显示：在实验前期（5月和6月）,喜食植物个体特征基本上无明显规律;在实验后期（7月和8月）,随着高原鼠兔取食强度增大,高原鼠兔喜食植物的地上生物量、平均高度、分蘖枝数、分蘖枝长度、丛幅均呈下降趋势;叶片长度和叶片数均呈先上升后下降态势。2.高原鼠兔喜食植物个体特征的增长率对照组显著高于高密度处理组（P<0.05）。以上结果表明(1)高寒草甸豆类植物在其生长后期与高原鼠兔的取食强度呈一定的负相关关系;高原鼠兔取食强度在阈值（中、低密度）内有利于垂穗披碱草的生长,但超过其阈值的取食强度不利于其生长。(2)高原鼠兔高强度的取食对其喜食植物个体的生长率有明显的抑制作用。     

繁殖期高原鼠兔的行为时间分配与后代存活率的关系

2002年4-8月份,在中国科学院海北高寒草甸生态系统定位站附近,采用标志流放、直接观察法和解剖法对青藏高原特有的植食性小哺乳动物———高原鼠兔(Ochotonacurzoniae)的行为时间分配、繁殖特征和后代存活率等方面进行了研究。结果表明,雌、雄成体平均地面活动时间占总时间的比例分别为88.67%和89.88%,在不同的繁殖时段,成体的各种行为时间分配存在显著的变化,并影响后代的存活率。幼体从出生到15d的存活率和雌、雄性成体的每次移动距离以及雌性成体的地面活动强度都显著的正相关;从15d到45d的存活率和雄性成体的地面活动强度、观望强度显著的正相关。在相同的观察时期,高原鼠兔雌、雄成体的一些行为时间分配存在显著差异,如雄性成体地面移动距离、频次在繁殖前期显著的高于雌性成体;雄性成体的观望强度在6、7月份显著高于雌性成体。说明雄性成体在领域防卫中较雌性成体承担更多的责任,雌、雄成体在育幼活动中的繁殖投入存在互补性。     

BREEDING ECOLOGY OF TURNSTONES ARENARIA INTERPRES AT HAZEN CAMP, ELLESMERE ISLAND, N.W.T.

Turnstones arrive on Ellesmere Island in late May or early June. Pair-formation takes place during migration, or after arrival in courtship groups along the beaches, or on the nest territory, depending on weather conditions. Pair-formation was not observed at Hazen Camp in 1966 as most birds were already paired when observations began on 3 June. The preferred nesting habitat was Dryas-hummocked tundra closely associated with a marsh, stream, or pond. A census area of 240 ha supported 13 breeding pairs, possibly 14; the total number of pairs breeding in the Hazen Camp study area was estimated to be 70 (3.04 pairs/km²). Egg-laying began on 10 June, with 46% of the first eggs laid 13–15 June. 62% of the sets were completed between 19 and 21 June. Both sexes incubated, the female regularly and the male sporadically. Hatching was also well synchronised; most clutches hatched between 7 and 14 July. Nest success was high (79%). After hatching territories dissolved and family groups moved freely over the tundra, concentrating at ponds where food was readily available for the young. Both adults attended the young during the pre-fledging period, but the females apparently departed long before the young fledged. Males left once the young could fly and the adult fall migration was complete by early August with the exception of late breeders. Most of the young departed in the second half of August. Fall migration is complete by late August or early September. The breeding season appears to be timed so that the young are raised when food is most abundant. Food supply (dipterous insects, especially adult chironomids) was highest from 8 to 12 July at the peak of the hatching period. While food supply for the young declined during the growing period, the early departure of half the adult population, and family movements over the tundra, appeared to reduce the food demand correspondingly. Food appeared to influence the distribution of breeding pairs markedly, restricting them to the vicinity of marshes, streams, and ponds. Territoriality displayed by Turnstones is believed to be closely associated with the protection of the nest against predators and adult food requirements during incubation; it also seems likely that territory has at least a local effect in regulating the number of breeding pairs.     

Field experiments on sugar-beet downy mildew (Peronospora farinosa)

The numbers of sugar-beet plants infected with downy mildew in experimental crops increased slowly over a period of 8–15 weeks from late May. Few new infections appeared after the middle of August, although less than half the plants were then infected. Most infected plants recovered, and recovery was most rapid and complete in young plants, irrespective of the weather. Plants infected when young produced small roots, but their sugar content and juice purity at harvest was similar to those of uninfected plants. Plants first infected in late July and early August had the smallest sugar content and most juice impurities.     

Population biology of the weasel Mustela nivalis on British game estates

The mean year-class ratio in 6 samples of weasels (total n = 477) ranged from 59% to 84% young, and mean age from 0.79 to 1.16 yr. There was no difference in age structure between samples from 5 game estates and 1 reserve. Mean annual mortality of weasels of both sexes and all ages was 75-90%. In 12 pregnant weasels the mean number of embryos, observed from April to June, was 5.6. There was a definite anoestrous season in winter. Records of the number of weasels killed on game estates show that weasels and stoats reacted differently to the first outbreak of myxomatosis in England in 1954; and that weasel populations are capable of enormous sudden increases (usually associated with "mouse years"). These increases are probably due largely to summer litters produced by precocious juveniles, and also to some adults breeding a second time (both possibilities confirmed from ovarian histology on this material). Traditional gamekeeping practice may influence the seasonal pattern of mortality of weasels (highest in spring) but its effects are probably short-lived.     

地表覆盖物对高原鼠兔栖息地利用的影响

对地表覆盖物对高原鼠兔栖息地利用的作用进行了研究, 地表覆盖物增加后, 高原鼠兔能依据其程度及毗邻生境状况, 或减少地面活动增加对洞道系统的利用; 或转移到较安全区域; 同时摄食行为也发生变化, 显著增加用于防御的时间, 且取食区域几乎集中于洞口附近。研究表明, 高原鼠兔视地表覆盖物为一种捕食风险源, 并对此具有一定的评估能力, 其行为反应实质上是通过对食物获取与风险大小的权衡而做出的一种行为决策。间接捕食风险是高原鼠兔在选择和利用栖息地时所必须考虑的权衡因子, 也是一个重要的摄食代价。     

Distribution and abundance of small mammals in relation to habitat in Pureora Forest Park

Populations of ship rats (Rattus rattus), Norway rats (R. norvegicus), feral house mice (Mus musculus), stoats (Mustela erminea), weasels (M. nivalis), and ferrets (M. furo) were sampled with killtraps every three months from November 1982 to November 1987 in logged and unlogged native forest and in exotic plantations of various ages at Pureora Forest Park, central North Island. Mice (n=522 collected) were fewest in unlogged native forest, more abundant in road edge cutover forest, and most abundant in a young (5-10 year old) plantation. Traps catching most mice were set in dense ground cover under a low, sparse canopy. Ship rats (n=1793) were absent from the young plantation, present but not abundant in older exotic forest, and abundant in all native forest regardless of logging history. Traps set on warmer, steeper sites caught most ship rats, and those set in early successional habitats caught fewest. There was a marked reciprocal relationship between the distributions of ship rats and of mice: the proportion of mice in the total catch of rodents decreased significantly at the least, disturbed forest sites (P <0.001). Most (81%) Norway rats (n=43) were caught in a single trap in unlogged native forest on the bank of a stream. Stoats (n=57) were most abundant in the older exotic plantations; weasels (n=16) in the young plantation and along road edges in native forest; and ferrets (n=11) in unlogged native forest. Hedgehogs (n=290) were common in unlogged native forest far from any roads and also in older exotic forest. Our data suggest that selective logging and conversion to exotics have different effects on each of the six species we monitored. We hypothesise that (1) selective logging is likely to stimulate temporary increases in the numbers of mice and weasels, but not rats or stoats, and (2) after conversion to exotic forest, mice and occasionally weasels will be abundant at first but will gradually be replaced by ship rats and stoats as the forest matures.